Obstentrics_Williams

Obstentrics_Williams. Studies that have attempted to correlate fetal heart rate patterns with brain injury primarily have examined infants identiied in medicolegal actions. Phelan and Ahn (1994) reported that among 48 fetuses later found to be neurologically impaired, a persistent nonreactive fetal heart rate tracing was already present at the time of admission in 70 percent. They concluded that fetal neurological injury occurred predominately before arrival to the hospital. When they looked retrospectively at heart rate patterns in 209 brain-injured newborns, they concluded that there was not a single unique pattern associated with fetal neurological injury (Ahn, 1996). Graham and associates (2006) reviewed the world literature published between 1966 and 2006 on the efect of fetal heart rate monitoring to prevent perinatal brain injury and found no beneit.


Obstentrics_Williams

Obstentrics_Williams. Fetal heart rate patterns necessary for perinatal brain damage have been studied in experimental animals. .1yers (1972) described the efects of complete and partial asphyxia in rhesus monkeys. Complete asphyxia was produced by total occlusion of umbilical blood low that led to prolonged deceleration (Fig. 24-26). Fetal arterial pH did not drop to 7.0 until approximately 8 minutes after complete cessation of oxygenation and umbilical low. At least 10 minutes of such prolonged deceleration was required before there was evidence of brain damage in surviving fetuses. Myers (1972) also produced partial asphyxia in rhesus monkeys by impeding maternal aortic blood flow. This resulted in ...A �EEI0). /0 5 1005 10 Asphyxia (min) 0. .Cordclamp010 120 20 40 0)0 .. :JQ) .0


Obstentrics_Williams

Obstentrics_Williams. .Cordclamp010 120 20 40 0)0 .. :JQ) .0 FIGURE 24-26 Prolonged deceleration in a rhesus monkey shown with blood pressure and biochemical changes during total occlusion of umbilical cord blood flow. (Data from Myers, 1972.) analgesia was used in 55 percent. The length of the second stage, even in those lasting up to 6 hours or more, was not related to neonatal outcome. These results were attributed to careful use of electronic monitoring and scalp pH measurements. These investigators concluded that there is no compelling reason to intervene with a possibly diicult forceps or vacuum extraction because a certain number of hours have elapsed. They observed, however, that after 3 hours in the second stage, delivery by cesarean or other operative method increased progressively. By 5 hours, the prospects for spontaneous delivery in the subse quent hour were only 10 to 15 percent.


Obstentrics_Williams

Obstentrics_Williams. Newer guidelines have been promoted by the Consensus Com mittee (2016) for second-stage labor. These recommend allowing a nullipara to push for at least 3 hours and a multipara to push for at least 2 hours before second-stage labor arrest is diagnosed. One caveat is that maternal and fetal status should be reassuring. These authors provide options to these times before cesarean deliv ery is performed. Namely, longer durations may be appropriate as long as progress is documented. Also, a specific maximal length of undergo operative delivery has not been identiied.


Obstentrics_Williams

Obstentrics_Williams. Intuitively, the goal to lower cesarean delivery rates is best balanced with one to ensure neonatal safety. And, it is problematic that no robust data on neonatal outcomes support the safety of allowing prolonged second-stage labor. Data from many evaluations reveal that serious newborn consequences attend second-stage labors longer than 3 hours (Allen, 2009; Bleich, 2012; Laughon, 2014; Leveno, 2016; Rosenbloom, 2017). Other data, when adjusted for labor variables, show no diference in neonatal complications for these longer second stages (Cheng, 2004; Le Ray, 2009; Rouse, 2009). Grobman and colleagues (2016) have argued that the absolute number of such adverse outcomes is small and "overall outcomes remain good." That said, some of the complications are severe. Thus, to fully ascertain specific efect of these guidelines on morbidity rates, randomized controlled trials are needed.


Obstentrics_Williams

Obstentrics_Williams. It is possible that prolonged first-stage labor presages that with the second stage. Nelson and associates (2013) studied the relationships between the lengths of the irst and second stages of labor in 12,523 nulliparas at term delivered at Parkland Hospital. The second stage signiicantly lengthened concomitantly with increasing irst-stage duration. The 95th percentile was 15.6 and 2.9 hours for the first and second stages, respectively. Women with irst stages lasting longer than 15.6 hours (>95th percetile) had a 16-percent rate of second-stage labor lasting 3 hours (95th percentile). his compared with a 4.5-percent rate of prolonged second stages in women with irst-stage labors lasting <95th percentile.


Obstentrics_Williams

Obstentrics_Williams. With full cervical dilation, most women cannot resist the urge to "bear down" or "push" each time the uterus contracts (Chap. 22, p. 438). The combined force created by contractions of the uterus and abdominal musculature propels the fetus downward. At times, force created by abdominal musculature is compromised suiciently to slow or even prevent spontaneous vaginal delivery. Heavy sedation or regional analgesia may reduce the reflex urge to push and may impair the ability to contract abdominal muscles efectively. In other instances, the inherent urge to push is overridden by the intense pain created by bearing down. Two approaches to second-stage pushing in women with epidural analgesia have yielded contradictory results. The irst advocates pushing forcefully with contractions after complete dilation, regardless of the urge to push. With the second, analgesia inusion is stopped and pushing begins only ater the woman regains the sensory urge to bear down. Fraser and coworkers (2000)


Obstentrics_Williams

Obstentrics_Williams. dilation, regardless of the urge to push. With the second, analgesia inusion is stopped and pushing begins only ater the woman regains the sensory urge to bear down. Fraser and coworkers (2000) found that delayed pushing reduced diicult operative deliveries, whereas Manyonda and associates (1990) reported the opposite. Hansen and colleagues (2002) randomly assigned 252 women with epidural analgesia to one of the two approaches. No adverse maternal or neonatal outcomes were linked to delayed pushing despite signiicantly prolonging second-stage labor. Plunkett and coworkers (2003), in a similar study, confirmed these indings.


Obstentrics_Williams

Obstentrics_Williams. Descent of the leading edge of the presenting part to the level of the ischial spines (0 station) is deined as engagement. A higher station at the onset of labor is signiicantly linked with subsequent dystocia (Friedman, 1965, 1976; Handa, 1993). Roshanfekr and associates (1999) analyzed fetal station in 803 nulliparas at term in active labor. At admission, the third with the fetal head at or below 0 station had a 5-percent cesarean delivery rate. This compared with a 14-percent rate for those with higher stations. The prognosis for dystocia, however, was not related to incrementally higher fetal head stations above the pelvic midplane (0 station). Importantly, 86 percent of nulliparous women without fetal head engagement at diagnosis of active labor delivered vaginally. These observations apply especially for parous women because the head typically descends later in labor.


Obstentrics_Williams

Obstentrics_Williams. Various labor factors have been implicated as causes of uterine dysfunction. As described, neuraxial analgesia can slow labor and has been associated with lengthening both first and second stages of labor and slowing the rate of fetal descent.


Obstentrics_Williams

Obstentrics_Williams. Chorioamnionitis is associated with prolonged labor, and some clinicians have suggested that this maternal intrapartum infection itself contributes to abnormal uterine activity. Satin and coworkers (I992) studied the efects of chorioamnionitis on oxytocin stimulation in 266 pregnancies. Infection diagnosed late in labor was found to be a marker of cesarean delivery performed for dystocia. Speciically, 40 percent of women developing chorioamnionitis after requiring oxytocin for dysfunctional labor later required cesarean delivery for dystocia. However, this was not a marker in women diagnosed as having chorioamnionitis early in labor. It is likely that uterine infection in this clinical setting is a consequence of dysfunctional, prolonged labor rather than a cause of dystocia.


