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ANESTHESIA ALERT
• Nervous system. Pregnancy increases sensitivity to inhaled and local anesthetics, but decreases sensitivity to vasopressors. The increased sensitivity to volatile anesthetics may require up to a 30% reduction in the minimum alveolar concentration, even as early as the first trimester. The decreased sensitivity to vasopressors requires larger doses.
Additional considerations
Though elective surgery should always be postponed until after pregnancy, indicated surgery can be done during any trimester; however, the risks of spontaneous abortion and preterm delivery are lowest during the second trimester.
All pregnant patients should have fetal heart rate monitoring. The American College of Obstetrics and Gynecology (ACOG) recommends pre- and post-operative fetal monitoring for pre-viable fetuses, and
simultaneous pre- and post-operative fetal and uterine contraction monitoring for viable fetuses.
Whether to use intraoperative fetal monitoring depends on fetal viability, the type of surgery being performed, and whether facilities and staff are available for cesarean delivery and neonatal care.
Remember also that many patients are concerned about how medications used during surgery might affect their unborn babies. Embryogenesis is the highest-risk period for structural changes, and there are several known teratogens, such as hyperthermia, radiation and certain medications, such as Coumadin. Pre-operative patient counseling is important to dispel any misconceptions or fears about properly administered anesthetics.
Dr. Toledo (p-toledo@md.northwestern.edu) is an obstetric anesthesiologist at Northwestern University Feinberg School of Medicine in Chicago.
