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In order to determine the characteristics of anesthesia-related maternal mortality in the United States, Hawkins et al analyzed data from the Centers for Disease Control and Prevention’s ongoing National Pregnancy Mortality Surveillance System from 1979-1990. Death was classified as pregnancy related if it occurred during pregnancy or within one year after delivery and was thought to result from complications of the pregnancy, events initiated by the pregnancy, or worsening of the mother’s condition due to the effects of pregnancy. Unfortunately, the medical records of the patients in the study were not available for review.
During the 11 years of the study, 129 maternal deaths associated with an obstetric delivery were identified. Sixty-seven of the deaths (52%) occurred in association with general anesthesia, 33 with regional anesthesia, four with sedation, and, in 25 cases, the form of anesthesia was unknown. Most of the deaths associated with general anesthesia were due to problems of airway management, including aspiration or failed intubation. Among those women who died as a result of regional anesthesia, 70% had an epidural. Deaths in this category were usually due to local anesthetic toxicity or a high block. Cesarean section was the route of delivery for 82% of women with anesthesia-related deaths.
The anesthesia deaths-related maternal mortality rate declined from 4.3/1,000,000 live births in the first three years of the study (1979-1981) to 1.7/1,000,000 in the final three years (1988-1990). Deaths due to general anesthesia remained stable, while mortality resulting from regional anesthesia fell after 1984, coinciding with the withdrawal of 0.75% bupivacaine from use in obstetric patients by the Food and Drug Administration. Comparing the risk of maternal death associated with general anesthesia to that of regional anesthesia, the authors calculated that the case-fatality risk ratio for general anesthesia rose from 2.3 before 1985 to 16.7 after 1985.
The authors conclude that most maternal deaths due to complications of anesthesia result from general anesthesia performed during cesarean section. Problems encountered in airway management, particularly during emergency cesarean deliveries, contribute to most of these deaths. (Hawkins JL, et al. Anesthesiology 1997;86:277-284.)
This paper by Hawkins et al represents the first analysis of anesthesia-related deaths during pregnancy in the United States. While some of the data are incomplete and certain assumptions have been made in the analysis, the information is of great importance. It is troubling that the number of deaths due to general anesthesia has not declined throughout this study. Rather, the fall in maternal mortality associated with anesthesia over the 11 years of analysis is due to a decline in the number of deaths resulting from regional anesthesia.
What factors contribute to the higher maternal mortality associated with cesarean delivery? Certainly, much of the risk must be associated with emergency cesarean deliveries in compromised patients. Regional anesthesia is more difficult to administer to a morbidly obese woman, the very patient for whom general anesthesia is a greater risk. Likewise, patients with severe preeclampsia who have a coagulopathy are not candidates for regional anesthesia, yet their hypertension increases the likelihood of complications during general anesthesia. In an accompanying editorial (Anesthesiology 1997;86:273-275), Dr. David Chestnut recommends early consultation with an anesthesiologist and placement of an epidural block in women at increased risk for complications with general anesthesia.