Obstentrics_Williams

Obstentrics_Williams. Membrane rupture at term without spontaneous uterine contractions complicates approximately 8 percent of pregnancies. In the past, labor stimulation was initiated if contractions did not begin ater 6 to 12 hours. Practice-changing research included that of Hannah (1996) and Peleg (1999) and their associates, who enrolled a total of 5042 pregnancies with ruptured membranes in a randomized investigation. They measured the efects of induction versus expectant management and also compared induction using intravenous oxytocin with that using prostaglandin E2 gel. There were approximately 1200 pregnancies in each of the four study arms. They concluded that labor induction with intravenous oxytocin was preferred management. This was based on signiicantly fewer intrapartum and postpartum infections in women whose labor was induced. There were no signiicant differences in cesarean delivery rates. Subsequent analysis by Hannah and coworkers (2000) indicated higher rates of adverse outcomes when


Obstentrics_Williams

Obstentrics_Williams. in women whose labor was induced. There were no signiicant differences in cesarean delivery rates. Subsequent analysis by Hannah and coworkers (2000) indicated higher rates of adverse outcomes when expectant management at home was compared with in-hospital observation. Mozurkewich and associates (2009) reported lower rates of chorioamnionitis, metritis, and neonatal intensive care unit admissions for women with term ruptured membranes whose labors were induced compared with those managed expectantly. At Parkland Hospital, labor is induced soon ater admission when ruptured membranes are confirmed at term. In those with hypotonic contractions or with advanced cervical dilation, oxytocin is selected to lower potential hyperstimulation risk. In those with an unfavorable cervix and no or few contraction, prostaglandin E\ (misoprostol) is chosen to promote cervical ripening and contractions. he beneit of prophylactic antibiotics in women with ruptured membranes before labor at term is


Obstentrics_Williams

Obstentrics_Williams. few contraction, prostaglandin E\ (misoprostol) is chosen to promote cervical ripening and contractions. he beneit of prophylactic antibiotics in women with ruptured membranes before labor at term is unclear (Passos, 2012). However, in those with membranes ruptured longer than 18 hours, antibiotics are instituted for group B streptococcal infection prophylaxis (Chap. 64, p. 1221).


Obstentrics_Williams

Obstentrics_Williams. Labor can be too slow, but it also can be abnormally rapid. Precipitous labor and delivey is extremely rapid labor and delivery. It may result from an abnormally low resistance of the soft parts of the birth canal, from abnormally strong uterine and abdominal contractions, or rarely from the absence of painful sensations and thus a lack of awareness of vigorous labor. Precipitous labor terminates in expulsion of the fetus in less than 3 hours. Using this definition, 25,260 live births-3 percent-were complicated by precipitous labor in the United States in 2013 (Martin, 2015). Despite this incidence, little published information describes maternal and perinatal outcomes.


Obstentrics_Williams

Obstentrics_Williams. For the mother, precipitous labor and delivery seldom are accompanied by serious maternal complications if the cervix is efaced appreciably and compliant, if the vagina has been stretched previously, and if the perineum is relxed. Conversely, vigorous uterine contractions combined with a long, firm cervix and a noncompliant birth canal may lead to uterine rupture or extensive lacerations of the cervix, vagina, vulva, or perineum (Sheiner, 2004). It is in these latter circumstances that amnionic-luid embolism most likely develops (Chap. 41, p. 785). Precipitous labor is frequently followed by uterine atony. The uterus that contracts with unusual vigor bore delivery is likey to be hypotonic ater delivey. In one report of 99 term pregnancies, short labors were more common in multiparas who typically had contractions at intervals less than 2 minutes. Precipitous labors have been linked to cocaine abuse and associated with placental abruption, meconium, postpartum hemorrhage, and low Apgar


Obstentrics_Williams

Obstentrics_Williams. had contractions at intervals less than 2 minutes. Precipitous labors have been linked to cocaine abuse and associated with placental abruption, meconium, postpartum hemorrhage, and low Apgar scores (Mahon, 1994).


Obstentrics_Williams

Obstentrics_Williams. For the neonate, adverse perinatal outcomes from rapid labor may be increased considerably for several reasons. he tumultuous uterine contractions, often with negligible intervals of relaxation, prevent appropriate uterine blood low and fetal oxygenation. Resistance of the birth canal may rarely cause intracranial trauma. Acker and coworkers (1988) reported that Erb or Duchenne brachial palsy was associated with such labors in a third of cases. Finally, during an unattended birth, the newborn may fall to the floor and be injured, or it may need resuscitation that is not immediately available.


Obstentrics_Williams

Obstentrics_Williams. As treatment, analgesia is unlikely to modiy these unusually forceful contractions to a significant degree. he use of tocolytic agents such as magnesium sulfate or terbutaline is unproven in these circumstances. Use of general anesthesia with agents that impair uterine contractibility such as isoflurane is often excessively heroic. Certainly, any oxytocin being administered should be stopped immediately. Fetopelvic disproportion arises from diminished pelvic capacity, from abnormal fetal size or presentation, or more usually from both. he pelvic inlet, midpelvis, or pelvic outlet may be contracted solely or in combination. ny contraction of the pelvic diameters that diminishes pelvic capacity can create dystocia during labor. Normal pelvic dimensions are additionally discussed and illustrated in Chapter 2 (p. 30).


Obstentrics_Williams

Obstentrics_Williams. Using clinical measures, it is important to identiy the shortest anteroposterior diameter through which the fetal head must pass. Before labor, the fetal biparietal diameter averages from 9.5 to as much as 9.8 cm. Therefore, it might prove diicult or even impossible for some fetuses to pass through a pelvic inlet that has an anteroposterior diameter <10 cm. Mengert (1948) and Kaltreider (1952), employing x-ray pelvimetry, demonstrated that the incidence of diicult deliveries rises when either the anteroposterior diameter of the inlet is < 10 cm or the transverse diameter is < 12 cm. As expected, when both diameters are contracted, dystocia rates are much greater than when only one is contracted. Either of these measures is used to consider a pelvis contracted.


Obstentrics_Williams

Obstentrics_Williams. he anteroposterior diameter of the inlet, which is the obstetrical conjugate, is commonly approximated by manually measuring the diagonal conjugate, which is approximately 1.5 cm greater. Ascertainment of these measures is described in Chapter 2 (p. 30). herefore, inlet contraction usually is defined as a diagonal conjugate < 11.5 cm. A small woman is likely to have a small pelvis, but she is also likely to have a small neonate. homs (1937) studied 362 nulliparas and found that the mean birthweight of their ofspring was significantly lower-280 g-in women with a small pelvis than in those with a medium or large pelvis.


Obstentrics_Williams

Obstentrics_Williams. as the rise in this pressure above a resting pressure baseline. hese investigators also introduced the concept of Montevideo units to deine uterine activity (Chap. 23, p. 443). With this deinition, uterine performance is the product of contraction intensity in mm Hg multiplied by the number of contractions in a 10-minute span. For example, three contractions in 10 minutes, each of 50 mm Hg intensity, would equal 150 Montevideo units. During the irst 30 weeks of pregnancy, uterine activity is comparatively quiescent. Contractions are seldom greater than 20 mm Hg, and these have been equated with those irst described by John Braxton Hicks. Uterine activity increases gradually after 30 weeks, and it is noteworthy that these Braxton Hicks contractions also increase in intensity and frequency. Uterine activity is further enhanced during the last weeks of pregnancy. During this phase, the cervix ripens (Chap. 21, p. 409).


Obstentrics_Williams

Obstentrics_Williams. According to Caldeyro-Barcia and Poseiro (1960), clinical labor usually commences when uterine activity reaches values between 80 and 120 Montevideo units. his translates into approximately three contractions of 40 mm Hg every 10 minutes. Importantly, no clear-cut division marks labor onset, which is a gradual and progressive transition.


Obstentrics_Williams

Obstentrics_Williams. In irst-stage labor, uterine contractions progressively grow in intensity from approximately 25 mm Hg at labor commencement to 50 mm Hg at its end. At the same time, the frequency advances from three to ive contractions per 10 minutes, and uterine baseline tone rises from 8 to 12 mm Hg. Uterine activity is further enhanced during second-stage labor, aided by maternal pushing. Indeed, contraction intensity of 80 to 100 mm Hg is typical, and the uterus contracts as frequently as ive to six times each 10 minutes. Hauth and coworkers (1986) quantiied uterine contraction pressures in 109 women at term who received oxytocin for labor induction or augmentation. Most of these women achieved 200 to 225 Montevideo units, and 40 percent had up to 300 units to efect delivery. The authors suggested that these levels of uterine activity should be sought before consideration of cesarean delivery for presumed dystocia (Chap. 23, p. 443).


Obstentrics_Williams

Obstentrics_Williams. Interestingly, the duration of uterine contractions-60 to 80 seconds-does not lengthen appreciably from early active labor through the second stage (Bakker, 2007; Pontonnier, 1975). Presumably, this duration constancy serves fetal respiratory gas exchange. During a uterine contraction, as the intrauterine pressure exceeds that of the intervillous space, respiratory gas exchange is halted. This leads to functional fetal "breath holding," which has a 60-to 80-second limit that remains relatively constant.


