The pharmacokinetics of remifentanil in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass

Remifentanil is a potent opioid with a short duration of action. It has the potential for large-dose opioid anesthesia without an obligatory prolonged period of mechanical ventilation. However, because of high clearance and r apid tissue distribution, cardiopulmonary bypass (CPB) may influence its ph armacokinetics and alter drug requirements. We administered remifentanil by continuous infusion to 68 patients having coronary artery bypass graft sur gery during CPB with hypothermia to describe the effects of these intervent ions on its pharmacokinetics. Remifentanil concentrations were measured bef ore, during, and after CPB. Disposition was best described by a two-compart ment model. The volume of distribution increased by 86% with institution of CPB and remained increased after CPB. Elimination clearance decreased by 6 .37% for each degree Celsius decrease from 37 degreesC.