Bispectral index for improving anaesthetic delivery and postoperative recovery

Abstract

Background: The use of clinical signs may not be reliable to measure the hypnotic component of anaesthesia. The use of bispectral index to guide the dose of anaesthetics may have certain advantages over clinical signs.

Objectives: The objective of this review was to assess whether bispectral index (BIS) reduced anaesthetic use, recovery times, recall awareness and cost.

Search strategy: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1990 to May 2007), EMBASE (1990 to May 2007) and reference lists of articles.

Selection criteria: We included randomized controlled trials comparing BIS with clinical signs (CS) in titrating anaesthetic agents.

Data collection and analysis: Two authors independently assessed trial quality, extracted data and analysed the data. We contacted study authors for further details.

Main results: We included 20 studies with 4056 participants. Seven recent trials are still awaiting assessment. BIS-guided anaesthesia reduced the requirement for propofol by 1.30 mg/kg/hr (578 participants; 95% confidence interval (CI) -1.97 to -0.62) and for volatile anaesthetics (desflurane, sevoflurane, isoflurane) by 0.17 minimal alveolar concentration equivalents (MAC) (689 participants; 95% CI -0.27 to -0.07). Irrespective of the anaesthetic, BIS reduced the recovery times: time for eye opening by 2.43 min (996 participants; 95% CI -3.60 to -1.27), response to verbal command by 2.28 min (717 participants; 95% CI -3.47 to -1.09), time to extubation by 3.05 min (1057 participants; 95% CI -3.98 to -2.11) and orientation by 2.46 min (316 participants; 95% CI -3.21 to -1.71). BIS shortened the duration of postanaesthesia care unit stay by 6.83 min (584 participants; 95% CI -12.08 to -1.58) but did not reduce time to home readiness (329 participants; 95% CI -30.11 to 16.09). The BIS-guided anaesthesia significantly reduced the incidence of intraoperative recall awareness in surgical patients with high risk of awareness (OR 0.20, 95% CI 0.05 to 0.79).

Authors' conclusions: Anaesthesia guided by BIS within the recommended range (40 to 60) could improve anaesthetic delivery and postoperative recovery from relatively deep anaesthesia. In addition, BIS-guided anaesthesia has a significant impact on reduction of the incidence of intraoperative recall in surgical patients with high risk of awareness.