What's New in Obstetric Anesthesia? The 2011 Gerard W. Ostheimer Lecture

Toledo, Paloma MD, MPH

doi: 10.1213/ANE.0b013e3182367a94
Obstetric Anesthesiology: Special Article

The “What's New in Obstetric Anesthesia” lecture was established by the Society for Obstetric Anesthesia and Perinatology in 1975 to update members on the preceding year's medical literature. In 1995, the lecture was renamed in honor of Gerard W. Ostheimer, an obstetric anesthesiologist from Brigham and Women's Hospital who contributed significantly to the knowledge and practice of obstetric anesthesia. The Ostheimer lecturer reviews the obstetric anesthesia, obstetric, perinatology, and health services literature to identify articles that are relevant to the practice of obstetric anesthesiology. This review summarizes the most relevant publications from the 2010 literature.

Published ahead of print October 14, 2011

From the Department of Anesthesiology and Center for Healthcare Equity/Institute for Healthcare Studies, Northwestern University, Feinberg School of Medicine, Chicago, Illinois.

Funding: This project was supported by grant number F32HS020122 from the Agency for Healthcare Research and Quality (principal investigator: Paloma Toledo, MD, MPH). The content is solely the responsibility of the author and does not necessarily represent the official views of the Agency for Healthcare Research and Quality.

The author declares no conflict of interest.

Reprints will not be available from the author.

Address correspondence to Paloma Toledo, MD, MPH, Northwestern University, Feinberg School of Medicine, 251 E. Huron St., F5–704, Chicago, IL 60611. Address e-mail to p-toledo@md.northwestern.edu.

Accepted August 30, 2011

Published ahead of print October 14, 2011

Article Outline

The “What's New in Obstetric Anesthesia” lecture was established by the Society for Obstetric Anesthesia and Perinatology in 1975 to update members on the preceding year's medical literature. The 2010 contents of 75 journals were reviewed for articles that were of relevance to the practice of obstetric anesthesiology. Articles were scored on significance, innovation, approach, and overall impact to obstetric anesthesiology. From the 1115 articles screened, 150 articles were presented in the Ostheimer syllabus at the Society for Obstetric Anesthesia and Perinatology 2011 Annual Meeting. The articles chosen for this review were selected for their importance to the practice of obstetric anesthesiology or because of controversy generated by the article. This review focuses on innovations relevant to the initiation, management, and maintenance of labor analgesia; anesthetic management of cesarean deliveries; changes in obstetric management affecting the practice of obstetric anesthesiology; and advances in neonatal resuscitation.

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Infectious Complications of Labor Analgesia

Although infectious complications after neuraxial procedures are rare,1,2 if not recognized or treated, they may have devastating consequences, such as paralysis or death.3 A review of 179 published cases of postdural puncture meningitis revealed 3 mortalities, all of whom were obstetric patients.3 In early 2010, the Centers for Disease Control and Prevention (CDC) published a case series describing 5 cases of bacterial meningitis after intrapartum spinal analgesia in Ohio and New York.4 In 4 of the cases, Streptococcus salivarius was the confirmed organism, and the presumed mechanism of transmission was droplet transmission directly from the oropharynx or through contamination of sterile equipment. Specifically, the anesthesiologists involved in the cases were implicated; S. salivarius was identified using polymerase chain reaction methodology from the anesthesiologist in the Ohio cluster, and the anesthesiologist was the only common exposure in the 3 cases in New York. This underscores the importance of not only wearing a surgical mask, but also ensuring proper fit (i.e., covering the nose and mouth), and changing masks between cases as recommended by the American Society of Anesthesiologists (ASA) and Healthcare Infection Control Practices Advisory Committee of the CDC (Table 1, reference 1).5

Skin flora is often implicated in the etiology of spinal epidural abscesses. In a prospective randomized controlled trial of 849 patients undergoing gastrointestinal, thoracic, gynecologic, or urological surgery, the effect of skin preparation with chlorhexidine–alcohol or povidone–iodine on surgical site infection within 30 days of surgery was evaluated.6 The rate of surgical site infection was lower in the chlorhexidine group (relative risk 0.59, 95% confidence interval [CI]: 0.41 to 0.85), as was the time to development of infection (P = 0.004; log-rank test). Although there have been no direct comparisons of chlorhexidine–alcohol to povidone–iodine in reduction of infectious complications after neuraxial procedures, one study found that chlorhexidine is superior to povidone–iodine in reducing colonization of epidural catheters,7 whereas other studies have demonstrated a reduction in central line and arterial line colonization.8,9

