MODEL-DRIVEN CLOSED-LOOP FEEDBACK INFUSION OF ATRACURIUM AND VECURONIUM DURING HYPOTHERMIC CARDIOPULMONARY BYPASS

Objectives: This study was designed to investigate the performance of a computer-controlled infusion if atracurium and vecuronium during car diac surgery requiring hypothermic cardiopulmonary bypass, Design: Pro spective,randomized study. Setting: A single university hospital. Part icipants: Twenty patients scheduled for cardiac surgery, Interventions : After induction of anesthesia with fentanyl and diazepam, 10 patient s were randomly allocated to receive a bolus of atracurium and 10 pati ents a bolus dose of vecuronium to facilitate endotracheal intubation. the initial bolus was followed by a computer-controlled closed-loop f eedback infusion of atracurium or vecuronium until the patients were t ransferred to the postoperative intensive care unit. The desired level of neuromuscular blockade, as measured by EMG, was set to 90%. Anesth esia was maintained with a mixture of oxygen and air and either enflur ane or halothane. Measurements and Main Results: The groups were simil ar with respect to patient characteristics. Except during hypothermic CPB, the controller kept the neuromuscular blockade near the set point in both groups, During hypothermic CPB the maximal oscillation of mus cle relaxation was within 10% from the set point, When CPB was initiat ed, the mean rates of infusion of the muscle relaxants increased from the pre-CPB values, but the change of the infusion rate was not statis tically significant for atracurium. During the remainder of CPB, the i nfusion requirements of both muscle relaxants were greatly reduced, bu t rewarming essentially returned the infusion requirements to pre-CPB values. Conclusions: The computer-controlled infusion can be used for the administration of atracurium and vecuronium during CPB. Copyright (C) 1997 by W.B. Saunders Company.