Pediatrics_Nelson

Pediatrics_Nelson. The position of the heart in infants is more midline than in older children. The first heart sound is normal, whereas the second heart sound may not be split in the first day of life. Decreased splitting of the second heart sound is noted in PPHN, transposition of the great vessels, and pulmonary atresia. Heart murmurs in newborns are common in the delivery room and during the first day of life. Most of these murmurs are transient and are due to closure of the ductus arteriosus, peripheral pulmonary artery stenosis, or a small ventral septal defect. Pulses should be palpated in the upper and lower extremities (over the brachial and femoral arteries). Blood pressure in the upper and lower extremities should be measured in all patients with a murmur or heart failure. An upperto-lower extremity gradient of more than 10 to 20 mm Hg suggests coarctation of the aorta.


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Pediatrics_Nelson. The liver may be palpable 2 cm below the right costal margin. The spleen tip is less likely to be palpable. A left-sided liver suggests situs inversus and asplenia syndrome. Both kidneys should be palpable in the first day of life with gentle, deep palpation. The first urination occurs during the first day of life in more than 95% of normal term infants.


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Pediatrics_Nelson. Abdominal masses usually represent hydronephrosis or dysplastic-multicystic kidney disease. Less often, masses indicate ovarian cysts, intestinal duplication, neuroblastoma, or mesoblastic nephroma. Masses should be evaluated immediately with ultrasound. Abdominal distention may be caused by intestinal obstructions, such as ileal atresia, meconium ileus, midgut volvulus, imperforate anus, or Hirschsprung disease. Meconium stool is passed normally within 48 hours of birth in 99% of term infants. The anus should be patent. An imperforate anus is not always visible; the first temperature taken with a rectal thermometer should be taken carefully. The abdominal wall musculature may be absent, as in prune-belly syndrome, or weak, resulting in diastasis recti. Umbilical hernias are common in African American infants. The umbilical cord should be inspected to determine the presence of two arteries and one vein and the absence of an urachus or a herniation of abdominal contents, as occurs with


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Pediatrics_Nelson. American infants. The umbilical cord should be inspected to determine the presence of two arteries and one vein and the absence of an urachus or a herniation of abdominal contents, as occurs with an omphalocele. The latter is associated with extraintestinal problems, such as genetic trisomies and hypoglycemia (Beckwith-Wiedemann syndrome). Bleeding from the cord suggests a coagulation disorder, and a chronic discharge may be a granuloma of the umbilical stump or, less frequently, a draining omphalomesenteric cyst or urachus. Erythema around the umbilicus is omphalitis and may cause portal vein thrombophlebitis and subsequent extrahepatic portal hypertension. The herniation of bowel through the abdominal wall 2 to 3 cm lateral to the umbilicus is a gastroschisis.


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Pediatrics_Nelson. Available @ StudentConsult.com At term, the testes should be descended into a well-formed pigmented and rugated scrotum. The testes occasionally are in the inguinal canal; this is more common among preterm infants, as is cryptorchidism. Scrotal swelling may represent a hernia, transient hydrocele, in utero torsion of the testes, or, rarely, dissected meconium from meconium ileus and peritonitis. Hydroceles are clear and readily seen by transillumination, whereas testicular torsion in the newborn may present as a painless, dark swelling. The urethral opening should be at the end of the penis. Epispadias or hypospadias alone should not raise concern about pseudohermaphroditism. However, if no testes are present in the scrotum and hypospadias is present, problems of sexual development should be suspected. Circumcision should be deferred with hypospadias because the foreskin is often needed for the repair. The normal prepuce is often too tight to retract in the neonatal period.


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Pediatrics_Nelson. The female genitalia normally may reveal a milky whiteor blood-streaked vaginal discharge as a result of maternalhormone withdrawal. Mucosal tags of the labia majora arecommon. Distention of an imperforate hymen may produce hydrometrocolpos and a lower midline abdominalmass as a result of an enlarged uterus. Clitoral enlargementwith fusion of the labial-scrotal folds (labia majora) suggests adrenogenital syndrome or exposure to masculinizingmaternal hormones. Examination of the extremities should involve assessment of length, symmetry, and presence of hemihypertrophy, atrophy, polydactyly, syndactyly, simian creases, absent fingers, overlapping fingers, rocker-bottom feet, clubfoot, congenital bands, fractures, and amputations. The spine should be examined for evidence of sacral hair tufts, a dermal sinus tract above the gluteal folds, congenital scoliosis (a result of hemivertebra), and soft tissue masses such as lipomas or meningomyeloceles.


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Pediatrics_Nelson. The hips should be examined for congenital dysplasia (dislocation). Gluteal fold asymmetry or leg length discrepancy is suggestive of dysplasia, but the examiner should perform the Barlow test and the Ortolani maneuver to evaluate the stability of the hip joint. These tests determine whether the femoral head can be displaced from the acetabulum (Barlow test) and then replaced (Ortolani maneuver). The neurologic examination should include assessment ofactive and passive tone, level of alertness, primary neonatal Sepsis, pneumonia Inflammation, pulmonary hypertension, ARDS Meconium aspiration pneumonia Mechanical obstruction, inflammation, pulmonary hypertension Persistent pulmonary hypertension of the newborn Pulmonary hypertension Diaphragmatic hernia Pulmonary hypoplasia, pulmonary hypertension Cyanotic heart disease with decreased pulmonary Right-to-left shunt as in pulmonary atresia, tetralogy of Fallot blood flow


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Pediatrics_Nelson. Diaphragmatic hernia Pulmonary hypoplasia, pulmonary hypertension Cyanotic heart disease with decreased pulmonary Right-to-left shunt as in pulmonary atresia, tetralogy of Fallot blood flow Cyanotic heart disease with increased pulmonary Mixing lesion as in single ventricle or truncus arteriosus blood flow Cyanotic heart disease with congestive heart failure Pulmonary edema and poor cardiac output as in hypoplastic left heart and coarctation of aorta Heart failure alone Pulmonary edema and poor cardiac contractility as in sepsis, myocarditis, supraventricular tachycardia, or complete heart block; high-output failure as in PDA or vein of Galen or other arteriovenous malformations Maternal sedative drugs Hypoventilation, apnea Intracranial hemorrhage CNS depression, seizure Neuromuscular disease Hypotonia, hypoventilation, pulmonary hypoplasia HEMATOLOGIC Hypoglycemia CNS depression, congestive heart failure


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Pediatrics_Nelson. Intracranial hemorrhage CNS depression, seizure Neuromuscular disease Hypotonia, hypoventilation, pulmonary hypoplasia HEMATOLOGIC Hypoglycemia CNS depression, congestive heart failure ARDS, Acute respiratory distress syndrome; CNS, central nervous system; PDA, patent ductus arteriosus.


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Pediatrics_Nelson. (primitive) reflexes, deep tendon reflexes, spontaneousmotor activity, and cranial nerves (involving retinal examination, extraocular muscle movement, masseter power asin sucking, facial motility, hearing, and tongue function).The Moro reflex, present at birth and gone in 3 to 6 months,is one of the primary newborn reflexes. It is elicited by sudden, slight dropping of the supported head from a slightlyraised supine position, which should elicit opening of thehands and extension and abduction of the arms, followed by upper extremity flexion and a cry. The palmar grasp ispresent by 28 weeks’ gestation and gone by 4 months of age.Deep tendon reflexes may be brisk in a normal newborn; 5to 10 beats of ankle clonus are normal. The Babinski signis extensor (upgoing). The sensory examination can be evaluated by withdrawal of an extremity, grimace, and cryin response to painful stimuli. The rooting reflex (turningof the head toward light tactile stimulation of the perioralarea) is present by


Pediatrics_Nelson

Pediatrics_Nelson. be evaluated by withdrawal of an extremity, grimace, and cryin response to painful stimuli. The rooting reflex (turningof the head toward light tactile stimulation of the perioralarea) is present by 32 weeks’ gestation.


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Pediatrics_Nelson. Special Conditions Requiring Resuscitation in the Delivery Room Available @ StudentConsult.com Acrocyanosis (blue color of the hands and feet with pinkcolor of the rest of the body) is common in the delivery roomand is usually normal. Central cyanosis of the trunk, mucosal membranes, and tongue can occur at any time after birth andis always a manifestation of a serious underlying condition.Cyanosis is noted with 4 to 5 g/dL of deoxygenated hemoglobin. Central cyanosis can be caused by problems in manydifferent organ systems, although cardiopulmonary diseasesare the most common (Table 58-10). Respiratory distress syndrome, sepsis, and cyanotic heart disease are the threemost common causes of cyanosis in infants admitted to aneonatal intensive care unit. A systematic evaluation of theseand other causes of cyanosis is required for every cyanoticinfant after prompt administration of oxygen, with or withoutassisted ventilation.


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Pediatrics_Nelson. Various congenital anomalies can interfere with vital organ function after birth (see Table 58-9). Some malformations, such as choanal atresia and other lesions obstructing the airway, may complicate ventilation. Intrathoracic lesions, such as cysts or diaphragmatic hernia, interfere with respiration. Other malformations that obstruct the gastrointestinal system at the level of the esophagus, duodenum, ileum, or colon may lead to aspiration pneumonia, intestinal perforation, or gangrene. Gastroschisis and omphalocele are associated with exposed bowel on the abdominal wall. Omphalocele is often associated with other malformations, whereas intestinal necrosis is more common in gastroschisis.


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Pediatrics_Nelson. Shock in the delivery room is manifested by pallor, poor capillary refill time, lack of palpable pulses, hypotonia, cyanosis, and eventually cardiopulmonary arrest. Blood loss before or during labor and delivery is a common cause of shock in the delivery room. Blood loss may be caused by fetal-maternal hemorrhage, placenta previa, vasa previa, twin-to-twin transfusion syndrome, or displacement of blood from the fetus to the placenta as during asphyxia (asphyxia pallida). Hemorrhage into a viscus, such as the liver or spleen, may be noted in macrosomic infants, and hemorrhage into the cerebral ventricles may produce shock and apnea in preterm infants. Anemia, hypoalbuminemia, hypovolemia, and shock at birth are common manifestations of Rh immune hydrops.


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Pediatrics_Nelson. Severe intrauterine bacterial sepsis may present with shock in the delivery room or immediately after the infant is transferred to the nursery. Typically these infants are mottled, hypotonic, and cyanotic and have diminished peripheral pulses. They have a normal hemoglobin concentration but may manifest neutropenia, thrombocytopenia, and disseminated intravascular coagulation. Peripheral symmetrical gangrene (purpuric rash) often is a sign of hypotensive shock in infants with severe congenital bacterial infections. Congenital left ventricular cardiac obstruction (critical aortic steno-sis or hypoplastic left heart syndrome) also produces shock, although not usually in the delivery room.


Pediatrics_Nelson

Pediatrics_Nelson. Treatment of newborn infants with shock should involve the management approaches used for the sick infant. Problems may be anticipated through knowledge of the infant’s immune status, evidence of hydrops, or suspicion of intrauterine infection or anomalies. Stabilization of the airway and institution of respiratory support are essential. Hypovolemic shock should be managed with repeated boluses of 10 to 15 mL/kg of normal saline or lactated Ringer solution. If severe immune hemolysis is predicted, blood typed against the mother’s blood should be available in the delivery room and should be given to the newborn if signs of anemia and shock are present. Thereafter, all blood should be crossmatched with the infant’s and mother’s blood before transfusion. Drugs such as dopamine, epinephrine, or cortisol may improve cardiac output and tissue perfusion.


