Reduction in the incidence of awareness using BIS monitoring

TLDR

Explicit recall occurs in about 0.2 % of patients receiving general anaesthesia with muscle relaxants. The study aimed to determine whether BIS‑guided anaesthesia could significantly reduce the incidence of explicit recall. Researchers monitored 4,945 consecutive surgical patients with BIS, targeting values of 40–60, and interviewed them for explicit recall at three time points. BIS monitoring lowered explicit recall from 0.18 % in the historical control to 0.04 %, with most cases occurring when BIS exceeded 60 during intubation, and the overall incidence was significantly reduced.

Abstract

Explicit recall (ER) is evident in approximately 0.2% of patients given general anaesthesia including muscle relaxants. This prospective study was performed to evaluate if cerebral monitoring using BIS to guide the conduction of anaesthesia could reduce this incidence significantly.A prospective cohort of 4945 consecutive surgical patients requiring muscle relaxants and/or intubation were monitored with BIS and subsequently interviewed for ER on three occasions. BIS values between 40 and 60 were recommended. The results from the BIS-monitored group of patients was compared with a historical group of 7826 similar cases in a previous study when no cerebral monitoring was used.Two patients in the BIS-monitored group, 0.04%, had ER as compared with 0.18% in the control group (P < 0.038). Both BIS-monitored patients with ER were aware during intubation when they had high BIS values (> 60) for 4 min and more than 10 min, respectively. However, periods with high BIS = 4 min were also evident in other patients with no ER. Episodes with high BIS, 4 min or more, were found in 19% of the monitored patients during induction, and in 8% of cases during maintenance.The use of BIS monitoring during general anaesthesia requiring endotracheal intubation and/or muscle relaxants was associated with a significantly reduced incidence of awareness as compared with a historical control population.