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Pediatrics_Nelson. Fruits Buy fewer juices Have no juices in the refrigerator Increase eating fruits Keep a bowl of fruits in the kitchen Vegetables Increase eating veggies Have a bowl of veggies in the refrigerator Cooperation, competition, and social interaction such as building a house of veggies a systematic approach that promotes multidisciplinary brief, office-based interventions for obese children as well as reducing weight. Before enrolling any patient in a weight-loss program, the clinician must have a clear idea of that individual’s expectations. Patients with unrealistic expectations should not be enrolled until these are changed to realistic and attainable goals. Using the pneumonic described, the clinician should guide the patient who seeks weight reduction to create SMART goals: Specific, Measurable, Attainable, Realistic, and Timely.


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Pediatrics_Nelson. Surgical treatment may be advocated as a preferred and cost-effective solution for certain children and adolescents. The role of bariatric surgery in the treatment of obese children or adolescents is controversial. The concerns about surgery to treat obesity in young populations include whether or not surgery is cost effective; how to ensure healthy growth through to adulthood; what support services are needed after surgery; compliance with the postoperative nutrition regimen; and attendance at appointments for long-term follow-up and care. There is very limited evidence available to adequately estimate long-term safety, effectiveness, cost effectiveness or durability of bariatric surgery in growing children. The existing evidence suggests that bariatric surgery in severely obese adolescent results in significant weight loss and improvements in comorbidities and quality of life. Postoperative complications (both physical and psychological), compliance, and follow-up may be more


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Pediatrics_Nelson. results in significant weight loss and improvements in comorbidities and quality of life. Postoperative complications (both physical and psychological), compliance, and follow-up may be more problematic in adolescents than adults, and long-term data on safety, effectiveness, and cost remain largely unavailable.


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Pediatrics_Nelson. Pediatric undernutrition is usually the result of inadequatefood supply, access, or utilization; poor access to health andsanitation; and/or inappropriate feeding or child care practices.The greatest risk of undernutrition is in utero through age 2.Various guidelines can be used to classify pediatric malnutrition (Table 30-1). International references are established that allow normalization of anthropometric measures in terms of z scores. Other measurements include height and weight for age,weight for height, BMI, and mid-upper arm circumference. Thegreatest consequence of undernutrition is death, but significantintellectual and physical disability exists in many who survive.


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Pediatrics_Nelson. Protein-energy malnutrition (PEM) is a spectrum of conditions caused by varying levels of protein and calorie deficiencies. Primary PEM is caused by social or economic factors that result in a lack of food. Secondary PEM occurs in children with various conditions associated with increased caloric requirements (infection, trauma, cancer) (Fig. 30-1), increased caloric loss (malabsorption), reduced caloric intake (anorexia, cancer, oral intake restriction, social factors), or a combination of these three variables. Protein and calorie malnutrition may From Grover Z, Ee LC: Protein energy malnutrition, Pediatr Clin North Am 56:1055–1068, 2009 BMI, Body mass index; HFA, height for age; MUAC, mid-upper arm circumference; NCHS, U.S. National Center for Health Statistics; SD, standard deviation; WFA, weight for age; WFH, weight for height; WHO, World Health Organization. Severe infection, 35


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Pediatrics_Nelson. WFA, weight for age; WFH, weight for height; WHO, World Health Organization. Severe infection, 35 Figure 30-1 Increased energy needs with stress. (Adapted from Wilmore D: The Metabolic Management of the Critically Ill, New York, 1977, Plenum Publishing. Revised in Walker W, Watkins J, editors: Nutrition in Pediatrics: Basic Science and Clinical Application. Boston, 1985, Little, Brown.) be associated with other nutrient deficiencies, which may be evident on physical examination (Table 30-2). Available @ StudentConsult.com Failure to Thrive


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Pediatrics_Nelson. Available @ StudentConsult.com Failure to Thrive Pediatric undernutrition in the United States is often termed failure to thrive and describes circumstances in which a child fails to gain weight appropriately or, in more severe cases, experiences failure in linear growth or head circumference. The terms organic and nonorganic failure to thrive have lost favor in recognition of the frequent interplay between underlying medical conditions that may cause maladaptive behaviors. Similarly, social and behavioral factors that initially may have been associated with feeding problems (see Chapter 21), and poor growth also may be associated with medical problems, including frequent minor acute illnesses.


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Pediatrics_Nelson. Marasmus results from the body’s physiologic response to inadequate calories and nutrients. Loss of muscle mass and subcutaneous fat stores can be confirmed by inspection or palpation and quantified by anthropometric measurements. The head may appear large but generally is proportional to the body length. Edema usually is absent. The skin is dry and thin, and the hair may be thin, sparse, and easily pulled out. Marasmic children may be apathetic, weak, and may be irritable when touched. Bradycardia and hypothermia signify severe and life-threatening malnutrition. Inappropriate or inadequate weaning practices and chronic diarrhea are common findings in developing countries. Stunting (impaired linear growth) results from a combination of malnutrition, especially micronutrients, and recurrent infections.


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Pediatrics_Nelson. Kwashiorkor results from inadequate protein intake in thepresence of fair to good caloric intake. The hypoalbuminemicstate results in pitting edema that starts in the lower extremities and ascends with increasing severity. Other factors, such asacute infection, toxins, and possibly specific micronutrient oramino acid imbalances, are likely to contribute to the etiology.The major clinical manifestation of kwashiorkor is that the body weight is near normal for age; weight alone does not accurately reflect the nutritional status because of edema. Physical Physical Signs of Nutritional Deficiency Disorders Depigmented skin Purpura Scrotal, vulval dermatitis Alopecia Depigmented, dull hair, easily pluckable Anemias (iron, vitamin B12, vitamin E, folate, and copper) Protein, thiamine Calories, protein, vitamin B6, niacin, riboflavin Riboflavin, essential fatty acids, biotin Calories, protein Vitamins C, K Riboflavin Zinc, biotin, protein Protein, calories, copper


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Pediatrics_Nelson. Calories, protein, vitamin B6, niacin, riboflavin Riboflavin, essential fatty acids, biotin Calories, protein Vitamins C, K Riboflavin Zinc, biotin, protein Protein, calories, copper Eye (vision) Adaptation to dark Color discrimination Bitot spots, xerophthalmia, keratomalacia Vitamins A, E, zinc Vitamin A Vitamin A


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Pediatrics_Nelson. Marasmus Riboflavin, iron Vitamins B6, niacin, riboflavin Vitamins C, K examination reveals a relative maintenance of subcutaneous adipose tissue and a marked atrophy of muscle mass. Edemavaries from a minor pitting of the dorsum of the foot to generalized edema with involvement of the eyelids and scrotum.The hair is sparse; is easily plucked; and appears dull brown, red, or yellow-white. Nutritional repletion restores hair color,leaving a band of hair with altered pigmentation followed by aband with normal pigmentation (flag sign). Skin changes arecommon and range from hyperpigmented hyperkeratosis toan erythematous macular rash (pellagroid) on the trunk andextremities. In the most severe form of kwashiorkor, a superficial desquamation occurs over pressure surfaces (“flaky paint”rash). Angular cheilosis, atrophy of the filiform papillae of thetongue, and monilial stomatitis are common. Enlarged parotidglands and facial edema result in moon facies; apathy and disinterest in eating are


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Pediatrics_Nelson. cheilosis, atrophy of the filiform papillae of thetongue, and monilial stomatitis are common. Enlarged parotidglands and facial edema result in moon facies; apathy and disinterest in eating are typical of kwashiorkor. Examination of


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Pediatrics_Nelson. Riboflavin, iron, niacin, folate, vitamin B12 Iron Vitamins B6, B12, niacin, riboflavin, folate Protein Fluoride Vitamins A, B12, zinc Vitamin A, zinc Iodine Neurologic Sensory, motor neuropathy Ataxia, areflexia Ophthalmoplegia Tetany Retardation Dementia, delirium Poor position sense, ataxia Vitamins D, C Vitamin C, copper Vitamin D, calcium Vitamin C Thiamine, selenium, Thiamine, vitamins E, B6, B12 Vitamin E Vitamin E, thiamine Vitamin D, Ca2+, Mg2+ Iodine, niacin Vitamin E, niacin, thiamine Thiamine, vitamin B12 the abdomen may reveal an enlarged, soft liver with an indefinite edge. Lymph node and tonsils are commonly atrophic.Chest examination may reveal basilar rales. The abdomen isdistended, and bowel sounds tend to be hypoactive. These children often have concurrent wasting and edema in addition to stunting. These children exhibit features of dermatitis, neurologic abnormalities, and fatty liver.


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Pediatrics_Nelson. These children often have concurrent wasting and edema in addition to stunting. These children exhibit features of dermatitis, neurologic abnormalities, and fatty liver. The basal metabolic rate and immediate nutrient needs decrease in cases of malnutrition. When nutrients are provided, themetabolic rate increases, stimulating anabolism and increasing nutrient requirements. The body of the malnourished child mayhave compensated for micronutrient deficiencies with lower metabolic and growth rates, and refeeding may unmask thesedeficiencies. Nutritional rehabilitation should be initiated and advanced slowly to minimize these complications. The initialapproach involves correction of dehydration and anti-infective(bacteria, parasites) therapy if indicated. Oral rehydration isrecommended over intravenous fluid to avoid excessive fluid and solute load and resultant heart or renal failure.


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Pediatrics_Nelson. When nutritional rehabilitation is initiated, calories can be safely started at 20% above the child’s recent intake. If no estimate of the caloric intake is available, 50% to 75% of the normal energy requirement is safe. High-calorie oral solutions or ready-to-use therapeutic foods (a mixture of powdered milk, peanuts, sugar, vitamins, and minerals) are frequently used in developing countries. Nutritional rehabilitation can be complicated by refeeding syndrome, which is characterized by fluid retention, hypophosphatemia, hypomagnesemia, and hypokalemia. Careful monitoring of laboratory values and clinical status with severe malnutrition is essential.


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Pediatrics_Nelson. When nutritional rehabilitation has begun, caloric intakecan be increased 10% to 20% per day, monitoring for electrolyte imbalances, poor cardiac function, edema, or feedingintolerance. If any of these occurs, further caloric increasesare not made until the child’s status stabilizes. Caloric intake is increased until appropriate regrowth or catch-up growth isinitiated. Catch-up growth refers to gaining weight at greaterthan 50th percentile for age and may require 150% or more ofthe recommended calories for an age-matched, well-nourishedchild. A general rule of thumb for infants and children up to3 years of age is to provide 100 to 120 kcal/kg based on ideal weight for height. Protein needs also are increased as anabolismbegins and are provided in proportion to the caloric intake.Vitamin and mineral intake in excess of the daily recommendedintake is provided to account for the increased requirements;this is frequently accomplished by giving an age-appropriatedaily multiple vitamin,


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Pediatrics_Nelson. and mineral intake in excess of the daily recommendedintake is provided to account for the increased requirements;this is frequently accomplished by giving an age-appropriatedaily multiple vitamin, with other individual micronutrientsupplements as warranted by history, physical examination,or laboratory studies. Iron supplements are not recommendedduring the acute rehabilitation phase, especially for childrenwith kwashiorkor, for whom ferritin levels are often high. Additional iron may pose an oxidative stress; iron supplementationis associated with higher morbidity and mortality.