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Pediatrics_Nelson. Birth injury refers to avoidable and unavoidable injury to the fetus during the birth process. Caput succedaneum is a diffuse, edematous, often dark swelling of the soft tissue of the scalp that extends across the midline and suture lines. In infants delivered from a face presentation, soft tissue edema of the eyelids and face is an equivalent phenomenon. Caput succedaneum may be seen after prolonged labor in full-term and preterm infants. Molding of the head often is associated with caput succedaneum and is the result of pressure that is induced from overriding the parietal and frontal bones against their respective sutures. A cephalhematoma is a subperiosteal hemorrhage that does not cross the suture lines surrounding the respective bones. A linear skull fracture rarely may be seen underlying a cephalhematoma. With time, the cephalhematoma may organize, calcify, and form a central depression.


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Pediatrics_Nelson. Infants with cephalhematoma and caput succedaneum require no specific treatment. Occasionally a premature infant may develop a massive scalp hemorrhage. This subgaleal bleeding and the bleeding noted from a cephalhematoma may cause indirect hyperbilirubinemia requiring phototherapy. Retinal and subconjunctival hemorrhages are common but usually are small and insignificant. No treatment is necessary.


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Pediatrics_Nelson. Spinal cord or spine injuries may occur in the fetus as a result of the hyperextended star gazing posture. Injuries also may occur in infants after excessive rotational (at C3–4) or longitudinal (at C7–T1) force is transmitted to the neck during vertex or breech delivery. Fractures of vertebrae are rare; trauma may cause direct damage to the spinal cord, leading to transection and permanent sequelae, hemorrhage, edema, and neurologic signs. Rarely, a snapping sound indicating cord transection rather than vertebral displacement is heard at the time of delivery. Neurologic dysfunction usually involves complete flaccid paralysis, absence of deep tendon reflexes, and absence of responses to painful stimuli below the lesion. Painful stimuli may elicit reflex flexion of the legs. Infants with spinal cord injury often are flaccid, apneic, and asphyxiated, all of which may mask the underlying spinal cord transection.


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Pediatrics_Nelson. Injury to the nerves of the brachial plexus may result from excessive traction on the neck, producing paresis or complete paralysis. The mildest injury (neurapraxia) is edema; axonotmesis is more severe and consists of disrupted nerve fibers with an intact myelin sheath; neurotmesis, or complete nerve disruption or root avulsion, is most severe. Erb-Duchenne paralysis involves the fifth and sixth cervical nerves and is the most common and usually mildest injury. The infant cannot abduct the arm at the shoulder, externally rotate the arm, or supinate the forearm. The usual picture is one of painless adduction, internal rotation of the arm, and pronation of the forearm. The Moro reflex is absent on the involved side, and the hand grasp is intact. Phrenic nerve palsy (C3, C4, and C5) may lead to diaphragmatic paralysis and respiratory distress. Elevation of the diaphragm caused by nerve injury must be differentiated from elevation caused by eventration resulting from congenital weakness


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Pediatrics_Nelson. to diaphragmatic paralysis and respiratory distress. Elevation of the diaphragm caused by nerve injury must be differentiated from elevation caused by eventration resulting from congenital weakness or absence of diaphragm muscle. Klumpke paralysis is caused by injury to the seventh and eighth cervical nerves and the first thoracic nerve, resulting in a paralyzed hand and, if the sympathetic nerves are injured, an ipsilateral Horner syndrome (ptosis, miosis). Complete arm and hand paralysis is noted with the most severe form of damage to C5, C6, C7, C8, and T1. Treatment of brachial plexus injury is supportive and includes positioning to avoid contractures. Active and passive range of motion exercises also may be beneficial. If the deficit persists, nerve grafting may be beneficial.


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Pediatrics_Nelson. Facial nerve injury may be the result of compression of the seventh nerve between the facial bone and the mother’s pelvic bones or the physician’s forceps. This peripheral nerve injury is characterized by an asymmetric crying face whose normal side, including the forehead, moves in a regular manner. The affected side is flaccid, the eye does not close, the nasolabial fold is absent, and the side of the mouth droops at rest. If there is a central injury to the facial nerve, only the lower two thirds of the face (not the forehead) are involved. Complete agenesis of the facial nucleus results in a central facial paralysis; when this is bilateral, as in Möbius syndrome, the face appears expressionless.


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Pediatrics_Nelson. Skull fractures are rare, are usually linear, and require no treatment other than observation for very rare, delayed (1 to 3 months) complications (e.g., leptomeningeal cyst). Depressed skull fractures are unusual, but may be seen with complicated forceps delivery and may need surgical elevation. Fractures of the clavicle usually are unilateral and are noted in macrosomic infants after shoulder dystocia. Often a snap is heard after a difficult delivery, and the infant exhibits an asymmetrical Moro response and decreased movement of the affected side. The prognosis is excellent; many infants require no treatment or a simple figure of eight bandage to immobilize the bone. Extremity fractures are less common than fractures of the clavicle and involve the humerus more often than the femur. Treatment involves immobilization and a triangular splint bandage for the humerus and traction suspension of the legs for femoral fractures. The prognosis is excellent.


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Pediatrics_Nelson. Fractures of the facial bones are rare, but dislocation of the cartilaginous part of the nasal septum out of the vomeral groove and columella is common. Clinical manifestations include feeding difficulty, respiratory distress, asymmetrical nares, and a flattened, laterally displaced nose. Treatment reduces the dislocation by elevating the cartilage back into the vomeral groove.


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Pediatrics_Nelson. Visceral trauma to the liver, spleen, or adrenal gland occurs in macrosomic infants and in extremely premature infants, with or without breech or vaginal delivery. Rupture of the liver with subcapsular hematoma formation may lead to anemia, hypovolemia, shock, hemoperitoneum, and disseminated intravascular coagulation. Infants with anemia and shock who are suspected to have an intraventricular hemorrhage but with a normal head ultrasound examination should be evaluated for hepatic or splenic rupture. Adrenal hemorrhage may be asymptomatic, detected only by finding calcified adrenal glands in normal infants. Infants with severe adrenal hemorrhage may exhibit a flank mass, jaundice, and hematuria, with or without shock.


Pediatrics_Nelson

Pediatrics_Nelson. After birth, a newborn remains covered by amniotic fluid and situated in a cold environment (20° C to 25° C). An infant’s skin temperature may decrease 0.3° C/min, and the core temperature may decrease 0.1º C/min in the delivery room. In the absence of an external heat source, the infant must increase metabolism substantially to maintain body temperature.


Pediatrics_Nelson

Pediatrics_Nelson. Heat loss occurs through four basic mechanisms. In the cold delivery room, the wet infant loses heat predominantly by evaporation (cutaneous and respiratory loss when wet or in low humidity), radiation (loss to nearby cold, solid surfaces), and convection (loss to air current). When the infant is dry, radiation, convection, and conduction (loss to object in direct contact with infant) are important causes of heat loss. After birth, all high-risk infants should be dried immediately to eliminate evaporative heat losses. A radiant or convective heat source should be provided for these high-risk infants. Normal term infants should be dried and wrapped in a blanket.


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Pediatrics_Nelson. The ideal environmental temperature is the neutral thermal environment, the ambient temperature that results in the lowest rate of heat being produced by the infant and maintains normal body temperature. The neutral thermal environmental temperature decreases with increasing gestational and postnatal age. Ambient temperatures less than the neutral thermal environment result in increasing rates of oxygen consumption for heat production, which is designed to maintain normal body temperature. If the ambient temperature decreases further or if oxygen consumption cannot increase sufficiently (due to hypoxia, hypoglycemia, or drugs), the core body temperature decreases.


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Pediatrics_Nelson. Heat production by a newborn is created predominantly by nonshivering thermogenesis in specialized areas of tissue containing brown adipose tissue. Brown fat is highly vascular, contains many mitochondria per cell, and is situated around large blood vessels, resulting in rapid heat transfer to the circulation. The vessels of the neck, thorax, and interscapular region are common locations of brown fat. These tissues also are innervated by the sympathetic nervous system, which serves as a primary stimulus for heat production by brown adipose cells. Shivering does not occur in newborns.


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Pediatrics_Nelson. Severe cold injury in an infant is manifested by acidosis, hypoxia, hypoglycemia, apnea, bradycardia, pulmonary hemorrhage, and a pink skin color. The color is caused by trapping of oxygenated hemoglobin in the cutaneous capillaries. Many of these infants appear dead, but most respond to treatment and recover. Milder degrees of cold injury in the delivery room may contribute to metabolic acidosis and hypoxia after birth. Conversely, hypoxia delays heat generation in cold-stressed infants. Treatment of severe hypothermia should involve resuscitation and rapid warming of core (e.g., lung and stomach) and external surfaces. Fluid resuscitation also is needed to treat hypovolemia seen in many of these infants. Reduced core temperature (32° C to 35° C) in the immediate newborn period often requires only external warming with a radiant warmer, incubator, or both.


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Pediatrics_Nelson. Exposure to ambient temperatures above the neutral thermal environment results in heat stress and an elevated core temperature. Sweating is uncommon in newborns and may be noted only on the forehead. In response to moderate heat stress, infants may increase their respiratory rate to dissipate heat. Excessive environmental temperatures may result in heatstroke or in hemorrhagic shock encephalopathy syndrome. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com Hypocalcemia is common in sick and premature newborns. Calcium levels are higher in cord blood than in maternal blood because of active placental transfer of calcium to the fetus. Fetal calcium accretion in the third trimester approaches 150 mg/kg/24 hr; fetal bone mineral content doubles between 30 and 40 weeks of gestation. All infants show a slight decline of serum calcium levels after birth, reaching a trough level at 24 to 48 hours, the point at which hypocalcemia usually occurs. Total serum calcium levels of less than 7 mg/dL and ionized calcium levels of less than 3 to 3.5 mg/dL are considered hypocalcemia.


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Pediatrics_Nelson. The etiology of hypocalcemia varies with the time of onset and the associated illnesses of the child. Early neonatal hypocalcemia occurs in the first 3 days of life and is often asymptomatic. Transient hypoparathyroidism and a reduced parathyroid response to the usual postnatal decline of serum calcium levels may be responsible for hypocalcemia in premature infants and infants of diabetic mothers. Congenital absences of the parathyroid gland with DiGeorge syndrome is a cause of hypocalcemia. Hypomagnesemia (<1.5 mg/dL) may be seen simultaneously with hypocalcemia, especially in infants of diabetic mothers. Treatment with calcium alone does not relieve symptoms or increase serum calcium levels until hypomagnesemia is also treated. Sodium bicarbonate therapy, phosphate release from cell necrosis, transient hypoparathyroidism, and hypercalcitoninemia may be responsible for early neonatal hypocalcemia associated with asphyxia. Early-onset hypocalcemia associated with asphyxia often occurs


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Pediatrics_Nelson. transient hypoparathyroidism, and hypercalcitoninemia may be responsible for early neonatal hypocalcemia associated with asphyxia. Early-onset hypocalcemia associated with asphyxia often occurs with seizures as a result of hypoxic-ischemic encephalopathy


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Pediatrics_Nelson. Late neonatal hypocalcemia, or neonatal tetany, often is the result of ingestion of high phosphate–containing milk or the inability to excrete the usual phosphorus in commercial infant formula. Hyperphosphatemia (>8 mg/dL) usually occurs in infants with hypocalcemia after the first week of life. Vitamin D deficiency states and malabsorption also have been associated with late-onset hypocalcemia. The clinical manifestations of hypocalcemia and hypomagnesemia include apnea, muscle twitching, seizures, laryngospasm, Chvostek sign (facial muscle spasm when the side of the face over the seventh nerve is tapped), and Trousseau sign (carpopedal spasm induced by partial inflation of a blood pressure cuff). The latter two signs are rare in the immediate newborn period.