Obstentrics_Williams

Obstentrics_Williams. readily be depressed by the inger. At greater intensities, the uterine wall then becomes so hard that it resists easy depression. Uterine contractions usually are not associated with pain until their strength exceeds 15 mm Hg. Presumably, this is the minimum pressure required to distend the lower uterine segment and cervix. It follows that Braxton Hicks contractions exceeding 15 mm Hg may be perceived as uncomfortable because distention of the uterus, cervix, and birth canal is generally thought to produce discomfort.


Obstentrics_Williams

Obstentrics_Williams. Hendricks (1968) observed that "the clinician makes great demands upon the uterus." The uterus is expected to remain well relaxed during pregnancy, to contract efectively but intermittently during labor, and then to remain in a state of almost constant contraction for several hours postpartum. Figure 24-28 demonstrates an example of normal uterine activity during labor. Uterine activity progressively and gradually rises from early through late labor. Interestingly, uterine contractions after birth are identical to those resulting in delivery of the newborn. Logically, the uterus that performs poorly before delivery is also prone to atony and puerperal hemorrhage. J.A. 5-26-60 Intrauterine pressure (mm Hg) Delivery 2:54 PM. 8:45 A.M. 10:20 A.M. 1:10ePM. 2:30 PM. 3:30 PM. 5:20 P.M.


Obstentrics_Williams

Obstentrics_Williams. J.A. 5-26-60 Intrauterine pressure (mm Hg) Delivery 2:54 PM. 8:45 A.M. 10:20 A.M. 1:10ePM. 2:30 PM. 3:30 PM. 5:20 P.M. Caldeyro-Barcia and Poseiro (1960) also observed empirically that uterine contractions are clinically palpable only after their intensity exceeds 10 mm Hg. Moreover, until the intensity of contractions reaches 40 mm Hg, the uterine wall can FIGURE 24-28 Intrauterine pressure recorded through a single catheter. A. Prelabor. B. Early labor. C. Active labor. D. Late labor. E. Spontaneous activity Y2 hour postpartum. F. Spontaneous activity 2Y2 hours postpartum. (Redrawn from Hendricks (H: Uterine contractility changes in the early puerperium, (lin Obstet Gynecol. 1968 Mar;11 (1 ):125-144.) , I of the --contraction Amnionic pressure[1 0 Tonus -.A


Obstentrics_Williams

Obstentrics_Williams. Amnionic pressure[1 0 Tonus -.A FIGURE 24-29 Schematic representation of the normal contractile wave of labor. Large uterus on the let shows the four points at which intramyometrial pressure was recorded with microballoons. Four corresponding pressure tracings are shown in relation to each other by shading on the small uteri at top. (Adapted with permission from (aldeyro-Barcia R, Poseiro JJ: Physiology ofthe uterine contraction. (lin Obstet Gynecol 1960 3:386.) • Origin and Propagation of Contractions


Obstentrics_Williams

Obstentrics_Williams. The normal contractile wave of labor originates near the uterine end of one of the fallopian tubes. hus, these areas act as "pacemakers" (Fig. 24-29). he right pacemaker usually predominates over the left and starts most contractile waves. Contractions spread from the pacemaker area throughout the uterus at 2 em/sec, and the whole organ is depolarized within 15 seconds. his depolarization wave propagates downward toward the cervix. Intensity is greatest in the fundus, and it diminishes in the lower uterus. his phenomenon is thought to relect the reduced myometrial thickness from the fundus to the cervix. Presumably, this descending pressure gradient serves to direct fetal descent toward the cervix and to eface the cer vix. Importantly, all parts of the uterus are synchronized and reach their peak pressure almost simultaneously, giving rise to the curvilinear waveform shown in Figure 24-29. Young and Zhang (2004) have shown that the initiation of each contraction is triggered by a


Obstentrics_Williams

Obstentrics_Williams. their peak pressure almost simultaneously, giving rise to the curvilinear waveform shown in Figure 24-29. Young and Zhang (2004) have shown that the initiation of each contraction is triggered by a tissue-level bioelectrical event.


Obstentrics_Williams

Obstentrics_Williams. The pacemaker theory also serves to explain the varying intensity of adjacent coupled contractions shown in panels A and B of Figure 24-28. Such coupling was termed incoordination by Caldeyro-Barcia and Poseiro (1960). A contractile wave begins in one cornual-region pacemaker but does not synchronously depolarize the entire uterus. As a result, another contraction begins in the contralateral pacemaker and produces the second contractile wave ofthe couplet. hese small contractions alternating with larger ones appear to be typical of early labor. Indeed, labor may progress with such uterine activity, albeit at a slower pace. hese authors also observed that labor would progress slowly ifregular contractions were hypotonicthat is, contractions with intensity <25 mm Hg or frequency <2 per 10 minutes.


Obstentrics_Williams

Obstentrics_Williams. Terms for the description and quantiication of uterine contractions have been recommended by the American College of Obstetricians and Gynecologists (2017b). Normal uterine activiy is defined as five or fewer contractions in 10 minutes, averaged during a 30-minute span. Tachysystole is more than ive contractions in 10 minutes, averaged over 30 minutes. Tachysystole can be applied to spontaneous or induced labor. he term hyperstimulation was abandoned. Stewart and associates (2012) prospectively studied uterine tachysystole in 584 women undergoing labor induction with misoprostol at Parkland Hospital. A higher rate of adverse neonatal outcomes was not associated with an increasing number of contractions per 10 minutes or per 30 minutes. Counts of six or more contractions in 10 minutes, however, were significantly associated with fetal heart rate decelerations.


Obstentrics_Williams

Obstentrics_Williams. Electrodes for fetal heart rate evaluation and catheters for uterine contraction measurement are both associated with infrequent but potentially serious complications. Rarely, an intrauterine pressure catheter during placement may lacerate a fetal vessel in the placenta. Also with insertion, placental and possibly uterine perforation can cause hemorrhage, abruption, serious morbidity, and spurious recordings that have resulted in inappropriate management. Severe cord compression has been described from entanglement with the pressure catheter. Injury to the fetal scalp or breech by a heart rate electrode is rarely severe. However, application at some other site-such as the eye in face presentations-can be serious.


Obstentrics_Williams

Obstentrics_Williams. Both the fetus and the mother may be at greater risk of infection from internal monitoring (Faro, 1990). Scalp wounds from the electrode may become infected, and subsequent cranial osteomyelitis has been reported (Brook, 2005; Eggink, 2004; McGregor, 1989). The American Academy of Pediatrics and the American College of Obstetricians and Gynecologists (2017) have recommended that certain maternal infections, including human immunodeficiency virus (HIV), herpes simplex virus, and hepatitis Biand C virus, are relative contraindications to internal fetal monitoring. Adamsons K, Myers E: Late decelerations and brain tolerance of the fetal monkey to intrapartum asphyxia. Am J Obstet Gyneco1o128:893, 197 Ahn MO, Korst L, Phelan JP: Intrapartum fetal heart rate patterns in 209 brain damaged infants. Am J Obstet GynecoIo174:492, 1996


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Obstentrics_Williams. Ahn MO, Korst L, Phelan JP: Intrapartum fetal heart rate patterns in 209 brain damaged infants. Am J Obstet GynecoIo174:492, 1996 Alfirevic Z, Devane 0, Gyte GM, et al: Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour. Cochrane Database Syst Rev 2:CD006066, 2017 Ambia M1, Yule SS, Wells E: Does fetal bradycardia during eclamptic seizure necessitate cesarean delivery? Unpublished data, 20o17 Amer-Wihlin I, Arulkumaran S, Hagberg H, et al: Fetal electrocardiogram: ST waveform analysis in intrapartum surveillance. BJOG 114: 1191,2007 Amer-Wahlin 1, Hellsten C, Noren H, et al: Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomized controlled trial. Lancet 358:534, 200o1 American Academy of Pediatrics and the American College of Obstetricians and Gynecologists: Guidelines for Perinatal Care, 8th ed. Elk Grove Village, AAP, 2017


