Comparison of the effects of sodium nitroprusside and isoflurane during rewarming on cardiopulmonary bypass

Abstract

Objectives: Afterdrop in core temperatures after discontinuation of cardiopulmonary bypass (CPB) is reported to be a sign of inadequate total body rewarming on CPB. The purpose of this study was to compare the effects of three different drug regimens on hemodynamic stability and the uniformity of rewarming during the rewarming period of CPB. Design: This prospective randomized study was performed in the Anesthesiology Department of the University of Istanbul. Participants: Sixty-six patients undergoing uncomplicated valve replacement and aortocoronary bypass grafting surgery were studied. Interventions: Anesthesia was maintained with isoflurane and fentanyl infusion during the prebypass and the postbypass periods. Patients were allocated into three groups by the initiation of CPB. Group 1 (n = 22): fentanyl infusion + diazepam + sodium nitroprusside (SNP) (in the rewarming period), group 2 (n = 22): fentanyl infusion + isoflurane, group 3, control (n = 22): fentanyl infusion + diazepam. Rectal, esophageal, and forearm temperatures were monitored throughout the study. Measurements and Main Results: None of the durational and temperature data showed significant differences between groups 1 and 2. In the control group, afterdrop in esophageal temperature was significantly higher than groups 1 and 2 (group 1: −1.4 ± 0.9°C, group 2: −1.44 ± 0.8°C, group 3: −2.1 ± 0.65°C). In group 1, the number of patients whose mean arterial pressure (MAP) decreased below 45 mmHg was significantly higher than group 2 ( p = 0.002). Mean SNP infusion rate and mean isoflurane concentration during the rewarming period were calculated as 1.55 ± 0.8 μg/kg/min and 0.775 ± 0.27%, respectively. Conclusions: Isoflurane produced more stable hemodynamic conditions than SNP during the rewarming period, improved the uniformity of rewarming, and permitted earlier extubation in the intensive care unit (ICU). It is concluded that isoflurane alone is capable of fulfilling the anesthesia needs during hypothermia and the rewarming period of CPB.