Measurement of the efficacy of 2% lipid in reversing bupivacaine- induced asystole in isolated rat hearts

BACKGROUND: The reversal efficacy of 2% lipid emulsion in cardiac asystole induced by different concentrations of bupivacaine is poorly defined and needs to be determined. METHODS: Forty-two male Sprague–Dawley rats were randomly divided into seven groups: B40, B60, B80, B100, B120, B140 and B160, n = 6. The Langendorff isolated heart perfusion model was used, which consisted of a balanced perfusion with Krebs-Henseleit solution for 25 minutes and a continuous infusion of 100 μmol/L bupivacaine until asystole had been induced for 3 minutes. The hearts in the seven groups were perfused with Krebs-Henseleit solution containing a 2% lipid emulsion, and 40, 60, 80, 100, 120, 140 or 160 μmol/L bupivacaine, respectively. Cardiac recovery was defined as a spontaneous and regular rhythm with a rate-pressure product > 10% of the baseline value for more than 1 minute. Our primary outcome was the rate-pressure product 25 minutes after cardiac recovery. Other cardiac function parameters were also recorded. RESULTS: All groups demonstrated cardiac recovery. During the recovery phase, heart rate, rate-pressure product, the maximum left ventricular pressure rise and decline in heart rate in the B120-B160 groups was significantly lower than those in the B40-B80 groups (P < 0.05). The concentration of bupivacaine and the reversal effects of a 2% lipid emulsion showed a typical transoid S-shaped curve, R(2) = 0.9983, IC(50) value was 102.5 μmol/L (95% CI: 92.44 - 113.6). CONCLUSIONS: There is a concentration-response relationship between the concentrations of bupivacaine and the reversal effects of 2% lipid emulsion.