Anesthetic Risk in Obstetric Patients

Anesthetic Risk in Obstetric Patients

To understand anesthetic risk in obstetric patients it is important first to fully appreciate obstetric risk in general. Although the majority of women of childbearing age are healthy and would be considered to be at very good operative surgical risk, pregnancy, certain maternal/fetal factors, and preexisting medical conditions significantly increase surgical and obstetric risks

Pregnancy-Related Mortality

Pregnancy-related mortality is usually calculated as the number of pregnancy-related deaths divided by the number of live births. Although this number has decreased nearly 100-fold since 1900, it has not changed appreciably since 1982. In fact, perhaps due to better reporting, it has risen slightly in the United States to 11.8 deaths per 100,000 live births in the period 1991-1999. Roughly similar rates (between 6.1 and 12 per 100,000) have been reported from Canada and the United Kingdom. Overall mortality was higher for women > 35 years old, black patients, and patients without prenatal care. The leading causes of death associated with a live birth were pulmonary embolism (21%), pregnancy-induced hypertension (19%), and other medical conditions (17%). Major causes of death associated with a stillbirth were hemorrhage (21%), pregnancy-induced hypertension (20%), and sepsis (19%). Only 34% of patients died within 24 hour of delivery, whereas 55% died between 1 and 42 days, and another 11% died between 43 days and 1 year.

In addition to pulmonary embolism and preeclampsia/pregnancy-induced hypertension, amniotic fluid embolism and intracranial hemorrhage emerge as important additional causes of death.

Some investigators have examined the incidence of severe obstetric morbidity and its relationship to mortality as a more sensitive measure of outcome. Data from the United Kingdom suggest that incidence of severe obstetric morbidity is 12 per 1000 delivery, or 100 times more common that mortality. Risk factors included age > 34 years, nonwhite ethnic group, multiple pregnancy, history of hypertension, previous postpartum hemorrhage, and emergency cesarean delivery. By far the most common morbidities encountered in obstetrics are severe hemorrhage and severe preeclampsia

Anesthetic Mortality

Anesthesia accounts for approximately 2-3% of maternal deaths. Data collected between 1985 and 1990 suggest a maternal mortality of 32 deaths per 1,000,000 live births due to general anesthesia and 1.9 deaths per 1,000,000 live births due to regional anesthesia. More recent data between 1991 and 1999 suggest a lower overall maternal mortality from anesthesia (about 1.6 deaths per 1,000,000 live births), possibly due to greater use of regional anesthesia for labor and cesarean section. Most deaths occur during or after cesarean section. Moreover, the risk of an adverse outcome appears to be much greater with emergency than with elective cesarean sections