PSEUDOCHOLINESTERASE-ACTIVITY REDUCTION DURING CARDIOPULMONARY BYPASS- THE ROLE OF DILUTIONAL PROCESSES AND PHARMACOLOGICAL AGENTS

1. Pseudocholinesterase (ChE) activity is a determinant of the elimina tion kinetics of several drugs used in anesthesia. The time course of ChE activity was investigated in 16 patients undergoing cardiosurgery for a cardiopulmonary bypass (CPB) in normothermia or hypothermia. 2. The onset of the CPB was accompanied by a decrease in ChE activity (-3 7%) (P<0.05) and protein; concentration (-24%) (P<0.05). The quotient ChE activity/protein concentration was numerically reduced to a smalle r extent (-15%) (P>0.05). After the CPB was finished, ChE activity and the protein concentration remained low for the remaining operation ti me. 3. There was no difference in ChE activity, measured in vitro at 3 7 degrees C, between the normothermic and hypothermic group (P>0.05). 4. There was no correlation between heparin concentration in serum and reduction of ChE activity in vitro (P>0.05). In vitro, the ChE activi ty was not affected by either heparin in doses as high as 10,000 U/ml or aprotinin in doses as high as 10,000 U/ml (P>0.05). 5. Conclusions: (1) ChE activity is reduced by CPB mainly by hemodilution and (2) the pharmacological agents used in the present anesthetic technique (hepa rin, aprotinin, midazolam, fentanyl, propofol and mivacurium) do not i nhibit ChE activity at therapeutic serum concentrations. (C) 1998 Else vier Science Inc.