USE OF SEDATIVE, ANALGESIC, AND ANESTHETIC DRUGS DURING LABOR AND DELIVERY - BANE OR BOON

The use of sedative, analgesic and anesthetic drugs during labor and delivery is viewed by many as potentially dangerous to both the mother and the fetus. Apnea of the newborn infant secondary to use of these agents at high doses, frequently observed during the 1930''s and 1940''s, was proposed earlier as a major cause of brain injury at birth. Recent animal experimental studies suggest that these agents may prevent fetal asphyxia or, if fetal asphyxia is present, reduce its severity, i.e., they offer the possibility of therapeutic intervention in the circumstance of asphyxia of the fetus. These agents may act therapeutically by depressing fetal brain metabolism, thus increasing fetal tolerance to asphyxia; increasing the O2 supply to the fetus by diminishing maternal sympathetic nervous system activity, decreasing uterine blood vessel tone, and improving uterine blood flow; diminishing the forces of labor, further increasing net O2 transfer to the asphyxiated fetus; and/or moderating any large increases in maternal and fetal serum glucose concentration. A high concentration of glucose in the serum significantly and sometimes dramatically increases the pathologic response of the brain to asphyxia, by augmenting the extent to which lactic acid accumulates in brain tissue during asphyxia. A high lactic acid concentration in brain tissue causes the development of brain edema and tissue necrosis. The role of sedative, analgesic and anesthetic drugs used during pregnancy and labor apparently is greatly misunderstood and their status within obstetrics requires careful re-examination.