Abstract: AIM: To investigate the effects of remifentanil on heart rate (HR) and heart rate variability (HRV) in patients and isolated rat hearts, and approach its mechanism of action. METHODS: Clinical research: 40 patients were divided into two groups randomly: remifentanil-only-group(Group R, n =20) and pre-atropine-group (Group A, n =20). Group A were given atropine 0.5 mg (i. m.) 30 min before remifentanil administration. Remifentanil 2 μg/kg was administrated with TCI pump at speed of 1 μg·kg^-1·min^-1. HR and Low frequency High frequency(LF/HF) were observed and recorded before and after administration. Animal experiment: 24 SD rats were divided into three groups randomly (n =8): control group (Group C), 10 ng/mL remifentanil group (Group R10) and 30 ng/mL remifentanil group (Group R30). The isolated rat hearts were perfused with Langendorff apparatus. HR and LVDP were monitored continuously. RESULTS: HR and LF/HF in Group R were decreased significantly (P <0.05) at each observed point after remifentanil administration. But in Group A, the changes of HR and LF/HF were not observed. Compared with Group A, the HR and LF/HF at each observed point were decreased (P <0.05). Between Group R and Group A, HR and LF/HF had significant differences(P <0.05). In animal experiment there was no significant difference of HR and LVDP in the three groups. CONCLUSION: Intravenous injection of remifentanil decreases HR and HRV of patients markedly. The inhibitory effects of remifentanil on heart can be reversed by atropine. Based on animal experiment we conclude that the depression of remifentanil on heart is caused by inhibiting central nervous system or interfereing balance of autonomic nerve system.

Key words: remifentanil, heart rate, heart rate variability, isolated rat heart perfusion, mechanism