Cerebral protective effects of different doses of propofol during mild hypothernuc CPB / 中华麻醉学杂志

ABSTRACT

Objective To assess the cerebral protective effects of different doses of propofol during mild hypothermic cardiopulmonary bypass (32℃-35℃) .Methods Thirty consecutive ASA Ⅱ-Ⅲ patients aged 18-50 years, undergoing elective cardiac surgery under mild hypothermic CPB were randomly divided into 3 groups in group Ⅰ and Ⅱ the patients were given a bolus of propofol 1 mg kg-1 at the beginning of CPB followed by propofol infusion at a rate of 3 mg ? kg -1? h -1 (group Ⅰ ) or 6 mg? kg-1 ?h-1 (group D ) till the end of CPB and in group Ⅲthe patients received midazolam infusion at 0.2 mg? kg-1 h-1 instead of propofol. Anesthesia was induced with intravenous midazolam 0.15 mgkg-1 ,fentanyl 5 ?g kg-1 and vecuronium 0.1 mg? kg-1 .After tracheal intubation fentanyl 30-50 ?g kg-1 was infused during CPB and muscle relaxation was maintained with intermittent iv boluses of vecuronium. Surgery was performed with mild hypothermic CPB(32℃-35℃ ) .Arterial blood pH and PaCO2 were maintained within normal range and MAP was maintained at 50-80 mm Hg during CPB. Hematocrit was maintained at 25%-30% .Internal jugular vein(IJV) was cannulated and the catheter was advanced retrogradely till jugular bulb. Naso-pharyngeal temperature was monitored. Blood samples were taken simultaneously from artery and UV befor CPB (A) ,when mild hypothermia was being stably maintained(B) ,when the patients were rewarmed to 361 (C)and 30min(D),4-6 h(E)and 24 h(F) after discontinuation of CPB, for determination of cerebral oxygen metabolism and balance, cerebral lactate production (CLP), blood malondialdehyde (MDA) and superoxide dismutase (SOD) levels. CLP was calculated from arterial-cerebral venous blood lactate difference /arterial blood lactate concentration. Lactate oxygen index (LOI) was calculated from arterial-cerebral venous blood lactate difference /arterial-cerebral venous blood O2 content difference.Results In group I (low propofol dose) 30% patients developed cerebral O2 inbalance during rewarming but blood MDA, CLP and LOI were decreased. In midazolam group (group Ⅲ) cerebral O2 balance was improved but there was no depression of blood MDA, CLP and LOI. In groupⅡ (high propofol dose) cerebral oxygenation was improved and blood MDA level, CLP and LOI were significantly decreased.Conclusion The study shows that propofol infusion at a rate of 6 mg?kg-1? h-1 during CPB can improve cerebral oxygenaton, inhibit blood MDA level, CLP and LOI, and plays a role in the cerebral protection during cardiac surgery with CPB, but more vasoconstrictors are needed.