Effects of dexmedetomidine on hemodynamics and myocardial injury in patients with pulmonary hypertension undergoing mitral valve replacement

Abstract

Objective To investigate the effects of dexmedetomdine on hemodynamics and myocardial injury in patients with pulmonary hypertension undergoing mitral valve replacement.Methods Forty ASA Ⅱ or Ⅲ patients with pulmonary hypertension,aged 18-64 yr,undergoing mitral valve replacement,were randomized into 2 groups (n =20 each):control group (group C) and dexmedetomidine group (group D).Anesthesia was induced with iv midazolam 0.05 mg/kg,sufentanil 1 μg/kg,etomidate 0.3 mg/kg and rocuronium 0.6 mg/kg and maintained with combined intravenous-inhalational anesthesia.Narcotrend index values were maintained at 40-50.The patients were tracheal intubated and mechanically ventilated.A loading dose of dexmedetomidine 1 μg/kg was injected intravenously over 10 min after intubation followed by infusion at 0.5 μg· kg-1· h-1 until the end of operation in group D.While the equal volume of normal saline was given in group C.Venous blood samples were taken immediately before dexmedetomidine administration,at 10 min after termination of cardiopulmonary bypass (CPB),at the end of operation,and at 6 and 24 h after operation for determination of plasma levels of creatine kinase MB (CK-MB) and cardiac troponin Ⅰ (cTnI) by ELISA.Before and after administration of dexmedetomidine,at skin incision,at sternum splitting,before and after CPB,and at the end of operation,HR,MAP,mean pulmonary arterial pressure (MPAP),cardiac output (CO),systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) were detected by using Swan-Ganz catheter and Vigilance Ⅱ monitor.The requirement for vasoactive drugs and condition of spontaneous heart beats were recorded.Results In group D,each hemodynamic parameter was maintained stable at skin incision and sternum splitting,and MPAP was decreased after CPB and maintained at a lower level.The plasma levels of CK-MB and cTnI,consumption of phenylephrine and dopamine,and requirement for epinephrine were significantly lower in group D than in group C (P ＜ 0.05).There was no significant difference in the consumption of milrinone and rate of spontaneous heart beat between the two groups (P ＞ 0.05).Conclusion During mitral valve replacement for patients with pulmonary hypertension,dexmedetomidine infused at 0.05 μg·kg-1· h-1 after a loading dose of 1 μg/kg is helpful in maintaining systemic circulation and pulmonary circulation stable and provides myocardial protection to some extent. Key words: Dexmedetomidine ; Hemodynamics; Heart valve prosthesis implantation; Myocardial injury