This year the ASA issued its first practice advisory for the prevention, diagnosis, and management of infectious complications associated with neuraxial techniques.5 In addition to recommending the use of chlorhexidine (preferrably with alcohol) for skin preparation, they also recommended conducting a history and physical examination before initiation of the neuraxial block to identify patients at risk for infection, removing all jewelry (rings and watches), hand-washing, and wearing a cap, mask, and sterile gloves. Additional recommendations include using a sterile occlusive dressing at the catheter insertion site and limiting the disconnection and reconnection of neuraxial delivery systems to minimize the risk of infections. These guidelines for infection control now more closely parallel those of the Association of Anesthetists of Great Britain and Ireland.10 However, in contrast to the Association of Anesthetists of Great Britain and Ireland, the ASA does not recommend the use of sterile gowns for neuraxial procedures.

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Antithrombotic Therapy and Pregnancy

The American Society of Regional Anesthesia (ASRA) convened the 3rd ASRA consensus conference and released updated guidelines for regional anesthesia in patients receiving antithrombotic or thrombolytic therapy.11 These guidelines now include a section that addresses antithrombotic therapy and pregnancy. Because there is a relative paucity of outcome data regarding neuraxial management in the anticoagulated parturient, ASRA suggests following the guidelines for the surgical patients with regards to initiation of neuraxial procedures and postpartum thromboprophylaxis. Special considerations for obstetric management include the following: (1) women taking anticoagulants should transition to low molecular weight heparin (LMWH) or unfractionated heparin (UH) no later than 36 weeks' gestation; (2) LMWH should be discontinued 36 hours before delivery and the patient converted to UH if necessary; and (3) IV UH should be discontinued 4 to 6 hours before delivery. Postpartum, prophylactic dosing can begin 12 hours after vaginal delivery, or epidural catheter removal, whichever occurs later. A 24-hour delay is required for the first dose of UH or LMWH if (1) the patient underwent a cesarean delivery, (2) therapeutic dosing is required (regardless of the mode of delivery), or (3) blood was present during neuraxial needle or catheter placement. Of note, these guidelines contrast with the guidelines of the Royal College of Obstetricians and Gynaecologists.12 The American College of Obstetricians and Gynecologists recently updated their Practice Bulletin on thromboembolism in pregnancy.13 Although they recommend ASRA guidelines for the timing of neuraxial blockade in parturients, they suggest a more liberal approach in the initiation of postpartum thromboprophylaxis. It is therefore advisable to have a multidisciplinary review of institutional anticoagulation policies for obstetric patients.

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Maintenance of Labor Analgesia

The optimal method for maintaining labor analgesia has been another controversial area in obstetric anesthesia. Several studies have demonstrated that timed intermittent boluses (i.e., the infusion pump is programmed to delivered a set volume of epidural solution at regular intervals) are superior to a continuous epidural infusion.1416 The presumed mechanism is more effective spread of the local anesthetic–opioid solution within the epidural space.17 However, currently available commercial epidural infusion pumps cannot deliver timed boluses with patient-controlled epidural analgesia (PCEA). One center designed a software program to enable an infusion syringe pump to deliver PCEA with a timed bolus function.18 Healthy laboring women were randomized to receive timed boluses with PCEA or an equal hourly volume of local anesthetic through a continuous infusion with PCEA. In contrast to the previous studies,1416 the investigators did not find a difference in the incidence of breakthrough pain between the 2 groups; however, they did observe the need for less drug, a longer duration of effective analgesia, and a small increase in maternal satisfaction in the timed bolus group.