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Obstentrics_Williams. American Academy of Pediatrics and the American College of Obstetricians and Gynecologists: Guidelines for Perinatal Care, 8th ed. Elk Grove Village, AAP, 2017 American College of Obstetricians and Gynecologists: Amnioinfusion does not prevent meconium aspiration syndrome. Committee Opinion No. 346, October 2006, Reairmed 2016 American College of Obstetricians and Gynecologists: Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles. Practice Bulletin No. 106, July 2009, Reairmed 2017 a American College of Obstetricians and Gynecologists: Management of intrapartum fetal heart rate tracings. Practice Bulletin No. 116, November 2010, Reairmed 2017b American College of Obstetricians and Gynecologists: Summary: delivery of a newborn with meconium-stained amniotic fluid. Committee Opinion No. 689, March 2017c


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Obstentrics_Williams. American College of Obstetricians and Gynecologists: Summary: delivery of a newborn with meconium-stained amniotic fluid. Committee Opinion No. 689, March 2017c American College of Obstetricians and Gynecologists, American Academy of Pediatrics: Neonatal encephalopathy and neurologic outcome. Washington, ACOG,o2014 Ananth CV, Chauhan SP, Chen HY, et al: Electronic fetal monitoring in the United States. Obstet Gynecol 121(5):927,o2013 Anderson BL, Scerbo MW, Belfore A, et al: Time and number of displays impact critical signal detection in fetal heart rate tracings. Am J Perinatol 28(6):435,o2011 Angel J, Knuppel R, Lake M: Sinusoidal fetal heart rate patterns associated with intravenous butorphanol administration. Am J Obstet Gynecol 149:465, 1984 Anyaegbunam M, Ditchik A, Stoessel R, et al: Vibroacoustic stimulation of the fetus entering the second stage oflabor. Obstet Gynecol 83:963, 1994 Api 0, Carvalho JS: Fetal dysrhythmias. Best Pract Res Clin Obstet Gynaecol 22(1):31, 2008


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Obstentrics_Williams. Arikan GM, Scholz HS, Petru E, et al: Cord blood oxygen saturation in vigorous infants at birth: what is normal? BJOG 107:987,o2000 Ayres-de-Campos 0, Bernardes J, Costa-Pereira A, et al: Inconsistencies in classiication by experts of cardiotocograms and subsequent clinical decision. BJOG 106:1307, 1999 Bakker JJ, Verhoeven CJ, Janssen PF, et al: Outcomes after internal versus external tocodynamometry for monitoring labor. N Engl J Med 362:306, 2010 Bakker PC, Kurver PH, Duik OJ, et al: Elevated uterine activity increases the risk offetal acidosis at birth. Am J Obstet Gynecol 196:313,o2007 Ball RH, Parer JT: he physiologic mechanisms of variable decelerations. Am J Obstet Gynecol 166:1683, 1992 Bannerman CG, Grobman WA, Antoniewicz L: Assessment of the concordance among 2-tier, 3-tier, and 5-tier fetal heart rate classiication systems. Am J Obstet GynecoI205(3):288.e1, 2011


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Obstentrics_Williams. Bannerman CG, Grobman WA, Antoniewicz L: Assessment of the concordance among 2-tier, 3-tier, and 5-tier fetal heart rate classiication systems. Am J Obstet GynecoI205(3):288.e1, 2011 Banta HD, Thacker SB: Electronic fetal monitoring: lessons from a formative case of health technology assessment. Int J Technol Assess Health Care 18:762,o2002 Becker JH, Bax L, Amer-Wahlin I, et al: ST analysis of the fetal electrocardiogram in intrapartum fetal monitoring. Obstet Gynecol 119:145,2012 Belfort A, Saade GR, hom E, et al: A randomized trial of intrapartum fetal ECG ST-segment analysis. N Engl J Med 373(7):632, 2015 Blackwell Sc, Groman WA, Antoniewicz L, et al: Interobserver and intraobserver reliability of the NICHD 3-tier fetal heart rate interpretation system. Am J Obstet Gynecol 8.e1,2011 Blackwell SC, Moldenhauer J, Hassan 55, et al: Meconium aspiration syndrome in term neonates with normal acid-base status at delivery: is it diferent? Am J Obstet Gynecol 184: 1422, 2001


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Obstentrics_Williams. Blackwell SC, Moldenhauer J, Hassan 55, et al: Meconium aspiration syndrome in term neonates with normal acid-base status at delivery: is it diferent? Am J Obstet Gynecol 184: 1422, 2001 Bloom SL, Spong CY, hon E, et al: Fetal pulse oximetry and cesarean delivery. N Engl J Med 335:21, 2006 Bloom SL, Swindle RG, McIntire DO, et al: Fetal pulse oximetry: duration of desaturation and intrapartum outcome. Obstet Gynecol 93: 1036, 1999 Boehm FH: Prolonged end stage fetal heart rate deceleration. Obstet Gynecol 45:579, 1975 Brocato B, Lewis 0, Mulekar M, et al: Obesity's impact on intrapartum electronic fetal monitoring. J Matern Fetal Neonatal Med August 30, 2017 [Epub ahead of print] Brook I: Infected neonatal cephalohematomas caused by anaerobic bacteria. J Perinat Med 33(3):255, 2005


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Obstentrics_Williams. Brook I: Infected neonatal cephalohematomas caused by anaerobic bacteria. J Perinat Med 33(3):255, 2005 Bullens LM, van Runnard Heimel pJ, van der Hout-van der Jaqt MB, et al: Interventions for intrauterine resuscitation in suspected fetal distress during term labor: a systematic review. Obstet Gynecol Surv 70(8):524, 2015 Cahill AG, Roehl A, Odibo AO, et al: Association and prediction of neonatal acidemia. Am J Obstet Gynecol 207:206.e1, 2012 Caldeyro-Barcia R, Poseiro JJ: Physiology of the uterine contraction. Clin Obstet Gynecol 3:386, 1960 Chen HY, Chauhan SP, Ananth C: Electronic fetal heart monitoring and its relationship to neonatal and infant mortaliry in the United States. Am J Obstet GynecoIo204(6):491.e1, 2011 Clapp JF, Peress NS, Wesley M, et al: Brain damage after intermittent partial cord occlusion in the chronically instrumented fetal lamb. Am J Obstet Gynecol 159:504, 1988


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Obstentrics_Williams. Clapp JF, Peress NS, Wesley M, et al: Brain damage after intermittent partial cord occlusion in the chronically instrumented fetal lamb. Am J Obstet Gynecol 159:504, 1988 Clark SL, Gimovsky ML, Miller FC: The scalp stimulation test: a clinical alternative to fetal scalp blood sampling. m J Obstet Gyneco1o148:274, 1984 Clark SL, Nageotte MP, Garite TJ, et al: Intrapartum management of category II fetal heart rate tracings: towards standardization of care. Am J Obstet GynecoIo209(2):89,o2013 Coletta J, Murphy E, Rubeo Z, et al: The 5-tier system of assessing fetal heart rate tracings is superior to the 3-tier system in identiying fetal acidemia. Am J Obstet Gynecol 206:226.e1, 2012 Cook VD, Spinnato JA: Terbutaline tocolysis prior to cesarean section for fetal distress. J Matern Fetal Med 3:219, 1994 Dad N, Abushama M, Konje JC, et al: What is the role of amnioinfusion in modern day obstetrics? J Matern Fetal Neonatal Med 29(17):2823,o2016


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Obstentrics_Williams. Wagner BP, N edelcu J, Vlartin E: Delayed postischemic hypothermia improves long-term behavioral outcome after cerebral hypoxia-ischemia in neonatal rats. Pediatr Res 51 (3):354, 2002 Walker J: Foetal anoxia. J Obstet Gynaecol Br Commonw 61:162, 1953 � enstrom K, Andrews W, Maher JE: Amnioinfusion survey: prevalence protocols and complications. Obstet Gynecol 86:572, 1995 Westgate J, Harris M, Curnow JSH, et al: Plymouth randomized trial of cardiotocogram only versus ST waveform plus cardiotocogram for intrapartum monitoring in 2400 cases. Am J Obstet GynecoIr169:1151, 1993 Westgate JA, Bennet L, De Haan HH, et al: Fetal heart rate overshoot during repeated umbilical cord occlusion in sheep. Obstet Gynecol 97:454, 2001 Wiberg-Itzel E, Lipponer C, Norman M, et al: Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress: randomised controlled multicenter trial. BMJ 336: 1284, 2008