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Pediatrics_Nelson. In most cases, cow’s milk–based formulas are tolerated and provide an appropriate mix of nutrients. Other easily digested foods, appropriate for the age, also may be introduced slowly. If feeding intolerance occurs, lactose-free or semielemental formulas should be considered.


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Pediatrics_Nelson. Malnourished children are more susceptible to infection, especially sepsis, pneumonia, and gastroenteritis. Hypoglycemia is common after periods of severe fasting but may also be a sign of sepsis. Hypothermia may signify infection or, with bradycardia, may signify a decreased metabolic rate to conserve energy. Bradycardia and poor cardiac output predispose the malnourished child to heart failure, which is exacerbated by acute fluid or solute loads. Micronutrient deficiencies also can complicate malnutrition. Vitamin A and zinc deficiencies are common in the developing world and are an important cause of altered immune response and increased morbidity and mortality. Depending on the age at onset and the duration of the malnutrition, malnourished children may have permanent growth stunting (from malnutrition in utero, infancy, or adolescence) and delayed development (from malnutrition in infancy or adolescence). Environmental (social) deprivation may interact with the effects of the


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Pediatrics_Nelson. (from malnutrition in utero, infancy, or adolescence) and delayed development (from malnutrition in infancy or adolescence). Environmental (social) deprivation may interact with the effects of the malnutrition to impair further development and cognitive function.


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Pediatrics_Nelson. Micronutrients include vitamins and trace elements. In industrialized societies, frank clinical deficiencies are unusual in healthy children, but they can and do occur in certain high-risk circumstances. Risk factors include diets that are consistently limited in variety, especially with the exclusion of entire food groups, malabsorption syndromes, and conditions causing high physiologic requirements. Various common etiologies of vitamin and nutrient deficiency states are highlighted in Table 31-1, and characteristics of vitamin deficiencies are outlined in Table 31-2. Treatment is noted in Table 31-3.


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Pediatrics_Nelson. Water-soluble vitamins are not stored in the body except for vitamin B12; intake therefore alters tissue levels. Absorption from the diet is usually high, and the compounds exchange readily between intracellular and extracellular fluids; excretion is via the urine. Water-soluble vitamins typically function as coenzymes in energy, protein, amino acid, and nucleic acid metabolism; as cosubstrates in enzymatic reactions; and as structural components. Available @ StudentConsult.com The principal forms of vitamin C are ascorbic acid and the oxidized form, dehydroascorbic acid. Ascorbic acid accelerateshydroxylation reactions in many biosynthetic reactions, including hydroxylation of proline in the formation of collagen. Theneeds of full-term infants for ascorbic acid and dehydroascorbicacid are calculated by estimating the availability in human milk.


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Pediatrics_Nelson. A deficiency of ascorbic acid results in the clinical manifestations of scurvy. Infantile scurvy is manifested by irritability, bone tenderness with swelling, and pseudoparalysis of the legs. The disease may occur if infants are fed unsupplemented cow’s milk in the first year of life or if the diet is devoid of fruits Vegans (strict) Protein, vitamins B12, D, riboflavin, iron Breastfed infant Vitamins K, D Bulimia, anorexia nervosa Electrolytes, other deficiencies Parenteral alimentation Essential fatty acids, trace elements Alcoholism Calories, vitamin B1, B6, folate Malabsorption syndromes Vitamins A, D, E, K, zinc, essential fatty acids Cholestasis Vitamins E, D, K, A, zinc, essential fatty acids Sulfonamides Folate Phenytoin, phenobarbital Vitamins D, K, folate Mineral oil Vitamins A, D, E, K Antibiotics Vitamin K Isoniazid Vitamin B6 Antacids Iron, phosphate, calcium Digitalis Magnesium, calcium Penicillamine Vitamin B6


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Pediatrics_Nelson. Transcobalamin II or intrinsic Vitamin B12 factor deficiency Other digestive enzyme Carbohydrate, fat, protein deficiencies Menkes kinky hair syndrome Copper Acrodermatitis enteropathica Zinc Reduced exposure to direct Vitamin D sunlight and vegetables. Subperiosteal hemorrhage, bleeding gums and petechiae, hyperkeratosis of hair follicles, and a succession of mental changes characterize the progression of the illness. Anemia secondary to bleeding, decreased iron absorption, or abnormal folate metabolism is also seen in chronic scurvy. Treatment is noted in Table 31-3. Available @ StudentConsult.com The B vitamins thiamine, riboflavin, and niacin are routinely added to enriched grain products; deficiencies in normal hosts are rare in the United States. Levels from human milk reflect maternal intake, and deficiency can develop in breastfed infants of deficient mothers.


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Pediatrics_Nelson. Vitamin B1 functions as a coenzyme in biochemical reactions related to carbohydrate metabolism, decarboxylation of α-ketoacids and pyruvate, and transketolase reactions of the pentose pathway. Thiamine also is involved in the decarboxylation of branched-chain amino acids. Thiamine is lost during milk pasteurization and sterilization.


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Pediatrics_Nelson. Thiamine deficiency occurs in alcoholics and has beenreported in adolescents who have undergone bariatric surgery forsevere obesity. Infantile beriberi occurs between 1 and 4 months of age in breastfed infants whose mothers have a thiamine deficiency (alcoholism), in infants with protein-calorie malnutrition,in infants receiving unsupplemented hyperalimentation fluid, and in infants receiving boiled milk. Acute wet beriberi with cardiac symptoms and signs predominates in infantile beriberi.Anorexia, apathy, vomiting, restlessness, and pallor progress todyspnea, cyanosis, and death from heart failure. Infants withberiberi have a characteristic aphonic cry; they appear to be crying, but no sound is uttered. Other signs include peripheral neuropathy and paresthesias. For treatment see Table 31-3.


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Pediatrics_Nelson. Vitamin B2 is a constituent of two coenzymes, riboflavin 5′-phosphate and flavin-adenine dinucleotide, essential components of glutathione reductase and xanthine oxidase, which are involved in electron transport. A deficiency of riboflavin affects glucose, fatty acid, and amino acid metabolism. Riboflavin and its phosphate are decomposed by exposure to light and by strong alkaline solutions. Ariboflavinosis is characterized by an angular stomatitis; glossitis; cheilosis; seborrheic dermatitis around the nose and mouth; and eye changes that include reduced tearing, photophobia, corneal vascularization, and the formation of cataracts. Subclinical riboflavin deficiencies have been found in diabetic subjects, children in families with low socioeconomic status, children with chronic cardiac disease, and infants undergoing prolonged phototherapy for hyperbilirubinemia.


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Pediatrics_Nelson. Niacin consists of the compounds nicotinic acid and nicotinamide (niacinamide). Nicotinamide, the predominant form of the vitamin, functions as a component of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). Niacin is involved in multiple metabolic processes, including fat synthesis, intracellular respiratory metabolism, and glycolysis. In determining the needs for niacin, the content of tryptophan in the diet must be considered because tryptophan is converted to niacin. Niacin is stable in foods and withstands heating and prolonged storage. Approximately 70% of the total niacin equivalents in human milk are derived from tryptophan. Pellagra, or niacin deficiency disease, is characterized by weakness, lassitude, dermatitis, photosensitivity, inflammation of mucous membranes, diarrhea, vomiting, dysphagia, and, in severe cases, dementia.


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Pediatrics_Nelson. Coenzyme in ketoacid Beriberi: polyneuropathy, calf Inborn errors of lactate Liver, meat, milk, cereals, decarboxylation (e.g., tenderness, heart failure, edema, metabolism; boiling milk nuts, legumes pyruvate → acetyl-CoA ophthalmoplegia destroys B1 transketolase reaction) Meat, vegetables Folate DNA synthesis Megaloblastic anemia; neural Goat milk deficient; drug Liver, greens, vegetables, tube defects antagonists; heat inactivates cereals, cheese D Maintain serum calcium, Rickets: reduced bone Prohormone of 25and Fortified milk, cheese, phosphorus levels mineralization 1,25-vitamin D liver; sunlight E Antioxidant Hemolysis in preterm infants; May benefit patients with Seeds, vegetables, germ areflexia, ataxia, ophthalmoplegia G6PD deficiency oils, grains CoA, Coenzyme A; FAD, flavin adenine dinucleotide; G6PD, glucose-6-phosphate dehydrogenase; NAD, nicotinamide adenine dinucleotide. *Biotinidase deficiency.


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Pediatrics_Nelson. Vitamin B6 diarrhea, failure to thrive, listlessness, hyperirritability, and Vitamin B6 refers to three naturally occurring pyridines: seizures. Children receiving isoniazid or penicillamine may pyridoxine (pyridoxol), pyridoxal, and pyridoxamine. The require additional vitamin B6 because the drug binds to the phosphates of the latter two pyridines are metabolically and vitamin. Vitamin B6 is unusual as a water-soluble vitamin in functionally related and are converted in the liver to the coen-that very large doses (≥500 mg/day) have been associated with zyme form, pyridoxal phosphate. The metabolic functions of a sensory neuropathy. vitamin B6 include interconversion reactions of amino acids, conversion of tryptophan to niacin and serotonin, metabolic reactions in the brain, carbohydrate metabolism, immune Folate development, and the biosynthesis of heme and prostaglandins. The pyridoxal and pyridoxamine forms of the vitamin are destroyed by heat; heat treatment was responsible for


Pediatrics_Nelson

Pediatrics_Nelson. metabolism, immune Folate development, and the biosynthesis of heme and prostaglandins. The pyridoxal and pyridoxamine forms of the vitamin are destroyed by heat; heat treatment was responsible for vita-


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Pediatrics_Nelson. Decision-Making Algorithms min B6 deficiency and seizures in infants fed improperly pro-Available @ StudentConsult.com cessed formulas. Goat’s milk is deficient in vitamin B6. Dietary deprivation or malabsorption of vitamin B6 in chil- dren results in hypochromic microcytic anemia, vomiting, Vitamin A Severe deficiency with Infants: 7,500–15,000 U/day IM, followed by oral 5000–10,000 U/day for 10 days. xerophthalmia Children 1–8 yr of age: oral 5,000–10,000 U/kg/day for 5 days or until recovery. Children >8 yr of age and adults: oral 500,000 U/day for 3 days; then 50,000 U/day for 14 days; then 10,000–20,000 U/day for 2 mo. Deficiency without Infants <1 yr of age: 100,000 U/day orally, q4–6mo. corneal changes Children 1–8 yr of age: 200,000 U/day orally, q4–6mo. Children >8 yr and adults: 100,000 U/day for 3 days, followed by 50,000 U/day for 10 days.


