Comparison of amino add levels in brain during different anesthesias in patients undergoing coronary artery bypass grafting under CPB

Objective To compare the amino acid levels in brain during different anesthesias in patients undergoing coronary artery bypass grafting (CABG) under CPB. Methods Eighty ASA Ⅱ or Ⅲ patients aged 45-64 yr undergoing CABG under CPB were randomly divided into 2 groups (n=40 each) : group Ⅰ propefol (P) and group Ⅱ sevoflurane (S). The patients were premeditated with intransuscular morphine 0.2 mg/kg and scopolamine 0.3 mg. Anesthesia was induced with midazolam, etomidate, fentanyl and vecuronium. The patients were mechanically ventilated after tracheal intubation. Anesthesia was maintained with TCI of propofol (target plasma concentration was set at 1-2 μg/ml) in group P or sevoflurane inhalation (end-tidal concentration 0.5%-1.0% ) in group S combined with remifentanil infusion at 0.2-0.4 μg·kg-1 ·min-1 and intermittent iv boluses of vecuronium.Radial artery was cannulated for BP monitoring. Right internal jugular vein was retrogradely cannulated for blood sampling. BIS was maintained at 40-50. Blood samples were taken from right jugular bulb immediately before incision (T1), at 5 min after the beginning of CPB (T2), at 5 min after termination of cooling (T3), immediately and at 30 and 60 min after nasepharyngeal temperature was rewarmed to 37℃(T4-6) for determination of plasma concentrations of glutamic acid (Glu),γ-aminobytyric acid (GABA) and glycine (Gly). The excitatory toxicity index (ETI) was calculated. Results Glu concentration and ETI were significantly lower, GABA concentration was significantly higher at T4-6 and Gly concentration higher at T4 in group P than in group S (P<0.01).Conclusion Propofol can inhibit the release of excitatory amino acids in the brain leading to a new balance between excitatory and inhibitory amino acids. Key words: Propofol;  Amino acids;  Brain;  Cardiopulmonary bypass;  Coronary artery bypass