Combined Use of Isoflurane and Sodium Nitroprusside During Active Rewarming on Cardiopulmonary Bypass: A Prospective, Comparative Study

AIMS: To evaluate and compare the effect of isoflurane, sodium nitroprusside (SNP) and combined use of isoflurane and SNP on body rewarming and haemodynamic stability during active rewarming on cardiopulmonary bypass (CPB). SUBJECTS AND METHODS: In a prospective, randomised study 75 adult patients scheduled for coronary artery bypass grafting (CABG) under CPB were studied in three groups of 25 patients each. During active rewarming, patients of group I received SNP infusion in CPB, group-II received isoflurane through vaporiser in gas circuit of the CPB machine and group III received a combination of isoflurane inhalation (0.2-0.5%) + SNP in low doses (<1mg/kg/min). RESULTS: Mean requirements of SNP to achieve maximum pump flow during rewarming were 1.48 ± 0.65 mg/kg/min (range 0.3-3.5 mg/kg/min) in group I and 0.75 ± 0.25 mg/kg/min (range 0.2-0.85 mg/kg/min) in group III. Mean isoflurane concentration required to achieve maximum pump flow during rewarming was 0.95 ± 0.35% (range 0.2-1.5%) in group II and 0.35 ± 0.1 (range 0-0.4%) in group III. The requirements of SNP and isoflurane in group III were significantly less than group I and II (p<0.001). The haemodynamic stability was better in SNP + isoflurane group with significantly lesser requirement of inotropes. Four-scaled assessment for rewarming evaluation failed to show significant statistical difference amongst the groups. CONCLUSIONS: All three drug regimens were equally effective in terms of uniform rewarming of the body on CPB. However, combined use of SNP and isoflurane in low doses provides haemodynamic stability during CPB and is superior to either drug alone.

Keywords
Sodium nitroprusside, isoflurane, coronary artery bypass grafting, cardiopulmonary bypass, rewarming and afterdrop