In order to investigate the ability of a computer-assisted continuous infusion ( CACI) The institution of cardiopulmonary bypass (CPB) causes profounds changes in the pharinacokinetics of most drugs, leading to unpredictable plasma levels and possibly to unpredictable effects. It may be important to the anaesthetist to develop the ability to either maintain stable plasma levels or change them to new but predictable plasma levels of intravenous anaesthetic agents during cardiac surgery with hypothermic CPB.The purpose of this study was to investigate the ability of a pharmacokinetically-dfiven computer-assisted continuous infusion (CACI) system to maintain a stable and predicted plasma level of sufentanil during hypothermic CPB.The CAC1 system used in this investigation has been used in the maintenance of fentanyl anaesthesia before CPB in patients undergoing coronary revascularization, In this initial report, CACI was effective and accurate in closely approaching the set central compartment concentrations whether it was used to maintain a fixed concentration or to vary concentrations according to the clinical judgement of the anaesthetist. MethodsAfter institutional approval, ten patients scheduled for elective primary coronary revascularization gave informed consent and were entered into this study. Mean ---SD age was 61 • 11 yr (range 39-75), and the preoperative left ventlicular function was good (mean -+ SD angiographic ejection fraction = 0.51 -+ 0.1). Preoperative betaadrenergic and calcium entry blocking medications were given on the day of surgery.All patients were premedicated with lorazepam 0.02 mg'kg -1 PO and morphine 0.1 mg.kg -l IM 60-90 rain before the expected time of induction. After arrival in the induction room, standard monitoring systems consisting of a five lead ECG, a radial artery catheter and a thermodilution pulmonary artery eathetcr were inserted.General anaesthesia was induced with diazepam (0.5 mgbkg -I) and pancuronium (0.1 mg'kg-l), and was maintained with enflurane (0-2 per cent inspired concentrations) and oxygen (100 per cent). Ten minutes before the expected beginning of CPB, a computer-assisted continuous infusion of sufentanil set to reach and maintain a central compartment concentration of 5 ng'ml -t was (!AN J ANAESTH 1987 ,' 34:6 / pp566-9

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