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What’s New in Obstetric Anesthesia in 2011? Reducing Maternal Adverse Outcomes and Improving Obstetric Anesthesia Quality of Care

Butwick, Alexander, MBBS, FRCA, MS

doi: 10.1213/ANE.0b013e31826af982
Obstetric Anesthesiology: Special Article
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This article accompanied the “What’s New in Obstetric Anesthesia?” lecture presented at the Society for Obstetric Anesthesia and Perinatology Annual Meeting in May 2012. The invited lecturer reviewed the obstetric, obstetric anesthesiology, perinatology, and key medical literature published in 2011. This review identifies key topics and themes from the 2011 literature relevant to the science and clinical practice of obstetric anesthesiology and the interdisciplinary care of obstetric patients. Specific topics include health care policy issues that affect pregnant women, updated information on maternal mortality and morbidity, and clinical and outcomes-based research related to anesthetic practices for women undergoing cesarean delivery.

Published ahead of print September 13, 2012

From the Department of Anesthesia, Stanford University School of Medicine, Stanford, California.

Accepted for publication July 16, 2012.

Published ahead of print September 13, 2012

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.anesthesia-analgesia.org).

This is a special article that accompanies the Gerard W. Ostheimer lecture, which was presented at the Annual Meeting of the Society of Obstetric Anesthesia and Perinatology in Monterey (May 2012).

The author declares no conflicts of interest.

Reprints will not be available from the author.

Address correspondence to Alexander Butwick, MBBS, FRCA, MS, Department of Anesthesia (MC: 5640), Stanford University School of Medicine, 300 Pasteur Dr., Stanford, CA 94305. Address e-mail to ajbut@stanford.edu.

The aim of this review is to identify key topics and themes from articles published in 2011 relevant to the science and clinical practice of obstetric anesthesiology and the provision of interdisciplinary care to obstetric patients. Specific topics addressed in this article include health care policy issues that affect pregnant women, updated information on maternal mortality and morbidity, and clinical and outcomes-based research related to anesthetic practices for women undergoing cesarean delivery. To provide background and supporting information for these key topics, relevant scientific data and information sourced from articles published before and after 2011 are also included within this review.

This review is intended to summarize important themes of the “What’s New in Obstetric Anesthesia?” lecture, which was presented at the Society for Obstetric Anesthesia and Perinatology Annual Meeting in May 2012. The lecture was accompanied with a syllabus containing individualized summary descriptions for key articles published in 2011. A detailed description of the methodology for article selection and the syllabus (including table of contents) is provided in the Appendix (see Supplemental Digital Content 1, http://links.lww.com/AA/A461).

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HEALTH CARE POLICY AND MATERNAL HEALTH

Fundamental changes in the nature and delivery of health care within the United States (US) are likely to lead to important changes in maternal health, obstetric, perinatal and obstetric anesthesia services with increased focus on the delivery of accountable or “cost-conscious” health care.

In the US, women have faced considerable challenges in obtaining health insurance that provides adequate coverage for maternity care. Only 12% of insurers provide comprehensive maternity coverage (Ref. 1 in Table 1), and more than one-third of all pregnant women lack insurance before pregnancy.1 Under the Patient Protection and Affordable Care Act, signed into law in March 2010,2 states were expected to provide essential health services to all uninsured persons with incomes up to 133% of the federal poverty level. In addition, subsidies were to be made available to uninsured women for purchasing health insurance through state insurance exchanges, and enrollees’ dependent children were to have access to health insurance up to their 26th birthday (Ref. 2 in Table 1). It was hoped that access to insurance coverage for currently uninsured women would improve, with the vast majority of individuals estimated to have health coverage by 2014. On June 28, 2012, the Supreme Court decided to uphold nearly all the provisions of the Affordable Care Act (Ref. 3 in Table 1). However, the court limited the power of federal government to penalize states that decide not to participate in the expansion of Medicaid, which means some Medicaid populations will not be eligible for federal subsidies to obtain health insurance on insurance exchanges.3 Only time will tell what impact current and future federal and individual state-wide health care reform will have on women of childbearing age who currently lack health insurance.

