Neuropsychological function in children with cyanotic heart disease undergoing corrective cardiac surgery: effect of two different rewarming strategies

OBJECTIVE: Hypothermia conventionally used in cardiopulmonary bypass necessitates rewarming to normothermic temperatures, which has been shown to be associated with neuropsychological injury. We studied the effects of two different rewarming strategies on postoperative neuropsychological function in cyanotic paediatric patients undergoing elective primary intracardiac repair of tetralogy of Fallot with the aid of cardiopulmonary bypass. METHODS: This was a randomised clinical study undertaken in the cardiothoracic centre of a tertiary level referral and teaching hospital. Eighty children, aged 6-15 years undergoing elective primary intracardiac repair of tetralogy of Fallot using cardiopulmonary bypass under moderate hypothermia at 28 degrees C were included in this study. The patients were randomly allocated into two groups of 40 each. Group 1 patients were rewarmed to a nasopharyngeal temperature of 33 degrees C while group 2 patients were rewarmed to a nasopharyngeal temperature of 37 degrees C before weaning them off cardiopulmonary bypass. The anaesthetic and bypass management was standardised for both the groups. All patients were assessed for neuropsychological function preoperatively and on the fifth postoperative day using the MISIC tests. The amount of blood loss and need for blood and blood product transfusion postoperatively, need for pacing, increased inotropes or vasodilator use and time to extubation were also noted. Serum s-100beta levels were measured post anaesthetic induction and at 24h postoperatively. RESULTS: There was a significant deterioration in neuropsychological function postoperatively in the patients in group 2 (37 degrees C) as compared to their preoperative function. This was associated with higher s-100beta levels 24h postoperatively in group 2 (37 degrees C) compared to group 1 (33 degrees C) patients. The time to extubation was longer in group 1 (33 degrees C). No significant differences were noted in the amount of postoperative blood loss, blood and blood product use, inotrope or vasodilator use and the need for pacing. CONCLUSION: Weaning off bypass at 33 degrees C is associated with lesser postoperative neuropsychological dysfunction compared to rewarming to 37 degrees C before weaning off bypass. This may be used as a tool to decrease neurologic morbidity following cardiac surgery in children with congenital cyanotic heart disease.