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Pediatrics_Nelson. Children 1–8 yr of age: 200,000 U/day orally, q4–6mo. Children >8 yr and adults: 100,000 U/day for 3 days, followed by 50,000 U/day for 10 days. Deficiency IM given only to those patients with malabsorption in whom oral dosing is not possible. Infants: 7,500–15,000 U/day for 10 days. Children 1–8 yr of age: 17,500–35,000 U/day for 10 days. Children >8 yr of age and adults: 100,000 U/day for 3 days, then 50,000 U/day for 14 days. Give follow-up oral multivitamin that contains vitamin A: LBW infants: no dose established, children ≤8 years of age: 5,000–10,000 U/day, children >8 yr of age and adults: 10,000–20,000 U daily. Malabsorption syndrome Children >8 yr of age and adults: oral 10,000–50,000 U/day of water-miscible product. (prophylaxis) Cystic fibrosis 1,500–10,000 U/day prophylaxis (CF Foundation). Measles WHO recommendations: single dose, repeating the dose next day and at 4 wk for children with eye findings: 6 mo to 1 yr of age: 100,000 U; >1 yr of age: 200,000 U.


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Pediatrics_Nelson. Measles WHO recommendations: single dose, repeating the dose next day and at 4 wk for children with eye findings: 6 mo to 1 yr of age: 100,000 U; >1 yr of age: 200,000 U. Niacin Pellagra Children: 50–100 mg tid. Adults: 50–100 mg/day, max 100 mg/day. Pyridoxine (B6) Seizures Neonates and infants: initial 50–100 mg/day orally, IM, IV, SC. Drug-induced Children: 10–50 mg/day as treatment, 1–2 mg/kg/day as prophylaxis. deficiencies Adults: 100–200 mg/day as treatment, 25–100 mg/day as prophylaxis. Dietary deficiency Children: 5–25 mg/day for 3 wk, then 1.5–2.5 mg/day in a multivitamin product. Adults: 10–20 mg/day for 3 wk. Riboflavin (B2) Children: 2.5–10 mg/day in divided doses. Adults: 5–30 mg/day in divided doses. Ascorbic acid Scurvy Children: 100–300 mg/day in divided doses orally, IM, IV, or SC for several days. Adults: 100–250 mg/day one to two times/day.


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Pediatrics_Nelson. Ascorbic acid Scurvy Children: 100–300 mg/day in divided doses orally, IM, IV, or SC for several days. Adults: 100–250 mg/day one to two times/day. Data from Lexi-Comp Inc., Hudson, Ohio, 2004; table from Kronel S, Mascarenhas: Vitamin deficiencies and excesses. In Burg FD, Ingelfinger JR, Polin RA, Gershon AA, editors: Current Pediatric Therapy, Philadelphia, 2006, Elsevier, Table 3, pp 104–105. bid, Two times per day; CF, cystic fibrosis; IM, intramuscular; IV, intravenous; LBW, low birth weight; PO, by mouth; q, every; SC, subcutaneous; tid, three times per day; WHO, World Health Organization.


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Pediatrics_Nelson. A variety of chemical forms of folate are nutritionally active. Folate high requirement of the vitamin to support erythropoiesis. functions in transport of single-carbon fragments in synthesis of Other conditions with risk of deficiency include pregnancy, nucleic acids and for normal metabolism of certain amino acids alcoholism, and treatment with anticonvulsants (phenytand in conversion of homocysteine to methionine. Food sources oin) or antimetabolites (methotrexate). First occurrence and include green leafy vegetables, oranges, and whole grains; folate recurrence of neural tube defects are reduced significantly fortification of grains is now routine in the United States. by maternal supplementation during embryogenesis. Because


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Pediatrics_Nelson. Folate deficiency, characterized by hypersegmented neu-closure of the neural tube occurs before usual recognition of trophils, macrocytic anemia, and glossitis, may result from pregnancy, all women of reproductive age are recommended a low dietary intake, malabsorption, or vitamin-drug inter-to have a folate intake of at least 400 μg/day as prophylaxis. actions. Deficiency can develop within a few weeks of birth because infants require 10 times as much folate as adults rela-Vitamin B12 tive to body weight but have scant stores of folate in the newborn period. Folate is particularly heat labile. Heat-sterilizing


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Pediatrics_Nelson. Decision-Making Algorithms home-prepared formula can decrease the folate content by Available @ StudentConsult.com half. Evaporated milk and goat’s milk are low in folate. Patients with chronic hemolysis (sickle cell anemia, thalassemia) may require extra folate to avoid deficiency because of the relatively Vitamin B12 is one of the most complex of the vitaminmolecules, containing an atom of cobalt held in a corrin ring (similar to that of iron in hemoglobin). The cobalt ionis at the active center of the ring and serves as the site forattachment of alkyl groups during their transfer. The vitamin functions in single-carbon transfers and is intimatelyrelated to folate function and interconversions. Vitamin B12 is essential for normal lipid and carbohydrate metabolism inenergy production and in protein biosynthesis and nucleicacid synthesis.


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Pediatrics_Nelson. In contrast to other water-soluble vitamins, absorption of vitamin B12 is complex, involving cleavage of the vitamin from dietary protein and binding to a glycoprotein called intrinsic factor, which is secreted by the gastric mucosa (parietal cells). The cobalamin–intrinsic factor complex is efficiently absorbed from the distal ileum. As vitamin B12 is absorbed into the portal circulation, it is transported bound to a specific protein, transcobalamin II. Its large stores in the liver also are unusual for a water-soluble vitamin. Efficient enterohepatic circulation normally protects from deficiency for months to years. Dietary sources of the vitamin are animal products only. Strict vegetarians should take a vitamin B12 supplement.


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Pediatrics_Nelson. Vitamin B12 deficiency in children is rare. Early diagnosisand treatment of this disorder in childhood are importantbecause of the danger of irreversible neurologic damage.Most cases in childhood result from a specific defect inabsorption (see Table 31-2). Such defects include congenital pernicious anemia (absent intrinsic factor), juvenile pernicious anemia (autoimmune), and deficiency of transcobalamin II transport. Gastric or intestinal resection and smallbowel bacterial overgrowth also cause vitamin B12 deficiency. Exclusively breastfed infants ingest adequate vitaminB12 unless the mother is a strict vegetarian without supplementation.


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Pediatrics_Nelson. Depression of serum vitamin B12 and the appearance of hypersegmented neutrophils and macrocytosis (indistinguishable from folate deficiency) are early clinical manifestations of deficiency. Vitamin B12 deficiency also causes neurologic manifestations, including depression, peripheral neuropathy, posterior spinal column signs, dementia, and eventual coma. The neurologic signs do not occur in folate deficiency, but administration of folate may mask the hematologic signs of vitamin B12 deficiency, while the neurologic manifestations progress. Patients with vitamin B12 deficiency also have increased urine levels of methylmalonic acid. Most cases of vitamin B12 deficiency in infants and children are not of dietary origin and require treatment throughout life. Maintenance therapy consists of repeated monthly intramuscular injections, although a form of vitamin B12 is administered intranasally.


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Pediatrics_Nelson. Fat-soluble vitamins generally have stores in the body, and dietary deficiencies generally develop more slowly than for water-soluble vitamins. Absorption of fat-soluble vitamins depends on normal fat intake, digestion, and absorption. The complexity of normal fat absorption and the potential for perturbation in many disease states explains the more common occurrence of deficiencies of these vitamins. Available @ StudentConsult.com


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Pediatrics_Nelson. The basic constituent of the vitamin A group is retinol.Ingested plant carotene or animal tissue retinol estersrelease retinol after hydrolysis by pancreatic and intestinal enzymes. Chylomicron-transported retinol esters arestored in the liver as retinol palmitate. Retinol is transportedfrom the liver to target tissues by retinol-binding protein,releasing free retinol to the target tissues. The kidney thenexcretes the retinol-binding protein. Diseases of the kidneydiminish excretion of retinol-binding protein, whereas liverparenchymal disease or malnutrition lowers the synthesis ofretinol-binding protein. Specific cellular binding proteinsfacilitate the uptake of retinol by target tissues. In the eye, retinol is metabolized to form rhodopsin; the action of light onrhodopsin is the first step of the visual process. Retinol alsoinfluences the growth and differentiation of epithelia. Theclinical manifestations of vitamin A deficiency in humansappear as a group of ocular signs termed


Pediatrics_Nelson

Pediatrics_Nelson. step of the visual process. Retinol alsoinfluences the growth and differentiation of epithelia. Theclinical manifestations of vitamin A deficiency in humansappear as a group of ocular signs termed xerophthalmia. The earliest symptom is night blindness, which is followed by xerosis of the conjunctiva and cornea. Untreated, xerophthalmia can result in ulceration, necrosis, keratomalacia, and a permanent corneal scar. Clinical and subclinical vitamin A deficiencies are associated with immunodeficiency; increased risk of infection, especially measles; and increasedrisk of mortality, especially in developing nations. Xerophthalmia and vitamin A deficiency should be urgently treated.Hypervitaminosis A also has serious sequelae, includingheadaches, pseudotumor cerebri, hepatotoxicity, and teratogenicity.


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Pediatrics_Nelson. Eight naturally occurring compounds have vitamin E activity. The most active of these, α-tocopherol, accounts for 90% of the vitamin E present in human tissues and is commercially available as an acetate or succinate. Vitamin E acts as a biologic antioxidant by inhibiting the peroxidation of polyunsaturated fatty acids present in cell membranes. It scavenges free radicals generated by the reduction of molecular oxygen and by the action of oxidative enzymes.


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Pediatrics_Nelson. Vitamin E deficiency occurs in children with fat malabsorption secondary to liver disease, untreated celiac disease,cystic fibrosis, and abetalipoproteinemia. In these children, without vitamin E supplementation, a syndrome of progressive sensory and motor neuropathy develops; the first signof deficiency is loss of deep tendon reflexes. Deficient preterminfants at 1 to 2 months of age have hemolytic anemia characterized by an elevated reticulocyte count, an increased sensitivity of the erythrocytes to hemolysis in hydrogen peroxide,peripheral edema, and thrombocytosis. All the abnormalities are corrected after oral, lipid, or water-soluble vitaminE therapy. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com Cholecalciferol (vitamin D3) is the mammalian form of vitamin D and is produced by ultraviolet irradiation of inactive precursors in the skin. Ergocalciferol (vitamin D2) is derived from plants. Vitamin D2 and vitamin D3 require further metabolism to become active. They are of equivalent potency. Clothing, lack of sunlight exposure, and skin pigmentation decrease generation of vitamin D in the epidermis and dermis.


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Pediatrics_Nelson. Vitamin D (D2 and D3) is metabolized in the liver to calcidiol, or 25-hydroxyvitamin D (25-[OH]-D); this metabolite, which has little intrinsic activity, is transported by a plasma-binding globulin to the kidney, where it is converted to the most active metabolite calcitriol, or 1,25-dihydroxyvitamin D (1,25-[OH]2-D). The action of 1,25-(OH)2-D results in a decrease in the concentration of messenger RNA (mRNA) for collagen in bone and an increase in the concentration of mRNA for vitamin D–dependent calcium-binding protein in the intestine (directly mediating increased intestinal calcium transport). The antirachitic action of vitamin D probably is mediated by provision of appropriate concentrations of calcium and phosphate in the extracellular space of bone and by enhanced intestinal absorption of these minerals. Vitamin D also may have a direct anabolic effect on bone. 1,25-(OH)2-D has direct feedback to the parathyroid gland and inhibits secretion of parathyroid hormone.


