Effects of different sedation depths of propofol on brain injury in patients undergoing cardiac valve replacement with cardiopulmonary bypass

Objective To evaluate the effects of different sedation depths of propofol on brain injury in patients undergoing cardiac valve replacement with cardiopulmonary bypass (CPB).Methods Forty-five ASA physical status Ⅲ or Ⅳ patients of both sexes,aged 26-64 yr,weighing 50-85 kg,scheduled for elective cardiac valve replacement with CPB,were divided into 3 groups according to intraoperative sedation depths (n =15each):30 ≤ bispectral index (BIS) value ＜ 40 (group A) ; 40 ≤ BIS value ≤ 50 (group B) ; 50 ＜ BIS value ≤ 60(group C).Anesthesia was induced with iv injection of lidocaine,midazolam,sulfentanil,etomidate and vecuronium.The patients were tracheally intubated and mechanically ventilated.PET CO2 was maintained at 35-45 mm Hg.Anesthesia was maintained with iv infusion of propofol at a rate of 7,5 and 3 mg· kg-1 · h-1 in A,B and C groups,respectively,intermittent iv boluses of sulfentanil and pipecuronium,and intermittent inhalation of sevoflurane.The infusion rate of propofol was adjusted to maintain the corresponding anesthesic depth in each group.Before CPB (T1),at 30 min of CPB (T2),immediately after termination of CPB (T3) and at 1 h after the end of CPB (T4),blood samples were obtained from the jugular bulb vein and radial artery for determination of plasma S-100β protein concentration and for blood gas analysis,and the arterial to venous blood oxygen content difference (Dj-aO2),cerebral O2 extraction rate (CERO2) and jugular bulb venous to arterial blood lactic acid content difference (Dj-aL) were calculated.Results Compared with group C,the plasma S-100β protein concentrations were significantly decreased,SjvO2 was increased,and Dj-aO2 and CERO2 were decreased at T3-4,and Da-jL was decreased at T3 in groups A and B (P ＜ 0.05).Compared with group B,the plasma S-100β protein concentrations were significantly decreased at T3-4,SjvO2 was increased at T2,Da-jO2 and CERO2 were decreased at T2,and DajL was decreased at T3 in group A (P ＜ 0.05).Conclusion Moderately deepened anesthetic depth of propofol (30≤ BIS value ＜ 40) is helpful in attenuating the brain injury in patients undergoing cardiac valve replacement with CPB. Key words: Propofol;  Conscious sedation;  Cardiopulmonary bypass;  Brain injuries