Pediatrics_Nelson

Pediatrics_Nelson. Neonatal hypocalcemia may be prevented in high-risk neonates by administration of IV or oral calcium supplementation at a rate of 25 to 75 mg/kg/24 hr. Early asymptomatic hypocalcemia of preterm infants and infants of diabetic mothers often resolves spontaneously. Symptomatic hypocalcemia should be treated with 2 to 4 mL/kg of 10% calcium gluconate given intravenously and slowly over 10 to 15 minutes, followed by a continuous infusion of 75 mg/kg/24 hr of elemental calcium. If hypomagnesemia is associated with hypocalcemia, 50% magnesium sulfate, 0.1 mL/kg, should be given by intramuscular injection and repeated every 8 to 12 hours. The treatment of late hypocalcemia includes immediatemanagement, as in early hypocalcemia, plus the initiation offeedings with low-phosphate formula. Subcutaneous infiltration of IV calcium salts can cause tissue necrosis; oral supplements are hypertonic and may irritate the intestinal mucosa.


Pediatrics_Nelson

Pediatrics_Nelson. Infants may become passively and physiologically addicted to medications or to drugs of abuse (heroin, methadone, barbiturates, tranquilizers, amphetamines) taken chronically by the mother during pregnancy; these infants subsequently may have signs and symptoms of drug withdrawal. Many of these pregnancies are at high risk for other complications related to IV drug abuse, such as hepatitis, acquired immunodeficiency syndrome (AIDS), and syphilis. In addition, the LBW rate and the long-term risk for sudden infant death syndrome are higher in the infants of these high-risk women.


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Pediatrics_Nelson. Neonatal withdrawal signs and symptoms usually begin at 1to 5 days of life with maternal heroin use and at 1 to 4 weekswith maternal methadone addiction. Clinical manifestations of withdrawal include sneezing, yawning, ravenous appetite,emesis, diarrhea, fever, diaphoresis, tachypnea, high-pitchedcry, tremors, jitteriness, poor sleep, poor feeding, and seizures. The illness tends to be more severe during methadonewithdrawal. The initial treatment includes swaddling in blankets in a quiet, dark room. When hyperactivity is constant,and irritability interferes with sleeping and feeding, or whendiarrhea or seizures are present, pharmacologic treatmentis indicated. Seizures usually are treated with phenobarbital. The other symptoms may be managed with replacementdoses of a narcotic (usually tincture of opium) to calm theinfant; weaning from narcotics may be prolonged over 1 to2 months.


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Pediatrics_Nelson. Cocaine use during pregnancy is associated with pretermlabor, abruptio placentae, neonatal irritability, and decreasedattentiveness. Infants may be small for gestational age and havesmall head circumferences. Usually no treatment is needed. Maternal diseases during pregnancy can affect the fetus directly or indirectly (Table 59-1). Autoantibody-mediated diseases can have direct consequences on the fetus and neonate because the antibodies are usually of the IgG type and can cross the placenta to the fetal circulation. Mild Large for gestational age, hypoglycemia Fetal hyperglycemia—produces hyperinsulinemia promoting growth Severe Growth retardation Vascular disease, placental insufficiency Drug addiction Intrauterine growth restriction, neonatal Direct drug effect, plus poor diet withdrawal Graves disease Transient thyrotoxicosis Placental immunoglobulin passage of thyrotropin receptor antibody


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Pediatrics_Nelson. Graves disease Transient thyrotoxicosis Placental immunoglobulin passage of thyrotropin receptor antibody Hyperparathyroidism Hypocalcemia Maternal calcium crosses to fetus and suppresses fetal parathyroid gland Hypertension Intrauterine growth restriction, intrauterine Placental insufficiency, fetal hypoxia fetal demise placenta after sensitization of mother Myasthenia gravis Transient neonatal myasthenia Immunoglobulin to acetylcholine receptor crosses the placenta Myotonic dystrophy Neonatal myotonic dystrophy Autosomal dominant with genetic anticipation Phenylketonuria Microcephaly, retardation, ventricular septal Elevated fetal phenylalanine levels defect Rh or other blood group Fetal anemia, hypoalbuminemia, hydrops, Antibody crosses placenta directed at fetal cells with sensitization neonatal jaundice antigen From Stoll BJ, Kliegman RM: The fetus and neonatal infant. In Behrman RE, Kliegman RM, Jenson HB, editors: Nelson textbook of pediatrics, ed 16, Philadelphia,


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Pediatrics_Nelson. From Stoll BJ, Kliegman RM: The fetus and neonatal infant. In Behrman RE, Kliegman RM, Jenson HB, editors: Nelson textbook of pediatrics, ed 16, Philadelphia, WB Saunders, 2000. Antiphospholipid syndrome is associated with thrombophilia and recurrent pregnancy loss. Antiphospholipid antibodies are found in 2% to 5% of the general healthy population, but they also may be associated with systemic lupus erythematosus and other rheumatic diseases. Obstetric complications arise from the prothrombotic effects of the antiphospholipid antibodies on placental function. Vasculopathy, infarction, and thrombosis have been identified in mothers with antiphospholipid syndrome. Antiphospholipid syndrome can include fetal growth impairment, placental insufficiency, maternal preeclampsia, and premature birth.


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Pediatrics_Nelson. Idiopathic thrombocytopenic purpura (ITP) is seen in approximately 1 to 2 per 1000 live births and is an immune process in which antibodies are directed against platelets. Platelet-associated IgG antibodies can cross the placenta and cause thrombocytopenia in the fetus and newborn. The severely thrombocytopenic fetus is at increased risk for intracranial hemorrhage. ITP during pregnancy requires close maternal and fetal management to reduce the risks of life-threatening maternal hemorrhage and trauma to the fetus at delivery. Postnatal management involves observation of the infant’s platelet count. For infants who have evidence of hemorrhage, sin-gle-donor irradiated platelets may be administered to control the bleeding. The infant may benefit from an infusion of intravenous immunoglobulin. Neonatal thrombocytopenia usually resolves within 4 to 6 weeks.


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Pediatrics_Nelson. Immune abnormalities in systemic lupus erythematosus (SLE)can lead to the production of anti-Ro (SS-A) and anti-La (SS-B)antibodies that can cross the placenta and injure fetal tissue.The most serious complication is damage to the cardiac conducting system, which results in congenital heart block. The heart block observed in association with maternal SLE tends to be complete (third degree), although less advanced blocks havebeen observed. The mortality rate is approximately 20%; mostsurviving infants require pacing. Neonatal lupus may occur and is characterized by skin lesions (sharply demarcated erythematous plaques or central atrophic macules with peripheralscaling with predilection for the eyes, face, and scalp), thrombocytopenia, autoimmune hemolysis, and hepatic involvement.


Pediatrics_Nelson

Pediatrics_Nelson. Birth asphyxia Birth injury (macrosomia, shoulder dystocia) Congenital anomalies (lumbosacral dysgenesis—caudal regression) Congenital heart disease (ventricular and atrial septal defects, transposition of the great arteries, truncus arteriosus, double-outlet right ventricle, coarctation of the aorta) Hyperbilirubinemia (unconjugated) Hypocalcemia Hypoglycemia Hypomagnesemia Neurologic disorders (neural tube defects, holoprosencephaly) Organomegaly Polycythemia (hyperviscosity) Renal disorders (double ureter, renal vein thrombosis, hydronephrosis, renal agenesis) Respiratory distress syndrome Small left colon syndrome Transient tachypnea of the newborn


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Pediatrics_Nelson. Respiratory distress syndrome Small left colon syndrome Transient tachypnea of the newborn Graves disease is associated with thyroid-stimulating antibodies. The prevalence of clinical hyperthyroidism in pregnancy has been reported to be about 0.1% to 0.4%; it is thesecond most common endocrine disorder during pregnancy(after diabetes). Neonatal hyperthyroidism is due to thetransplacental passage of thyroid-stimulating antibodies;hyperthyroidism can appear rapidly within the first 12 to 48hours. Symptoms may include intrauterine growth restriction, prematurity, goiter (may cause tracheal obstruction),exophthalmos, stare, craniosynostosis (usually coronal),flushing, heart failure, tachycardia, arrhythmias, hypertension, hypoglycemia, thrombocytopenia, and hepatosplenomegaly. Treatment includes propylthiouracil, iodine drops, and propranolol. Autoimmune induced neonatal hyperthyroidism usually resolves in 2 to 4 months.


Pediatrics_Nelson

Pediatrics_Nelson. Diabetes mellitus that develops during pregnancy (gestational diabetes is noted in about 5% of women) or diabetes that is present before pregnancy adversely influences fetal and neonatal well-being. The effect of diabetes on the fetus depends, in part, on the severity of the diabetic state: age of onset of diabetes, duration of treatment with insulin, and presence of vascular disease. Poorly controlled maternal diabetes leads to maternal and fetal hyperglycemia that stimulates the fetal pancreas, resulting in hyperplasia of the islets of Langerhans. Fetal *Trimethoprim, triamterene, phenytoin, primidone, phenobarbital, carbamazepine.


Pediatrics_Nelson

Pediatrics_Nelson. hyperinsulinemia results in increased fat and protein synthesis, producing a fetus that is large for gestational age. After birth, hyperinsulinemia persists, resulting in fasting neonatal hypoglycemia. Strictly controlling maternal diabetes during pregnancy and preventing hyperglycemia during labor and delivery prevent macrosomic fetal growth and neonatal hypoglycemia. Additional problems of the diabetic mother and her fetus and newborn are summarized in Table 59-2.


