Comparison of the effects of etomidate versus propofol on cerebral oxygen metabolism in patients undergoing abdominal surgery

Objeoctive To compare the effects of etomidate and propofol on cerebral oxygen metabolism in patients undergoing abdominal surgery.Methods Thirty-six ASA Ⅰ or Ⅱ patients aged 30-64 yr weighing 42-73 kg undergoing abdominal surgery under general anesthesia were randomly divided into 2 groups (n=18 each):group E etomidate and group P propofol.Left radial artery was cannulated for continuous direct BP monitoring.A catheter was inserted into right internal jugular vein(LJV) and advanced cephalad until jngatar bulb for blood sampling.Both groups received midazolam 0.08 ms/ks,fentanyl 3μg/kg and vecurunium 0.1 mg/kg and in addition group P received propofol 1.5 mg/ks and group E etomidate 0.3 mg/kg respectively for induction of anesthesia.Anesthesia was maintained with propofol infusion at 4-6 mg·kg-1·h-1 in group P and etomidate infusion at 0.4-0.7 mg·kg-1·h-1 in group E and intermittent iv boluses of fentanyl and vecuronium.ECG,MAP,HR,SpO2 and PET CO2 were continuously monitored.Blood samples were taken from radial artery and IJV for blood gas analysis and lactic acid measurement before induction of anesthesia(T1),immediately after intubation (T2),30 min after skin incision (T3) and at the end of operation(T4).The rate of cerebral O2 extraction (CERO2) was calculated.Results The hemodynamic variables were within the normal range throughout the anesthesia and operation.The oxygen saturation and oxygen partial pressure of both arterial and venous blood(SaO2,SjvO2,PaO2,PjvO2) rose significantly after induction of anesthesia in both groups.There was no significant difference in arterial and venous blood lactic acid level and SaO2,SjvO2,CaO2,CjvO2,Da-jvO2 or CERO2 at all time points between the two groups.Conclusion Both etomidate and propofol combined with midazolam and fentanyl can decrease cerebral O2 metabolic rate and there is no significant difference between the two groups. Key words: Etomidate; Propofol; Brain; Oxygen consumption