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Pediatrics_Nelson. Vitamin D deficiency appears as rickets in children and as osteomalacia in postpubertal adolescents. Inadequate direct sun exposure and vitamin D intake are sufficient causes, butother factors, such as various drugs (phenobarbital, phenytoin) and malabsorption, may increase the risk of developmentof vitamin-deficiency rickets. Breastfed infants, especiallythose with dark-pigmented skin, are at risk for vitamin Ddeficiency. The pathophysiology of rickets results from defective bone growth, especially at the epiphyseal cartilage matrix, which fails to mineralize. The uncalcified osteoid results in a wide, irregular zone of poorly supported tissue, the rachitic metaphysis. This soft, rather than hardened, zone produces many of the skeletal deformities through compression and lateral bulging or flaring of the ends of bones.


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Pediatrics_Nelson. The clinical manifestations of rickets are most common during the first 2 years of life and may become evident only after several months of a vitamin D–deficient diet. Craniotabes is caused by thinning of the outer table of the skull, which when compressed feels like a Ping-Pong ball to the touch. Enlargement of the costochondral junction (rachitic rosary) and thickening of the wrists and ankles may be palpated. The anterior fontanelle is enlarged, and its closure may be delayed. In advanced rickets, scoliosis and exaggerated lordosis may be present. Bowlegs or knock-knees may be evident in older infants, and greenstick fractures may be observed in long bones.


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Pediatrics_Nelson. The diagnosis of rickets is based on a history of poor vitamin D intake and little exposure to direct ultraviolet sunlight.The serum calcium usually is normal but may be low; the serum phosphorus level usually is reduced, and serum alkaline phosphatase activity is elevated. When serum calciumlevels decline to less than 7.5 mg/dL, tetany may occur. Levelsof 24,25-(OH)2-D are undetectable, and serum 1,25-(OH)2-Dlevels are commonly less than 7 ng/mL, although 1,25-(OH)2-D levels also may be normal. The best measure of vitamin D status is the level of 25-(OH)-D. Characteristic radiographicchanges of the distal ulna and radius include widening; concavecupping; and frayed, poorly demarcated ends. The increasedspace seen between the distal ends of the radius and ulna andthe metacarpal bones is the enlarged, nonossified metaphysis.


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Pediatrics_Nelson. Breastfed infants born of mothers with adequate vitamin D stores usually maintain adequate serum vitamin D levels for at least 2 months, but rickets may develop subsequently if these infants are not exposed to the sun or do not receive supplementary vitamin D. The American Academy of Pediatrics recommends vitamin D supplementation of all breastfed infants in the amount of 400 IU/day, started soon after birth and given until the infant is taking more than 1000 mL/day of formula or vitamin D–fortified milk (for age >1 year). Toxic effects of excessive chronic vitamin D may include hypercalcemia, muscle weakness, polyuria, and nephrocalcinosis. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com The plant form of vitamin K is phylloquinone, or vitamin K1. Another form is menaquinone, or vitamin K2, one of a series of compounds with unsaturated side chains synthesized by intestinal bacteria. Plasma factors II (prothrombin), VII, IX, and X in the cascade of blood coagulation factors depend on vitamin K for synthesis and for post-translational conversion of their precursor proteins. The post-translational conversion of glutamyl residues to carboxyglutamic acid residues of a prothrombin molecule creates effective calcium-binding sites, making the protein active. Other vitamin K–dependent proteins include proteins C, S, and Z in plasma and γ-carboxyglutamic acid–containing proteins in several tissues. Bone contains a major vitamin K–dependent protein, osteocalcin, and lesser amounts of other glutamic acid–containing proteins.


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Pediatrics_Nelson. Phylloquinone is absorbed from the intestine and transported by chylomicrons. The rarity of dietary vitamin K deficiency in humans with normal intestinal function suggests that the absorption of menaquinones is possible. Vitamin K deficiency has been observed in subjects with impaired fat absorption caused by obstructive jaundice, pancreatic insufficiency, and celiac disease; often these problems are combined with the use of antibiotics that change intestinal flora. Hemorrhagic disease of the newborn, a disease more common among breastfed infants, occurs in the first few weeks of life. It is rare in infants who receive prophylactic intramuscular vitamin K on the first day of life. Hemorrhagic disease of the newborn usually is marked by generalized ecchymoses, gastrointestinal hemorrhage, or bleeding from a circumcision or umbilical stump; intracranial hemorrhage can occur, but


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Pediatrics_Nelson. Table 31-4 Characteristics of Trace Mineral Deficiencies MINERAL FUNCTION MANIFESTATIONS OF DEFICIENCY COMMENTS SOURCES Iron Heme-containing macromolecules (e.g., hemoglobin, cytochrome, and myoglobin) Anemia, spoon nails, reduced muscle and mental performance History of pica, cow’s milk, gastrointestinal bleeding Meat, liver, grains, legumes Selenium Antioxidant; glutathione Keshan cardiomyopathy in China Endemic areas; long-term TPN Meat, vegetables peroxidase TPN, Total parenteral nutrition. is uncommon. The American Academy of Pediatrics recommends that parenteral vitamin K (0.5 to 1 mg) be given to all newborns shortly after birth.


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Pediatrics_Nelson. TPN, Total parenteral nutrition. is uncommon. The American Academy of Pediatrics recommends that parenteral vitamin K (0.5 to 1 mg) be given to all newborns shortly after birth. The major minerals are those that require intakes of more than 100 mg/day and contribute at least 0.1% of total body weight. There are seven essential major minerals: calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. Ten trace minerals, which constitute less than 0.1% of body weight, have essential physiologic roles. Characteristics of trace mineral deficiencies are listed in Table 31-4. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com Calcium is the most abundant major mineral. Ninety-nine percent of calcium is in the skeleton; the remaining 1% is in extracellular fluids, intracellular compartments, and cell membranes. The nonskeletal calcium has a role in nerve conduction, muscle contraction, blood clotting, and membrane permeability. There are two distinct bone calcium phosphate pools—a large, crystalline form and a smaller, amorphous phase. Bone calcium constantly turns over, with concurrent bone reabsorption and formation. Approximately half of bone mineral accretion occurs during adolescence. Bone mineral density peaks in early adulthood and is influenced by prior and concurrent dietary calcium intake, exercise, and hormone status (testosterone, estrogen).


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Pediatrics_Nelson. Calcium intake can come from a variety of sources, with dairy products providing the most common and concentrated source. The calcium equivalent of 1 cup of milk (about 300 mg of calcium) is ¾ cup of plain yogurt, 1.5 oz of cheddar cheese, 2 cups of ice cream, 4⁄5 cup of almonds, or 2.5 oz of sardines. Other sources of calcium include some leafy green vegetables (broccoli, kale, collards); lime-processed tortillas; calcium-precipitated tofu; and calcium-fortified juices, cereals, and breads.


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Pediatrics_Nelson. There is no classic calcium deficiency syndrome because blood and cell levels are closely regulated. The body can mobilize skeletal calcium and increase the absorptive efficiency of dietary calcium. Osteoporosis that occurs in childhood is related to protein-calorie malnutrition, vitamin C deficiency, steroid therapy, endocrine disorders, immobilization and disuse, osteogenesis imperfecta, or calcium deficiency (in premature infants). It is believed that the primary method of prevention of postmenopausal osteoporosis is to ensure maximum peak bone mass by providing optimal calcium intake during childhood and adolescence. Bone mineral status can be monitored by dual-energy x-ray absorptiometry. No adverse effects are observed in adults with dietary calcium intakes of 2.5 g/day. There is concern that higher intakes may increase the risk of urinary stone formation, constipation, and decreased renal function and may inhibit intestinal absorption of other minerals (iron, zinc).


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Pediatrics_Nelson. Available @ StudentConsult.com Gastrointestinal Bleeding Anemia Failure to Thrive


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Pediatrics_Nelson. Iron, the most abundant trace mineral, is used in the synthesis of hemoglobin, myoglobin, and enzyme iron. Bodyiron content is regulated primarily through modulation ofiron absorption, which depends on the state of body ironstores, the form and amount of iron in foods, and the mixture of foods in the diet. There are two categories of ironin food. The first is heme iron, present in hemoglobin and myoglobin, which is supplied by meat and rarely accountsfor more than one fourth of the iron ingested by infants.The absorption of heme iron is relatively efficient and is notinfluenced by other constituents of the diet. The second category is nonheme iron, which represents the preponderanceof iron intake consumed by infants and exists in the formof iron salts. The absorption of nonheme iron is influencedby the composition of consumed foods. Enhancers of non-heme iron absorption are ascorbic acid, meat, fish, and poultry. Inhibitors are bran, polyphenols (including the tannatesin tea), and


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Pediatrics_Nelson. influencedby the composition of consumed foods. Enhancers of non-heme iron absorption are ascorbic acid, meat, fish, and poultry. Inhibitors are bran, polyphenols (including the tannatesin tea), and phytic acid, a compound found in legumes andwhole grains. The percent intestinal absorption of the smallamount of iron in human milk is 10%; 4% is absorbed from iron-fortified cow’s milk formula and from iron-fortified infant dry cereals.


Pediatrics_Nelson

Pediatrics_Nelson. In a normal term infant, there is little change in total bodyiron and little need for exogenous iron before 4 months ofage. Iron deficiency is rare in term infants during the first4 months, unless there has been substantial blood loss (seeChapter 62). After about 4 months of age, iron reserves become marginal, and, unless exogenous sources of iron areprovided, the infant becomes progressively at risk for anemiaas the iron requirement to support erythropoiesis and growthincreases (see Chapter 150). Premature or low birth weightinfants have a lower amount of stored iron because significantamounts of iron are transferred from the mother in the third trimester. In addition, their postnatal iron needs are greaterbecause of rapid rates of growth and when frequent phlebotomy occurs. Iron needs can be met by supplementation(ferrous sulfate) or by iron-containing complementary foods.Under normal circumstances, iron-fortified formula should be the only alternative to breast milk in infants


Pediatrics_Nelson

Pediatrics_Nelson. can be met by supplementation(ferrous sulfate) or by iron-containing complementary foods.Under normal circumstances, iron-fortified formula should be the only alternative to breast milk in infants younger than1 year of age. Premature infants fed human milk may developiron deficiency anemia earlier unless they receive iron supplements. Formula-fed preterm infants should receive iron-fortified formula.


Pediatrics_Nelson

Pediatrics_Nelson. In older children, iron deficiency may result from inadequate iron intake with excessive cow’s milk intake or from intake of foods with poor iron bioavailability. Iron deficiency also can result from blood loss from such sources as menses or gastric ulceration. Iron deficiency affects many tissues (muscle and central nervous system) in addition to producing anemia. Iron deficiency and anemia have been associated with lethargy and decreased work capacity and impaired neurocognitive development, the deficits of which may be irreversible when onset is in the first 2 years of life.


