Neuroprotective Effect Of Ketamine In Patients Undergoing Cardiac Surgery Under Cardiopulmonary Bypass.

Objective To investigate the neuroprotective effect of ketamine by measuringthe changes of brain oxygen metabolism, plasma tumor necrosis factor-a (TNF-a),interleukin-6 (IL-6) and S100βprotein concentrations in patients undergoing cardiacsurgery performed under CPB.Methods: Fourty ASAⅡ～Ⅲpatients undergoing elective mitral valvereplacement(MVR) under CPB were randomly divided into two groups with 20 caseseach: ketamine group (K) and control group (C).Anesthesia was induced andmaintainrd with midazolam,sufentanyl and pipecuronium. After induction, bolus of 2mg.kg^-1 ketamine was given intravenously followed by a continuous infusion of50μg.kg^-1.min^-1 in group K until the end of operation. In group. C,equal volume ofnormal saline was given instead of ketamine. Radial artery was cannulated forcontinuous MAP mornitoring. Right internal jugular vein was cannulated and the catheterwas advanced in a cephalad direction into the jugular bulb. Blood samples were takenfrom radial artery and jugular vein bulb after induction of aesthesia (before ketamineinjection)(T1), 20min after CPB(T2), at the end of CPB(T3), at the end of operation (T4)and 24 hours after operation (T5)respectively. In each time point, the changes of arterialand jugular venous hemoblobin saturation(SaO₂ and SjvO₂)were observed,and cerebraloxygen extraction rate (CERO₂) was calculated by the artery-venous difference ofoxygen content. Plasma TNF-a, IL-6 and S100βprotein concentration in jugular veinbulb were determined by ELISA. The correlations between TNF-a, IL-6 and S100βprotein were analysed respectively.Resultsâ‘ Cerebral oxygen extraction rate (CERO₂) in group K weresignificantly lower than that in group C at T2～4 (P＜0.05).â‘¡Plasma TNF-αandIL-6 concentrations were significantly higher at T2～5 than those at T1 in both groups(P＜0.05). In group K, TNF-αconcentrations at T2～5, IL-6 concentrations at T2～4were significantly lower than those in group C (P＜0.05).â‘¢Plasma S100βproteinconcentration was increased obviously at T2～5 compared with T1 in both groups and was significantly lower in group K than in group C at T2～5(P＜0.05).â‘£The correlationbetween S100βand TNF-a concentrations at T2～5 was 0.815, 0.791, 0.684, 0.572respectively (P＜0.05); The correlation between S100βand IL-6 concentrations at T2～4was 0.785, 0.824, 0.703 respectively (P＜0.05).Conclusions 1. Ketamine can significantly decrease cerebral oxygen metabolismand inhibit the elevation of TNF-α,IL-6 and S100βprotein concentrations induced byCPB.2. Ketamine has neuroprotective effect to some extent during cardiac surgery.Inhibiting the release of proinflammatory cytokines might be one of its neuroprotectivemechanisms.