Pediatrics_Nelson

Pediatrics_Nelson. Other maternal illnesses, such as severe pulmonary disease(cystic fibrosis), cyanotic heart disease, and sickle cell anemia,may reduce oxygen availability to the fetus. Severe hypertensive or diabetic vasculopathy can result in uteroplacentalinsufficiency. The fetus and the newborn may also be adverselyaffected by the medications used to treat maternal illnesses.These effects may appear as teratogenesis (Table 59-3) or as anadverse metabolic, neurologic, or cardiopulmonary adaptationto extrauterine life (Table 59-4). Acquired infectious diseasesof the mother also may affect the fetus or newborn adversely. Table 59-4 Agents Acting on Pregnant Women That May Adversely Affect the Newborn Infant AGENT POTENTIAL CONDITION(S) Acebutolol IUGR, hypotension, bradycardia Acetazolamide Metabolic acidosis Amiodarone Bradycardia, hypothyroidism Aspirin Neonatal bleeding, prolonged gestation Atenolol IUGR, hypoglycemia Bromides Rash, CNS depression, IUGR


Pediatrics_Nelson

Pediatrics_Nelson. Amiodarone Bradycardia, hypothyroidism Aspirin Neonatal bleeding, prolonged gestation Atenolol IUGR, hypoglycemia Bromides Rash, CNS depression, IUGR Captopril, enalapril Transient anuric renal failure, oligohydramnios Caudal-paracervical anesthesia with mepivacaine (accidental Bradypnea, apnea, bradycardia, convulsions introduction of anesthetic into scalp of infant) Cholinergic agents (edrophonium, pyridostigmine) Transient muscle weakness CNS depressants (narcotics, barbiturates, benzodiazepines) during CNS depression, hypotonia labor Fluoxetine Possible transient neonatal withdrawal, hypertonicity, minor anomalies Ibuprofen Oligohydramnios, PPHN Indomethacin Oliguria, oligohydramnios, intestinal perforation, PPHN Intravenous fluids during labor (e.g., salt-free solutions) Electrolyte disturbances, hyponatremia, hypoglycemia Magnesium sulfate Respiratory depression, meconium plug, hypotonia Methimazole Goiter, hypothyroidism


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Pediatrics_Nelson. Magnesium sulfate Respiratory depression, meconium plug, hypotonia Methimazole Goiter, hypothyroidism Morphine and its derivatives (addiction) Withdrawal symptoms (poor feeding, vomiting, diarrhea, restlessness, yawning and stretching, dyspnea and cyanosis, fever and sweating, pallor, tremors, convulsions) Oxytocin Hyperbilirubinemia, hyponatremia Phenobarbital Bleeding diathesis (vitamin K deficiency), possible long-term reduction in IQ, sedation Propranolol Hypoglycemia, bradycardia, apnea Propylthiouracil Goiter, hypothyroidism Reserpine Drowsiness, nasal congestion, poor temperature stability Sulfonamides Interfere with protein binding of bilirubin; kernicterus at low levels of serum bilirubin, hemolysis with G6PD deficiency Stoll BJ, Kliegman RM: The fetus and neonatal infant. In Behrman RE, Kliegman RM, Jenson HB, editors: Nelson textbook of pediatrics, ed 16, Philadelphia, WB Saunders, 2000.


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Pediatrics_Nelson. Stoll BJ, Kliegman RM: The fetus and neonatal infant. In Behrman RE, Kliegman RM, Jenson HB, editors: Nelson textbook of pediatrics, ed 16, Philadelphia, WB Saunders, 2000. CNS, Central nervous system; G6PD, glucose-6-phosphate dehydrogenase; IUGR, intrauterine growth restriction; PPHN, persistent pulmonary hypertension of the newborn. The principal determinants of fetal disease include the fetal genotype and the in utero environment. Variation in environmental factors rather than the fetal genetics plays a more significant role in determining overall fetal well-being, although a genetically abnormal fetus may not thrive as well or survive. The ability to assess a fetus genetically, biochemically, and physically is greatly enhanced through the development of amniocentesis, fetoscopy, chorionic villus sampling, fetal blood sampling, genetic testing of circulating fetal DNA in the mother’s blood, and real-time ultrasonography.


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Pediatrics_Nelson. Fetuses subjected to abnormal maternal, placental, or fetal conditions that restrain growth are a high-risk group and traditionally classified as having intrauterine growth restriction (IUGR).The terms IUGR and SGA (small for gestational age) are notsynonymous. IUGR represents a deviation from expectedgrowth patterns. The decreased fetal growth associated with IUGR is an adaptation to unfavorable intrauterine conditions that result in permanent alterations in metabolism, growth, anddevelopment. IUGR most frequently occurs with a variety ofmaternal conditions that are associated with preterm delivery.SGA describes an infant whose birth weight is statistically lessthan the 10th percentile or two standard deviations below themean birth weight for gestational age. The cause of SGA may bepathologic, as in an infant with IUGR, or nonpathologic, as in an infant who is small but otherwise healthy (Table 60-1).


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Pediatrics_Nelson. Only about 50% of IUGR infants are identified before delivery.Measurement and recording of maternal fundal height in conjunction with serial ultrasound assessment of the fetus (growthrate, amniotic fluid volume, malformations, anomalies, and Doppler velocimetry of uterine, placental, and fetal blood flow) can aid detection. When suspected and identified, IUGR and SGA fetuses must be monitored for fetal well-being, and appropriate maternal care needs to be instituted (see Chapter 58).


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Pediatrics_Nelson. At birth, infants who are mildly to moderately SGA appear smaller than normal with decreased subcutaneous fat. More severely affected infants may present with a wasted appearancewith asymmetrical findings, including larger heads for the size of the body (central nervous system sparing), widened anterior fontanelles, small abdomen, thin arms and legs, decreased subcutaneous fat, dry and redundant skin, decreased muscle mass, and thin (often meconium-stained) umbilical cord. Gestational age is often difficult to assess when based on physical appearance and perceived advanced neurologic maturity. Physical examination should detail the presence of dysmorphic features, abnormal extremities, or gross anomalies that might suggest underlying congenital malformations, chromosomal defects, or exposure to teratogens. Hepatosplenomegaly, jaundice, and skin rashes in addition to ocular disorders,


Pediatrics_Nelson

Pediatrics_Nelson. Age (young and advanced) Cigarette smoking Genetics (short stature, weight) Illnesses during pregnancy (preeclampsia, severe diabetes, chronic hypertension, connective tissue disease) Infections (intrauterine) Lack of good prenatal care Oligohydramnios Poor nutrition Race (African American) Chromosomal abnormality and nonchromosomal syndromes Congenital infections Inborn errors of metabolism Multiple gestations Insulin resistance or reduced insulin or insulin-like growth factor-1


Pediatrics_Nelson

Pediatrics_Nelson. Chromosomal abnormality and nonchromosomal syndromes Congenital infections Inborn errors of metabolism Multiple gestations Insulin resistance or reduced insulin or insulin-like growth factor-1 Antimetabolites (methotrexate) Heavy metals (mercury, lead) Hydantoin Narcotics (morphine, methadone) Steroids (prednisone) Substance and illicit drug use (alcohol, cocaine) Warfarin such as chorioretinitis, cataracts, glaucoma, and cloudy cornea, suggest the presence of a congenital infection or inborn error of metabolism. Infants with severe IUGR or SGA, particularly in conjunction with fetal distress, may have problems at birth that include respiratory acidosis, metabolic acidosis, asphyxia, hypoxemia, hypotension, hypoglycemia, polycythemia, meconium aspiration syndrome, and persistent pulmonary hypertension of the newborn.


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Pediatrics_Nelson. Management of IUGR and SGA infants is usually symptomatic and supportive. The diagnostic evaluation at birth should be directed at identifying the cause of the IUGR and SGA, if possible. The consequences of IUGR and SGA depend on the etiology, severity, and duration of growth retardation. The mortality rates of infants who are severely affected are 5 to 20 times those of infants who are appropriate for gestational age. Postnatal growth and development depend in part on the etiology, the postnatal nutritional intake, and the social environment. Infants who have IUGR and SGA secondary to congenital infection, chromosomal abnormalities, or constitutional syndromes remain small throughout life. Infants who have growth inhibited late in gestation because of uterine constraints, placental insufficiency, or poor nutrition have catch-up growth and, under optimal environmental conditions, approach their inherited growth and development potential. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com Hydrops fetalis is caused by immune and nonimmune conditions. Hydrops fetalis is a fetal clinical condition of excessivefluid accumulation in the skin and one or more other bodycompartments, including the pleural space, peritoneal cavity,pericardial sac, or placenta with resultant high morbidity andmortality. Hydrops initially was described in association withRhesus blood group isoimmunization. The use of Rho (D)immune globulin has reduced the incidence of isoimmune fetalhydrops. Concurrently the incidence of nonimmune hydropshas increased as a cause of this severe clinical condition.


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Pediatrics_Nelson. Fetal hydrops results from an imbalance of interstitial fluidaccumulation and decreased removal of fluid by the capillariesand lymphatic system. Fluid accumulation can be secondary tocongestive heart failure, obstructed lymphatic flow, or decreasedplasma oncotic pressure (hypoproteinemic states). Edema formation is the final common pathway for many disease processesthat affect the fetus, including fetal cardiac, genetic, hematologic, metabolic, infection, or malformation syndromes.


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Pediatrics_Nelson. The diagnostic workup of the hydropic fetus should focus on discovering the underlying cause. Maternal findings may include hypertension, anemia, multiple gestation, thickened placenta, and polyhydramnios, whereas fetal findings may include tachycardia, ascites, scalp and body wall edema, and pleural and pericardial effusion. Invasive fetal testing may be indicated. Amniocentesis provides amniotic fluid samples for karyotype, culture, alpha-fetoprotein, and metabolic and enzyme analysis. Percutaneous umbilical cord blood sampling can provide fetal blood for chromosomal analysis and hematologic and metabolic studies and provide a source for intervention (fetal transfusion for profound anemia).


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Pediatrics_Nelson. Management depends on the underlying cause and the gestational age of the fetus. Resuscitative efforts at delivery are often required. It is often necessary to remove ascitic fluid from the abdomen or pleural fluid to improve ventilation. Profound anemia necessitates immediate transfusion with packed red blood cells. The overall mortality for infants with nonimmune hydrops is approximately 50%. If the diagnosis is made before 24 weeks of gestation with subsequent premature delivery, the survival rate is approximately 4% to 6%. Available @ StudentConsult.com


Pediatrics_Nelson

Pediatrics_Nelson. Respiratory distress that becomes manifested by tachypnea, intercostal retractions, reduced air exchange, cyanosis, expiratory grunting, and nasal flaring is a nonspecific response to serious illness. The differential diagnosis of respiratory distress includes pulmonary, cardiac, hematologic, infectious, anatomic, and metabolic disorders that may involve the lungs directly or indirectly. Surfactant deficiency causes respiratory distress syndrome (RDS), resulting in cyanosis and tachypnea; infection produces pneumonia, shown by interstitial or lobar infiltrates; meconium aspiration results in a chemical pneumonitis with hypoxia and pulmonary hypertension; hydrops fetalis causes anemia and hypoalbuminemia with high-output heart failure and pulmonary edema; and congenital or acquired pulmonary hypoplasia causes pulmonary hypertension and pulmonary insufficiency. It also is clinically useful to differentiate the common causes of respiratory distress according to gestational age (Table


Pediatrics_Nelson

Pediatrics_Nelson. hypoplasia causes pulmonary hypertension and pulmonary insufficiency. It also is clinically useful to differentiate the common causes of respiratory distress according to gestational age (Table 61-1).


Pediatrics_Nelson

Pediatrics_Nelson. In addition to the specific therapy for the individual disorder, supportive care and evaluation of the infant with respiratory distress can be applied to all the problems mentioned earlier (Table 61-2). Blood gas monitoring and interpretation are key components of general respiratory care.


