The Protective Effect Of Dexmedetomidine Against Cerebral Ischemic Injury Of Patients Undergoing Cardiac Valve Replacement Surgery With Cardiopulmonary Bypass

Objective To evaluate the protective effect of dexmedetomidine against cerebral ischemic injury of patients undergoing cardiac valve replacement surgery with cardiopulmonary bypass(CPB).Methods Thirty patients undergoing cardiac valve replacement surgery were allocated randomly into study group (n=15) and control group (n=15). As basal blood samples from arterial and jugular bulb catheters were drawn (T1), dexmedetomidine (0.5μg/kg bolus and infusion at a rate of0.5μg/kg/h) was administered to patients in study group. Arterial and jugular venous blood gas analyses, determining jugular venous oxygen saturation (SjvO2), the arterial to jugular venous oxygen content difference (Ca-jO2), cerebral oxygen extraction (ERO2), were performed after induction (T2),5min after the initiation of cardiopulmonary bypass (CPB)(T3), hypothermia stability period(nasopharyngeal temperature, NPT28-30℃, T4), rewarming to NPT at34℃(T5), and10min after CPB(T6) and at the end of operation (T7). Plasma S-100B protein (S-100B) and neuron-specific enolase (NSE) measurements were performed at T1, T3, T5,T6and T7time point.Results There was no difference between groups regarding age, body weight, Left Ventricular Ejection Fractions before operation, aortic clamping time, extracorporeal circulation time, the lowest NPT, pump flow(p>0.05); and hematocrit, arterial pH, arterial partial pressure of oxygen, arterial partial pressure of carbon dioxide, mean blood pressure at any time point(p>0.05). There was no difference between groups of SjvO2at T1. SjvO2was reduced significantly after induction in both groups (p <0.05), and increased significantly at T3and T4compared to that of T1and T2(p <0.05). SjvO2reduced significantly in the control groups during rewarming period (T5) compared to the study group (p<0.05). SjvO2reduced to that the basal level10minutes after CPB. Da-vO2, ERO2reduced significantly during hypothermia period, and increased during rewarming period, and decreased to the basal level at the end of surgery. Arterial and jugular venous lactate, glucose increased significantly during CPB, but there was no difference between groups (p<0.05). Plasma NSE and S-100B protein increased in both groups at T6and T7compared to that at T1(p<0.05of study group and p<0.01of control group). Plasma NSE and S-100B protein in the study group was significantly lower than in the control group at T6and T7(p>0.05). Conclusion Dexmedetomidine can reduce cerebral oxygen uptake rate in rewarming period during cardiopulmonary bypass, avoid cerebral oxygen supply and demand imbalance in the rewarming period, and can reduce cerebral ischemic injury, which exerts cerebral protective effect on patients undergoing cardiac valve replacement surgery with cardiopulmonary bypass.