Background and Goal of Study: Few studies evaluated the impact of depth of anaesthesia monitoring on sevoflurane consumption. This prospective randomized study tested the hypothesis that state entropy monitoring is associated with reduced sevoflurane use and faster emergence in patients undergoing colo-rectal surgery.
Materials and Methods: After institutional ethics committee approval, 50 ASA II-III patients were included in the study. Patients having given written informed consent were randomized in two groups: a control (CG) and an entropy (EG) groups. In the CG group, the target expired fraction of sevoflurane (Fetsevo) was adjusted according to haemodynamic and clinical parameters. In the EG group, Fetsevo was adjusted to maintain the state entropy values between 40 and 50. All patients were ventilated using a closed circuit (Zeus respirator, Dräger, Germany).
In addition to sevoflurane, patients received also sufentanil using a target control infusion system (target cerebral concentration: 0.25 ng/ml) that was stopped at the end of the distal colic anastomosis. Sevoflurane administration was stopped in both groups at skin closure. State entropy values were measured continuously (M-Entropy module, GE Healthcare, Helsinky, Finland) in both groups, but were blunted to the anaesthesiologist managing patients in CG group. Volume of sevoflurane used per hour of anaesthesia, time to tracheal extubation, and median state entropy values were compared between the two groups using a Mann Whithney-U test. Data are presented as median [interquartiles]. A p< 0.05 was considered significant.
Results and Discussion: Patients demographics were not different between groups. Duration of surgery was 135 [109-157] min in the CG and 161 [134-193] min in the EG groups (p=0.03)
IHypotensive episodes were more frequent in CG group (12%) than in EG group (0%) (p=0.03). Post-anaesthesia care unit length of stay (PACU) and piritramide consumption during PACU stay were not different between groups.
Conclusion(s): In the conditions of our study, spectral entropy monitoring
was associated with a reduction in sevoflurane use and a faster emergence.