Effect of dexmedetomidine on rabbit heart rate: in vitro and in vivo experiments / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effect of dexmedetomidine on heart rate (HR) of rabbits through in vitro and in vivo experiments, and investigate the mechanism by which dexmedetomidine lowered HR.Methods In vitro experiment Healthy adult rabbits of both sexes, weighing 2.0-2.5 kg, aged 8-10 weeks, were studied.The 24 isolated hearts passively perfused in a Langendorff apparatus were randomly divided into 3 groups (n =8 each) using a random number table control group (group C) , and dexmedetomidine 3 and 30 ng/ml groups (D1 and D2 groups).The isolated hearts were continuously perfused with K-H solution for 45 min in group C.After 15 min of equilibration, the isolated hearts were perfused for 30 min with K-H solution containing dexmedetomidine 3 and 30 ng/ml in D1 and D2 groups, respectively.At 15 min of equilibration, and at 15 and 30 min of perfusion with K-H solution containing dexmedetomidine, HR and left ventricular systolic pressure (LVSP) were recorded.In vivo experiment Twenty-five healthy adult rabbits of both sexes, weighing 2.0-2.5 kg, aged 8-10 weeks, were randomly divided into 5 groups (n=5 each) using a random number table dexmedetomidine 3, 6, 9, 12, and 15 μg/kg groups (D3, D6, D9, D12, D15groups), to receive the corresponding doses of dexmedetomidine which was intravenously infused over 10 min.HR and mean arterial pressure were monitored and recorded before administration (T0) , and at 15 and 40 min after administration (T1,2).The correlation between doses of dexmedetomidine and change rate of HR was tested by Spearman correlation analysis.Results In vitro experiment Compared with group C, no significant changes were found in HR and LVSP at each time point in D1 and D2 groups (P＞0.05).In vivo experiment Compared with those at T0 , HR at T1 in D6 and D9 groups, HR at T1,2 in D12 and D15 groups, and mean arterial pressure at T1,2in D6, D9, and D12 groups were significantly decreased (P＜0.05) , and no significant change was found in HR at each time point in group D3 (P＞0.05).The correlation coefficient between doses of dexmedetomidine and change rate of HR was 0.944 (P＜0.05).Conclusion The mechanism by which dexmedetomidine lowers HR of rabbits is not related to direct inhibition of sinoatrial nodes, but associated with the balance of autonomic nervous system.