A clinically relevant issue is defining the optimal dose and time interval for the timed boluses of local anesthetic. After initiation of combined spinal epidural analgesia with intrathecal bupivacaine and fentanyl, and a lidocaine–epinephrine epidural test dose, Wong et al. randomized 190 healthy, term, nulliparous women to 1 of 3 timed bolus groups.19 Patients received a volume of 2.5 mL of bupivacaine 0.625 mg/mL with fentanyl 1.95 μg/mL every 15 minutes (group 2.5/15), 5 mL every 30 minutes (group 5/30), or 10 mL every 60 minutes (group 10/60), in addition to PCEA. Although there was a reduction in total hourly bupivacaine consumption in the 10/60 group, the reduction was not clinically significant (10.4 mg/h in group 2.5/15, 10 mg/h in group 5/30, and 8.8 mg/h in group 10/60; P = 0.005), nor were there differences among groups in any of the secondary outcomes including the number of manual boluses required for breakthrough pain, pain scores, or satisfaction with analgesia. The authors stated that the drug concentrations and bolus variables used in the study are not practical for clinical practice, because the incidence of breakthrough pain requiring manual physician boluses was high in all groups (64%, 50%, and 50% in groups 2.5/15, 5/30, and 10/60, respectively; P = 0.72). Future studies should investigate other volume/time interval/drug concentration combinations, as well as whether the reduced local anesthetic consumption observed with the timed bolus technique influences delivery outcomes (i.e., reduction in instrumental vaginal deliveries), as suggested by a study published in 2011.20

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Hypotension is the most common complication of spinal anesthesia for cesarean delivery21 and can have significant adverse consequences for both the mother and the fetus. Although many strategies have been proposed to prevent hypotension, most have been ineffective at completely eliminating hypotension.21 Phenylephrine has become the vasopressor of choice in obstetrics, and there is evidence to suggest that prophylactic phenylephrine infusions significantly reduce the incidence of hypotension in comparison with physician-delivered boluses of phenylephrine.2224 However, most of the previous studies have used a high-dose infusion regimen (100 μg/min), and the safety and necessity of this practice has been questioned.25 Two studies published last year evaluated the use of prophylactic fixed-rate phenylephrine infusions on maternal hemodynamics.26,27 In one randomized controlled trial, healthy parturients undergoing elective cesarean delivery under spinal anesthesia were assigned to receive either a placebo or 1 of 4 fixed-rate phenylephrine infusions (25, 50, 75, or 100 μg/min).26 The authors found that there was no difference among the placebo and 4 phenylephrine groups in the number of times that physicians needed to intervene to maintain maternal systolic blood pressure within 20% of baseline. Furthermore, there were no differences between the control group and the phenylephrine infusion groups in the accuracy of blood pressure control (measured using the median absolute performance error), intraoperative nausea, or need for antiemetics. Comparison of the 4 phenylephrine groups demonstrated that there was more reactive hypertension with escalating doses of phenylephrine, and intraindividual variability of blood pressure measurement (wobble) was highest in the 100 μg/min group. These findings suggest that there may not be a benefit to phenylephrine infusions in comparison with physician-delivered boluses; however, if an infusion is used, it is prudent to start with lower doses (25 to 50 μg/min) because they were as effective as higher doses and were associated with less reactive hypertension.

In a second randomized controlled trial the hemodynamic effects of 3 fixed-rate phenylephrine infusions (25, 50, and 100 μg/min) were studied using a suprasternal Doppler to measure cardiac output.27 The investigators found a dose-dependent decrease in cardiac output over time, parallel to a decrease in heart rate. Similar to the previous study, there were no differences in the number of times that physicians needed to intervene for hyper- or hypotension among the 3 groups; however, there was a decrease in the incidence of nausea with increasing phenylephrine doses. Future work should address whether phenylephrine infusions confer a significant benefit over physician-delivered boluses. Given that it is now becoming easier to noninvasively measure cardiac output, a second question is whether using maternal blood pressure or cardiac output as the target variable results in better outcomes.

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Evidence suggests that severe acute pain in the postpartum period may predict the development of chronic pain.28 Identification of women at high risk for acute pain through surveys, noninvasive tests to evaluate pain modulation such as diffuse noxious inhibitory control test, or genetic testing is therefore of great interest to obstetric anesthesiologists.29,30 In one prospective cohort study, the association between genetic polymorphisms in the adenosine triphosphate-binding cassette subfamily B member–1 (ABCB 1) gene and the development of chronic pain after cesarean deliveries was evaluated.30 The ABCB 1 gene codes a protein that may modulate morphine entry into the central nervous system and therefore affect its analgesic efficacy. All patients (n = 620) received spinal anesthesia with intrathecal bupivacaine and morphine 0.1 mg. While there were no differences in morphine consumption, pain scores, or opioid-related side effects among the common polymorphisms, there was a trend towards more pain at 3 months postpartum in women with a specific polymorphism (T allele of C3435T polymorphism).

