Heart rate variability dynamics during controlled hypotension with nicardipine, remifentanil and dexmedetomidine

BACKGROUND: This study was done to investigate how nicardipine, remifentanil and dexmedetomidine affect the balance of the autonomic nervous system in patients receiving controlled hypotension under general anaesthesia by evaluating heart rate variability indices. METHODS: Sixty-two patients were randomly allocated to either the nicardipine-sevoflurane (Group N, n = 21), remifentanil-sevoflurane (Group R, n = 21) or dexmedetomidine-sevoflurane (Group D, n = 20) group for controlled hypotension during orthognathic surgery. Electrocardiogram data acquisition was done after vital sign stabilization following anaesthesia induction (T1) and 30 min after controlled hypotension was induced (T2). RESULTS: Total power and low frequency (LF) power was significantly decreased at T2 compared with T1 in all groups, while a decrease in high frequency (HF) power was only observed in Group N (P < 0.001). LF/HF ratios of Group R and D were significantly suppressed at T2 compared with T1 (P = 0.001 and P < 0.001, respectively), but was increased Group N (P = 0.009). The LF/HF ratio of Group N was significantly higher than Group R and D at T2 (P < 0.001 in both), with Group D showing a significantly lower LF/HF ratio compared with Group R (P < 0.001). CONCLUSIONS: Remifentanil and dexmedetomidine did not have sympathetic nervous system-stimulating effects during controlled hypotension, while remifentanil seemed to be superior in preserving the overall balance in autonomic nervous system activity. Nicardipine was found to stimulate the sympathetic nervous system, which may be problematic in patients vulnerable to disturbances in the autonomic nervous system.