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Obstentrics_Williams. Yam J, Chua S, Arulkumaran S: Intrapartum fetal pulse oximetty. Part I: principles and technical issues. Obstet Gynecol Surv 55: 163, 2000 Yang M, Stout MJ, Lopez ]D, et al: Association of fetal heart rate baseline change and neonatal outcomes. Am] PerinatoI34(9):879, 2017 Young BK, Katz M, Wilson SJ: Sinusoidal fetal heart rate, 1. Clinical significance. Am] Obstet GynecoIr136:587, 1980a Young BK, Weinstein HM: Moderate fetal bradycardia. Am J Obstet Gynecol 126:271, 1976 Young DC, Gray ]H, Luther ER, et al: Fetal scalp blood pH sampling: its value in an active obstetric unit. Am J Obstet GynecoIr136:276, 1980b Young RC, Zhang P: Functional separation of deep cytoplasmic calcium from subplasmalemmal space calcium in cultured human uterine smooth muscle cells. Cell Calcium 36(1):11, 2004 Zalar RW, Quilligan EJ: The influence of scalp sampling on the cesarean section rate for fetal distress. Am J Obstet Gynecol 135:239, 1979


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Obstentrics_Williams. Zalar RW, Quilligan EJ: The influence of scalp sampling on the cesarean section rate for fetal distress. Am J Obstet Gynecol 135:239, 1979 GENERAL PRINCIPLES .s..s...........s....s....s..s... 486 ANALGESIA AND SEDATION DURING LABOR ........ 487 REGIONAL ANALGESIA ..........s...s...s..s..s....s.. 488 SPINAL (SUBARACHNOID) BLOCK .....s............ 490 EPIDURAL ANALGESIA .s...s...s.....s.....s......... 492 LOCAL INFILTRATION FOR CESAREAN DELIVERY ....s. 497 GENERAL ANESTHESIA ......s..............s....s.. 498 POSTPARTUM ANALGESIA .s.......s...s....s....s..s.. 500


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Obstentrics_Williams. LOCAL INFILTRATION FOR CESAREAN DELIVERY ....s. 497 GENERAL ANESTHESIA ......s..............s....s.. 498 POSTPARTUM ANALGESIA .s.......s...s....s....s..s.. 500 We are indebted to Sir James .Simpson, the discoverer of chloroorm, or the introduction of anaesthesia into obstetrical practice. He employed ether or this purpose in 184, and replaced it by chloroorm. Every one agrees as to the marked beneits derived from anaesthesia when operative procedures are to be undertaken, but there is stil considerable dference of opinion as to the advisabiliy of its routine employment in normal labour. -]. Whitridge Williams (1903)


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Obstentrics_Williams. -]. Whitridge Williams (1903) As cited by Williams, anesthetic techniques were a most welcome addition to obstetrics. That said, obstetrical anesthesia presents unique challenges. Labor begins without warning, and anesthesia may be required within minutes of a full meal. Vomiting with potential aspiration of the gastric contents is a constant threat due to delayed gastric emptying during pregnancy. Disorders of pregnancy such as preeclampsia, placental abruption, or sepsis further compound provision of obstetrical anesthesia.


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Obstentrics_Williams. Of all anesthesia-related deaths in the United States from 1995 to 2005,i3.6 percent were in pregnant women (Li, 2009). Creanga and colleagues (2017) analyzed deaths of women during or within 1 year of pregnancy in the United States from 2011 through 2013. Of these deaths, they found that 3 of 2009 (0.2 percent) were attributable to anesthesia complications. As shown in Table 25-1, between 1979 and 2002, anesthesia-related maternal mortality rates decreased nearly 60 percent, and currently approximately ive deaths per million live births are attributed to anesthesia complications.


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Obstentrics_Williams. About two thirds of deaths associated with general anesthesia are caused by intubation failure or induction problems during cesarean delivery. Deaths associated with regional analgesia are caused by high spinal or epidural blocks-26 percent; respiratory failure-19 percent; and drug reaction-19 percent. he improved case-fatality rate for general anesthesia is especially notable considering that such anesthesia is now used for the highest-risk patients and the most hurried emergencies, that is, decision-to-incision intevals < 15 minutes (Bloom, 2005). 25-1 . Case-Fatality Rates and Rate Ratios of Anesthesia-Related Deaths During Cesarean Delivery by Type of Anesthesia in the United States, ,979-2002 aDeaths per million general or regional anesthetics. (I = confidence interval. Data from Hawkins, 201s1.


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Obstentrics_Williams. Data from Hawkins, 201s1. The most signiicant factor linked to lower maternal mortality rates is the greater use of regional analgesia (Hawkins, 2011). In-house anesthesia coverage that is available around the clock is certainly another contributing factor. Logically, with increased use of regional analgesia, there are now reports of complications with these techniques. Indeed, compared to pre-1990 data, post-1990 obstetrical anesthesia was associated with more legal claims involving regional analgesia (Davies, 2009). In a recent analysis of 466,442 obstetrical hospital discharges, complications associated with regional analgesia accounted for 81 percent of anesthesia-related adverse events (Guglielminotti, 2015).


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Obstentrics_Williams. For the fetus, recent human studies suggest that single, relatively short exposure to general anesthetic and sedation is unlikely to have negative efects on subsequent behavior or learning. his evidence is presented in Chapter 46 (p. 901). That said, in 2016, the Food and Drug Administration (FDA) warned that repeated or lengthy use of general anesthetic and sedation drugs in pregnant women during their third trimester may afect fetal brain development. Listed drugs include inhalation agents used in general anesthesia as well as lorazepam, ketamine, propofol, and midazolam. Notably, the American College of Obstetricians and Gynecologists (2016a) and the Society for Obstetric Anesthesia and Perinatology (2017) have voiced concerns with this statement and cited the lack of signiicant human data, especially in pregnant women, to underpin this warning.


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Obstentrics_Williams. he American College of Obstetricians and Gynecologists (2017a) recognizes that a woman's request for labor pain relief is suicient medical indication for its provision. Identification of any of the risk factors shown in Table 25-2 should prompt consultation with anesthesia personnel to permit a joint management plan. This plan should include strategies to minimize the need for emergency anesthesia. Goals for optimizing obstetrical anesthesia services have been established by the American College of Obstetricians and Gynecologists (2017 a) and the American Society of Anesthesiologists (2016) and include: TABLE 25-2. Maternal Factors That May Prompt Anesthetic Consultation Obstructive lesions: edema, anatomical abnormalities, trauma Decreased range of motion in opening the mouth or small Obstetrical complications with a high risk of operative delivery Matenal medical complications such as cardiopulmon 1.


Obstentrics_Williams

Obstentrics_Williams. Obstetrical complications with a high risk of operative delivery Matenal medical complications such as cardiopulmon 1. Availability of a licensed practitioner who is credentiled to administer n appropriate anesthetic whenever necessary and to maintain support of vital unctions in an obstetrical emergency. 2. Availability of anesthesia personnel to permit the start of a cesarean delivery within 30 minutes of the decision to perform the procedure. 3. Anesthesia personnel immediately available to perform an emergency cesarean delivery during the active labor of a woman attempting vaginal birth ater cesarean (Chap. 31, p. 597). 4. Appointment of a qualified anesthesiologist to be responsible for all anesthetics administered. 5. Availability of a qualified physician with obstetrical privileges to perform operative vaginal or cesarean delivery during administration of anesthesia. 6.


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Obstentrics_Williams. 5. Availability of a qualified physician with obstetrical privileges to perform operative vaginal or cesarean delivery during administration of anesthesia. 6. Availability of equipment, facilities, and support personnel equal to that provided in any surgical suite. 7. Immediate availability of personnel, other than the surgical team, to assume responsibility for resuscitation of a depressed newborn (Chap. 32, p. 606).


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Obstentrics_Williams. 7. Immediate availability of personnel, other than the surgical team, to assume responsibility for resuscitation of a depressed newborn (Chap. 32, p. 606). To meet these goals, 24-hour, in-house anesthesia coverage is usually necessary. Providing such service in smaller facilities is more challenging-a problem underscored by the fact that approximately a third of all hospitals providing obstetrical care perform fewer than 500 deliveries per year. The financial burden incurred to provide 24/7 obstetrical anesthesia coverage may result in cost deicits (Bell, 2000). Compounding this burden, some third-party payers have denied reimbursement for epidural analgesia in the absence of a specific medical indication-an approach repudiated by the American College of Obstetricians and Gynecologists (2017a). Regarding obstetricians, they should be proficient in local and pudendal analgesia. These may be administered in appropriately selected circumstances described on page 489.