In a retrospective study from Finland, a survey assessing the presence, intensity, and duration of postpartum pain was sent to women 1 year after delivery to evaluate whether there was a difference in the development of chronic pain by mode of delivery.31 Six hundred women were invited to participate, half of whom had vaginal deliveries and the other half having had cesarean deliveries. The incidence of persistent pain was high in both groups; 18% of cesarean delivery responders and 10% of vaginal delivery responders reported persistent pain (P = 0.01); 4% and 1%, respectively, reported daily pain. Similar to the findings of Eisenach et al.,28 these investigators found that patients with persistent pain had higher recall of pain on the first postpartum day. It is not possible to exclude recall bias, however, because patients with chronic pain may have overestimated the severity of their pain immediately postpartum.28,31

Transversus abdominis plane (TAP) blockade is an adjuvant analgesia technique used improve postcesarean delivery analgesia.32 The TAP block was initially described as a blind procedure32; recent studies have described performing the block with ultrasound guidance.33,34 While it has been shown that the TAP block, as part of a multimodal pain management including intrathecal morphine, does not improve postcesarean delivery analgesia,33 no study had directly compared analgesia after TAP block with intrathecal morphine. In a prospective randomized controlled trial, healthy women undergoing elective cesarean deliveries under spinal anesthesia were assigned to receive intrathecal morphine or a postoperative TAP block.35 All patients received a standardized postoperative multimodal pain regimen. Not surprisingly, the patients who received intrathecal morphine had a longer duration to first analgesic request, less postoperative analgesic consumption, and less pain with movement in the first 4 hours, compared to the TAP block group. Therefore spinal anesthesia with intrathecal morphine remains the most effective technique for providing postcesarean delivery analgesia due to its ability to treat somatic and visceral pain.36 However, TAP blockade likely has a role in several patient groups: those who are not candidates for intrathecal morphine, those in whom neuraxial anesthesia is contraindicated, patients who undergo general anesthesia for cesarean delivery, or those who have breakthrough pain after spinal anesthesia with neuraxial morphine.

While the use of this technique is promising for improving analgesia, anesthesiologists should remain cautious while performing TAP blocks. A 2009 study that measured serum lidocaine concentrations after TAP blockade with 40 mL of 1% lidocaine found that 1 of the 12 participants had a potentially toxic serum lidocaine concentration within 15 minutes of the procedure.37 Limited conclusions can be drawn from this study because lidocaine is rarely used for TAP blockade. Griffiths et al. measured venous concentrations of unbound ropivacaine after bilateral TAP blocks for 24 hours postinjection in 28 patients undergoing elective gynecologic surgery under general anesthesia.38 Ultrasound-guided, bilateral TAP blocks using 3 mL/kg ropivacaine were performed after the induction of anesthesia. Venous blood samples were drawn every 15 minutes for the first hour, every 30 minutes in the second hour, and at 3, 4, 12, and 24 hours after injection. The peak plasma concentration occurred 30 minutes after the block, and remained above the “neurotoxic threshold” until 90 minutes after the TAP block. Ten of the 28 patients exceeded a potentially toxic threshold of 0.15 μg/mL of unbound ropivacaine. Because patients had received general anesthesia, serum ropivacaine levels could not be correlated to clinical signs or symptoms of neurotoxicity. Althought neither of the 2 aforementioned studies was performed in pregnant women, clinicians should be cognizant of the potential for local anesthetic toxicity when performing TAP blocks.

