Cardiac resuscitation after incremental overdosage with lidocaine, bupivacaine, levobupivacaine, and ropivacaine in anesthetized dogs

There is no information comparing the ability to reverse the cardiotoxic ef fects associated with incremental overdosage of bupivacaine (BUP) to levobu pivacaine (LBUP), ropivacaine (ROP), or lidocaine (LIDO). Open-chest dogs w ere randomized to receive incremental escalating infusions of BUP, LBUP, RO P, and LIDO to the point of cardiovascular collapse (mean arterial pressure [MAP] less than or equal to 45 mm Hg). Hypotension and arrhythmias were tr eated with epinephrine, open-chest massage, and advanced cardiac life suppo rt protocols, respectively. Outcomes were defined as the following: success ful (stable rhythm and MAP greater than or equal to 55 mm Hg for 20 min), s uccessful with continued therapy (stable rhythm and MAP <55 mm Hg after 20 min), or death. Continued therapy was required in 86% of LIDO dogs compared with only 10%-30% of the other dogs (P < 0.002). Mortality from BUP, LBUP, ROP, and LIDO was 50%, 30%, 10%, and 0%, respectively. Myocardial depressi on was primarily responsible for the profound hypotension, as the occurrenc e of lethal arrhythmias preceding resuscitation was not different among loc al anesthetics. Epinephrine-induced ventricular fibrillation occurred more frequently in BUP-intoxicated dogs than in dogs given LIDO or ROP (P < 0.05 ). The un bound plasma concentrations at collapse were larger for ROP, 19.8 <mu>g/mL (10-39 mug/mL), compared with BUP, 5.7 mug/mL (3-11 mug/mL); wher eas the concentrations of LBUP, 9.4 mug/mL (5-18 mug/mL) and BUP were not s ignificantly different from each other.