Pediatrics_Nelson

Pediatrics_Nelson. The diagnosis of iron deficiency anemia is established by the presence of a microcytic hypochromic anemia, low serum ferritin levels, low serum iron levels, reduced transferrin saturation, normal to elevated red blood cell width distribution, and enhanced iron-binding capacity. The mean corpuscular volume and red blood cell indices are reduced, and the reticulocyte count is low. Iron deficiency may be present without anemia. Clinical manifestations are noted in Table 31-4. Treatment of iron deficiency anemia includes changes in the diet to provide adequate iron and the administration of 2 to 6 mg iron/kg/24 hr (as ferrous sulfate) divided bid or tid. Reticulocytosis is noted within 3 to 7 days of starting treatment. Oral treatment should be continued for 5 months. Rarely, intramuscular or intravenous iron therapy is needed if oral iron cannot be given. Parenteral therapy carries the risk of anaphylaxis and should be administered according to a strict protocol, including a test dose.


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Pediatrics_Nelson. Available @ StudentConsult.com Zinc is the second most abundant trace mineral and is important in protein metabolism and synthesis, in nucleic acid metabolism, and in stabilization of cell membranes. Zinc functions as a cofactor for more than 200 enzymes and is essential to numerous cellular metabolic functions. Adequate zinc status is especially crucial during periods of growth and for tissue proliferation (immune system, wound healing, skin and gastrointestinal tract integrity); physiologic functions for which zinc is essential include normal growth, sexual maturation, and immune function.


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Pediatrics_Nelson. Dietary zinc is absorbed (20% to 40%) in the duodenum and proximal small intestine. The best dietary sources of zinc are animal products, including human milk, from which it is readily absorbed. Whole grains and legumes also contain moderate amounts of zinc, but phytic acid inhibits absorption from these sources. On a global basis, poor bioavailability secondary to phytic acid is thought to be a more important factor than low intake in the widespread occurrence of zinc deficiency. Excretion of zinc occurs from the gastrointestinal tract. In the presence of ongoing losses, such as in chronic diarrhea, requirements can drastically increase.


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Pediatrics_Nelson. Zinc deficiency dwarfism syndrome was first described in a group of children in the Middle East with low levels of zinc in their hair, poor appetite, diminished taste acuity, hypogonadism, and short stature. Zinc supplementation reduces morbidity and mortality from diarrhea and pneumonia and enhances growth in developing countries. Mild to moderate zinc deficiency is considered to be highly prevalent in developing countries, particularly in populations with high rates of stunting. Mild zinc deficiency occurs in older breastfed infants without adequate zinc intake from complementary foods or in young children with poor total or bioavailable zinc intake in the general diet. A high infectious burden also may increase the risk of zinc deficiency in developing countries. Acute, acquired severe zinc deficiency occurs in patients receiving total parenteral nutrition without zinc supplementation and in premature infants fed human milk without fortification. Clinical manifestations of mild


Pediatrics_Nelson

Pediatrics_Nelson. zinc deficiency occurs in patients receiving total parenteral nutrition without zinc supplementation and in premature infants fed human milk without fortification. Clinical manifestations of mild zinc deficiency include anorexia, growth faltering, and immune impairment. Moderately severe manifestations include delayed sexual maturation, rough skin, and hepatosplenomegaly. The signs of severe deficiency include acral and periorificial erythematous, scaling dermatitis; growth and immune impairment; diarrhea; mood changes; alopecia; night blindness; and photophobia.


Pediatrics_Nelson

Pediatrics_Nelson. Diagnosis of zinc deficiency is challenging. Plasma zinc concentration is most commonly used, but levels are frequently normal in conditions of mild deficiency; levels in moderate to severe deficiency are typically less than 60 μg/dL. Acute infection also can result in depression of circulating zinc levels. The standard for the diagnosis of deficiency is response to a trial of supplementation, with outcomes such as improved linear growth or weight gain, improved appetite, and improved immune function. Because there is no pharmacologic effect of zinc on these functions, a positive response to supplementation is considered evidence of a preexisting deficiency. Clinically an empirical trial of zinc supplementation (1 μg/kg/day) is a safe and reasonable approach in situations in which deficiency is considered possible.


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Pediatrics_Nelson. Acrodermatitis enteropathica is an autosomal recessive disorder that begins within 2 to 4 weeks after infants have been weaned from breast milk. It is characterized by an acute perioral and perianal dermatitis, alopecia, and failure to thrive. The disease is caused by severe zinc deficiency from a specific defect of intestinal zinc absorption. Plasma zinc levels are markedly reduced, and serum alkaline phosphatase activity is low. Treatment is with high-dose oral zinc supplements. A relatively uncommon condition associated with presentation of severe zinc deficiency is due to a defect in the secretion of zinc from the mammary gland, resulting in abnormally low milk zinc concentrations. Breastfed infants, especially those born prematurely, present with classic signs of zinc deficiency: growth failure, diarrhea, and dermatitis. Because there is no defect in the infant’s ability to absorb zinc, treatment consists of supplementing the infant with zinc for the duration of breastfeeding,


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Pediatrics_Nelson. failure, diarrhea, and dermatitis. Because there is no defect in the infant’s ability to absorb zinc, treatment consists of supplementing the infant with zinc for the duration of breastfeeding, which can be successfully continued. Subsequent infants born to the mother will also need zinc supplementation if breastfed. Zinc is relatively nontoxic. Excess intake produces nausea, emesis, abdominal pain, headache, vertigo, and seizures.


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Pediatrics_Nelson. Dental enamel is strengthened when fluoride is substituted for hydroxyl ions in the hydroxyapatite crystalline mineral matrix of the enamel. The resulting fluoroapatite is more resistant to chemical and physical damage. Fluoride is incorporated into the enamel during the mineralization stages of tooth formation and by surface interaction after the tooth has erupted. Fluoride is similarly incorporated into bone mineral and may protect against osteoporosis later in life. Because of concern about the risk of fluorosis, infants should not receive fluoride supplements before 6 months of age. Commercial formulas are made with defluoridated water and contain small amounts of fluoride. The fluoride content of human milk is low and is not influenced significantly by maternal intake. Practitioners should evaluate all potential fluoride sources and conduct a caries risk assessment before prescribing fluoride supplementation.


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Pediatrics_Nelson. Kliegman RM, Stanton B, St. Geme J, et al: Nelson textbook of pediatrics, ed 19, Philadelphia, 2011, Saunders. Chap. 41–51 Eidelman AI, Schanler RJ: American Academy of Pediatrics Section on Breastfeeding. Breastfeeding and the Use of Human Milk, Pediatrics 129(3):827–841, 2012 Centers for Disease Control and Prevention: Racial and ethnic differences in breastfeeding initiation and duration, by state National Immuniza tion Survey, United States, 2004–2008, MMWR Morb Mortal Wkly Rep 59(11):327–334, 2010 http://www.nal.usda.gov http://www.choosemyplate.gov www.pediatrics.org/cgi/content/full/102/3/e38 Gribble JN, Murray NJ, Menotti EP: Reconsidering childhood undernutri tion: can birth spacing make a difference? An analysis of the 2002–2003 El Salvador National Family Health Survey, Matern Child Nutr 5:49–63, 2009 Boschert S, Robinson T: Fight obesity with specific, countable goals, Pediatric News 1, Oct 2012


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Pediatrics_Nelson. Salvador National Family Health Survey, Matern Child Nutr 5:49–63, 2009 Boschert S, Robinson T: Fight obesity with specific, countable goals, Pediatric News 1, Oct 2012 Grover Z, Ee LC: Protein energy malnutrition, Pediatr Clin North Am 56:1055–1068, 2009 Krebs NF, Hambidge KM: Trace elements. In Duggan C, Watkins JB, Walker WA, editors: Nutrition in pediatrics: basic science and clinical applications, ed 4, Hamilton, Ontario, 2008, BC Decker, pp 67–82 Penny ME: Protein-energy malnutrition: pathophysiology, clinical conse quences, and treatment. In Duggan C, Watkins JB, Walker WA, editors: Nutrition in pediatrics: basic science and clinical applications, ed 4, Hamil ton, Ontario, 2008, BC Decker, pp 127–142 Wagner CL, Greer FR: Section on Breastfeeding and Committee on Nutrition, American Academy of Pediatrics: Prevention of rickets and vitamin D defi ciency: new guidelines for vitamin D intake, Pediatrics 122:1142–1152, 2008 Larry A. Greenbaum and Raed Bou-Matar 7


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Pediatrics_Nelson. American Academy of Pediatrics: Prevention of rickets and vitamin D defi ciency: new guidelines for vitamin D intake, Pediatrics 122:1142–1152, 2008 Larry A. Greenbaum and Raed Bou-Matar 7 Water is the most plentiful constituent of the human body. Total body water (TBW) as a percentage of body weight varies with age. The fetus has a high TBW, which gradually decreases to about 75% of birth weight for a term infant. Premature infants have a higher TBW content than term infants. During the first year of life, TBW decreases to about 60% of body weight and basically remains at this level until puberty. At puberty, the fat content of females increases more than that of males, who acquire more muscle mass than females. Because fat has low water content, and muscle has high water content, by the end of puberty TBW in males remains at 60%, but it decreases to 50% of body weight in females. During dehydration, TBW decreases and is a smaller percentage of body weight.


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Pediatrics_Nelson. TBW has two main compartments: intracellular fluid (ICF) and extracellular fluid (ECF). In the fetus and newborn, the ECF volume is larger than the ICF volume. The normal postnatal diuresis causes an immediate decrease in the ECF volume. This decrease in ECF volume is followed by continued expansion of the ICF volume because of cellular growth. By 1 year of age, the ratio of the ICF volume to the ECF volume approaches adult levels. The ECF volume is 20% to 25% of body weight, and the ICF volume is 30% to 40% of body weight (Fig. 32-1). With puberty, the increased muscle mass of males results in a higher ICF volume than in females.


Pediatrics_Nelson

Pediatrics_Nelson. The ECF is divided further into plasma water and interstitial fluid (see Fig. 32-1). Plasma water is about 5% of body weight. The blood volume, given a hematocrit of 40%, is usually 8% of body weight, although it is higher in newborns and young infants. The interstitial fluid, normally 15% of body weight, can increase dramatically in diseases associated with edema, such as heart failure, protein-losing enteropathy, liver failure, and nephrotic syndrome.


Pediatrics_Nelson

Pediatrics_Nelson. The composition of solutes in the ICF and ECF is different.Sodium and chloride are the dominant cation and anion in the ECF. Potassium is the most abundant cation in the ICF, and proteins, organic anions, and phosphate are the most plentiful anions in the ICF. The dissimilarity between theanions in the ICF and the ECF is determined largely by thepresence of intracellular molecules that do not cross the cellmembrane, the barrier separating the ECF and the ICF. Incontrast, the difference in the distribution of cations—sodium and potassium—is due to the activity of the Na+,K+-ATPase pump, which extrudes sodium from cells in exchange forpotassium.