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Obstentrics_Williams. Regarding obstetricians, they should be proficient in local and pudendal analgesia. These may be administered in appropriately selected circumstances described on page 489. Hawkins (2010) emphasized that labor pain is a highly individual response to variable stimuli that are uniquely received and interpreted (Fig.


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Obstentrics_Williams. Hawkins (2010) emphasized that labor pain is a highly individual response to variable stimuli that are uniquely received and interpreted (Fig. These stimuli are modified by emotional, motivational, cognitive, social, and cultural circumstances. Labor pain caused by uterine contractions and cervical dilation is transmitted through visceral aferent sympathetic nerves entering the spinal cord from Tto through Lt. Later in labor, perineal stretching transmits painful stimuli through the pudendal nerve and sacral nerves S2 through 54' Cortical responses to pain and anxiety during labor are complex and may be inluenced by maternal expectations for childbirth, her age, preparation through education, emotional support, and other factors. Pain perception is heightened by fear and the need to move into various positions. A woman may be motivated to have a certain type of birthing experience, and these opinions will influence her judgment regarding pain management.


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Obstentrics_Williams. Maternal physiological responses to labor pain can influence maternal and fetal well-being and labor progress. For example, hyperventilation may induce hypocarbia. A greater metabolic rate augments oxygen consumption. Increases in cardiac output and vascular resistance may raise maternal blood pressure. Pain, stress, and anxiety trigger release of stress hormones such as Cortical responses to pain pain, anxle y, age, FIGURE 25-' Sources of pain during labor and maternal physiological responses. (Reproduced with permission from Hawkins JL: Epidural analgesia for labor and delivery, N Engl J Med. 2010 Apr 22;362(16):1503-1510.) cortisol and �-endorphins. The sympathetic nervous system response to pain leads to a marked elevation in circulating catecholamines that can adversely afect uterine activity and uteroplacental blood low. Efective analgesia attenuates or eliminates these responses.


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Obstentrics_Williams. If uterine contractions and cervical dilatation cause discomfort, pain relief is ofered. If neuraxial analgesia is contraindicated or unavailable or is declined, a narcotic from Table 25-3 plus one of the tranquilizer-antiemetic drugs such as promethazine (Phenergan) is usually appropriate. With a successful program of analgesia and sedation, the mother ideally rests quietly between contractions. In this circumstance, discomfort usually is felt at the acme of an efective uterine contraction.


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Obstentrics_Williams. Meperidine, 50 to 100 mg, with promethazine, 25 mg, may be administered intramuscularly at intervals of 2 to 4 hours. A more rapid efect is achieved by giving meperidine intravenously in doses of 25 to 50 mg every 1 to 2 hours. Whereas analgesia is mximal 30 to 45 minutes after an intramuscular injection, it develops almost immediately following intravenous administration. Meperidine readily crosses the placenta and can have a prolonged half-life in the newborn (American College of Obstetricians and Gynecologists, 20l7a). Its depressant efect in the fetus follows closely behind the peak maternal analgesic efect. TABLE 25-3. Some Parenteral Analgesic Agents for Labor Pain Meperidine 25-50 mg (IV) Q 1-2 hr 5 min (IV) �.1A8-20 hr 50-100 mg (1M) Q 2-4 hr 30-45 min (1M) �60 hr Fentanyl 50-100 tg (IV) Q 1 hr 1 min �5 hr Morphine 2--5 mg (IV) Q 4 hr 5 min (IV) �.7 hr IV = intravenously, 1M = intramuscularly; Q = every.


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Obstentrics_Williams. According to Bricker and Lavender (2002), meperidine is the most common opioid used worldwide for pain relief during labor. In one randomized study at Parkland Hospital, patientcontrolled intravenous analgesia with meperidine was found to be an inexpensive and reasonably efective method for labor analgesia (Sharma, 1997). Women randomized to self-administered analgesia were given a 50-mg meperidine plus 25-mg promethazine dose intravenously as an initial bolus. hereafter, an infusion pump was set to deliver 15 mg of meperidine every 10 minutes as needed until delivery. Neonatal sedation, as measured by the need for naloxone treatment in the delivery room, was identiied in 3 percent of newborns. Both meperidine and its metabolite, normeperidine, are lipophilic and readily cross the placenta. Analgesia with meperidine was associated with lower Apgar scores in comparison to epidural analgesia (Sharma, 2004). Normeperidine is a strong respiratory depressant that has a significantly longer


Obstentrics_Williams

Obstentrics_Williams. Analgesia with meperidine was associated with lower Apgar scores in comparison to epidural analgesia (Sharma, 2004). Normeperidine is a strong respiratory depressant that has a significantly longer half-life than meperidine and is likely responsible for the fetal side efects of meperidine.


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Obstentrics_Williams. his synthetic opioid receptor agonist-antagonist analgesic, given in 1-to 2-mg intravenous doses, compares favorably with 40 to 60 mg of meperidine. Its major side efects are somnolence, dizziness, and dysphoria. Neonatal respiratory depression is reported to be less than with meperidine. Importantly, the two drugs are not given contiguously because butorphanol antagonizes the narcotic efects of meperidine. Butorphanol has been associated with transient sinusoidal fetal heart rate patterns (Hatjis, 1986). This is another mixed opioid receptor agonist-antagonist analgesic. It can be given intramuscularly, intravenously, or subcutaneously. he usual dose is 10 to 20 mg, administered every 4 to 6 hours irrespective of the route of administration. Small doses of nalbuphine may also be used to treat pruritus associated with neuraxial opioids.


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Obstentrics_Williams. This short-acting and potent synthetic opioid may be given in doses of 50 to 1 00 �g intravenously every hour. Its main disadvantage is its short duration of action, which requires frequent dosing or use of a patient-controlled intravenous infusion pump. This is a synthetic opioid with an extremely rapid onset of action. It is hydrolyzed rapidly, resulting in a half-life of 3.5 minutes (Ohashi, 2016). Although it readily crosses the placenta, it is quickly metabolized or redistributed within the fetus (Kan, 1998). Various dosing regimens have been studied, and single boluses appear to mirror the periodic uterine contraction pattern. Infusions, on the other hand, have been reported to cause maternal apnea (Waring, 2007). Due to the aforementioned risks, only trained personnel should administer it, and only under strictly controlled circumstances. Efficacy and Safety of Parenteral Agents


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Obstentrics_Williams. Efficacy and Safety of Parenteral Agents Hawkins and colleagues (1997) reported that four of 129 maternal anesthetic-related deaths were from parenteral sedation-one from aspiration, two from inadequate ventilation, and one from overdosage. Opioids used during labor may cause newborn respiratory depression. Naloxone is a narcotic antagonist capable of reversing this respiratory depression. It acts by displacing the narcotic from specific receptors in the central nervous system. Withdrawal symptoms may be precipitated in recipients who are physically dependent on narcotics. For this reason, naloxone is contraindicated in a newborn of a narcotic-addicted mother.


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Obstentrics_Williams. Inhaled nitrous oxide has a rapid onset and ofset that provides analgesia during episodic contractions. It can be self-administered as a mixture of 50-percent nitrous oxide and 50-percent oxygen premixed in a single cylinder (Entonox) or using a blender that mixes the two gases from separate tanks (Nitronox). he gases are connected to a breathing circuit through a one-way valve that opens only during inspiration. he use of intermittent nitrous oxide for labor pain is generally regarded s safe for the mother and newborn, but pain control is less efective than epidural analgesia (Barbieri, 2014; Likis, 2014). In many cases, nitrous oxide simply serves to delay more deinitive neuraxial analgesia. For maximal eicacy, nitrous oxide is inhaled 30 seconds prior to the start of a contraction, although this prevents adequate rest for the mother. Nitrous oxide is also associated with nausea and vomiting. The environmental and health risk of its use without proper scavenging remains to be


Obstentrics_Williams

Obstentrics_Williams. although this prevents adequate rest for the mother. Nitrous oxide is also associated with nausea and vomiting. The environmental and health risk of its use without proper scavenging remains to be carefully evaluated (King, 2014).


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Obstentrics_Williams. Various nerve blocks have been developed over the years to provide pain relief during labor and/or delivery. These include pudendal, paracervical, and neuraxial blocks such as spinal, epidural, and combined spinal-epidural techniques. Some of the more commonly used nerve block anesthetics, along with their usual concentrations, doses, and durations of action, are summarized in Table 25-4. he dose of each agent varies widely and is dependent on the particular nerve block and physical status of the woman. he onset, duration, and quality of analgesia can be enhanced by raising the volume and/or concentration. his can be done safely only by incrementally administering small-volume boluses of the agent and by careully monitoring early warning signs of toxicity. Administration of these agents must be followed by appropriate monitoring for adverse reactions. Equipment and personnel to manage these reactions must be immediately available.