Table 1

Table 1

Other important changes in health care delivery likely to affect anesthesiologists and other health care providers include (i) the adoption of health information technology, such as electronic health records, and electronic counseling; (ii) incentives to improve clinical practice; (iii) improvements in patient access to health-related information about practitioners and therapeutic options; and (iv) integration of accountable care organizations and quality measures with pay-for-performance strategies.4 In particular, accountable care organizations have been promoted as a new payment model for quality-driven and cost-conscious health care delivery.5 Current models for health care delivery, reimbursement and regulatory oversight will almost certainly transition toward more accountable care-basedsystems in the near future.5,6 Obstetrical care providers will also be held accountable for quality service; health care reform may change obstetrical practice, such as reducing the rate of elective inductions of labor for nonclinical indications (e.g., maternal fatigue or physician preference).7

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PREVENTIVE CARE AND MATERNAL HEALTH

New recommendations by the Institute of Medicine for improving preventive services for women (including pregnant women and women of childbearing age) were introduced in 2011; these recommendations have been adopted by the US Department of Health and Human Services (Ref. 4 in Table 1). A number of initiatives relevant to maternal health are central to these recommendations, including screening procedures for gestational diabetes mellitus at 24 and 28 weeks’ gestation, comprehensive lactation support and counseling programs, and annual well-woman visits, which provide the opportunity to counsel and treat women identified as high-risk before pregnancy and to optimize prenatal assessment and postnatal follow-up.8 These initiatives highlight the importance of preventive care services as a model for improving women’s health and wellness before, during, and after pregnancy. These policies emphasizing improved access to preventive care for women of childbearing age will likely reduce adverse maternal outcomes, including a decrease in the number of unintended, unhealthy pregnancies.9 As a consequence, obstetric anesthesiologists will have many opportunities to become more involved in the development of new, interdisciplinary, health care models for the maternal care of low-risk and high-risk women: antenatal referrals for women with anticipated complicated anesthesia care, multidisciplinary maternity care teams, improved education, and system-wide protocols for managing acute maternal illness (early-warning scoring systems, low-fidelity and high-fidelity training).

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MATERNAL MORTALITY

Evidence indicates that the global maternal mortality rates have decreased in recent years. Using multinational data sources (including vital registration, national surveys, censuses, and surveillance systems of maternal mortality) and alternative modeling approaches, Lozano et al.10 reported that maternal mortality globally has declined over the last 2 decades: 409,100 deaths (uncertainty interval = 382,900–437,900) in 1990 to 273,500 deaths (uncertainty interval = 256,300–291,700) in 2011. Notable decreases in the rate of direct and indirect maternal deaths (2.8% annual decrease between 1990 and 2011) as well as the number of HIV-related deaths between 2003 and 2011 were believed to be important contributors to this overall decline in global maternal death rates. Despite this favorable reduction in worldwide maternal deaths, only 13 countries are likely to meet the Millennium Development Goal 5 target of reducing the maternal mortality ratio by two-thirds between 1990 and 2015.11

Recent maternal mortality reports, originating from developed countries with well-resourced health care systems, provided updated epidemiologic and etiologic data on maternal mortality. The United Kingdom (UK) Eighth Report of the Confidential Enquires into Maternal Death comprised epidemiologic and relevant clinical data for 261 women who died during the triennium 2006 to 2008.12 There was a notable reduction in the overall maternal death ratea compared with the previous triennium 2003 to 200513 (11.39 [95% CI = 10.09–12.86] vs 13.95 [95% CI = 12.45 –15.64] per 100,000 maternities, respectively). Of ongoing concern is that preexisting or new medical conditions aggravated by the physiologic effects of pregnancy (cardiac disease, other indirect non-neurologic diseases, neurologicdisease) were the top 3 leading causes of maternal death (maternal mortality rates = 2.31, 2.14, and 1.57 deaths per 100,000 maternities, respectively). In this UK report and the 4 prior Confidential Enquiries, deaths from indirect causes outnumbered those from direct causes. Of note, the main reason for the decrease in direct deaths (in the most recent report) was a significant reduction in deaths from thromboembolism and other direct causes, such as hemorrhage.12 It is uncertain whether a relative increase in the prevalence of high-risk medical disorders among women of childbearing age and continuing high rates of substandard care have contributed to the higher rate of indirect maternal deaths in these reports. The California Pregnancy-Associated Mortality Review published its first statewide maternal mortality review for maternal deaths that occurred between 2002 and 2003 (Ref. 5 in Table 1). As in the UK report, the California review found that the leading cause of pregnancy-related death was cardiac disease, which accounted for 20% of all 98 pregnancy-related deaths. In both reports (UK and California), a number of sociodemographic factors were associated with high rates of maternal mortality, including African race, obesity, and advanced maternal age (older than 40 years). Despite the obvious differences between the UK and US health care systems, these reports reveal that improvements are needed to advance the overall quality of interdisciplinary and subspecialist maternal care, as well as patient access to experienced maternal care providers, such as maternal-fetal medicine specialists for high-risk patients.