Pediatrics_Nelson

Pediatrics_Nelson. Proper cell functioning requires close regulation of plasma osmolality and intravascular volume; these are controlled by independent systems for water balance, which determines osmolality, and sodium balance, which determines volume status. Maintenance of a normal osmolality depends on control of water balance. Control of volume status depends on regulation of sodium balance.


Pediatrics_Nelson

Pediatrics_Nelson. The plasma osmolality is tightly controlled between 285 and 295 mOsm/kg through regulation of water intake and urinary water losses. A small increase in the plasma osmolality stimulates thirst. Urinary water losses are regulated by the secretion of antidiuretic hormone (ADH), which increases in response to an increasing plasma osmolality. ADH, by stimulating renal tubular reabsorption of water, decreases urinary water losses. Control of osmolality is subordinate to maintenance of an adequate intravascular volume. When significant volume depletion is present, ADH secretion and thirst are stimulated, regardless of the plasma osmolality.


Pediatrics_Nelson

Pediatrics_Nelson. Volume depletion and volume overload may cause significant morbidity and mortality. Because sodium is the principal extracellular cation and is restricted to the ECF, adequate body sodium is necessary for maintenance of intravascular volume. The kidney determines sodium balance because there is little homeostatic control of sodium intake, although salt craving occasionally occurs, typically in children with chronic renal salt loss. The kidney regulates sodium balance by altering the percentage of filtered sodium that is reabsorbed along the nephron. The renin-angiotensin system is an important regulator of renal sodium reabsorption and excretion. The juxtaglomerular apparatus produces renin in response to decreased effective intravascular volume. Renin cleaves angiotensinogen, producing angiotensin I, which angiotensin-converting enzyme converts into angiotensin II. The actions of angiotensin


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Pediatrics_Nelson. Figure 32-1 Compartments of total body water, expressed as percentage of body weight, in an older child or adult. (From Greenbaum LA: Pathophysiology of body fluids and fluid therapy. In Kliegman RM, Stanton, BF, St Geme JW, et al, editors: Nelson Textbook of Pediatrics, 19th ed. Philadelphia, 2011, Saunders, p 212.e1.) II include direct stimulation of the proximal tubule to increase sodium reabsorption and stimulation of the adrenal gland to increase aldosterone secretion, which increases sodium reabsorption in the distal nephron. In contrast, volume expansion stimulates the synthesis of atrial natriuretic peptide, which increases urinary sodium excretion.


Pediatrics_Nelson

Pediatrics_Nelson. Maintenance intravenous (IV) fluids are used in children whocannot be fed enterally. Along with maintenance fluids, childrenmay require concurrent replacement fluids if they have excessive ongoing losses, such as may occur with drainage from a nasogastric tube. In addition, if dehydration is present, the patient alsoneeds to receive deficit replacement (see Chapter 33). Maintenance fluids are composed of a solution of water, glucose, sodium, potassium, and chloride. This solution replaces electrolyte losses from the urine and stool, as well as water losses from the urine, stool, skin, and lungs. The glucose in maintenance fluids provides approximately 20% of the normal caloric needs of the patient. This percentage is enough to prevent the development of starvation ketoacidosis and diminishes the protein degradation that would occur if the patient received no calories.


Pediatrics_Nelson

Pediatrics_Nelson. Maintenance fluids do not provide adequate calories, protein, fat, minerals, or vitamins. Patients should not remain on *The maximum total fluid per day is normally 2400 mL. †The maximum fluid rate is normally 100 mL/hr. maintenance therapy indefinitely; parenteral nutrition (see Chapter 34) should be used for children who cannot be fed enterally for more than a few days. Daily water losses are measurable (urine and stool) and not measurable (insensible losses from the skin and lungs). Failure to replace these losses leads to a thirsty child and, ultimately, a dehydrated child. Table 32-1 provides a system for calculating 24-hour maintenance water needs based on the patient’s weight. Sodium and potassium are given in maintenance fluids to replace losses from urine and stool.


Pediatrics_Nelson

Pediatrics_Nelson. After calculation of water needs and electrolyte needs,children typically receive either 5% dextrose (D5) in ¼ normal saline (NS) plus 20 mEq/L of potassium chloride (KCl)or D5 in ½ NS plus 20 mEq/L of KCl. Children weighing lessthan 10 kg do best with the solution containing ¼ NS (38.5 mEq/L) because of their high water needs per kilogram. In contrast, larger children and adults may receive the solutionwith ½ NS (77 mEq/L). These guidelines assume that thereis no disease process present that would require an adjustment in either the volume or the electrolyte composition ofmaintenance fluids. Children with renal insufficiency maybe hyperkalemic or unable to excrete potassium and maynot tolerate 20 mEq/L of KCl. In children with complicatedpathophysiologic derangements, it may be necessary toadjust the electrolyte composition and rate of maintenancefluids empirically based on electrolyte measurements andassessment of fluid balance.


Pediatrics_Nelson

Pediatrics_Nelson. There are three sources of normal water loss—the components of maintenance water (see Chapter 32): urine (60%), insensible losses from the skin and lungs (35%), and stool (5%) (Table 33-1). Sweating is not insensible and, in contrast to evaporative losses, sweat contains water and electrolytes. A variety of clinical situations modify normal maintenance water balance (Table 33-2). Evaporative skin water losses can be higher in neonates, especially premature infants who are under radiant warmers or undergoing phototherapy. Burns can result in massive losses of water and electrolytes (see Chapter 44). Fever increases insensible losses. Tachypnea or a tracheostomy increases evaporative losses from the lungs. The gastrointestinal tract is potentially a source of considerable water and electrolyte losses. A child who has large amounts of gastrointestinal losses should have these losses measured and replaced with an appropriate replacement solution (Table 33-3).


Pediatrics_Nelson

Pediatrics_Nelson. Urine output is normally the largest cause of water loss. Diseases such as renal failure and the syndrome of inappropriate antidiuretic hormone (SIADH) can lead to a decrease in urine volume. Maintenance fluids in a patient with oliguria or anuria produce fluid overload. In contrast, other conditions produce an increase in urine volume; these include the polyuric phase of acute tubular necrosis, diabetes mellitus, and diabetes insipidus. When the urine output is excessive, the patient must receive more than standard maintenance fluids to prevent dehydration.


Pediatrics_Nelson

Pediatrics_Nelson. The approach to decreased or increased urine output is similar (Table 33-4). Insensible losses are replaced by a solution that is administered at a rate one third of the normal maintenance rate. Placing the anuric child on “insensibles” theoretically maintains an even fluid balance, with the caveat that one third of maintenance fluid is only an estimate of insensible losses. This rate may need to be adjusted based on monitoring of the patient’s weight and hydration status. An oliguric child needs to receive a urine replacement solution. Most children with polyuria (except for children with diabetes mellitus [see Chapter 171]) should be placed on insensible fluids plus urine replacement. Sodium: 55 mEq/L Solution: 5% dextrose in ¼ normal saline + 20 mEq/L sodium bicarbonate + 20 mEq/L potassium chloride Replace stool mL/mL every 1–6 hr Potassium: 25 mEq/L Bicarbonate: 15 mEq/L Sodium: 60 mEq/L Solution: normal saline + 10 mEq/L potassium chloride Replace output mL/mL every 1–6 hr


Pediatrics_Nelson

Pediatrics_Nelson. Potassium: 25 mEq/L Bicarbonate: 15 mEq/L Sodium: 60 mEq/L Solution: normal saline + 10 mEq/L potassium chloride Replace output mL/mL every 1–6 hr Potassium: 10 mEq/L Chloride: 90 mEq/L Place the patient on insensible Place the patient on insensible fluids (⅓ maintenance) fluids (⅓ maintenance) Replace urine output mL/mL Measure urine electrolytes with half normal saline Replace urine output mL/mL with a solution that is based on the measured urine electrolytes


Pediatrics_Nelson

Pediatrics_Nelson. Replace urine output mL/mL with a solution that is based on the measured urine electrolytes Output from surgical drains and chest tubes, when significant, should be measured and replaced. Third space lossesmanifest with edema and ascites and are due to a shift of fluid from the intravascular space into the interstitial space. Thirdspace losses cannot be quantitated. Nonetheless, these lossescan be large and lead to intravascular volume depletion, despiteweight gain from edema or ascites. Replacement of third spacefluid is empirical but should be anticipated in patients who areat risk, such as children who have burns or abdominal surgery.Third space losses and chest tube output are isotonic and usually require replacement with an isotonic fluid, such as normal saline or Ringer’s lactate. Adjustments in the amount ofreplacement fluid for third space losses are based on continuing assessment of the patient’s intravascular volume status.


Pediatrics_Nelson

Pediatrics_Nelson. Dehydration, most often due to gastroenteritis, is common in children. The first step in caring for a dehydrated child is to assess the degree of dehydration. The degree of dehydration dictates the urgency of the situation and the volume of fluid needed for rehydration. Table 33-5 summarizes the clinical features that are present with varying degrees of dehydration. A patient with mild dehydration has few clinical signs or symptoms. The history may describe decreased intake but Infants and young children Thirsty, alert; restless Thirsty; restless or lethargic; Drowsy; limp, cold, sweaty, cyanotic extremities; may irritable be comatose Older children Thirsty, alert Thirsty, alert (usually) Usually conscious (but at reduced level), apprehensive; cold, sweaty, cyanotic extremities; wrinkled skin on fingers and toes; muscle cramps Respirations Normal Deep, may be rapid Deep and rapid Data from World Health Organization.


Pediatrics_Nelson

Pediatrics_Nelson. Respirations Normal Deep, may be rapid Deep and rapid Data from World Health Organization. more often increased fluid losses. An infant with moderate dehydration has demonstrable physical signs and symptoms. The patient needs fairly prompt intervention. A patient with severe dehydration is gravely ill. The decrease in blood pressure indicates that vital organs may be receiving inadequate perfusion (shock) (see Chapter 40). Such a patient should receive immediate and aggressive intravenous (IV) therapy. Clinical assessment of dehydration is only an estimate; the patient must be continually re-evaluated during therapy. The degree of dehydration is underestimated in hypernatremic dehydration because the osmotically driven shift of water from the intracellular space to the extracellular space helps to preserve the intravascular volume.


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Pediatrics_Nelson. Serum blood urea nitrogen (BUN) and creatinine concentrations are useful in assessing a child with dehydration. Volume depletion without renal insufficiency may cause a disproportionate increase in the BUN, with little or no change in the creatinine concentration. This is secondary to increased passive reabsorption of urea in the proximal tubule caused by appropriate renal conservation of sodium and water. This increase in the BUN may be absent or blunted in a child with poor protein intake because urea production depends on protein degradation. Conversely, the BUN may be disproportionately increased in a child with increased urea production, as occurs in a child with a gastrointestinal bleed or a child who is receiving glucocorticoids. A significant elevation of the creatinine concentration suggests renal injury. The urine specific gravity is usually elevated (≥1.025) incases of significant dehydration but decreases after rehydration.


