Global Perspectives on Obstetric Anesthesia: Challenges and Priorities for Advancing Maternal Health

The administration of bupivacaine results in dose-dependent blockade of sodium channels. Compared to lidocaine, bupivacaine 1) binds more strongly to resting/inactivated sodium channels, 2) dissociates from sodium channels during diastole more slowly than lidocaine, and 3) depresses the rapid phase of depolarization (Vmax). These actions combined result in a decrease in the availability of fast sodium channels in cardiac membranes, which slows depolarization. Thus, the primary cardiac toxicity of bupivacaine is a decrease in the rate of repolarization in the fast-conducting tissues of Purkinje fibers and ventricular muscle.

If cardiovascular toxicity occurs, advanced cardiac life support (ACLS) should be initiated immediately. Airway management is important in situations of impending cardiovascular and neurologic collapse. Early administration of 20% lipid emulsion is a major component of resuscitation, because cardiac arrest from LAST is different than typical out-of-the-hospital cardiac arrest scenarios. An IV bolus of 1.5 mL/kg of 20% lipid emulsion (Intralipid) is given over one minute, followed by an infusion of 0.25 mL/kg/min until at least 10 minutes after successful achievement of circulatory stability. The bolus dose may be repeated once or twice for continued cardiovascular instability and the infusion may be increased to 0.5 mL/kg/min. Propofol, which is a 10% lipid emulsion, should not be given because the dose required to treat toxicity would most likely result in significant hypotension.