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Obstentrics_Williams. Most often, serious toxicity follows inadvertent intravenous injection. Systemic toxicity from local anesthetics typically manifests in the central nervous and cardiovascular systems. For this reason, when epidural analgesia is initiated, dilute epinephrine is sometimes added and given as a test dose. A sudden significant rise in the maternal heart rate or blood pressure immediately after administration suggests intravenous catheter placement. his should halt further injection and should prompt catheter repositioning. Local anesthetic agents are manufactured in more than one concentration and ampule size, which raises the potential for dosing errors. aWithout epinephrine. bEsters are hydrolyzed by plasma cholinesterases and amides by hepatic clearance. D&C = dilatation and curettage. Data from Liu SS, Lin Y: Local anesthetics. In Barash P, Cullen B, Stoeling R, et al (eds): Clinical Anesthesia, 6th ed. Philadelphia, Lippincott Williams & Wilkins, 2009.


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Obstentrics_Williams. Data from Liu SS, Lin Y: Local anesthetics. In Barash P, Cullen B, Stoeling R, et al (eds): Clinical Anesthesia, 6th ed. Philadelphia, Lippincott Williams & Wilkins, 2009. Early symptoms are those of stimulation, but as serum levels rise, depression follows. Symptoms may include light-headedness, dizziness, tinnitus, metallic taste, and numbness of the tongue and mouth. Patients may show bizarre behavior, slurred speech, muscle fasciculation and excitation, and ultimately, generalized convulsions, followed by loss of consciousness.


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Obstentrics_Williams. hese manifestations generally develop later than those of cerebral toxicity. Moreover, no symptoms may develop because signs are usually induced by higher serum drug levels. he notable exception is bupivacaine, which is associated with neurotoxicity and cardiotoxicity at virtually idenricalilevels (Mulroy, 2002). Because of its toxicity risk, use of a 0.75-percent solution of bupivacaine for epidural injection has been proscribed by the FDA. Similar to neurotoxicity, cardiovascular toxicity is characterized first by stimulation and then by depression. Accordingly, hypertension and tachycardia are soon followed by hypotension, cardiac arrhythmias, and impaired uteroplacental perfusion. • Management of Local Anesthetic


Obstentrics_Williams

Obstentrics_Williams. • Management of Local Anesthetic Seizures and severe ventricular arrhythmias can follow large doses of local anesthetics that are given inadvertently. Labor and delivery units should be stocked with a 20-percent lipid emulsion solution (Intralipid). It is administered as a rapid intravenous bolus followed by an infusion upon the first sign of local anesthetic systemic toxicity (Neal, 2012). Controlling seizures and securing the airway are essential to prevent aspiration and hypoxemia. Benzodiazepines, such as midazolam or lorazepam, may be used to help control seizures, particularly if lipid emulsions are not available. Magnesium sulfate also controls convulsions (Chap 40, p. 736). Abnormal fetal heart follow and stem from maternal hypoxia. With proper manage ment, including supportive measures, the fetus usually recovers. herefore, it is best for the fetus and mother to delay delivery until the mother is stabilized.


Obstentrics_Williams

Obstentrics_Williams. herefore, it is best for the fetus and mother to delay delivery until the mother is stabilized. With proper treatment of local anesthetic systemic toxicity (LAST) with lipid emulsions, vital signs usually return to normal. The woman, however, should be monitored, placed in the lateral decubitus position to avoid aortocaval compression, and provided continued supportive care. Vasopressors can be used to support blood pressure. With cardiac arrest, emergency cesarean delivery is considered if maternal vital signs have not been restored within 5 minutes (Chap, 47, p. 931). As with convulsions, however, the fetus is likely to recover more quickly in utero once maternal cardiac output is reestablished.


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Obstentrics_Williams. Pain with vaginal delivery arises from stimuli from the lower genital tract. These are transmitted primarily through the pudendal nerve, the peripheral branches of which provide sensory innervation to the perineum, anus, vulva, and clitoris. The pudendal nerve passes beneath the sacrospinous ligament just as the ligament attaches to the ischial spine. Sensory nerve fibers of the pudendal nerve are derived from ventral branches of the S2 through S4 nerves.


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Obstentrics_Williams. The pudendal nerve block is a relatively safe and simple method of providing analgesia for spontaneous delivery. As shown in Figure 25-2, a tubular introducer is used to sheathe and guide a 15-cm-long 22-gauge needle into position near the pudendal nerve. The end of the introducer is placed against the vaginal mucosa just beneath the tip of the ischial spine. he in troducer allows 1.0 to 1.5 em of needle to at the injection site. he infection may spread posteriorly to the hip joint, into the gluteal musculature, or into the retropsoas space (Svancarek, 1977). his block usually provides satisfactory pain relief during irst-stage labor. How ever, because the pudendal nerves are not blocked during paracervical blockade, addi Ischial spine tional analgesia is required for delivery. For


Obstentrics_Williams

Obstentrics_Williams. Ischial spine tional analgesia is required for delivery. For Pudendal nerve paracervical blockade, usually 5 to 10 mL of lidocaine (1 to 2 percent) or chloroprocaine (3 percent) is injected into the cervix later ally at 3 and 9 o'clock. Because these anes thetics are relatively short acting, this block may have to be repeated during labor. Fetal bradycardia is a worrisome com plication that occurs with approximately 15 percent of paracervical blocks (Rosen, FIGURE 25-2 Local infiltration of the pudendal nerve. Transvaginal technique showing 2002). Bradycardia usually develops within the needle extended beyond the needle guard and passing through the sacrospinous 10 minutes and may last up to 30 minutes. ligament to reach the pudendal nerve.


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Obstentrics_Williams. ligament to reach the pudendal nerve. protrude beyond its tip, and the needle is pushed beyond the introducer tip into the mucosa. A mucosal wheal is made with 1 mL of I-percent lidocaine solution or an equivalent dose of another local anesthetic (see Table 25-4). To guard against intravascular infusion, aspiration is attempted before this and all subsequent injections. The needle is then advanced until it touches the sacrospinous ligament, which is iniltrated with 3 mL of lidocaine. he needle is advanced farther through the ligament. As the needle pierces the loose areolar tissue behind the ligament, resistance against the plunger drops. Another 3 mL of solution is injected in this region. Next, the needle is withdrawn into the introducer, which is moved to a point just above the ischial spine. The needle is inserted through the mucosa and a inal 3 mL is deposited. The procedure is then repeated on the other side.


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Obstentrics_Williams. Within 3 to 4 minutes of injection, a successful pudendal block will allow pinching of the lower vagina and posterior vulva bilaterally without pain. If delivery occurs before the pudendal block becomes efective and an episiotomy is indicated, then the fourchette, perineum, and adjacent vagina can be iniltrated with 5 to 10 mL of I-percent lidocaine solution directly at the planned episiotomy site. By the time of repair, the pudendal block usually has become efective. Pudendal block usually does not provide adequate analgesia when delivery requires extensive obstetrical manipulation. Moreover, such analgesia is usually inadequate for women in whom complete visualization of the cervix and upper vagina or manual exploration of the uterine cavity is indicated.


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Obstentrics_Williams. Infrequently, complications may follow this block. As previously described, intravascular injection of a local anesthetic agent may cause serious systemic toxicity. Hematoma formation from perforation of a blood vessel is most likely when there is a coagulopathy (Lee, 2004). Rarely, severe infection may originate Doppler studies have shown a rise in the pulsatility index of the uterine arteries following paracervical blockade. These observations support the hypothesis of drug-induced arterial vasospasm as a cause of fetal bradycardia (Manninen, 2000). For these reasons, paracervical block is not used in situations of potential fetal compromise.


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Obstentrics_Williams. Epidural, spinal, or combined spinal-epidural techniques are the most common methods used for pain relief during labor and delivery. In the United States in 2008, epidural analgesia was used in nearly 70 percent of mothers during labor and had a success rate of 98.8 percent. Neuraxial analgesia was used even more often in operative vaginal deliveries and supported 84 percent of forceps deliveries and 77 percent of vacuum extractions (Osterman, 2011).