Pediatrics_Nelson

Pediatrics_Nelson. Treatment of hypoxemia requires knowledge of normal values. In term infants, the arterial Pao2 level is 55 to 60 mm Hg at 30 minutes of life, 75 mm Hg at 4 hours, and 90 mm Hg at 24 hours. Preterm infants have lower values. Paco2 levels should be 35 to 40 mm Hg, and the pH should be 7.35 to 7.40. It is imperative that arterial blood gas analysis be performed in all infants with significant respiratory distress, whether or not cyanosis is perceived. Cyanosis becomes evident when there is 5 g of unsaturated hemoglobin; anemia may interfere with the perception of cyanosis. Jaundice also may interfere with the appearance of cyanosis. Capillary blood gas determinations are useful in determining blood pH and the Paco2 level but may result in falsely low blood Pao2 readings. Serial blood gas levels may be monitored by an indwelling arterial catheter placed in a peripheral artery or through the umbilical artery. Another method for monitoring blood gas levels is to combine capillary blood gas


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Pediatrics_Nelson. may be monitored by an indwelling arterial catheter placed in a peripheral artery or through the umbilical artery. Another method for monitoring blood gas levels is to combine capillary blood gas techniques with noninvasive methods used


Pediatrics_Nelson

Pediatrics_Nelson. Primary pulmonary hypertension of the neonate* Meconium aspiration pneumonia* Polycythemia Amniotic fluid aspiration Bacterial sepsis (GBS)* Transient tachypnea* Spontaneous pneumothorax Congenital anomalies (e.g., congenital lobar emphysema, cystic adenomatoid malformation, diaphragmatic hernia) Congenital heart disease Pulmonary hypoplasia Viral infection (e.g., herpes simplex, CMV) Inborn metabolic errors CMV, Cytomegalovirus; GBS, group B streptococcus. *Common. Chest radiograph To determine reticular granular pattern of RDS; to determine presence of pneumothorax, cardiomegaly, life-threatening congenital anomalies Arterial blood gas To determine severity of respiratory compromise, hypoxemia, and hypercapnia and type of acidosis; severity determines treatment strategy Complete blood count Hemoglobin/hematocrit to determine anemia and polycythemia; white blood cell count to determine neutropenia/ sepsis; platelet count and smear to determine DIC


Pediatrics_Nelson

Pediatrics_Nelson. Complete blood count Hemoglobin/hematocrit to determine anemia and polycythemia; white blood cell count to determine neutropenia/ sepsis; platelet count and smear to determine DIC Blood glucose To determine presence of hypoglycemia, which may produce or occur simultaneously with respiratory distress; to determine stress hyperglycemia Echocardiogram, ECG In the presence of a murmur, cardiomegaly, or refractory hypoxia; to determine structural heart disease or PPHN DIC, Disseminated intravascular coagulation; ECG, electrocardiogram; PPHN, primary pulmonary hypertension of the newborn; RDS, respiratory distress syndrome. to monitor oxygen (pulse oximetry or transcutaneous oxygen diffusion).


Pediatrics_Nelson

Pediatrics_Nelson. Metabolic acidosis, defined as a reduced pH (<7.25) and bicarbonate concentration (<18 mEq/L) accompanied by a normal or low Pco2 level, may be caused by hypoxia or by insufficient tissue perfusion. The origin of the disorder may be pulmonary, cardiac, infectious, renal, hematologic, nutritional, metabolic, or iatrogenic. The initial approach to metabolic acidosis is to determine the cause and treat the pathophysiologic problem. This approach may include, as in the sequence of therapy for hypoxia, increasing the inspired oxygen concentration; applying continuous positive airway pressure nasally; or initiating mechanical ventilation using positive end-expiratory pressure. Patients with hypotension produced by hypovolemia require fluids and may need inotropic or vasoactive drug support. If metabolic acidosis persists despite specific therapy, sodium bicarbonate (1 mEq/kg/dose) may be given by slow intravenous infusion. Near-normal or low Pco2 levels should be documented before sodium


Pediatrics_Nelson

Pediatrics_Nelson. metabolic acidosis persists despite specific therapy, sodium bicarbonate (1 mEq/kg/dose) may be given by slow intravenous infusion. Near-normal or low Pco2 levels should be documented before sodium bicarbonate infusion. The buffering effect of sodium bicarbonate results in increased Pco2 levels, unless adequate ventilation is maintained.


Pediatrics_Nelson

Pediatrics_Nelson. Respiratory acidosis, defined as an elevated Pco2 level and reduced pH without a reduction in the bicarbonate concentration, may be caused by pulmonary insufficiency or central hypoventilation. Most disorders producing respiratory distress can lead to hypercapnia. Treatment involves assisted ventilation but not sodium bicarbonate. If central nervous system depression of respirations is caused by placental passage of narcotic analgesics, assisted ventilation is instituted first, then the central nervous system depression is reversed by naloxone. RDS occurs after the onset of breathing and is associated with an insufficiency of pulmonary surfactant.


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Pediatrics_Nelson. The lining of the alveolus consists of 90% type I cells and 10% type II cells. After 20 weeks of gestation, the type II cells contain vacuolated, osmophilic, lamellar inclusion bodies, which are packages of surface-active material (Fig. 61-1). This lipoprotein surfactant is 90% lipid and is composed predominantly of saturated phosphatidylcholine (lecithin), but also contains phosphatidylglycerol, other phospholipids, and neutral lipids. The surfactant proteins, SP-A, SP-B, SP-C, and SP-D, are packaged into the lamellar body and contribute to surface-active properties and recycling of surfactant. Surfactant prevents atelectasis by reducing surface tension at low lung volumes when it is concentrated at end expiration as the alveolar radius decreases; surfactant contributes to lung recoil by increasing surface tension at larger lung volumes when it is diluted during inspiration as the alveolar radius increases. Without surfactant, surface tension forces are not reduced, and atelectasis


Pediatrics_Nelson

Pediatrics_Nelson. increasing surface tension at larger lung volumes when it is diluted during inspiration as the alveolar radius increases. Without surfactant, surface tension forces are not reduced, and atelectasis develops during end expiration as the alveolus collapses.


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Pediatrics_Nelson. The timing of surfactant production in quantities sufficient to prevent atelectasis depends on an increase in fetal cortisol levels that begins between 32 and 34 weeks of gestation. By 34 to 36 weeks, sufficient surface-active material is produced by the type II cells in the lung, is secreted into the alveolar lumen, and is excreted into the amniotic fluid. The concentration of


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Pediatrics_Nelson. Figure 61-1 Proposed pathway of synthesis, transport, secretion, and reuptake of surfactant in the type II alveolar cell. Phospholipids are synthesized in the smooth endoplasmic reticulum (ER). The glucose/ glycerol precursor may be derived from lung glycogen or circulating glucose. Phospholipids and surfactant proteins are packaged in the Golgi apparatus (GZ), emerge as small lamellar bodies (SLB), coalesce to mature lamellar bodies (MLB), migrate to the apical membrane, and are released by exocytosis into the liquid hypophase below the air-liquid interface. The tightly coiled lamellar body unravels to form the lattice (tubular) myelin figure (LMF), the immediate precursor to the phospholipid monolayer at the alveolar surface. Reuptake by endocytosis forms multivesicular bodies (MVB) that recycle surfactant. The enzymes, receptors, transporters, and surfactant proteins are controlled by regulatory processes at the transcriptional level in the nucleus (N). Corticosteroid and thyroid


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Pediatrics_Nelson. recycle surfactant. The enzymes, receptors, transporters, and surfactant proteins are controlled by regulatory processes at the transcriptional level in the nucleus (N). Corticosteroid and thyroid hormones are regulatory ligands that may accelerate surfactant synthesis. (From Hansen T, Corbet A: Lung development and function. In Taeusch HW, Ballard R, Avery ME, editors: Diseases of the Newborn, ed 6, Philadelphia, 1991, Saunders, p 465.) lecithin in amniotic fluid indicates fetal pulmonary maturity. Because the amount of lecithin is difficult to quantify, the ratio of lecithin (which increases with maturity) to sphingomyelin (which remains constant during gestation) (L/S ratio) is determined. An L/S ratio of 2:1 usually indicates pulmonary maturity. The presence of minor phospholipids, such as phosphatidylglycerol, also is indicative of fetal lung maturity and may be useful in situations in which the L/S ratio is borderline or possibly affected by maternal diabetes, which reduces lung


Pediatrics_Nelson

Pediatrics_Nelson. as phosphatidylglycerol, also is indicative of fetal lung maturity and may be useful in situations in which the L/S ratio is borderline or possibly affected by maternal diabetes, which reduces lung maturity. The absence of phosphatidylglycerol suggests that surfactant might not be mature.


Pediatrics_Nelson

Pediatrics_Nelson. A deficiency of pulmonary surfactant (most often due to prematurity) results in atelectasis, decreased functional residual capacity, arterial hypoxemia, and respiratory distress. Surfactant synthesis may also be reduced as a result of hypovolemia, hypothermia, acidosis, hypoxemia, and rare genetic disorders of surfactant synthesis. These factors also produce pulmonary artery vasospasm, which may contribute to RDS in larger premature infants who have developed sufficient pulmonary arteriole smooth muscle to produce vasoconstriction. Surfactant deficiency–induced atelectasis causes alveoli to be perfused but not ventilated, which results in a pulmonary shunt and hypoxemia. As atelectasis increases, the lungs become increasingly difficult to expand, and lung compliance decreases. Because the chest wall of the premature infant is very compliant, the infant attempts to overcome decreased lung compliance with increasing inspiratory pressures, resulting in retractions of the chest wall. The


Pediatrics_Nelson

Pediatrics_Nelson. chest wall of the premature infant is very compliant, the infant attempts to overcome decreased lung compliance with increasing inspiratory pressures, resulting in retractions of the chest wall. The sequence of decreased lung compliance and chest wall retractions leads to poor air exchange, an increased physiologic dead space, alveolar hypoventilation, and hypercapnia. A cycle of hypoxia, hypercapnia, and acidosis acts on type II cells to reduce surfactant synthesis and, in some infants, on the pulmonary arterioles to produce pulmonary hypertension.


Pediatrics_Nelson

Pediatrics_Nelson. Infants at greatest risk for RDS are premature and have an immature L/S ratio. The incidence of RDS increases with decreasing gestational age. RDS develops in 30% to 60% of infants between 28 and 32 weeks of gestation. Other risk factors include delivery of a previous preterm infant with RDS, maternal diabetes, hypothermia, fetal distress, asphyxia, male sex, white race, being the second-born of twins, and delivery by cesarean section without labor.


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Pediatrics_Nelson. RDS may develop immediately in the delivery room in extremely immature infants at 26 to 30 weeks of gestation. Some more mature infants (34 weeks’ gestation) may not show signs of RDS until 3 to 4 hours after birth, correlating with the initial release of stored surfactant at the onset of breathing accompanied by the ongoing inability to replace the surfactant owing to inadequate stores. Manifestations of RDS include cyanosis, tachypnea, nasal flaring, intercostal and sternal retractions, and grunting. Grunting is caused by closure of the glottis during expiration, the effect of which is to maintain lung volume (decreasing atelectasis) and gas exchange during exhalation. Atelectasis is well documented by radiographic examination of the chest, which shows a ground-glass haze in the lung surrounding air-filled bronchi (the air bronchogram) (Fig. 61-2). Severe RDS may show an airless lung field (whiteout) on a radiograph, even obliterating the distinction between the atelectatic lungs


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Pediatrics_Nelson. surrounding air-filled bronchi (the air bronchogram) (Fig. 61-2). Severe RDS may show an airless lung field (whiteout) on a radiograph, even obliterating the distinction between the atelectatic lungs and the heart.


