Heart rate and blood pressure power spectral analysis during calcium channel blocker induced hypotension.

PURPOSE: To observe heart rate (HRV) and blood pressure variability (BPV) as indices of neurocirculatory responses to induced hypotension with diltiazem and/or nicardipine for hip surgery.

METHODS: Thirty-six ASA I-II patients received diltiazem (group D, n = 12), nicardipine (group N, n = 12) or combination of diltiazem/nicardipine (group DN, n = 12). The intensity of HRV and BPV, was determined by spectral analysis of HRV and BPV before anesthesia (T0), just before induced hypotension (T1), and at 10 and 30 min after the start of induced hypotension (T2 and T3, respectively). The logarithmic HRV and BPV were integrated: sympathetic and parasympathetic mediated low frequency area (0.06-0.1 Hz, LF), parasympathetic related high frequency area (0.15-0.4 Hz, HF) and total frequency area (0.01-0.4 Hz). Blood loss was assessed by weighing gauzes and measuring suction.

RESULTS: Group DN had less blood loss (466 +/- 46 ml, mean +/- SEM) than group D (733 +/- 100 ml, P < 0.05). Diltiazem (11.4 +/- 0.9 microg x kg(-1) x min(-1)), and combination of diltiazem (0.25 +/- 0.01 mg x kg(-1)) and nicardipine (5.9 +/- 0.9 microg x kg(-1) x min(-1)) decreased LF-HRV at T2 and T3 (P < 0.05 vs T0 and T1), while nicardipine (8.1 +/- 0.8 microg x kg(-1) x min(-1)) showed increase in LF-HRV at T2 (P < 0.05 vs T1). HF-HRV unchanged through hypotension except for a decrease in group N at T3 (P < 0.05 vs T1). There were no increases in HF-BPV, and LF-BPV, except for a diltiazem induced decrease in LF-BPV at T3 (P < 0.05 vs T0 and T1).

CONCLUSION: Group D and group DN can be used for deliberate hypotension without an increase in sympathetically mediated LF-HRV.