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MATERNAL CARDIAC ARREST

In 2010, the American Heart Association (AHA) updated its guidelines for the treatment and procedures for maternal cardiac arrest.14 However, there has been ongoing controversy surrounding optimal resuscitation approaches for maternal cardiac arrest, such as effective chest compressions in the presence of left uterine displacement and the optimal location for performing perimortem cesarean delivery.15 Several papers published in 2011 clarified strategies for the clinical management of maternal cardiac arrest. Jeejeebhoy et al.16 performed a systematic literature review of resuscitation techniques during maternal arrest. Based on research reported in that review, chest compressions performed in the left lateral position may result in reduced force of chest compression; therefore, leftward displacement of the uterus is advocated to optimize chest compression efficacy. Current AHA guidelines recommend emergency cesarean delivery within 5 minutes after the onset of maternal cardiac arrest14; however, there are no recommendations as to the optimal location for performing perimortem cesarean delivery. During a simulation of maternal cardiac arrest in a labor room, Lipman et al.17 compared the elapsed time postarrest for transferring a mannequin to an operating room for subsequent perimortem cesarean delivery with the elapsed time taken to perform perimortem cesarean delivery on a mannequin in the labor room. The median time from commencing resuscitation to delivery was significantly longer for delivery in the operating room group versus the labor room (8.1 vs 4.3 minutes; P = 0.006). These data reinforce the AHA’s recommendation14 that initiating perimortem cesarean delivery in a labor room is preferable to avoid time delays that may negatively affect perinatal outcomes. To improve obstetric life-support training and education among obstetric and anesthetic staff, in-house drills and simulation-based training should be encouraged for initiating and maintaining resuscitation team practices for maternal cardiac arrest and perimortem cesarean delivery.18

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PREVENTABILITY AND MATERNAL DEATH

Preventability of maternal death has become a hotly debated topic.19 Variation among independent maternal mortality committees in determining root causes of death has likely resulted in marked variation in reported rates of preventable maternal deaths, for example, 22% to 40% in the US,20–22 (Ref. 5 in Table 1) and 70% direct deaths and 50% indirect deaths in the UK.12 Based on data from 49 maternal deaths in New Zealand between 2006 and 2009, Farquhar et al.23 devised a novel classification system that focused on contributory factors and potential avoidability for maternal death (defined as “aspects of care that, if identified, may have altered the outcome”). In this study, contributory factors and potential avoidability were found in 55% and 35% of deaths, respectively. Various organizational and management factors (e.g., lack of policies, protocols, or guidelines), personnel factors (e.g., inadequate knowledge, skills of staff, and interpersonal communication), and reduced access to care were specifically identified as important contributory factors for maternal death. Despite progress in delineating factors associated with preventability, validation studies are needed to assess the accuracy of this approach and other classification systems for identifying contributory factors leading to maternal death within different health care systems.

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ANESTHESIA-RELATED MORTALITY

National rates of anesthesia-related deaths in developed countries are extremely low. In the UK, the rate of deaths directly attributable to anesthesia was 0.31 per 100,000 maternities.12 In the US, there has been a sizable (59%) reduction in the rate of anesthesia-related mortality that has occurred from 1979–1981 to 1991–2002 (2.9 deaths per million live births and 1.2 deaths per million live births, respectively).24 In addition, the relative risk of death for general anesthesia versus neuraxial anesthesia in the US has decreased over time (6.7 between 1991 and 1996 to 1.7 between 1997 and 2002). Improvements in anesthetic monitoring, devices (notably the laryngeal mask), techniques for ventilation and intubation,25 and updated guidelines for difficult airway management26 have likely resulted in reductions in the rate of ventilation and intubation complications for obstetric patients undergoing general anesthesia.

