Epinephrine administration in lipid-based resuscitation in a rat model of bupivacaine-induced cardiac arrest: optimal timing.

BACKGROUND AND OBJECTIVES

The medical community commonly uses lipid emulsion combined with epinephrine in local anesthetic-induced cardiac arrest, but the optimal timing of epinephrine administration relative to lipid emulsion is currently unknown and needs to be determined.

METHODS

Thirty adult male Sprague-Dawley rats were subjected to bupivacaine-induced asystole and were then randomly divided into 3 groups. The temporal administration of epinephrine varied in each group: (1) immediately after the completion of the initial bolus of lipid emulsion therapy (postILE0); (2) immediately after cardiac arrest before the initial bolus of lipid emulsion (preILE); or (3) 1 minute after the completion of the initial bolus of lipid emulsion (postILE1). External chest compression was administered until the return of spontaneous circulation or the end of a 20-minute resuscitation period.

RESULTS

The postILE0, preILE, and postILE1 groups displayed different survival rates (100%, 30%, and 40%; P = 0.003). After return of spontaneous circulation, the rate-pressure product of the postILE0 group was higher than that of the postILE1 group (P < 0.001). Wet-to-dry lung weight ratio of preILE and postILE1 groups was higher than that of the postILE0 group (P < 0.05). The rate of damaged alveoli of the postILE0 group was lower than those of the preILE (P = 0.001) and postILE1 (P < 0.001) groups. Concentrations of bupivacaine in the cardiac tissues of the postILE0 group were lower than that of the postILE1 group (P = 0.01).

CONCLUSIONS

In the rat model of bupivacaine-induced cardiac arrest, the optimal timing for the administration of epinephrine to produce best outcomes of successful cardiopulmonary resuscitation is immediately after the completion of the lipid emulsion bolus. This optimal timing/therapeutic window is of paramount importance.