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Pediatrics_Nelson. The urine specific gravity is usually elevated (≥1.025) incases of significant dehydration but decreases after rehydration. With dehydration, a urinalysis may show hyaline and granularcasts, a few white blood cells and red blood cells, and 30 to 100 mg/dL of proteinuria. These findings usually are not associatedwith significant renal pathology, and they remit with therapy.Hemoconcentration from dehydration causes an increase inthe hematocrit and hemoglobin. Calculation of Fluid Deficit A child with dehydration has lost water; there is usually a concurrent loss of sodium and potassium. The fluid deficit is the percentage of dehydration multiplied by the patient’s weight (for a 10-kg child, 10% of 10 kg =1 L deficit). Approach to Dehydration


Pediatrics_Nelson

Pediatrics_Nelson. Approach to Dehydration The child with dehydration requires acute intervention to ensure that there is adequate tissue perfusion (see Chapter 40). This resuscitation phase requires rapid restoration of the circulating intravascular volume, which should be done with an isotonic solution, such as normal saline (NS) or Ringer’s lactate. Blood is an appropriate fluid choice for a child with acute blood loss. The child is given a fluid bolus, usually 20 mL/kg of the isotonic solution, over about 20 minutes. A child with severe dehydration may require multiple fluid boluses and may need to receive fluid at a faster rate. The initial resuscitation and rehydration is complete when signs of intravascular volume depletion resolve. The child typically becomes more alert and has a lower heart rate, normal blood pressure, and improved perfusion. With adequate intravascular volume, it is now appropriate to plan the fluid therapy for the next 24 hours (Table 33-6). To


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Pediatrics_Nelson. With adequate intravascular volume, it is now appropriate to plan the fluid therapy for the next 24 hours (Table 33-6). To Restore intravascular volume Normal saline: 20 mL/kg over 20 minutes Repeat as needed Rapid volume repletion: 20 mL/kg normal saline (maximum = 1 L) over 2 hours Calculate 24-hour fluid needs: maintenance + deficit volume Subtract isotonic fluid already administered from 24-hour fluid needs


Pediatrics_Nelson

Pediatrics_Nelson. Calculate 24-hour fluid needs: maintenance + deficit volume Subtract isotonic fluid already administered from 24-hour fluid needs Administer remaining volume over 24 hours using D5 ½ normal saline + 20 mEq/L KCl Replace ongoing losses as they occur ensure that the intravascular volume is restored, the patient receives an additional 20 mL/kg bolus of isotonic fluid over 2 hours. The child’s total fluid needs are added together (maintenance + deficit). The volume of isotonic fluids the patient has received as acute resuscitation is subtracted from this total. The remaining fluid volume is then administered over 24 hours. Potassium usually is not included in the IV fluids until the patient voids, unless significant hypokalemia is present. Children with significant ongoing losses need to receive an appropriate replacement solution. Available @ StudentConsult.com


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Pediatrics_Nelson. Available @ StudentConsult.com All calculations in fluid therapy are only approximations. Thus,the patient needs to be monitored during treatment with therapymodifications based on the clinical situation (Table 33-7). Hyponatremic dehydration occurs in children who have diarrhea and consume a hypotonic fluid (water or diluted formula). Volume depletion stimulates secretion of antidiuretic hormone, preventing the water excretion that should correct the hyponatremia. Some patients develop symptoms, predominantly neurologic, from the hyponatremia (see Chapter 35). Most patients with hyponatremic dehydration do well with the same general approach outlined in Table 33-6. Overly rapid correction of hyponatremia (>12 mEq/L/24 hr) should be avoided because of the remote risk of central pontine myelinolysis.


Pediatrics_Nelson

Pediatrics_Nelson. Hypernatremic dehydration is usually a consequenceof an inability to take in fluid, because of a lack of access, apoor thirst mechanism (neurologic impairment), intractableemesis, or anorexia. The movement of water from the intracellular space to the extracellular space during hypernatremic dehydration partially protects the intravascular volume.Urine output may be preserved longer, and there may be lesstachycardia. Children with hypernatremic dehydration areoften lethargic and irritable. Hypernatremia may cause fever, Clinical signs of depletion or overload Electrolytes hypertonicity, hyperreflexia, and seizures. More severe neurologic symptoms may develop if cerebral bleeding or thrombosis occurs.


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Pediatrics_Nelson. Overly rapid treatment of hypernatremic dehydration maycause significant morbidity and mortality. Idiogenic osmolesare generated within the brain during the development ofhypernatremia. Idiogenic osmoles increase the osmolalitywithin the cells of the brain, providing protection againstbrain cell shrinkage secondary to movement of water out of cells into the hypertonic extracellular fluid. These idiogenicosmoles dissipate slowly during correction of hypernatremia.With rapid lowering of the extracellular osmolality duringcorrection of hypernatremia, a new gradient may be createdthat causes water movement from the extracellular spaceinto the cells of the brain, producing cerebral edema. Possible manifestations of the resultant cerebral edema include altered mental status, seizures, and potentially lethal brainherniation.


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Pediatrics_Nelson. To minimize the risk of cerebral edema during correctionof hypernatremic dehydration, the serum sodium concentration should not decrease more than 12 mEq/L every 24 hours(Figure 33-1). The deficits in severe hypernatremic dehydration may need to be corrected over 2 to 4 days. The choice andrate of fluid are not nearly as important as vigilant monitoring of the serum sodium concentration and adjustment of thetherapy based on the result (see Figure 33-1). Nonetheless, theinitial resuscitation-rehydration phase of therapy remains thesame as for other types of dehydration.


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Pediatrics_Nelson. Mild to moderate dehydration from diarrhea of any cause canbe treated effectively using a simple, oral rehydration solution (ORS) containing glucose and electrolytes (see Chapter112). The ORS relies on the coupled transport of sodium andglucose in the intestine. Oral rehydration therapy has significantly reduced the morbidity and mortality from acute diarrhea but is underused in developed countries. It should beattempted for most patients with mild to moderate diarrhealdehydration. Oral rehydration therapy is less expensive thanIV therapy and has a lower complication rate. IV therapymay still be required for patients with severe dehydration;patients with uncontrollable vomiting; patients unable todrink because of extreme fatigue, stupor, or coma; or patients with gastric or intestinal distention. Rapidly absorbed ondansetron may be used to treat vomiting, thus facilitating oralrehydration.


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Pediatrics_Nelson. Restore intravascular volume: Normal saline: 20 mL/kg over 20 min (repeat until intravascular volume restored) Determine time for correction based on initial sodium concentration [Na] 145–157 mEq/L: 24hr [Na] 158–170 mEq/L: 48hr [Na] 171–183 mEq/L: 72hr [Na] 184–196 mEq/L: 84hr Administer fluid at a constant rate over the time for correction Typical fluid: D5 1/2 normal saline (with 20 mEq/L KCI unless contraindicated) Typical rate: 1.25–1.5 times maintenance Follow serum sodium concentration and adjust fluid based on clinical status and serum sodium concentration Signs of volume depletion Sodium decreases too rapidly Sodium decreases too slowly Replace excessive ongoing losses as they occur Decrease sodium concentration of IV fluid or increase rate of IV fluid Increase sodium concentration of IV fluid or decrease rate of IV fluid Administer normal saline (20 mL/kg) Figure 33-1 Strategy for correcting hypernatremic dehydration.


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Pediatrics_Nelson. Figure 33-1 Strategy for correcting hypernatremic dehydration. As a guideline for oral rehydration, 50 mL/kg of the ORSshould be given within 4 hours to patients with mild dehydration, and 100 mL/kg should be given over 4 hours to patientswith moderate dehydration. Supplementary ORS is given toreplace ongoing losses from diarrhea or emesis. An additional 10 mL/kg of ORS is given for each stool. Fluid intakeshould be decreased if the patient appears fully hydrated earlier than expected or develops periorbital edema. After rehydration, patients should resume their usual diet (breast milk,formula).


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Pediatrics_Nelson. When rehydration is complete, maintenance therapy should be started, using 100 mL of ORS/kg in 24 hours until the diarrhea stops. Breastfeeding or formula feeding should be maintained and not delayed for more than 24 hours. Patients with more severe diarrhea require continued supervision. The volume of ORS ingested should equal the volume of stool losses. If stool volume cannot be measured, an intake of 10 to 15 mL of ORS/kg/hr is appropriate. Parenteral nutrition (PN) is necessary when enteral feeding is inadequate to meet the nutritional needs of a patient. Enteral nutrition is always preferred because it is more physiologic, less expensive, and associated with fewer complications. Fewer complications are expected if at least some nutrition can be provided enterally.


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Pediatrics_Nelson. A variety of clinical situations necessitate PN (Table 34-1).Acute PN is frequently given in an intensive care unit when there is poor tolerance of enteral feeds, potentially secondary to a transient ileus; concerns regarding bowel ischemia; or the risk of aspiration pneumonia. Short bowel syndrome is the most common indication for long-term PN; it may be caused by a congenital gastrointestinal anomaly or acquired after necrotizing enterocolitis (see Chapter 63). Some patients with a chronic indication for PN eventually may be transitioned to partial or full enteral feedings. PN can be given via either a peripheral intravenous (IV) line or a central venous line. Long-term PN should be given via a central venous line (CVL). Acute PN may be given peripherally, although a temporary CVL often is used. Most children with cancer or receiving a bone marrow transplant have a


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Pediatrics_Nelson. CVL. A peripherally inserted central catheter is an excellent source of central access for acute PN because of the lower risk for complications than with a standard CVL.


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Pediatrics_Nelson. A peripheral IV line has two major limitations. First, it frequently fails, necessitating interruption of PN and potentiallypainful placement of a new line. Second, high-osmolality solutions cause phlebitis of peripheral veins; this limits the dextroseand amino acid content of peripheral PN. The dextrose contentof peripheral PN cannot be greater than 12%, with a lower limitif the amino acid concentration is high. Lipid emulsion has a low osmolality; therefore, it can be administered peripherallyvia the same IV line as the dextrose and amino acid solution. Patients can receive adequate nutrition via a peripheral IV line,but the volume of PN needs to be higher than is necessary whencentral access is available because of the limitations on dextrose and amino acid concentration. This situation may be problematic in patients who cannot tolerate larger fluid volumes.


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Pediatrics_Nelson. PN can provide calories, amino acids, electrolytes, minerals, essential fatty acids, vitamins, iron, and trace elements. The calories in PN are from dextrose and fat. The amino acids in PN are a potential source of calories, but they should be used predominantly for protein synthesis. PN is given as two separate solutions: a dextrose plus amino acid solution and a 20% lipid emulsion. The dextrose solution has all of the other components of PN except for fat. The dextrose concentration of peripheral PN is typically 10% to 12%, whereas central PN has a concentration of about 20%, although it may be increased to 25% to 30% in patients who are fluid restricted. To avoid hyperglycemia, the dextrose delivery is increased gradually when starting PN. Protein delivery in PN is via amino acids in the dextrose solution. The goal is 0.8 to 2 g protein/kg/24 hr for older children, 1.5 to 3 g/kg/24 hr for full-term and older infants, and 2.5 to 3.5 g/kg/24 hr for preterm infants.


