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Bispectral index for improving anaesthetic delivery and postoperative recovery

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Abstract

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Background

The use of clinical signs may not be reliable in measuring the hypnotic component of anaesthesia. The use of bispectral index to guide the dose of anaesthetics may have certain advantages over clinical signs. This is an update of a review originally published in 2007.

Objectives

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

Search methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 2), MEDLINE (1990 to 21 May, 2009), EMBASE (1990 to 14 May, 2009) and reference lists of articles. The original search was performed in May 2007.

Selection criteria

We included randomized controlled trials comparing BIS with standard practice criteria for titration of 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 31 trials. In studies using clinical signs as control, the results demonstrated a significant effect of the BIS‐guided anaesthesia in reducing the risk of intraoperative recall awareness among surgical patients with high risk of awareness (2493 participants; OR 0.24, 95% CI 0.08 to 0.69). This effect was not demonstrated in studies using end tidal anaesthetic gas monitoring as standard practice (1981 participants; OR 1.01, 95% CI 0.14 to 7.16). BIS‐guided anaesthesia reduced the requirement for propofol by 1.44 mg/kg/hr (662 participants; 95% CI ‐1.95 to ‐0.93), and for volatile anaesthetics (desflurane, sevoflurane, isoflurane) by 0.14 minimal alveolar concentration equivalents (MAC) (95% CI ‐0.22 to ‐0.05) in 928 participants. Irrespective of the anaesthetics used, BIS reduced the following recovery times: time for eye opening (2446 participants; by 2.14 min, 95% CI ‐2.99 to ‐1.29), response to verbal command (777 participants; by 2.73 min, 95% CI ‐3.92 to ‐1.54), time to extubation (1488 participants; by 2.87 min, 95% CI ‐3.74 to ‐1.99), and orientation (316 participants; by 2.57 min, 95% CI ‐3.30 to ‐1.85). BIS shortened the duration of postanaesthesia care unit stay by 7.63 min (95% CI ‐12.50 to ‐2.76) in 1940 participants but did not significantly reduce time to home readiness (329 participants; ‐7.01 min, 95% CI ‐30.11 to 16.09).

Authors' conclusions

BIS‐guided anaesthesia could reduce the risk of intraoperative recall in surgical patients with high risk of awareness in studies using clinical signs as a guide to anaesthetic practice but not in studies using end tidal anaesthetic gases as a guide. In addition, anaesthesia guided by the BIS within the recommended range could improve anaesthetic delivery and postoperative recovery from relatively deep anaesthesia.

PICOs

Population
Intervention
Comparison
Outcome

The PICO model is widely used and taught in evidence-based health care as a strategy for formulating questions and search strategies and for characterizing clinical studies or meta-analyses. PICO stands for four different potential components of a clinical question: Patient, Population or Problem; Intervention; Comparison; Outcome.

See more on using PICO in the Cochrane Handbook.

Plain language summary

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Monitoring the bispectral index (BIS) to improve anaesthetic delivery and patient recovery from anaesthesia

The results from this updated review indicate that BIS could be useful in guiding the anaesthetic dose to avoid the risk of intraoperative recall in surgical patients with high risk of awareness.  Furthermore, anaesthesia guided by BIS could improve anaesthetic delivery and recovery from anaesthesia.

General anaesthesia requires multiple agent administration to achieve unconsciousness (hypnotics), muscle relaxation, analgesia and haemodynamic control. Many anaesthesiologists rely on clinical signs alone to guide anaesthetic management. Bispectral index (BIS) is a scale derived from the measurement of cerebral electrical activity in anaesthetized patients so that the level of anaesthesia and drug delivery can be optimized. We systematically reviewed 31 randomized controlled studies to find out whether BIS can reduce the risk of intraoperative recall and reduce anaesthetic use and recovery times in adult surgical patients. The risk of intraoperative recall awareness was determined in selected patients who were at potentially high risk of awareness. Two studies (2493 patients) that used clinical signs as a guide to anaesthetic administration in the control group demonstrated a significant reduction in the risk of awareness with BIS monitoring. Two studies (1981 patients) compared BIS monitoring with end tidal anaesthetic gas monitoring as a guide to management of anaesthesia and this did not demonstrate any difference. No intraoperative recall awareness was reported in the trials in surgical patients with low risk of awareness. There was an overall reduction in volatile anaesthetic dose and the dose of propofol. Recovery from anaesthesia was quicker and post‐anaesthesia recovery care unit stay was shorter. The limitations of some of the clinical trials on BIS are discussed.