The present study was undertaken to evaluate the effect of pretreatment with 3 different cardiovascular depressants on attenuating the cardiovascular response to intubation.
METHOD: Eighty adult patients of ASA class I-II without history of cardiovascular disease, who were scheduled for non-cardiac surgeries, were assigned to 4 equal groups of 20 each by a randomized, double-blind design to receive pre-intubation dose of either saline placebo, esmolol 60 mg, magnesium sulfate (MgSO4) 3.6 gm or nicardipine 2 mg. After baseline heart rate and blood pressure readings, the study drug was given I.V. followed immediately with induction dose of thiamylal 5 mg/kg. Succinylcholine 1.5 mg/kg was given at 1 minute later and readings of HR, BP were taken at 1 minute after succinylcholine after which laryngoscopy and intubation were done. Anesthesia was maintained with 1% isoflurane in 50% N20 and 50% O2, and HR, BP readings were recorded every minute for 8 minutes after Intubation.
RESULT: Maximal increase (mean value) in heart rate after intubation was 19.5% in placebo, 21% in esmolol, 12% in MgSO4 and 48% in nicardipine group respectively. Maximal systolic BP increase (mean value) was 24.5% in placebo, 24% in esmolol, 15.6% in MgSO4 and 13.3% in nicardipine group. Esmolol and MgSO4 did not produce significant changes in heart rate, systolic BP or diastolic BP compared to placebo. Nicardipine, on the other hand, caused a significant reduction of systolic and diastolic BP at 1 and 2 minutes after drug administration and a significantly less increase in BP compared to that of placebo. However, there was a significant increase in heart rate associated with nicardipine after drug and after intubation.
DISCUSSION: Our study showed that none of the three drugs tested at the dose recommended by the manufacturer provided satisfactory obtunding effect on the intubation-induced cardiovascular response. Perhaps a combination of the above drugs would produce a better result, which warrants further studies.