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Obstentrics_Williams. Anesthetic in this block can be given as a single dose, can be partnered with an epidural catheter as combined spinalepidural analgesia, or can be administered as a continuous infusion. Injection of a local anesthetic into the subarachnoid space to efect analgesia has long been used for delivery. Advantages include rapid analgesia onset, short duration of action, and high success rate. he subarachnoid space during pregnancy is smaller, which likely results from internal vertebral venous plexus engorgement. Thus, in parturients, the same amount of anesthetic agent in the same volume of solution produces a much higher blockade than in nonpregnant women.


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Obstentrics_Williams. The irst stage of labor requires a sensory block to the level of the umbilicus (Tlo)' During the second stage of labor and for operative vaginal delivery, a sensory block of 52 through S4 is usually adequate to cover pain from perineal stretching and/ or instrumentation. Analgesic options include continuous lumbar epidural analgesia, combined spinal-epidural, continuous spinal analgesia, and other blocks such as pudendal and paracervical blocks.


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Obstentrics_Williams. Local anesthetic agents are usually given to establish a sensory block to the desired dermatome level. They are almost exclusively used in conjunction with neuraxial opioids. he mechanism of action is a function of the administration route and lipid solubility. Analgesia is induced by absorption into the vascular system (supraspinal), actions on the dorsal horns, and direct spread in the cerebrospinal fluid to the brainstem. Highly-soluble lipid opioids such as fentanyl and sufentanil have a rapid onset of action. But, because they are absorbed into lipid membranes and the epidural vasculature, their duration of action is short. Hydrophilic solutions such as morphine, on the other hand, provide extended analgesia (Lavoie, 2013). he major advantages of using such a combination are the rapid onset of pain relie, a decrease in shivering, and less dense motor blockade. Side efects are common and include pruritus and urinary retention. Nalbuphine, 2.5 to 5 mg intravenously, can be used to


Obstentrics_Williams

Obstentrics_Williams. onset of pain relie, a decrease in shivering, and less dense motor blockade. Side efects are common and include pruritus and urinary retention. Nalbuphine, 2.5 to 5 mg intravenously, can be used to treat pruritis without diminishing the analgesic efect.


Obstentrics_Williams

Obstentrics_Williams. A level of sensory blockade extending to the T 4 dermatome is desired for cesarean delivery. Depending on maternal size, 10 to 12 mg of bupivacaine in a hyperbaric solution or 50 to 75 mg of lidocaine hyperbaric solution is administered. The addition of opioid increases the rapidity of blockade onset, reduces shivering, and minimizes referred pain and other symptoms such as nausea and vomiting. The addition of a preservative-free morphine (Duramorph or Astramorph), 0.1 to 0.3 mg intrathecal or 2 to 4 mg epidural, provides pain control up to 24 hours postoperatively. Hypotension. Shown in Table 25-5 are some of the more common adverse events associated with neuraxial analgesia. Importantly, obese women have signiicantly impaired ventilation, and thus close clinical monitoring is imperative (Vricella, 2011). TABLE 25-5. Complications of Regional Analgesia Uncommon Inadvertant intrathecal, subdural, or intravascular injection of local anesthetic drugs Neurologic injury


Obstentrics_Williams

Obstentrics_Williams. TABLE 25-5. Complications of Regional Analgesia Uncommon Inadvertant intrathecal, subdural, or intravascular injection of local anesthetic drugs Neurologic injury Hypotension is a common complication that may develop soon after injection of the local anesthetic agent. It is the consequence of vasodilatation from sympathetic blockade and is compounded by obstructed venous return due to uter ine compression of the great vessels. In the supine position, even in the absence of maternal hypotension measured in the brachial artery, placental blood flow may still be significantly reduced. Treatment includes uterine displacement by left lat eral patient positioning, intravenous crystalloid hydration, and intravenous bolus injections of ephedrine or phenyleph rine.


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Obstentrics_Williams. Ephedrine is a sympathomimetic drug that binds to X-and 0-receptors but also indirectly enhances norepinephrine release. It raises blood pressure by raising heart rate and cardiac output and by variably elevating peripheral vascular resistance. In early animal studies, ephedrine preserved uteroplacental blood flow during pregnancy compared with ai-receptor agonists. Accordingly, it had been the preferred vasopressor for obstetrical use. Phenylephrine is a pure a-agonist and elevates blood pressure solely through vasoconstriction. A metaanalysis of seven randomized trials by Lee (2002a) suggests that the safety profiles of ephedrine and phenylephrine are comparable. Following their systematic review of 14 reports, Lee (2002b) questioned whether routine prophylactic ephedrine is needed for elective cesarean delivery. Although fetal acidemia has been reported with prophylactic ephedrine use, this was not observed with prophylactic phenylephrine use (Ngan Kee, 2004).


Obstentrics_Williams

Obstentrics_Williams. High or Total Spinal Blockade. Most often, high or total spinal blockade follows administration of an excessive dose of local anesthetic or inadvertent injection into the subdural or subarachnoid space. Subdral injection manifests as a high but patchy block even with a small dose of local anesthetic agent, whereas subarachnoid injection typically leads to complete spinal blockade with hypotension and apnea. hese conditions must be immediately treated to prevent cardiac arrest. In the undelivered woman: (1) the uterus is immediately displaced laterally to minimize aortocaval compression; (2) efective ventilation is established, preferably with tracheal intubation; and (3) intravenous fluids and vasopressors are given to correct hypotension. If chest compressions are to be performed, the woman is placed in the left-lateral position to allow left uterine displacement.


Obstentrics_Williams

Obstentrics_Williams. Postdural Puncture Headache. Leakage of cerebrospinal fluid (CSF) from the dura mater puncture site can lead to postdural puncture or "spinal headache." Presumably, when the woman sits or stands, the diminished CSF volume creates traction on pain-sensitive central nervous system structures. Another mechanism may be the compensatory cerebral vasodilation in response to the loss of CSF-the Monro-Kellie doctrine (Mokri, 2001).


Obstentrics_Williams

Obstentrics_Williams. Rates of this complication can be reduced by using a small-gauge spinal needle and avoiding multiple punctures. In a prospective, randomized study of ive diferent spinal needles, Vallejo and associates (2000) concluded that Sprotte and Whitacre needles had the lowest risks of postdural puncture headaches. Sprigge and Harper (2008) reported that the incidence of postdural puncture headache was 1 percent in more than 5000 women undergoing spinal analgesia. Postdural puncture headaches are much less frequent with epidural blockade because the dura mater is not intentionally punctured. he incidence of inadvertent dural puncture with epidural analgesia approximates 0.2 percent (Introna, 2012; Katircioglu, 2008). here is no good evidence that placing a woman absolutely lat on her back for several hours is efective in preventing this headache.


Obstentrics_Williams

Obstentrics_Williams. Once headache develops, it is managed aggressively, as expectant management increases hospital-stay lengths and subsequent emergency-room visits (Angle, 2005). Conservative management, such as luid administration and bed rest, is largely inefective. If not efectively treated, postdural puncture headache can persist as a chronic headache (Webb, 2012). Epidural blood patch is considered the gold standard for treatment. Typically, 10 to 20 mL of autologous blood obtained aseptically by venipuncture is injected into the epidural space. Further CSF leakage is halted by either mass efect or coagulation. Relief is almost always immediate, and complications are uncommon. The initial success rate of an epidural blood patch ranges from 61 to 73 percent (Paech, 2011). Performing a "prophylactic" blood patch is debatable and is thought not to be as efective as if performed after the headache develops (Scavone, 2004, 2015).


Obstentrics_Williams

Obstentrics_Williams. If a headache does not have the pathognomonic postural characteristics or persists despite treatment with a blood patch, other diagnoses are considered. Chisholm and Campbell (2001) described a case of superior sagittal sinus thrombosis that manifested as a postdural headache. Smarkusky and colleagues (2006) described pneumocephalus, which caused immediate cephalgia. Finally, intracranial and intraspinal subarachnoid hematomas have developed after spinal analgesia (Dawley, 2009; Liu, 2008). Convulsions. In rare instances, postdural puncture cephalgia is associated with temporary blindness and convulsions. Shearer and associates (1995) described eight such cases associated with 19,000 regional analgesic procedures done at Parkland Hospital. It is presumed that these too are caused by CSF hypotension. Immediate treatment of seizures and a blood patch were usually efective in these cases.