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Pediatrics_Nelson. The electrolyte and mineral composition of PN depends onthe age and the underlying illness. The 20% lipid emulsion provides essential fatty acids and calories. The lipid emulsion isstarted at a rate of 0.5 to 1 g/kg/24 hr, gradually increasing therate so that the patient receives adequate calories; this typicallyrequires 2.5 to 3.5 g/kg/24 hr. The lipid emulsion usually provides 30% to 40% of the required calories; it should not exceed60%. The serum triglyceride concentration is monitored as therate of lipid emulsion is increased, with reduction of the lipidemulsion rate if significant hypertriglyceridemia develops.


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Pediatrics_Nelson. There are many potential complications of PN. CVLs are associated with complications during insertion (pneumothorax or bleeding) and long-term issues (thrombosis). Catheter-related sepsis, most commonly due to coagulase-negative staphylococci, is common and, on occasion, necessitates catheter removal. Other potential pathogens are Staphylococcus aureus, gram-negative bacilli, and fungi. Electrolyte abnormalities, nutritional deficiencies, hyperglycemia, and complications from excessive protein intake (azotemia or hyperammonemia) can be detected with careful monitoring. The most concerning complication of long-term PN is cholestatic liver disease, which can lead to cirrhosis and liver failure. Current PN decreases the risk of liver disease by including reduced amounts of hepatotoxic amino acids. The best preventive strategy is early use of the gastrointestinal tract, even if only trophic feeds are tolerated.


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Pediatrics_Nelson. The kidney regulates sodium balance and is the principal site of sodium excretion. Sodium is unique among electrolytes because water balance, not sodium balance, usually determines its concentration. When the sodium concentration increases, the resultant higher plasma osmolality causes increased thirst and increased secretion of antidiuretic hormone (ADH), which leads to renal conservation of water. Both of these mechanisms increase the water content of the body, and the sodium concentration returns to normal. During hyponatremia, the fall in plasma osmolality decreases ADH secretion, and consequent renal water excretion leads to an increase in the sodium concentration. Although water balance usually is regulated by osmolality, volume depletion stimulates thirst, ADH secretion, and renal conservation of water. In fact, volume depletion takes precedence over osmolality; volume depletion stimulates ADH secretion, even if a patient has hyponatremia.


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Pediatrics_Nelson. The excretion of sodium by the kidney is not determined by the plasma osmolality. The patient’s effective plasma volume regulates the amount of sodium in the urine through a variety of regulatory systems, including the renin-angiotensinaldosterone system. In hyponatremia or hypernatremia, the underlying pathophysiology determines the urinary sodium concentration, not the serum sodium concentration. Available @ StudentConsult.com


Pediatrics_Nelson

Pediatrics_Nelson. Different mechanisms can cause hyponatremia (Fig. 35-1).Pseudohyponatremia is a laboratory artifact that is present when the plasma contains high concentrations of protein or lipid. It does not occur when a direct ion-selective electrode determines the sodium concentration, a technique that is increasingly used in clinical laboratories. In true hyponatremia, the measured osmolality is low, whereas it is normal in pseudohyponatremia. Hyperosmolality, resulting from mannitol infusion or hyperglycemia, causes a low serum sodium concentration because water moves down its osmotic gradient from the intracellular space into the extracellular space, diluting the sodium concentration. For every 100 mg/dL increment of the serum glucose, the serum sodium decreases by 1.6 mEq/L. Because the manifestations of hyponatremia are due to the low plasma osmolality, patients with hyponatremia caused by hyperosmolality do not have symptoms of hyponatremia and do not require correction of hyponatremia.


Pediatrics_Nelson

Pediatrics_Nelson. Classification of true hyponatremia is based on the patient’svolume status (see Fig. 35-1). In hypovolemic hyponatremia, the child has lost sodium from the body. Water balancemay be positive or negative, but there has been a higher netsodium loss than water loss; this is often due to oral or intravenous (IV) water intake, with water retention by the kidneys to compensate for the intravascular volume depletion. Ifthe sodium loss is due to a nonrenal disease (e.g., diarrhea),the urine sodium concentration is very low, as the kidneysattempt to preserve the intravascular volume by conservingsodium. In renal diseases, the urine sodium is inappropriately elevated.


Pediatrics_Nelson

Pediatrics_Nelson. Patients with hyponatremia and no evidence of volumeoverload or volume depletion have euvolemic hyponatremia. These patients typically have an excess of total bodywater and a slight decrease in total body sodium. Some ofthese patients have an increase in weight, implying that theyare volume overloaded. Nevertheless, they usually appearnormal or have only subtle signs of fluid overload. In syndrome of inappropriate ADH (SIADH), there is secretion of ADH that is not inhibited by either low serum osmolality or expanded intravascular volume. Retention of watercauses hyponatremia, and the expansion of the intravascular volume results in an increase in renal sodium excretion. Hyponatremia in hospitalized patients is often due to SIADHsecondary to stress in the presence of hypotonic fluids. SIADH (emesis, diarrhea) Glucocorticoid deficiency Nephrotic syndrome Skin (sweating or burns) Capillary leak


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Pediatrics_Nelson. SIADH (emesis, diarrhea) Glucocorticoid deficiency Nephrotic syndrome Skin (sweating or burns) Capillary leak Urine Na+ variable Thiazide or loop diuretics Acute or chronic renal failure Osmotic diuresis Postobstructive diuresis Polyuric phase of ATN Renal tubular damage (e.g., obstructive uropathy) Figure 35-1 Differential diagnosis of hyponatremia. Assessment of hyponatremia is a three-step process: (1) Determine if the osmolality is low; if yes, the patient has true hyponatremia. (2) Evaluate the patient’s volume status. (3) Determine the urine sodium concentration to help narrow the differential diagnosis. ATN, Acute tubular necrosis; SIADH, syndrome of inappropriate secretion of antidiuretic hormone.


Pediatrics_Nelson

Pediatrics_Nelson. SIADH is also associated with pneumonia, mechanical ventilation, meningitis, and other central nervous system disorders (trauma). Ectopic (tumor) production of ADH is rarein children. Infants can develop euvolemic hyponatremia asa result of excessive water consumption or inappropriatelydiluted formula.


Pediatrics_Nelson

Pediatrics_Nelson. In hypervolemic hyponatremia, there is an excess of total body water and sodium, although the increase in water isgreater than the increase in sodium. In renal failure, there isan inability to excrete sodium or water; the urine sodium maybe low or high, depending on the cause of the renal insufficiency. In other causes of hypervolemic hyponatremia, there is a decrease in the effective blood volume because of either third space fluid loss or poor cardiac output (see Chapter145). In response to the low effective blood volume, ADHcauses renal water retention, and the kidneys also retainsodium, leading to a low urine sodium concentration. Thepatient’s serum sodium concentration decreases when waterintake exceeds sodium intake, and ADH prevents the normalloss of excess water.


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Pediatrics_Nelson. Hyponatremia causes a fall in the osmolality of the extracellular space. Because the intracellular space then has a higher osmolality, water moves from the extracellular space to the intracellular space to maintain osmotic equilibrium. The increase in intracellular water may cause cells to swell. Brain cell swelling is responsible for most of the symptoms of hyponatremia. Neurologic symptoms of hyponatremia include anorexia, nausea, emesis, malaise, lethargy, confusion, agitation, headache, seizures, coma, and decreased reflexes. Patients may develop hypothermia and Cheyne-Stokes respirations. Hyponatremia can cause muscle cramps and weakness. Symptoms are more severe when hyponatremia develops rapidly; chronic hyponatremia can be asymptomatic because of a compensatory decrease in brain cell osmolality, which limits cerebral swelling.


Pediatrics_Nelson

Pediatrics_Nelson. Rapid correction of hyponatremia can produce central pontine myelinolysis. Avoiding more than a 12-mEq/L increase in the serum sodium every 24 hours is prudent, especially in chronic hyponatremia. Treatment of hypovolemic hyponatremia requires administration of IV fluids with sodium to provide maintenance requirements and deficit correction, as well as to replace ongoing losses (see Chapter 33). For children with SIADH, water restriction is the cornerstone of therapy. Children with hyponatremia secondary to hypothyroidism or cortisol deficiency need specific hormone replacement. Acute water intoxication rapidly self-corrects with transient restriction of water intake, which is followed by introduction of a normal diet. Treatment of hypervolemic hyponatremia centers on restriction of water and sodium intake, but disease-specific measures, such as dialysis in renal failure, also may be necessary.


Pediatrics_Nelson

Pediatrics_Nelson. Emergency treatment of symptomatic hyponatremia, such as seizures, uses IV hypertonic saline to increase the serum sodium concentration rapidly, which leads to a decrease in brain edema. One milliliter per kilogram of 3% sodium chloride increases the serum sodium by approximately 1 mEq/L. A child often improves after receiving 4 to 6 mL/kg of 3% sodium chloride. Available @ StudentConsult.com There are three basic mechanisms of hypernatremia (Fig. 35-2). Sodium intoxication is frequently iatrogenic in a hospital setting resulting from correction of metabolic acidosis with sodium bicarbonate. In hyperaldosteronism, there is renal retention of sodium and resultant hypertension; the hypernatremia is mild.


Pediatrics_Nelson

Pediatrics_Nelson. Hypernatremia resulting from water losses develops only if the patient does not have access to water or cannot drink adequately because of neurologic impairment, emesis, or anorexia. Infants are at high risk because of their inability to control their own water intake. Ineffective breastfeeding, often in a primiparous mother, can cause severe hypernatremic dehydration. High insensible losses of water are especially common in premature infants; the losses increase further as a result of radiant warmers or phototherapy for hyperbilirubinemia. Children with extrarenal causes of water loss have high levels of ADH and very concentrated urine.


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Pediatrics_Nelson. Children with diabetes insipidus have inappropriately diluted urine. Hereditary nephrogenic diabetes insipiduscauses massive urinary water losses. Because it is most commonly an X-linked disorder due to a mutation in the gene for the ADH receptor, it usually occurs in boys, who may have episodes of severe hypernatremic dehydration and failure to thrive. Acquired nephrogenic diabetes insipidus may be secondary to interstitial nephritis, sickle cell disease, hypercalcemia, hypokalemia, or medications (lithium or amphotericin). If the defect is due to central diabetes insipidus, urine output decreases and urine osmolality increases in response to administration of an ADH analog. Central causes of ADH deficiency include tumor, infarction, or trauma. There is no response to an ADH analog in a child with nephrogenic diabetes insipidus.


Pediatrics_Nelson

Pediatrics_Nelson. Diarrhea results in sodium and water depletion. Most children with gastroenteritis do not develop hypernatremia because they drink enough hypotonic fluid to compensate at least partially for stool water losses. Hypernatremia is most likely in a child with diarrhea who has inadequate intake because of emesis, lack of access to water, or anorexia. Some renal diseases, including obstructive uropathy, renal dysplasia, and juvenile nephronophthisis, can cause losses of sodium and water, potentially producing hypernatremia if the patient consumes insufficient water.