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Pediatrics_Nelson. During the first 72 hours, infants with untreated RDS haveincreasing distress and hypoxemia. In infants with severeRDS, the development of edema, apnea, and respiratoryfailure necessitates assisted ventilation. Thereafter, uncomplicated cases show a spontaneous improvement that oftenis heralded by diuresis and a marked resolution of edema. Complications include the development of a pneumothorax,a patent ductus arteriosus (PDA), and bronchopulmonarydysplasia (BPD). The differential diagnosis of RDS includesdiseases associated with cyanosis and respiratory distress (seeTable 58-10). Strategies to prevent preterm birth include maternal cervical cerclage, bed rest, treatment of infections, and administration of tocolytic medications. In addition, prevention of neonatal cold stress, birth asphyxia, and hypovolemia reduces the risk of RDS. If premature delivery is unavoidable, the antenatal administration of corticosteroids (e.g., betamethasone) to the


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Pediatrics_Nelson. Figure 61-2 Respiratory distress syndrome. The infant is intubated, and the lungs show a dense reticulonodular pattern with air bronchograms (A). To evaluate rotation on the frontal chest, the lengths of the posterior ribs are compared from left to right (arrows). Because the infant is supine, the side of the longer ribs indicates to which side the thorax is rotated. In this case, the left ribs are longer, and this radiograph is a left posterior oblique view. Surfactant was administered, resulting in significant improvement in the density of the lung (B). The right lung is slightly better aerated than the left. Uneven distribution of clearing is common. (From Hilton S, Edwards D: Practical Pediatric Radiology, ed 2, Philadelphia, 1994, Saunders.) mother (and thus to the fetus) stimulates fetal lung production of surfactant; this approach requires multiple doses for at least 48 hours.


Pediatrics_Nelson

Pediatrics_Nelson. After birth, RDS may be prevented or its severity reduced by intratracheal administration of exogenous surfactant immediately after birth in the delivery room or within a few hours of birth. A mammalian-derived surfactant is currently preferred. Exogenous surfactant can be administered repeatedly during the course of RDS in patients receiving endotracheal intubation, mechanical ventilation, and oxygen therapy. Additional management includes the general supportive and ventilation care presented in Table 61-3. The Pao2 level should be maintained between 60 and 70 mm Hg (oxygen saturation 90%), and the pH should be maintained above 7.25. An increased concentration of warm and humidified inspired oxygen administered by a nasal cannula or an oxygen hood may be all that is needed for larger premature infants. If hypoxemia (Pao2 <50 mm Hg) is present, and the needed inspired oxygen concentration is 70% to 100%, nasal continuous positive airway pressure should be added at


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Pediatrics_Nelson. Central nervous IVH, drugs, seizures, hypoxic injury system Respiratory Pneumonia, obstructive airway lesions, atelectasis, extreme prematurity (<1000 g), laryngeal reflex, phrenic nerve paralysis, severe RDS, pneumothorax Infectious Sepsis, necrotizing enterocolitis, meningitis (bacterial, fungal, viral) Gastrointestinal Oral feeding, bowel movement, gastroesophageal reflux, esophagitis, intestinal perforation Metabolic ↓ Glucose, ↓ calcium, ↓ PO2, ↓↑ sodium, ↑ ammonia, ↑ organic acids, ↑ ambient temperature, hypothermia Cardiovascular Hypotension, hypertension, heart failure, anemia, hypovolemia, change in vagal tone Idiopathic Immaturity of respiratory center, sleep state, upper airway collapse IVH, Intraventricular hemorrhage; RDS, respiratory distress syndrome.


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Pediatrics_Nelson. Idiopathic Immaturity of respiratory center, sleep state, upper airway collapse IVH, Intraventricular hemorrhage; RDS, respiratory distress syndrome. a distending pressure of 8 to 10 cm H2O. If respiratory failure ensues (Pco2 >60 mm Hg, pH <7.20, and Pao2 <50 mm Hg with 100% oxygen), assisted ventilation using a ventilator is indicated. Conventional rate (25 to 60 breaths/min), high-frequency jet (150 to 600 breaths/min), and oscillatory (900 to 3000 breaths/min) ventilators all have been successful in managing respiratory failure caused by severe RDS. Suggested starting settings on a conventional ventilator are fraction of inspired oxygen, 0.60 to 1.0; peak inspiratory pressure, 20 to 25 cm H2O; positive end-expiratory pressure, 5 cm H2O; and respiratory rate, 30 to 50 breaths/min.


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Pediatrics_Nelson. In response to persistent hypercapnia, alveolar ventilation (tidal volume − dead space × rate) must be increased. Ventilation can be increased by an increase in the ventilator’s rate or an increase in the tidal volume (the gradient between peak inspiratory pressure and positive end-expiratory pressure using a pressure-controlled ventilator). In response to hypoxia, the inspired oxygen content may be increased. Alternatively, the degree of oxygenation depends on the mean airway pressure. Mean airway pressure is directly related to positive end-expiratory pressure, flow, and inspiratory time. Increased mean airway pressure may improve oxygenation by improving lung volume, enhancing ventilation-perfusion matching. Because of the difficulty in distinguishing sepsis and pneumonia from RDS, broad-spectrum parenteral antibiotics (ampicillin and gentamicin) are administered for 48 to 72 hours, pending the recovery of an organism from a previously obtained blood culture.


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Pediatrics_Nelson. Available @ StudentConsult.com PDA is a common complication that occurs in many low birth weight infants who have RDS. The incidence of PDA is inversely related to the maturity of the infant. In term newborns, the ductus closes within 24 to 48 hours after birth. However, in preterm newborns, the ductus frequently fails to close, requiring medical or surgical closure. The ductus arteriosus in a preterm infant is less responsive to vasoconstrictive stimuli, which, when complicated with hypoxemia during RDS, may lead to a persistent PDA that creates a shunt between the pulmonary and systemic circulations.


Pediatrics_Nelson

Pediatrics_Nelson. During the acute phase of RDS, hypoxia, hypercapnia, and acidosis lead to pulmonary arterial vasoconstriction. The pulmonary and systemic pressures may be equal, and flow through the ductus may be small or bidirectional. When RDS improves and pulmonary vascular resistance declines, flow through the ductus arteriosus increases in a left-to-right direction. Significant systemic-to-pulmonary shunting may lead to heart failure and pulmonary edema. Excessive intravenous fluid administration may increase the incidence of symptomatic PDA. The infant’s respiratory status deteriorates because of increased lung fluid, hypercapnia, and hypoxemia.


Pediatrics_Nelson

Pediatrics_Nelson. Clinical manifestations of a PDA usually become apparent on day 2 to 4 of life. Because the left-to-right shunt directs flow to a low-pressure circulation from one of high pressure, the pulse pressure widens; a previously inactive precordium shows an extremely active precordial impulse, and peripheral pulses become easily palpable and bounding. The murmur of a PDA may be continuous in systole and diastole, but usually only the systolic component is auscultated. Heart failure and pulmonary edema result in rales and hepatomegaly. A chest radiograph shows cardiomegaly and pulmonary edema; a two-dimensional echocardiogram shows ductal patency; and Doppler studies show markedly increased left-to-right flow through the ductus.


Pediatrics_Nelson

Pediatrics_Nelson. Treatment of a PDA during RDS involves initial fluid restriction and diuretic administration. If there is no improvement after 24 to 48 hours, a prostaglandin synthetase inhibitor, indomethacin or ibuprofen, is administered. Contraindications to using indomethacin include thrombocytopenia (platelets <50,000/mm3), bleeding, serum creatinine measuring more than 1.8 mg/dL, and oliguria. Because 20% to 30% of infants do not respond initially to indomethacin and because the PDA reopens in 10% to 20% of infants, a repeat course of indomethacin or surgical ligation is required in some patients.


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Pediatrics_Nelson. Assisted ventilation with high peak inspiratory pressures and positive end-expiratory pressures may cause overdistention of alveoli in localized areas of the lung. Rupture of the alveolar epithelial lining may produce pulmonary interstitial emphysema as gas dissects along the interstitial space and the peribronchial lymphatics. Extravasation of gas into the parenchyma reduces lung compliance and worsens respiratory failure. Gas dissection into the mediastinal space produces a pneumomediastinum, occasionally dissecting into the subcutaneous tissues around the neck, causing subcutaneous emphysema. Alveolar rupture adjacent to the pleural space produces a pneumothorax (Fig. 61-3). If the gas is under tension, the pneumothorax shifts the mediastinum to the opposite side of the chest, producing hypotension, hypoxia, and hypercapnia.


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Pediatrics_Nelson. Figure 61-3 Pneumothorax. Right-sided hyperlucent pleural air is obvious. The findings of linear interstitial air and the resultant non-compliant but collapsed lung are noted. (From Heller RM, Kirchner SG: Advanced exercises in diagnostic radiology: the newborn, Philadel-phia, WB Saunders, 1979.) The diagnosis of a pneumothorax may be based on unequal transillumination of the chest and may be confirmed by chest radiograph. Treatment of a symptomatic pneumothorax requires insertion of a pleural chest tube connected to negative pressure or to an underwater drain. Prophylactic or therapeutic use of exogenous surfactant has reduced the incidence of pulmonary air leaks. Pneumothorax also is observed after vigorous resuscitation, meconium aspiration pneumonia, pulmonary hypoplasia, and diaphragmatic hernia. Spontaneous pneumothorax is seen in fewer than 1% of deliveries and may be associated with renal malformations.


Pediatrics_Nelson

Pediatrics_Nelson. BPD is a clinical diagnosis defined by oxygen dependence at36 weeks’ postconceptual age and accompanied by characteristic clinical and radiographic findings that correspond to anatomic abnormalities. Oxygen concentrations greater than 40%are toxic to the neonatal lung. Oxygen-mediated lung injuryresults from the generation of superoxides, hydrogen peroxide, and oxygen free radicals, which disrupt membrane lipids.Assisted ventilation with high peak pressures produces barotrauma, compounding the damaging effects of highly inspiredoxygen levels. In most patients, BPD develops after ventilationfor RDS that may have been complicated by PDA or pulmonary interstitial emphysema. Inflammation from prolongedassisted ventilation and repeated systemic and pulmonaryinfections may play a major role. Failure of RDS to improveafter 2 weeks, the need for prolonged mechanical ventilation,and oxygen therapy required at 36 weeks’ postconceptual ageare characteristic of patients with RDS in whom BPD


Pediatrics_Nelson

Pediatrics_Nelson. Failure of RDS to improveafter 2 weeks, the need for prolonged mechanical ventilation,and oxygen therapy required at 36 weeks’ postconceptual ageare characteristic of patients with RDS in whom BPD develops.BPD also may develop in infants weighing less than 1000 g whorequire mechanical ventilation for poor respiratory drive in theabsence of RDS. Fifty percent of infants of 24 to 26 weeks’ gestational age require oxygen at 36 weeks’ corrected age.