Despite a relative reduction in maternal deaths attributable to general anesthesia, it is important to conduct studies of airway complications occurring among obstetric patients receiving general anesthesia for cesarean delivery. Such studies help evaluate temporal trends of anesthetic-related adverse outcomes. A recent retrospective study from a single obstetrical center in Canada indicated that the rates of difficult and failed intubation among obstetric patients undergoing general anesthesia were 4.7% and 0.08%, respectively,27 but the reported rates of airway complications remained relatively static over a 20-year period. Other recent reports also indicate that airway complications occur rarely in obstetric anesthesia practice. The recent Confidential Enquiries report noted 1 maternal death from failure to ventilate in a patient undergoing general anesthesia.12 In a national UK registry of airway complications, 4 obstetric patients developed major airway complications after induction of general anesthesia over a 1-year study period.28 Because neuraxial blockade has overtaken the use of general anesthesia as the primary anesthesia modality for patients undergoing cesarean delivery,29–32 the secondary impact is that anesthesiologists have reduced exposure and training in performing general anesthesia for cesarean delivery. As a result, it is reassuring and somewhat surprising that the incidence of airway complications is not higher than reported. Nonetheless, vigilance in managing patients with anticipated or unanticipated difficult airways is recommended. Although failed intubation may not itself be lethal in the setting of emergency cesarean delivery, a persistent failed attempt to intubate prolongs apnea time, increases the risk of severe maternal hypoxemia, and may prove fatal if ventilation is initiated too late or mismanaged. When intubation fails, ventilation via a supraglottic device or a mask is advised to initiate and maintain adequate ventilation, and should be a core anesthetic skill for the management of a failed intubation.

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MATERNAL MORBIDITY

Over the last 2 decades, reduced maternal mortality rates in developed countries have led to an increasing focus on severe maternal morbidity or maternal near-miss events for assessing quality measures for obstetric care.22,33,34

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MATERNAL NEAR-MISS

Maternal near-miss means a woman almost died but survived during pregnancy, childbirth, or until the 42nd day postpartum.35 There are 3 frequently used approaches for defining maternal near-miss: (i) disease-specific criteria, such as preeclampsia, and severe postpartum hemorrhage; (ii) management-based criteria, such as intensive care unit admission, blood transfusion; and (iii) organ system dysfunction-based criteria. The lack of consensus for accurately defining maternal near-miss morbidity is reflected in the wide variability in the prevalence of near-miss morbidity: 0.6% to 15% for disease-based criteria, 0.04% to 4.54% for management-based criteria, and 0.14% to 0.92% for organ-based criteria.36

