THE article by Mhyre et al. 1in the current issue of Anesthesiology reviews anesthesia-related maternal mortality in Michigan over an 18-yr period. This is the third in a series of reviews that have examined maternal mortality in Michigan since the state began the Maternal Mortality Surveillance in 1950.
Before focusing on the current article, I would like to provide a brief overview of the evolution of anesthesia-related maternal mortality over the past three decades. Anesthesia-related maternal mortality is a remarkable success story and illustrates how a problem can be targeted and significantly reduced through scientific study followed by recommendations that alter practice patterns. Before 1984, the side effects of local anesthetics were poorly understood, and a majority of complications in obstetric anesthesia occurred in laboring patients or when epidural local anesthetics were administered for operative delivery. The first “call to arms” in obstetric anesthesia was an editorial in 1979 that raised concerns over bupivacaine- and etidocaine-induced cardiac toxicity.2This editorial and a second in 19843that outlined investigations spawned from the former led to the eventual withdrawal of 0.75% bupivacaine in obstetrics and altered the way in which local anesthetics were administered. Instead of administering concentrated local anesthetics as a bolus, epidural catheters were tested after insertion and/or all doses were fractionated. These simple measures and the use of dilute local anesthetics solutions to achieve and maintain labor analgesia resulted in a drastic reduction in the number of anesthesia-related maternal deaths, especially during labor.4In fact, I am unaware of a single maternal death during labor related to local anesthetic toxicity since 1984, during which time approximately 40 million parturients within the United States received epidural labor analgesia. This achievement is deserving of a pat on the back for obstetric anesthesia.
Although anesthesia-related maternal mortality was reduced, it was not eliminated. An examination of deaths after 1984 revealed that they now occurred primarily during operative delivery and were most often associated with general anesthesia.4Of concern, it was noted that although overall anesthesia-related maternal mortality was reduced despite the widespread use of epidural analgesia during labor, the rate of maternal mortality associated with general anesthesia remained unchanged. The physiologic changes of pregnancy were believed to be the major contributing factors that increased the risk of either aspiration or failed intubation during induction. This was the second call to arms for obstetric anesthesia.
Reducing the incidence of aspiration or failed intubation by either avoiding general anesthesia or standardizing airway management became the focus of attention. Recommendations included (1) increased utilization of regional anesthesia for both vaginal and operative delivery, (2) early epidural placement in patients at highest risk for urgent cesarean delivery, (3) use of algorithms for difficult intubation with adaptations for fetal distress, (4) equipment checklists for difficult intubation carts, (5) elective fiberoptic intubation in patients with anticipated difficult intubation, and (6) use of newer devices that facilitate ventilation (LMA ™[The Laryngeal Mask Company Limited, Le Rocher, Victoria, Mahe, The Seychelles]; LMA-Fastrach ™[LMA North America, San Diego, CA]; and Combitube [Tyco Healthcare Group, LP, Mansfield, MA], to mention a few). Although it remains to be determined whether these recommendations will further reduce maternal mortality, the current article provides tantalizing evidence that this may be the case.
At first glance, the current review of maternal mortality in Michigan reconfirms much of what we believe to be true in obstetric anesthesia: that anesthesia-related maternal mortality is exceedingly rare and that labor analgesia is safe. There were only eight deaths identified in which anesthesia was the primary cause, and none occurred during labor or were associated with local anesthetic toxicity. However, a closer examination of the deaths reveals a surprising and potentially ominous signal that may once again alter obstetric anesthesia dogma: No maternal deaths were associated with aspiration or failed intubation in the current series. Instead, all eight occurred during emergence or recovery and were related to either airway obstruction or hypoventilation. Weight and race were contributing factors in that 75% of the patients who died were obese (body mass index greater than 30) and 75% were African-American. Whether this trend will be widespread or is simply an aberration remains to be seen. However, at least two alarming trends within the US population may have been confounding factors in the current series and have the potential to impact obstetric anesthesia and maternal mortality in the future: obesity and advancing maternal age.
Obesity in America is reaching epidemic proportions.*It was estimated in 2003 that 32.2% of adults older than 20 yr were obese. The problem is prevalent throughout the United States, and the percentage is expected to continue increasing in the future. Obesity increases the risk of comorbidity, including diabetes, hypertension, and respiratory disease such as obstructive sleep apnea. In addition, obesity is an independent risk factor for cesarean delivery and increases obstetric, neonatal, surgical, and anesthetic risk.5Obesity associated morbidity is so problematic that our governing bodies are developing recommendations to assist with the care of these patients. The American College of Obstetricians and Gynecologists Committee Opinion #315: Obesity in Pregnancy, recommends consultation with an anesthesiologist before delivery as one of six major recommendations,6and the American Society of Anesthesiologists recently published Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea.7Not only are women becoming more obese, they also more often delay pregnancy until after age 35 years, and because advancing maternal age associates with additional risks,8every indication suggests that our patients will weigh more and present at an older age with additional coexisting disease in the future. I predict that these trends will affect each and every anesthetic practice and will not be limited to obstetrics.
With respect to obstetric anesthesia, if these trends hold true, they threaten to reverse three decades of reductions in anesthesia-related maternal mortality unless drastic measures are taken to reduce risks associated with larger, older, and sicker patients. Rather than resting on our laurels, it is time for a new call to arms. It is incumbent on each anesthesia practice to establish protocols that not only reduce anesthetic risks during labor and during induction, should general anesthesia be necessary, but also reduce risks associated with emergence from general anesthesia and during recovery. These protocols must also include measures that specifically address the peripartum and perioperative risks associated with obesity and obstructive sleep apnea with a special focus on reducing the risks of airway obstruction and hypoventilation after delivery and surgery. Unlike the two previous calls to arms, which were relatively easy to achieve because they primarily involved changes to anesthesia care, the current challenges outlined in this editorial will be significantly more difficult to achieve. Although not an impossible task, they will require coordinated and multidisciplinary efforts that involve anesthesia, obstetrics, primary care, nursing, and administration. Obstetric anesthesia has responded to challenges in the past, and I have every reason to believe we will do so once again.
Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina. rdangelo@wfubmc.edu