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Pediatrics_Nelson. The radiographic appearance of BPD is characterized initially by lung opacification and subsequently by development of cysts accompanied by areas of overdistention and atelectasis, giving the lung a spongelike appearance. The histopathology of BPD reveals interstitial edema, atelectasis, mucosal metaplasia, interstitial fibrosis, necrotizing obliterative bronchiolitis, and overdistended alveoli. The clinical manifestations of BPD are oxygen dependence, hypercapnia with a compensatory metabolic alkalosis, pulmonary hypertension, poor growth, and development of right-sided heart failure. Increased airway resistance with reactive airway bronchoconstriction also is noted and is treated with bronchodilating agents. Severe chest retractions produce negative interstitial pressure that draws fluid into the interstitial space. Together with cor pulmonale, these chest retractions cause fluid retention, necessitating fluid restriction and the administration of diuretics.


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Pediatrics_Nelson. Patients with severe BPD may need treatment withmechanical ventilation for many months. To reduce the riskof subglottic stenosis, a tracheotomy may be indicated. To reduce oxygen toxicity and barotrauma, ventilator settingsare reduced to maintain blood gases with slightly lower Pao2 (50 mm Hg) and higher Paco2 (50 to 75 mm Hg) levels thanfor infants during the acute phase of RDS. Dexamethasonetherapy may reduce inflammation, improve pulmonaryfunction, and enhance weaning of patients from assistedventilation. However, dexamethasone may increase the riskof cerebral palsy or abnormal neuromotor developmentaloutcome. Older survivors of BPD have hyperinflation, reactive airways, and developmental delay. They are at risk for severe respiratory syncytial virus pneumonia and as infantsshould receive prophylaxis against respiratory syncytialvirus. Retinopathy of Prematurity (Retrolental Fibroplasia) Available @ StudentConsult.com


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Pediatrics_Nelson. Retinopathy of prematurity (ROP) is caused by the acute and chronic effects of oxygen toxicity on the developing blood vessels of the premature infant’s retina. The completely vascularized retina of the term infant is not susceptible to ROP. ROP is a leading cause of blindness in very low birth weight infants (<1500 g). Excessive arterial oxygen tensions produce vasoconstriction of immature retinal vasculature in the first stage of this disease. Vaso-obliteration follows if the duration and extent of hyperoxia are prolonged beyond the time when vasoconstriction is reversible. Hypercarbia and hypoxia may contribute to ROP. The subsequent proliferative stages are characterized by extraretinal fibrovascular proliferation, forming a ridge between the vascular and avascular portions of the retina, and by the development of neovascular tufts. In mild cases, vasoproliferation is noted at the periphery of the retina. Severe cases may have neovascularization involving the entire retina,


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Pediatrics_Nelson. retina, and by the development of neovascular tufts. In mild cases, vasoproliferation is noted at the periphery of the retina. Severe cases may have neovascularization involving the entire retina, retinal detachment resulting from traction on vessels as they leave the optic disc, fibrous proliferation behind the lens producing leukokoria, and synechiae displacing the lens forward, leading to glaucoma. Both eyes usually are involved, but severity may be asymmetrical.


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Pediatrics_Nelson. The incidence of ROP may be reduced by careful monitoring of arterial blood gas levels in all patients receiving oxygen. Although there is no absolutely safe Pao2 level, it is wise to keep the arterial oxygen level between 50 and 70 mm Hg in premature infants. Infants who weigh less than 1500 g or who are born before 28 weeks’ gestational age (some authors say 32 weeks) should be screened when they are 4 weeks of age or more than 34 weeks’ corrected gestational age, whichever comes first. Laser therapy or (less often) cryotherapy may be used for vitreous hemorrhage or for severe, progressive vasoproliferation. Surgery is indicated for retinal detachment. Less severe stages of ROP resolve spontaneously and without visual impairment in most patients.


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Pediatrics_Nelson. Transient tachypnea of the newborn is a self-limited condition characterized by tachypnea, mild retractions, hypoxia, and occasional grunting, usually without signs of severe respiratory distress. Cyanosis, when present, usually requires treatment with supplemental oxygen in the range of 30% to 40%. Transient tachypnea of the newborn usually is noted in larger premature infants and in term infants born by precipitous delivery or cesarean section without prior labor. Infants of diabetic mothers and infants with poor respiratory drive as a result of placental passage of analgesic drugs are at risk. Transient tachypnea of the newborn may be caused by retained lung fluid or slow resorption of lung fluid. Chest radiographs show prominent central vascular markings, fluid in the lung fissures, overaeration, and occasionally a small pleural effusion. Air bronchograms and a reticulogranular pattern are not seen; their presence suggests another pulmonary process, such as RDS or pneumonia.


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Pediatrics_Nelson. Meconium-stained amniotic fluid is seen in 15% of predominantly term and post-term deliveries. Although the passage of meconium into amniotic fluid is common in infants born in the breech presentation, meconium-stained fluid should be considered clinically as a sign of fetal distress in all infants. The presence of meconium in the amniotic fluid suggests in utero distress with asphyxia, hypoxia, and acidosis. Aspiration of amniotic fluid contaminated with particulate meconium may occur in utero in a distressed, gasping fetus; more often, meconium is aspirated into the lung immediately after delivery. Affected infants have abnormal chest radio-graphs, showing a high incidence of pneumonia and pneumothoraces.


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Pediatrics_Nelson. Meconium aspiration pneumonia is characterized bytachypnea, hypoxia, hypercapnia, and small airway obstruction causing a ball-valve effect, leading to air trapping, over-distention, and extra-alveolar air leaks. Complete small airway obstruction produces atelectasis. Within 24 to 48 hours, a chemical pneumonitis develops in addition to the mechanical effects of airway obstruction. Abnormal pulmonary function may be caused by the meconium, in part, through inactivation of surfactant. Primary pulmonary hypertension of the newborn (PPHN) frequently accompanies meconium aspiration, with right-to-left shunting caused by increased pulmonary vascular resistance. The chest radiograph reveals patchy infiltrates, overdistention, flattening of the diaphragm, increased anteroposterior diameter, and a high incidence of pneumomediastinum and pneumothoraces. Comorbid diseases include those associated with in utero asphyxia that initiated the passage of meconium.


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Pediatrics_Nelson. Treatment of meconium aspiration includes general supportive care and assisted ventilation. Infants with a PPHN-like presentation should be treated for PPHN. If severe hypoxia does not subside with conventional or high-frequency ventilation, surfactant therapy, and inhaled nitric oxide, extracorporeal membrane oxygenation (ECMO) may be beneficial. Prevention of meconium aspiration syndrome involvescareful in utero monitoring to prevent asphyxia. When meconium-stained fluid is observed, the obstetrician should suction the infant’s oropharynx before delivering the rest ofthe infant’s body. If the infant is depressed with poor tone,minimal respiratory effort, and cyanosis, the infant’s oropharynx should be suctioned, the vocal cords visualized,and the area below the vocal cords suctioned to remove anymeconium from the trachea. Saline intrauterine amnioinfusion during labor may reduce the incidence of aspiration andpneumonia.


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Pediatrics_Nelson. PPHN occurs in post-term, term, or near-term infants. PPHN is characterized by severe hypoxemia, without evidence of parenchymal lung or structural heart disease. PPHN is often seen with asphyxia or meconium-stained fluid. The chest radiograph usually reveals normal lung fields rather than the expected infiltrates and hyperinflation that may accompany meconium aspiration. Additional problems that may lead to PPHN are congenital pneumonia, hyperviscosity-polycythemia, congenital diaphragmatic hernia, pulmonary hypoplasia, congenital cyanotic heart disease, hypoglycemia, and hypothermia. Total anomalous venous return associated with obstruction of blood flow may produce a clinical picture that involves severe hypoxia and that is initially indistinguishable from PPHN; however, a chest radiograph reveals severe pulmonary venous engorgement and a small heart. Echocardiography or cardiac catheterization confirms the diagnosis.


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Pediatrics_Nelson. Significant right-to-left shunting through a patent foramen ovale, through a PDA, and through intrapulmonary channels is characteristic of PPHN. The pulmonary vasculature often shows hypertrophied arterial wall smooth muscle, suggesting that the process of or predisposition to PPHN began in utero as a result of previous periods of fetal hypoxia. After birth, hypoxia, hypercapnia, and acidosis exacerbate pulmonary artery vasoconstriction, leading to further hypoxia and acidosis. Some infants with PPHN have extrapulmonary manifestations as a result of asphyxia. Myocardial injuries include heart failure, transient mitral insufficiency, and papillary muscle or myocardial infarction. Thrombocytopenia, right atrial thrombi, and pulmonary embolism also may be noted.


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Pediatrics_Nelson. The diagnosis is confirmed by echocardiographic examination, which shows elevated pulmonary artery pressures and sites of right-to-left shunting. Echocardiography also rules out structural congenital heart disease and transient myocardial dysfunction.


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Pediatrics_Nelson. Treatment involves general supportive care; correction of hypotension, anemia, and acidosis; and management of complications associated with asphyxia. If myocardial dysfunction is present, dopamine or dobutamine is needed. The most important therapy for PPHN is assisted ventilation. Reversible mild pulmonary hypertension may respond to conventional assisted ventilation. Patients with severe PPHN do not always respond to conventional therapy. Paralysis with a muscle relaxant may be needed to assist vigorous ventilation. Surfactant replacement seems to have no effect when PPHN is the primary diagnosis. If mechanical ventilation and supportive care are unsuccessful in improving oxygenation, inhaled nitric oxide, a selective pulmonary artery vasodilating agent, should be administered. If hypoxia persists, the patient may be a candidate for ECMO. Infants who require extremely high ventilator settings, marked by an alveolar-to-arterial oxygen gradient greater than 620 mm Hg, have a high


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Pediatrics_Nelson. persists, the patient may be a candidate for ECMO. Infants who require extremely high ventilator settings, marked by an alveolar-to-arterial oxygen gradient greater than 620 mm Hg, have a high mortality rate and benefit from ECMO if they do not respond to nitric oxide. In addition, the oxygenation index (OI) is used to assess the severity of hypoxemia and to guide the timing of interventions such as inhaled nitric oxide and ECMO. The OI is calculated using the equation OI = [(mean airway pressure × fraction of inspired oxygen)/Pao2] × 100. A high OI indicates severe hypoxemic respiratory failure.


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Pediatrics_Nelson. Available @ StudentConsult.com Although apnea typically is associated with immaturity of the respiratory control system, it also may be the presenting sign of other diseases or pathophysiologic states that affect preterm infants (see Table 61-3). A thorough consideration of possible causes is always warranted, especially with the onset or unexpected increase in the frequency of episodes of apnea (or bradycardia).


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Pediatrics_Nelson. Apnea is defined as the cessation of pulmonary airflow for a specific time interval, usually longer than 10 to 20 seconds. Bradycardia often accompanies prolonged apnea. Central apnea refers to a complete cessation of airflow and respiratory efforts with no chest wall movement. Obstructive apnearefers to the absence of noticeable airflow but with the continuation of chest wall movements. Mixed apnea, a combination of these two events, is the most frequent type. It may begin as a brief episode of obstruction followed by a central apnea. Alternatively, central apnea may produce upper airway closure (passive pharyngeal hypotonia), resulting in mixed apnea.


