Background and objective: Previous studies have shown that L-type voltage-sensitive Ca2+ channel blocking agents increased and the L-type Ca2+ channel activator Bay K 8644 reduced the general anaesthetic potency in animals. As the bispectral index correlates with the depth of sedation, we examined whether L-type Ca2+ channel blocking agents affect the bispectral index.
Methods: Thirty hypertensive patients (systolic arterial pressure >160 mmHg) presenting for total intravenous anaesthesia with propofol, fentanyl and ketamine were recruited. Bispectral index monitoring was commenced directly the patients arrived in the operating theatre. All patients were given either nicardipine or diltiazem intravenously at the discretion of the anaesthesiologist in charge.
Results: Twenty-three and seven patients received nicardipine or diltiazem, respectively. The bispectral index level (mean (95% confidence interval)) did not change with either drug. In the nicardipine group, the bispectral index at 0, 5, 10 and 15 min was 55 (52–58), 55 (51–59), 55 (52–59) and 56 (53–59), respectively. In the diltiazem group, values were 59 (48–71), 60 (51–70), 61 (52–71) and 61 (50–72), respectively. Both L-type Ca2+ channel blocking agents significantly decreased arterial pressure.
Conclusions: Clinical doses of nicardipine and diltiazem do not alter the bispectral index during general anaesthesia.