Effects of cardiopulmonary bypass with mild hypothermia on pharmacodynamics of rocuronium in infants undergoing cardiac surgery

Abstract

Objective To investigate the effects of cardiopulmonary bypass (CPB) with mild hypothermia on the pharmacodynamics of rocuronium in infants undergoing cardiac surgery.Methods Fifty ASA Ⅰ or Ⅱ and NYHA class Ⅰ or Ⅱ infants,aged 6 months-3 yr,weighing6-15 kg,undergoing repair ofventricular septal defect or atrial septal defect under CPB,were randomly divided into 2 groups ( n =25 each):profound hypothermia group and mild hypothermia group.The target temperature was controlled at 28-30 ℃ during CPB in profound hypothermia group,and at 32-34 ℃ during CPB in mild hypothermia group.Neuromuscular block was assessed by TOF-stimulation of ulnar nerve using with TOF-Watch accelerometer.Anesthesia was induced with midazolam O.1 mg/kg,propofol 2 mg/kg,fentanyl 6-8 μg/kg and rocuronium 600 μg/kg,and maintained with intermittent iv boluses of fentanyl and midazolam.The patients was tracheal intubated and mechanically venti1ated when the maximal depression of T1 was achieved.PETCO2 was maintained at 30-40 mm Hg.When T1 returned to 75％ of the control twitch,rocuronium 200 μg/kg was injected intravenously.The onset time,maximal N-M block time,clinical muscle relaxation time,and recovery index were recorded before CPB,during CPB and after CPB.Results Compared with profound hypothermia group,the onset time,maximal N-M block time and clinical muscle relaxation time were significantly shortened during CBP in mild hypothermia group ( P ＜ 0.05).Conclusion Compared with profound hypothermic CBP,mild hypothermic CBP can shorten the onset time and muscle relaxation time of rocuronium in infants undergoing cardiac surgery. Key words: Androstanols; Child; Hypothermia, induced; Cardiopulmonary bypass; Dose-re-sponse relationship,drug