The use of disease-specific criteria for defining maternal near-miss morbidity may be limited by the criteria’s lack of specificity because of different thresholds for defining disease and the severity of disease.37 Identifying patients with near-miss morbidity based on organ dysfunction may prove more advantageous. A working group of external experts affiliated with the World Health Organization (WHO) proposed near-miss criteria that incorporate complications as well as clinical and laboratory markers for organ dysfunction.35 To evaluate the accuracy of these criteria, Cecatti et al.38 performed a retrospective study using data from a cohort of women requiring intensive care admission for severe maternal morbidity. The investigators compared the WHO criteria against markers of organ dysfunction and failure using the maximum sequential organ failure score (SOFA) as a “gold standard.”39,40 The number of cases of maternal near miss defined by WHO was more than the number of women who had organ failure defined by the maximum SOFA score (194 patients versus 119 patients), which implies that the WHO criteria may be identifying less-severe cases of maternal morbidity with more favorable prognosis. However, other results were more encouraging; e.g., nearly all cases of organ failure in the cohort were identified by the WHO criteria (119 of 120 cases; sensitivity = 99%). In the UK, the routine use of a modified early obstetric warning system (MEOWS) has been promoted as a viable system for predicting maternal morbidity.41 MEOWS incorporates trigger thresholds for a number of different physiologic variables (such as temperature, systolic blood pressure, heart rate). A study of 676 obstetric patients showed that MEOWS had good sensitivity (89%), specificity (79%), negative predictive value (98%), and poor predictive value (39%).42 More population-wide studies and outcomes-based research are needed to assess the clinical impact of early-warning systems, such as MEOWS, and scoring systems for near-miss, such as the WHO criteria, as mechanisms for promoting greater awareness and earlier intervention of patients at high risk of developing severe maternal morbidity.Several studies have enhanced our understanding of risk factors associated with near-miss morbidity and the progression of severe maternal morbidity to death. Using administrative data from a US hospital discharge database (the Nationwide Inpatient Sample) and an alternative definition for maternal near-miss morbidity, Mhyre et al.43 assessed the association between maternal comorbid states and maternal near-miss morbidity or mortality. In that study, approximately 1.3 (95% CI = 1.3–1.4) per 1000 hospitalizations for childbirth were complicated by near-miss morbidity or mortality between 2003 and 2006. The highest rates of near-miss morbidity or mortality were observed for patients with specific medical disease states: pulmonary hypertension (98 cases per 1000 deliveries), malignancy (23 per 1000 deliveries), and systemic lupus erythematosus (21 per 1000 deliveries). Kayem et al.44 used data from the UK Confidential Enquires into Maternal Death databases and the UK Obstetric Surveillance System database to perform a cohort analysis to compare 476 women with severe maternal morbidities who survived with 100 women who died between 2003 and 2008. In this study, maternal death was associated with age 35 years and older (adjusted odds ratio [OR] = 2.36; 95% CI = 1.22–4.56); African ethnicity (adjusted OR = 1.38; 95% CI = 1.15–4.92); and unemployed, routine or manual occupation (adjusted OR = 2.19; 95% CI = 1.03–4.68). Although obesity was not found to be an independent predictor in this multivariate model, an association was found in a separate model using recent data between 2006 and 2008 (adjusted OR = 2.73; 95% CI = 1.15–6.46).44These studies reemphasize the importance of careful monitoring and regular ongoing multidisciplinary review, from the antenatal to the postpartum period, of obstetric patients with high-risk medical conditions and sociodemographic risk factors associated with maternal death.

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CARDIAC DISEASE AND MATERNAL MORBIDITY

The spectrum of congenital or acquired heart disease among pregnant patients is thought to vary across different geographical regions. In particular, there has also been a global increase in the reported birth prevalence of congenital heart disease over time (0.6 per 1000 live births between 1930 and 1934 to 9.1 per 1000 live births after 1995).45 Because of improvements in medical and surgical management, the life expectancy of many women with congenital heart disease has improved with an increasing number of patients surviving to their childbearing years.46

Pregnant patients with chronic heart disease are at risk of perinatal complications, cardiac-related morbidity and/or intensive care unit admission.47,48 These findings are supported by recent epidemiologic studies that used administrative data sourced from the Nationwide Inpatient Sample to highlight temporal trends and specific maternal/perinatal complications associated with chronic heart disease.49–51 Kuklina and Callaghan49 observed that a linear increase in the prevalence of delivery hospitalizations occurred between 1995 and 2006 for 4 specific categories of heart disease: congenital heart disease, rheumatic heart disorders, cardiomyopathy and/or congestive heart failure, and cardiac dysrhythmias (P < 0.01). Between 2004 and 2006, pregnant patients with chronic heart disease were at increased risk for developing major cardiorespiratory complications during a delivery hospitalization compared with patients without heart disease. Complications included cardiac arrest/ventricular fibrillation, acute myocardial infarction, in-hospital mortality, and adult respiratory distress syndrome (adjusted ORs = 82.3, 77.1, 20.1, and 13.8, respectively).49 Karamlou et al.50 reported that perinatal complications were more common among patients with congenital heart disease versus patients without congenital heart disease, including induction (37% vs 33%), cesarean delivery or surgically assisted birth (45% vs 35%), and preterm delivery (10% vs 7%) (P < 0.001 for all). Lastly, Opotowsky et al.51 observed that patients with congenital heart disease were at increased risk of adverse cardiac morbidity (a composite of death, heart failure, arrhythmia, cerebrovascular accident, embolic events, and unspecified cardiac complications of pregnancy) compared with women without congenital heart disease (adjusted OR = 8.4; 95% CI = 7.0–10.2).

