Effects of 20% Hpid emulsion on plasma and myocardial ropivacaine levels in rats

Abstract

Objective To investigate the effects of 20% lipid emulsion on plasma ropivacaine concentration and myocardial ropivacaine content in rats. Methods Sixty male pathogen-free SD rats weighing 220-270 g were randomly divided into 2 groups (n = 30 each): group A normal saline and group B lipid emulsion.The animals were anesthetized with intraperitoneal 4% pentobarbital 40 mg/kg. The femoral vein was cannulated for drug and fluid administration. ECG (lead Ⅱ) was continuously monitored. 1% ropivacainc 5 mg/kg was injected iv. A bolus of 20% lipid emulsion 5 ml/kg was then injected iv in group B, while in group A equal volume of normal saline was administered instead of 20% lipid emulsion. The animals were sacrificed at 5, 10,20, 40, 60 and 120 min after ropivacaine infusion (5 animals at each time point). Blood samples and myocardial specimens were taken for determination of plasma and myocardial ropivacaine levels by HPLC. Results Plasma ropivacaine concentration at 20 min after ropivacaine administration was significantly higher in group B than in group A. The myocardial ropivacaine concents at 5, 10 min after ropivacaine administration were significantly lower in group B than in group A. Conclusion 20% lipid emulsion infusion can bind ropivacaine and decreasee myocardial ropivacaine content thus reducing the cardiac toxicity of ropivacaine. Key words: Fat emulsions, intravenous; Amides; Myocardium; Drug toxicity