Risks to the infant relating to techniques of local anesthesia.

A more common problem associated with epidural and spinal anesthesia i s maternal hypotension. This i s due to sympathetic blockade, affecting the arterial äs well äs the venous circulation. Arterial relaxation wi l l lower the peripheral resistance, whi le venous relaxation tends to produce peripheral pooling of blood, and reduction in cardiac Output. The resulting hypotension may diminish the placental perfusion sufficiently to cause fetal asphyxia. This phenomenon may be aggraved by vena caval and aortic compression, if the parturient is placed in the supine Position (2) . The incidence and severity of maternal hypotension can be greatly reduced by rapidly in fus ing at least l liter of a crystalloid solution (Ringer ' s lactate) prior to induction of anesthesia. Hypotension, if it occurs, despite both this precaution and proper positioning of the mother (left uterine displacement), should be promptly corrected by administration of a small intravenous dose of a predominantly ß-adrenergic vasopressor (e.g., ephedrine, 10 15 mg) , -adrenergic drugs, even though capable of correcting maternal hypotension, may further aggravate fetal asphyxia by constricting the uteroplacental vasculature (3).