A novel study evaluated the use of continuous subfascial catheters for improving postoperative analgesia. In this randomized controlled study, 56 patients undergoing elective cesarean delivery under spinal anesthesia were assigned to receive a 48-hour continuous infusion of ropivacaine and ketoprofene through a multiorifice catheter placed above or below the fascia during surgical closure.39 Patients were given IV morphine patient-controlled analgesia to treat breakthrough pain. After 12 hours, there was almost a halving of the morphine consumption in the group that had the catheter placed below the fascia compared to above. Patients in the below-the-fascia group also had better analgesia at rest; however, there were no differences between the groups in pain with activity. A preliminary study by Carvalho et al. measured cytokines and inflammatory mediators from cesarean delivery wound exudates using a multiplex bead immunoassay.40 Thirty-eight women were randomized to receive either a continuous infusion of bupivacaine 5 mg/mL or saline at 2 mL/h. The authors found a decrease in interleukin-10 and an increase in substance P in wounds of patients in the bupivacaine group, suggesting a disruption of anti-inflammatory mechanisms. Future studies measuring inflammatory markers may be helpful in elucidating the relationship between wound inflammation and analgesia efficacy.39

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Cesarean Delivery

Investigators from the Consortium on Safe Labor evaluated data from 228,668 deliveries that occurred between 2002 and 2008. To describe current cesarean delivery practices, the data were weighted to represent a national sample.41 The overall cesarean delivery rate was 30.5%, of which approximately 1/3 were repeat cesarean deliveries. Only 28% of all women who were candidates for vaginal trial of labor after cesarean (TOLAC) attempted one. Of the women who attempted TOLAC, the success rate was 57%. A 3rd key finding from this study was that half of all women who underwent intrapartum cesarean deliveries for dystocia or cephalopelvic disproportion were delivered before 6 cm of cervical dilation.

The increase in cesarean delivery rates has become an issue of increasing public health concern. The CDC's National Center for Health Statistics estimated that 32.9% of all births in 2009 were cesarean deliveries (Table 1, reference 2); and the attempted TOLAC rate has decreased to 8% (Table 1, reference 3). Therefore, considerable attention has been given recently to strategies that may be used to reduce the number of cesarean deliveries. These strategies include increasing the TOLAC rate, creating regional networks to support TOLAC attempts at centers with the capability to immediately perform cesarean deliveries in cases of uterine rupture,42 reducing primary cesarean deliveries through use of new labor curves, and novel strategies involving anesthesiologists, such as the use of neuraxial anesthesia for external cephalic version (see below).

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Trial of Labor After Cesarean Delivery (TOLAC)

Through much of the 1980s and early 1990s, women with a previous cesarean delivery were actively encouraged to attempt TOLAC; however, during the mid-1990s there was a sharp decline in the TOLAC rate and a corresponding increase in the number of cesarean deliveries.43 While the cause of this decline is multifactorial, concern and publicity surrounding uterine rupture in women undergoing TOLAC, as well as professional guidelines from the American College of Obstetricians and Gynecologists and the ASA requiring the “immediate availability” of anesthesia and surgical personnel, likely contributed to the decrease in the TOLAC rate.43

In 2010, several articles addressed the safety of TOLAC and vaginal birth after cesarean.4446 In March 2010, the National Institutes of Health convened a consensus conference to evaluate the current state of the evidence for women undergoing TOLAC to inform patients and providers making decisions about delivery after previous cesarean delivery (Table 1, reference 4). The consensus panel concluded that a trial of labor is generally appropriate for most women after a previous low-transverse cesarean delivery. The group was concerned that many physicians and institutions currently do not allow TOLAC, and specifically called upon specialty societies to reassess the need for “immediate availability,” with specific reference to the inconsistency in this requirement relative to other obstetric complications of comparable risk. The data used for the consensus conference were summarized in a report in Obstetrics and Gynecology,43 and published in full as an evidence report by the Agency for Healthcare Research and Quality.47 In August, the American College of Obstetricians and Gynecologists issued an updated Practice Bulletin on vaginal birth after previous cesarean delivery.48 The Practice Bulletin identifies specific subpopulations of women as candidates for TOLAC, such as those with 2 previous low-transverse cesarean deliveries, twin gestations, those undergoing an induction of labor, and women with an unknown uterine scar (unless there was a high suspicion for a previous classical uterine incision). The Practice Bulletin also addresses analgesia for TOLAC. Historically, there has been concern that epidural labor analgesia masks the signs of uterine rupture; the guidelines specifically state that epidural analgesia may be used for women undergoing trial of labor without concern for patient safety. The final recommendations emphasize that while immediate availability of medical personnel is optimal, the ultimate decision to undergo a trial of labor should be made through a shared decision-making process between the patient and the health care provider. Patients should be counseled about the risks and benefits of the 2 modes of delivery (TOLAC versus elective repeat cesarean delivery), as well as hospital resources (availability of obstetrics, anesthesia, perinatologists, and operating room staff) before making their decision. Whether this change in language will lead to a substantive change of practice in institutions that currently do not support TOLAC remains to be seen.