Anesthesiologists and other obstetric providers are often keen to adhere to best management practices for managing high-risk patients, such as obstetric patients with cardiac disease. With this in mind, new guidelines were published in 2011 by the European Society of Cardiology to provide guidance for physicians caring for obstetric patients with cardiovascular diseases.52 These guidelines contain up-to-date research findings, educational tools for physicians caring for patients with cardiac disease, and ideas about implementing hospital-based programs for obstetric patients with cardiac disease.

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ANESTHESIA FOR CESAREAN DELIVERY

According to US birth data from 2008, the national rate of cesarean delivery remains high (32.3%).53 As a result, there is increasing focus on strategies and techniques for improving the quality of perioperative anesthesia as well as postanesthesia maternal outcomes for women who require cesarean delivery.

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SPINAL ANESTHESIA FOR CESAREAN DELIVERY

The dose of spinal bupivacaine used for neuraxial anesthesia for cesarean delivery has a direct bearing on maternal side effects (notably hypotension and nausea/vomiting) and on the duration and quality of perioperative anesthesia.54 Studies published in 2011 have enhanced our understanding of the risk versus benefits of low-dose versus conventional-dose intrathecal bupivacaine for achieving adequate surgical anesthesia and have provided new information for the effective doses (ED50 and ED95) of intrathecal levobupivacaine and bupivacaine.

Arzola and Wieczorek55 performed a systematic review and meta-analysis in which they pooled data from 12 randomized, controlled studies to assess anesthetic efficacy (based on the need for analgesic supplementation) and the maternal side-effect profile (specifically maternal hypotension, nausea/vomiting) of a low dose (<8 mg) versus a conventional dose (>8 mg) of intrathecal bupivacaine (hyperbaric or plain, with or without adjuvants) for women undergoing elective cesarean delivery. Low-dose bupivacaine was associated with a significantly higher risk of analgesic supplementation compared with a conventional dose (relative risk [RR] = 3.76; 95% CI = 2.38–5.92). In contrast, low-dose bupivacaine was significantly associated with a reduced risk of maternal side effects, including hypotension (RR = 0.78; 95% CI = 0.65–0.93) and nausea/vomiting (RR = 0.71; 95% CI = 0.55–0.93). These findings are limited by clinical and methodologic heterogeneity that existed among studies for hypotension (I2 = 29%; P = 0.19), as well as by a simplified and combined outcome measure for nausea or vomiting with a fixed-effects model. Bouvet et al.56 performed a dose-finding study to determine the ED50 and the ED95 values of intrathecal levobupivacaine, combined with sufentanil and morphine, for adequate perioperative anesthesia in 85 healthy patients undergoing elective cesarean delivery. (Levobupivacaine is not approved for spinal use in the US.) These values are presented in Table 2, and were found to be similar to those previously reported for plain bupivacainecombined with fentanyl and morphine.57 Using a similar approach, Carvalho et al.58 performed a dose-finding study to determine the effective dose of intrathecal hyperbaric bupivacaine, combined with fentanyl and morphine, in 42 morbidly obese patients undergoing elective cesarean delivery. The results for morbidly obese patients were compared with those from a historical non-obese cohort.59 Surprisingly, the ED50 and ED95 values for morbidly obese patients were observed to be greater than those for the historical non-obese control group (Table 2), which may have been attributable to a number of factors, including slower transfer of the patient from the sitting to supine position after block placement, longer surgical preparation time, and a longer perioperative period.

