The Bispectral Index (BIS) is an electroencephalogram-derived measure of anesthetic depth. We hypothesized that BIS can also indicate the adequacy of analgesia. Therefore we built a combined closed-loop anesthesia system using BIS as control variable and two proportional-differential control algorithms, a propofol and a remifentanil target-controlled infusion system. The effectiveness of such a closed-loop anesthesia system has been demonstrated in a prospective, randomized study.~Elimination of anesthetic agents, propofol in particular, is strongly reduced during liver transplantation. Closed-loop anesthesia could provide adequacy for requirements in respect to the various phases of transplantation. Two groups of patients are compared: one in which propofol and remifentanil are administered by the anesthesiologist, using target-controlled infusion systems, and one in which propofol and remifentanil are administered automatically by the combined closed-loop anesthesia system. In both groups the goal is to maintain BIS between 40 and 60, the range recommended by the manufacturer during anesthesia. We expect the combined closed-loop anesthesia system group to do better: i.e. diminished consumption of propofol (primary outcome measure).
To compare closed-loop anesthesia to manual administration of propofol and remifentanil during liver transplantation