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Progress of Labor

In a secondary analysis of the Consortium on Safe Labor dataset, Zhang et al. found that active labor may not begin until after 6-cm cervical dilation in many women,49 suggesting that many women are being diagnosed with dystocia before entering the active phase of labor, resulting in unnecessary cesarean deliveries. To model labor patterns, the investigators used interval-censored regression, a mathematical modeling technique that uses specific intervals of the labor curve to estimate the time required to dilate from one centimeter to the next, assuming that data are log-normally distributed.5053 Using this technique, the investigators found that the rates of cervical dilation in nulliparous and parous women are similar before 6-cm cervical dilation; after 6 cm, there is much faster acceleration for parous women.49 The authors constructed new partograms describing contemporary labor patterns based on their models. The use of these new partograms may reduce the cesarean delivery rate through reduction in cesarean deliveries performed for arrest of labor. A limitation of this work is that the model only included women who ultimately delivered vaginally; therefore, the results may be biased towards shorter labor as many of the women in the dataset were delivered by cesarean for dystocia before 6-cm cervical dilation.41 Another limitation is that the authors did not separately evaluate labor curves for obese and nonobese women. Such an analysis is clinically relevant, because labor progression is slower in overweight and obese women.54,55

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Anesthesia for External Cephalic Version

Current evidence regarding the use of neuraxial anesthesia on the success of external cephalic versions for breech presentation is conflicting. Weiniger et al. investigated the hypothesis that spinal anesthesia (bupivacaine 7.5 mg) compared to no anesthesia or systemic opioid analgesia would increase the success of external cephalic version in multiparous parturients.56 Spinal anesthesia increased the rate of successful versions (87% compared to 58% in the control group, P = 0.01, 95% CI of the difference in rate: 7.5% to 48%), with significantly improved analgesia. Another group conducted a retrospective cohort study of parturients between 35 and 36 weeks' gestation who underwent external cephalic versions with or without epidural anesthesia (T10 sensory level), and similarly found a higher success rate in the epidural anesthesia group.57 These 2 studies not only showed a benefit to neuraxial anesthesia, but demonstrated it in patient populations which are known to have a greater baseline predictive success of the external cephalic version (multiparous patients and patients at earlier gestational ages).

A meta-analysis of randomized controlled trials evaluating neuraxial compared to no anesthesia (or systemic analgesia) for external cephalic version identified a possible dose–response relationship between the density of the block and version success.58 Four studies (2 published and 2 in abstract form alone) that used less dense “analgesic” dosing found no difference in the success of versions, whereas denser “anesthetic” dosing was associated with an increased success rate. Thus far there have been no direct comparisons of anesthetic to analgesic neuraxial blockade, but it is possible that using higher-density blocks may lead to higher success rates, possibly through improved muscle relaxation and improved maternal comfort during the procedure.59 Future work should address whether the use of neuraxial anesthesia results in a reduction in the cesarean delivery rate, and therefore may be a more cost-effective strategy than neuraxial analgesia or systemic analgesia alone.

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Postpartum Hemorrhage

Several population-based surveillance studies have found that the incidence of postpartum hemorrhage (PPH) has increased in Canada, Australia, and the United Kingdom.6062

Two studies published in 2010 used similar methodology to evaluate trends in PPH in the United States and evaluate possible contributing factors.63,64 Both studies used data from the Nationwide Inpatient Sample, which is a nationally representative dataset, and evaluated ICD-9 codes associated with obstetric hemorrhage. Callaghan et al.64 analyzed the 1994 to 2006 Nationwide Inpatient Sample data on 10,481,197 deliveries; PIH was coded in 2.7% of deliveries. Uterine atony was identified as the cause of hemorrhage in 3/4 of all cases. Temporal evaluation of the trends in PPH revealed a 26% increase in the incidence of PPH over the 12-year period. There was a parallel increase in hemorrhage caused by atony, whereas hemorrhage due to nonatonic causes remained stable over time. The severity of hemorrhage also seems to have increased over time, because there was a doubling of the number of PPH cases that resulted in transfusion over the study period.

