Plasma propofol concentration and EEG burst suppression ratio during normothermic cardiopulmonary bypass

Background. During cardiopulmonary bypass (CPB), several factorsaffect drug disposition and action. This topic has not beenstudied extensively during normothermic CPB. In this study,we related propofol dose to plasma propofol concentration andburst suppression of the EEG during normothermic bypass. Methods. After institutional approval and informed consent,45 patients having cardiac surgery were assigned randomly toreceive propofol infusions at 4 (Group A), 5 (Group B) and 6(Group C) mg kg^–1 h^–1 during normothermic CPB. Inall patients, small to moderate doses of fentanyl were alsoadministered. Plasma propofol concentration and burst suppressionratio (BSR) were measured at the following times: (1) 10 minbefore CPB, (2) 10 min after the start of CPB, (3) 30 min afterthe start of the CPB, (4) just after aortic declamping, and(5) 60 min after CPB. Results. At baseline, plasma propofol concentrations were similaramong the three groups. After the start of CPB, the concentrationsof propofol decreased significantly by 41, 35, and 30% of controlvalues in Groups A, B, and C, respectively. In Group A, theconcentration of propofol during CPB remained unchanged at lessthan the concentration before bypass. In Groups B and C, plasmapropofol concentrations gradually increased during CPB to thepre-bypass concentrations. In Group A, BSR values did not changesignificantly during CPB. In Groups B and C, BSR values graduallyincreased and became significantly greater than baseline values.No patient reported intraoperative awareness. Conclusion. The pharmacokinetics and pharmacodynamics of propofolchange during normothermic CPB. During normothermic CPB, theefficacy of propofol may be enhanced compared with before CPB. Br J Anaesth 2003; 90: 122–6