Comparison Of Rocuronium Pharmacodynamics During Hypothermic Cardiopulmonary Bypass Between Membrane And Bubble Oxygenatros In Children

Summary: The dissimilar materials and their biocompatibility ofextracorporeal circuit have different influence on the pharmacology of manylipophilic anesthetics during cardiopulmonary bypass. Our studydemonstrated that the membrane oxygenator and the bubble oxygenator havea similar effect on the parmacodynamics of rocuronium during hypothermicCPB in pediatric congenital heart disease patients.Background: Neuromuscular relaxants are affected by many factors duringhypothermic cardiopulmonary bypass(CPB), such as property of prime fluid,hemodilution and hypothermia.But, the difference between the membraneoxygenator and the bubble oxygenator is still unknown.Objective: To evaluate effects of hypothermic CPB on the pharmacodynamicbehaviour of rocuronium and compare the effects between the membraneoxygenator and bubble oxygenator in children.Methods: Forty-three pediatric patients, ASA Ⅱ~Ⅲ, aged 6-12 yr,undergoing surgery for congenital heart disease(ASD or VSD), wererandomly assigned to either the group of membrane oxygenator (MO, n = 21) or the group of bubble oxygenator (BO, n = 22). All patients were premedicated with sodium phenobarbital 3 ~ 5 mg/kg and scopolamine 0.01~0.02 mg/kg. Anesthesia was induced with midazolam 0.1~0.2 mg/kg, fentanyl 10 ug/kg, and propofol 1~2 mg/kg. A baseline record of the neuromuscular monitoring was made after the loss of consciousness and it was stabilized for 5~10 min, then a bolus dose of rocuronium 600 ^g/kg was administered to the patients. Endotracheal intubation was performed when the twitch response was completely abolished. Anesthesia was maintained with propofol 2—4mg/kg/h with supplements of fentanyl 10 jig/kg and midazolam 0.1 ~ 0.2 mg/kg i.v. as required. Waning neuromuscular blockade was enhanced by the intravenous injection of constant maintenance doses of rocuromum (200 ug/kg) whenever the twitch tension attained 25% of its control before, during and after CPB. Spontaneous recovery of neuromuscular transmission to 75% of the control twitch tension was allowed to occur after the first maintenance dose of rocuronium in pre-CPB and post-CPB. The onset time, no response time, and time of the twitch tension return to 25% of the control (DUR 25%) were recorded. The time of the twitch tension return to 75% of the control (DUR 75%) and the recovery index (time from 25% to75% twitch recovery) were recorded in pre-CPB and post-CPB. The results were presented as means + SD. The comparisons between the groups were performed by Student's Mest and in the group were performed by ANOVA (analysis of variance) . A value of P < 0.05 was considered statistically significant. Results: The pharmacodynamic variables is longer during hypothermic CPBthan pre-CPB and post-CPB (P < 0.05); but during the hypothermic CPB, there were no significant differences in the onset time, no response time, and DUR 25% between the MO and BO groups (P > 0.05)(Tablel). Conclusions: The changes of rocuronium phamacodynamics during CPB and post-CPB suggest that rocuronium pharmacodynamics is affected by hypothermic CPB in children and the findings highlight the need for individually monitoring of neuromuscular blockade in this age group. The membrane oxygenator and the bubble oxygenator have a similar effect in the pharmacodynamics of rocuronium during hypothmic cardiopulmonary bypass.