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Maternal Mortality and Racial and Ethnic Disparities in Care

Historically, PPH has been 1 of the 3 leading causes of maternal mortality in the United States, along with hypertensive disorders and infections.65 The Pregnancy Mortality Surveillance system contains data on all pregnancy-related deaths in the United States starting in 1986. New data from the system revealed a shift in the causes of maternal death in the United States.66 Berg et al. evaluated data from 1998 to 2005, and found that the aggregate pregnancy-related mortality has increased to 14.5 per 100,000 live births, which is the highest rate in the past 20 years.66 The percentage of deaths attributable to hemorrhage and hypertensive disorders of pregnancy has steadily decreased, while the percentage from medical conditions has increased. Seven conditions now contribute almost equally to maternal mortality: hemorrhage, thrombotic pulmonary embolism, infection, hypertensive disorders of pregnancy, cardiomyopathy, cardiovascular conditions, and noncardiovascular medical conditions. The largest increase has been in the proportion of deaths associated with medical conditions, specifically cardiovascular conditions. Cardiovascular comorbidity was the leading cause of indirect maternal deaths in the United Kingdom between 2006 and 2008.67 Attempts should be made to identify and refer these high-risk women to appropriate centers for counseling and optimization of their medical care to further reduce mortality.

Despite a Healthy People 2010 goal to eliminate racial and ethnic disparities in medical care, no progress has been made in reducing racial disparities in maternal mortality (Table 1, reference 5). A racial/ethnic disparity persists in maternal mortality, with African-American women continuing to experience a 3- to 4-fold higher maternal mortality ratio than Caucasian women.65,66 Race and ethnicity data should be collected on all patients to facilitate research to understand the cause(s) of excess maternal mortality in minority patients (Table 1, reference 6).68

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Resuscitation with air or oxygen after birth asphyxia has been a hotly debated topic,69 because recent evidence suggests equivalent, and possibly superior, outcomes when resuscitation is initiated with room air.7073 Evidence of harm from oxygen therapy includes oxidative damage,73 as well as a possible association with increased rates of childhood malignancy.74,75 Yet professional societies have been hesitant to remove oxygen from their neonatal resuscitative guidelines. A definitive study to demonstrate a 3% reduction in mortality would require >7000 infants.76 In 2010, both the American Heart Association and the European Resuscitation Council issued updated guidelines on neonatal resuscitation.74,75 Both organizations now recommend initial resuscitation with air rather than oxygen. The need for supplemental oxygen should be guided by a pulse oximeter attached to the right upper extremity (preductal). Blended air and oxygen should only be used if there is no improvement in oxygenation. Dawson et al. used a prospective cohort of 468 term and preterm infants to create reference ranges (3rd to 97th percentiles) for oxygen saturation measurements in the first 10 minutes of life.77 It is important to note that in term infants, it takes approximately 8 minutes to reach an oxygen saturation >90%, and slightly longer in preterm infants. These curves should be used for guiding oxygen therapy. Table 2 shows targeted oxygen saturation values, by time of delivery, as recommended by the updated American Heart Association guidelines.78

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The articles discussed in this review of the 2010 literature highlight studies that not only will change clinical practice and guide policy but will eventually serve as the building blocks for future obstetrical anesthesia practice. With improved knowledge, we will continue to improve the quality and safety of care we deliver to parturients and their neonates.

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Name: Paloma Toledo, MD, MPH.

Contribution: This author wrote the manuscript.

Attestation: Paloma Toledo approved the final manuscript.

This manuscript was handled by: Cynthia A. Wong, MD.

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The author would like to thank the Society for Obstetric Anesthesia and Perinatology for the opportunity to review the literature, and the researchers and clinicians who contributed to the 2010 literature. Additionally, the author would like to sincerely thank Lawrence Tsen, MD, Roshan Fernando, FRCA, John Sullivan, MD, Barbara Scavone, MD, and Cynthia Wong, MD, for their mentorship and support, and finally, her parents, who made realizing this dream possible.

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