Effects Of Dexmedetomidine On Renal Blood Flow And Renal Function Of Patients Undergoing Valve Replacement

Objectives:1. To investigate Dexmedetomidine’s impact on renal blood flow (RBF) of patients undergoing cardiac valve replacement surgery via transesophageal echocardiography (TEE).2. To observe Dexmedetomidine’s impact on the concentration of neutrophil gelatinase-associated lipocalin (NGAL) and Cystatin C (Cys C) in blood.Methods:Thirty patients scheduled for cardiac valve replacement surgery in XiangYa hospital from May,2012to Nov,2012were randomized to two groups:C group (placebo) or D group. After a10-min initial dose of0.5μg/kg dexmedetomidine, D group received continuous intravenous infusion0.5-1.0μg/kg·h dexmedetomidine. The infusion started after anesthesia induction and the frist renal blood flow indexes were measured. Sevoflurane inhalation combined with sufentanil and midazolam and vecuronium were used to maintain reasonable levels of anesthesia, and the BIS value was maintained at the range of40-60. HR, MAP, CVP were recorded at entering the operating room (T1), before intubation (T2), after intubation (T3), the beginning of operation (T4), opening the chest(T5), the start of CPB (T6), clamping the aorta (T7), opening the aorta (T8), the end of CPB (T9), closing the chest (T10), leaving the OR (T11), entering the ICU (T12). To measure cardiac output, the diameter of left renal artery (D), left renal artery mean blood flow velocity (Vmean), left renal blood flow (RBF), left renal artery resistance index (RI), pulsatility index (PI) at after induction (T1),30min during cardiopulmonary bypass (T2),30min after cardiopulmonary bypass (T3). Recorded relevant datas of extracorporeal circulation:the use of liquid, the total volume of crystalloid and colloid, urine volume, ultrafiltration; recovery of heart beat, simultaneous recording of artery occlusion time, cardiopulmonary bypass time. Recorded relevant datas of ICU period:the duration of mechanical ventilation and ICU stay, usage of vasoactive agent, fluid intake and output, urine volume. The concentration of NGAL and Cys C in blood were messured before operation (T1),2h(T2),12h (T3),24h (T4) after the end of cardiopulmonary bypass.Results:1.There were no difference between the two groups in general, hemodynamics, BIS value, the usage of anesthetic drugsn the datas of the extracorporeal circulation and the period of ICU.2.CO before CPB was hinger than that of the period of CPB and after CPB in two groups; MAP during CPB was lower than that of before and after CPB in two groups.3.Renal blood flow indexes:renal blood flow of T1(after induction) in group D was lower than that of T2(30min during cardiopulmonary bypass) and T3(30min after cardiopulmonary bypass); T2and T3in group D were higher than correspondent time points in group C. There were no differences between two groups in diameter, Vmean, RBF, RI, PI.4. NGAL:The concentration at each time point (T2, T3, T4) after CPB compared with preoperative (T1) were increased (P <0.05) in group C and group D; but there were no differences among T2, T3or T4; T2, T3or T4in group D were lower than those in group C (P <0.05).Cys C:There were no differences between the two groups.Conclusion:1.Dexmedetomidine can increase renal blood flow during CPB and after CPB in patients undergoing cardiac valve replacement.2.Continuous intravenous infusion of dexmedetomidine during cardiac valve replacement surgery can alleviate increasing blood concentration of NGAL after cardiopulmonary bypass and alleviate renal injury induced by extracorporeal circulation, protect renal function.