Table 2

Table 2

Overall, these data suggest that low doses of intrathecal bupivacaine or levobupivacaine (<8 mg) are associated with intraoperative breakthrough pain in non-obese and morbidly obese patients. It is unclear whether the postulated advantages of a reduced duration of motor block and earlier time to maternal ambulation in patients receiving low-dose intrathecal local anesthesia truly lead to improved maternal satisfaction after cesarean delivery. In addition, other patient factors (e.g., genetic factors, maternal height, lumbar vertebral interspace, block position [sitting versus lateral]) and pharmacologic factors (e.g., influence of drug and dose of intrathecal adjuncts, use of vasopressors) can influence primary outcomes in dose-finding studies for intrathecal local anesthesia. For the time being, the use of a combined spinal-epidural technique is advised if low doses of intrathecal bupivacaine are considered for surgical anesthesia for cesarean delivery.54

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EPIDURAL “TOP-UP” FOR INTRAPARTUM CESAREAN DELIVERY

In the setting of urgent intrapartum cesarean delivery, the best epidural top-up for ensuring quick onset and adequate quality surgical anesthesia in a patient with a functioning epidural catheter for labor analgesia remains uncertain. Conducting a meta-analysis, Hillyard et al.60 compared epidural top-up solutions for providing adequate surgical anesthesia for cesarean delivery in patients who had received epidural labor analgesia. They pooled data from 11 randomized, controlled studies and compared 3 epidural top-up groups: 0.5% bupivacaine or levobupivacaine; lidocaine and epinephrine with or without fentanyl; and 0.75% ropivacaine. The quickest onset time was found for lidocaine and epinephrine with or without fentanyl compared with the group comprising bupivacaine/levobupivacaine or ropivacaine (overall mean difference in time of onset = −4.51 minutes (95% CI = −5.89 to −3.13 minutes). Bupivacaine/levobupivacaine was also associated with the highest risk of intraoperative block supplementation compared with the other drugs (RR = 2.03; 95% CI = 1.22–3.39). However, the study did not account for other methodologic factors that may have affected these outcome measures, including the definition of onset time, the method of block assessment, the dermatomal block height for ascertaining adequate surgical anesthesia, and the omission of studies investigating 3% 2-chloroprocaine and lidocaine/epinephrine/bicarbonate mixtures, which are probably the more frequently used top-up regimens in the US.30

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IV FLUID LOADING

In patients who receive spinal anesthesia for cesarean delivery, IV fluid administration is often performed to attenuate postspinal hypotension. Methods of fluid administration can vary according to the following: the timing of fluid infusion (before [preload], during coload, or after [postload] spinal anesthesia) and the type of fluid (crystalloid or colloidal solutions).61 Although a number of investigators have compared fluid coloading versus fluid preloading,62 it has been unclear whether crystalloid versus colloid coloading is advantageous. McDonald et al.63 performed a randomized, controlled study to compare the effects of 1-L crystalloid versus 1-L colloid (6% hydroxyethyl starch solution) coload on cardiac output in 60 women who underwent elective cesarean delivery with spinal anesthesia. At the time of spinal injection, the fluid infusion and a titrated phenylephrine infusion were jointly commenced, and cardiac output measurements were recorded with a suprasternal Doppler device. No between-group differences were observed in cardiac output, stroke volume, peak velocity, and corrected flow time up to 20 minutes postspinal injection, which suggests that crystalloid and colloid coload have equivalent effects on the maternal hemodynamic profile during onset of spinal anesthesia. However, one may surmise that these findings apply only to patients who receive a prophylactic phenylephrine infusion; optimal coloading fluid regimens in patients who do not receive a prophylactic phenylephrine infusion remain uncertain.