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Pediatrics_Nelson. A careful evaluation to determine the cause of apnea should be performed immediately in any infant with apnea. The incidence of apnea increases as gestational age decreases. Idiopathic apnea, a disease of premature infants, appears in the absence of any other identifiable disease states during the first week of life and usually resolves by 36 to 40 weeks of postconceptual age (gestational age at birth + postnatal age). The premature infant’s process of regulating respiration is especially vulnerable to apnea. Preterm infants respond paradoxically to hypoxia by developing apnea rather than by increasing respirations as in mature infants. Poor tone of the laryngeal muscles also may lead to collapse of the upper airway, causing obstruction. Isolated obstructive apnea also may occur as a result of flexion or extreme lateral positioning of the premature infant’s head, which obstructs the soft trachea.


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Pediatrics_Nelson. Treatment of apnea of prematurity involves administration of oxygen to hypoxic infants, transfusion of anemic infants, and physical cutaneous stimulation for infants with mild apnea. Methylxanthines (caffeine or theophylline) are the mainstay of pharmacologic treatment of apnea. Xanthine therapy increases minute ventilation, improves the carbon dioxide sensitivity, decreases hypoxic depression of breathing, enhances diaphragmatic activity, and decreases periodic breathing. Treatment usually is initiated with a loading dose followed by maintenance therapy. High-flow nasal cannula therapy and nasal continuous positive airway pressure of 4 to 6 cm H2O also are effective and relatively safe methods of treating obstructive or mixed apneas; they may work by stimulating the infant and splinting the upper airway. Continuous positive airway pressure also probably increases functional residual capacity, improving oxygenation.


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Pediatrics_Nelson. Embryonic hematopoiesis begins by the 20th day of gestationand is evidenced as blood islands in the yolk sac. In midgestation, erythropoiesis occurs in the liver and spleen; the bonemarrow becomes the predominant site in the last trimester.Hemoglobin concentration increases from 8 to 10 g/dL at12 weeks to 16.5 to 18 g/dL at 40 weeks. Fetal red blood cell(RBC) production is responsive to erythropoietin; the concentration of this hormone increases with fetal hypoxia and anemia.


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Pediatrics_Nelson. After birth, hemoglobin levels increase transiently at 6 to 12 hours, then decline to 11 to 12 g/dL at 3 to 6 months. A premature infant (<32 weeks’ gestational age) has a lower hemoglobin concentration and a more rapid postnatal decline of hemoglobin level, which achieves a nadir 1 to 2 months after birth. Fetal and neonatal RBCs have a shorter life span (70 to 90 days) and a higher mean corpuscular volume (110 to 120 fL) than adult cells. In the fetus, hemoglobin synthesis in the last two trimesters of pregnancy produces fetal hemoglobin (hemoglobin F), composed of two alpha chains and two gamma chains. Immediately before term, the infant begins to synthesize beta-hemoglobin chains; the term infant should have some adult hemoglobin (two alpha chains and two beta chains). Fetal hemoglobin represents 60% to 90% of hemoglobin at term birth. The levels decline to adult levels of less than 5% by 4 months of age.


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Pediatrics_Nelson. For a term infant, blood volume is 72 to 93 mL/kg, and for a preterm infant, blood volume is 90 to 100 mL/kg. The placenta and umbilical vessels contain approximately 20 to 30 mL/kg of additional blood that can increase neonatal blood volume and hemoglobin levels transiently for the first 3 days of life if clamping or milking (stripping) of the umbilical cord is delayed at birth. Delayed clamping may increase the risk of polycythemia and jaundice, but it improves glomerular filtration. Early clamping may lead to anemia, a cardiac murmur, poor peripheral perfusion, and less tachypnea. Hydrostatic pressure affects blood transfer between the placenta and the infant at birth. An undesired fetal-to-placental transfusion occurs if the infant is situated above the level of the placenta.


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Pediatrics_Nelson. The physiologic anemia noted at 2 to 3 months of age in term infants and at 1 to 2 months of age in preterm infants is a normal process that does not result in signs of illness and does not require any treatment. It is a physiologic condition believed to be related to several factors, including increased tissue oxygenation experienced at birth, shortened RBC life span, and low erythropoietin levels. Available @ StudentConsult.com Symptomatic anemia in the newborn period (Fig. 62-1) may be caused by decreased RBC production, increased RBC destruction, or blood loss.


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Pediatrics_Nelson. Available @ StudentConsult.com Symptomatic anemia in the newborn period (Fig. 62-1) may be caused by decreased RBC production, increased RBC destruction, or blood loss. Anemia caused by decreased production of RBCs appears at birth with pallor, a low reticulocyte count, and absence of erythroid precursors in the bone marrow. Potential causes of neonatal decreased RBC production include bone marrow failure syndromes (congenital RBC aplasia [Diamond-Blackfan anemia]), infection (congenital viral infections [parvovirus, rubella], acquired bacterial or viral sepsis), nutritional deficiencies (protein, iron, folate, vitamin B12), and congenital leukemia.


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Pediatrics_Nelson. Immunologically mediated hemolysis in utero may lead to erythroblastosis fetalis, or the fetus may be spared and hemolytic disease may appear in the newborn. Hemolysis of fetal erythrocytes is a result of blood group differences between the sensitized mother and fetus, which causes production of maternal IgG antibodies directed against an antigen on fetal cells. ABO blood group incompatibility with neonatal hemolysis develops only if the mother has IgG antibodies from a previous exposure to A or B antigens. These IgG antibodies cross the placenta by active transport and affect the fetus or newborn. Sensitization of the mother to fetal antigens may have occurred by previous transfusions or by conditions of pregnancy that result in transfer of fetal erythrocytes into the


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Pediatrics_Nelson. Normal or elevated reticulocyte count (> 5−10%) Coombs positive Isoimmunization: Rh (D antigen) ABO, C, c, E, G Duffy, Kell Other minor group Drug-induced (PCN) Coombs negative Blood smear Specific RBC dysmorphology Obtain incubated osmotic fragility test Elliptocytes Poikilocytes Stomatocytes Fragmentation Basophilic stippling Spherocytes Blood cultures, obtain maternal serum for IgG, IgM, HIV, RPR/FTA RBC morphology Hypochromic microcytic RBCs Normal RBC morphology Chronic fetomaternal bleed Chronic twin-to-twin transfusion Alpha-thalassemia trait Gamma-thalassemia Consider acute blood loss due to obstetric complications, external or internal hemorrhage, DIC/sepsis, bleeding dyscrasias Low reticulocyte count (0−2%) Obtain bone marrow Obtain hemoglobin electrophoresis, KB stain Obtain specific enzyme assay Diamond-Blackfan Aase syndrome Congenital dyserythropoietic anemias Refractory sideroblastic anemia Transcobalamin II deficiency Orotic aciduria No jaundiceJaundice Other


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Pediatrics_Nelson. Obtain specific enzyme assay Diamond-Blackfan Aase syndrome Congenital dyserythropoietic anemias Refractory sideroblastic anemia Transcobalamin II deficiency Orotic aciduria No jaundiceJaundice Other Galactosemia Alpha or gamma chain hemoglobinopathies Osteopetrosis Congenital leukemia Hemophagocytic histiocytosis syndromes Drugs (valproic acid, oxidizing agents) Congenital Enzymatic Defects G6PD Pyruvate kinase Hexokinase Glucose phosphate isomerase Others Infections Bacterial infections Parvovirus B19 TORCH infections Syphilis Malaria HIV


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Pediatrics_Nelson. Figure 62-1 Differential diagnosis of neonatal anemia. The physician obtains information from the family, maternal and labor and delivery histories, and laboratory tests, including hemoglobin, reticulocyte count, blood type, direct Coombs test, peripheral smear, red blood cell (RBC) indices, and bilirubin concentration. DIC, Disseminated intravascular coagulation; FTA, fluorescent treponemal antibody test; G6PD, glucose-6-phosphate dehydrogenase; HIV, human immunodeficiency virus; KB, Kleihauer-Betke; PCN, penicillin; RPR, rapid plasma reagin tests; TORCH, toxoplasmosis, other, rubella, cytomegalovirus, herpes simplex. (From Ohls RK: Anemia in the neonate. In Christensen RD, editor: Hematologic problems of the neonate, Philadelphia, 2000, Saunders, p 162.) maternal circulation, such as first-trimester abortion, ectopic pregnancy, amniocentesis, manual extraction of the placenta, version (external or internal) procedures, or normal pregnancy.


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Pediatrics_Nelson. ABO incompatibility with sensitization usually does not cause fetal disease other than extremely mild anemia. It may produce hemolytic disease of the newborn, which is manifested as significant anemia and hyperbilirubinemia. Because many mothers who have blood group O have IgG antibodies to A and B before pregnancy, the firstborn infant of A or B blood type may be affected. In contrast to Rh disease, ABO hemolytic disease does not become more severe with subsequent pregnancies. Hemolysis with ABO incompatibility is less severe than hemolysis in Rh-sensitized pregnancy, either because the anti-A or anti-B antibody may bind to nonerythrocytic cells that contain A or B antigen or because fetal erythrocytes have fewer A or B antigenic determinants than they have Rh sites. With the declining incidence of Rh hemolytic disease, ABO incompatibility has become the most common cause of neonatal hyperbilirubinemia requiring therapy—currently accounting for approximately 20% of clinically


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Pediatrics_Nelson. incidence of Rh hemolytic disease, ABO incompatibility has become the most common cause of neonatal hyperbilirubinemia requiring therapy—currently accounting for approximately 20% of clinically significant jaundice in the newborn.


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Pediatrics_Nelson. Erythroblastosis fetalis classically is caused by Rh bloodgroup incompatibility. Most Rh-negative women have noanti-Rh antibodies at the time of their first pregnancy. TheRh antigen system consists of five antigens: C, D, E, c, and e; the d type is not antigenic. In most Rh-sensitized cases, theD antigen of the fetus sensitizes the Rh-negative (d) mother,resulting in IgG antibody production during the first pregnancy. Because most mothers are not sensitized to Rh antigens at the start of pregnancy, Rh erythroblastosis fetalis isusually a disease of the second and subsequent pregnancies.The first affected pregnancy results in an antibody response inthe mother, which may be detected during antenatal screening with the Coombs test and determined to be anti-D antibody. The first affected newborn may show no serious fetaldisease and may manifest hemolytic disease of the newbornonly by the development of anemia and hyperbilirubinemia.Subsequent pregnancies result in an increasing severity


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Pediatrics_Nelson. may show no serious fetaldisease and may manifest hemolytic disease of the newbornonly by the development of anemia and hyperbilirubinemia.Subsequent pregnancies result in an increasing severity of response because of an earlier onset of hemolysis in utero. Fetal anemia, heart failure, elevated venous pressure, portal vein obstruction, and hypoalbuminemia result in fetal hydrops, which is characterized by ascites, pleural and pericardial effusions, and anasarca (see Chapter 60). The risk offetal death is high.


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Pediatrics_Nelson. The management of a pregnancy complicated by Rh sensitization depends on the severity of hemolysis, its effects on the fetus, and the maturity of the fetus at the time it becomes affected. The severity of the hemolysis can be assessed by the quantity of bilirubin transferred from the fetus to the amniotic fluid, quantified by spectrophotometric analysis of the optical density (at 450 nm) of amniotic fluid.