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GENERAL ANESTHESIA FOR CESAREAN DELIVERY

Patients with hypertensive disorders are at increased risk for a pregnancy-related hospitalization complicated by stroke64 and peripartum subarachnoid hemorrhage,65 and the risk may be compounded by general anesthesia in patients who require cesarean delivery. In a retrospective, population-wide study, Huang et al.66 observed that the risk of stroke was increased among Taiwanese women with preeclampsia who received general anesthesia for cesarean delivery compared with neuraxial anesthesia (adjusted hazard ratio = 2.38; 95% CI = 1.33–4.28). Techniques to attenuate the sympathetic response to laryngoscopy and intubation are advised to reduce the risk of adverse neurologic sequelae, such as intracranial hemorrhage, secondary to severe maternal hypertension. Remifentanil offers advantages as a useful anesthetic adjunct for blunting the cardiovascular response to intubation for patients undergoing general anesthesia for cesarean delivery.67 However, there is limited research assessing optimal remifentanil dosing regimens among severe preeclamptic patients in this setting.68 Park et al.69 compared the hemodynamic effects of remifentanil 0.5 or 1.0 µg/kg in 48 women with severe preeclampsia undergoing general anesthesia with a rapid-sequence induction (using sodium thiopental and succinylcholine) for cesarean delivery. After tracheal intubation, there was adequate attenuation of the maternal hemodynamic response (no significant increase in systolic arterial blood pressure above baseline) and catecholamine response (using assays of maternal plasma norepinephrine and epinephrine concentrations) in the groups receiving 0.5 and 1.0 µg/kg remifentanil. However, transient neonatal respiratory depression was noted in both groups, with evidence of mild maternal hypotension in 15% of mothers who received 1.0 µg/kg remifentanil.

Other population-wide studies from Taiwan have indicated that adverse perioperative and postoperative outcomes are associated with general anesthesia for cesarean delivery. Chang et al.70 reported that general anesthesia was independently associated with an increased risk of postpartum hemorrhage compared with spinal or epidural anesthesia (adjusted OR = 8.15; 95% CI = 6.43–10.33) in a cohort of >60,000 women with singleton pregnancies who underwent cesarean delivery over a 12-month period. Tsai et al.71 performed a retrospective cohort study assessing differences in surgical site infection among patients undergoing neuraxial anesthesia versus general anesthesia for cesarean delivery (n = 303,834). The risk of surgical site infection up to 30 days after surgery was significantly higher among patients undergoing general anesthesia compared with neuraxial anesthesia (adjusted OR = 3.73; 95% CI = 3.07–4.53). Of note, prophylactic antibiotics (dosing and timing of delivery) and body mass index were not accounted for in this study. Future studies are needed in patients from different geographical regions to validate the associations between general anesthesia and these adverse postoperative outcomes and to determine causality.

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CONCLUSION

The aims of the “What’s New in Obstetric Anesthesia?” lecture, syllabus, and review are to synthesize information from the medical literature to advance the science and practice of obstetric anesthesiology. This focused review of the 2011 literature aims to provide obstetric anesthesiologists and other obstetric care providers with a summary of important and new information on health policy, clinical practices, and clinical research to advance the interdisciplinary care of low-risk and high-risk obstetric patients, reduce the number and severity of adverse maternal outcomes, and improve anesthetic practices and care of patients undergoing cesarean delivery.

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DISCLOSURES

Name: Alexander Butwick, MBBS, FRCA, MS.

Contribution: This author wrote the manuscript.

Attestation: Alexander Butwick approved the final manuscript.

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

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ACKNOWLEDGMENTS

The author thanks the Society for Obstetric Anesthesia and Perinatology for the honor of being invited to give the Gerard W. Ostheimer “What’s New in Obstetric Anesthesia?” lecture at the 2012 Annual Meeting of the Society of Obstetric Anesthesia and Perinatology. The author also thanks the following people for their input and support: Dr. Brendan Carvalho, Dr. Farheen Mirza, Dr. Gillian Hilton, Dr. Edward Riley, Dr. Lawrence Tsen, Dr. Roshan Fernando, Dr. Paloma Toledo, Dr. Jill Mhyre, Dr. Ronald Pearl, and Ms. Stephanie Hsi. Lastly, the author also sincerely thanks Ms. Lindsey Hayford and other family members for their motivation and support during the period of literature review.

a In the Eighth Report of the Confidential Enquiries into Maternal Deaths in the United Kingdom, maternities are defined as the number of pregnancies that result in a live birth at any gestation or stillbirths occurring at or after 24 completed weeks of gestation. The maternal mortality rate in this report is defined as the number of direct and indirect deaths per 100,000 maternities. Direct maternal deaths are defined as “deaths resulting from conditions or complications or their management that are unique to pregnancy,” which occur in the antepartum, peripartum, or postpartum periods. Indirect maternal deaths are defined as “deaths resulting from previously existing disease, or disease that develops during pregnancy not as the result of direct obstetric causes, but which were aggravated by the physiological effects of pregnancy.”
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