Abstract: We identified 4245 possible studies from the initial search. Of those studies, four studies (256 participants) met the inclusion criteria. One more study is awaiting classification. Studies were, conducted in single-centre surgical and mixed medical-surgical ICUs. BIS monitor was used to assess the level of sedation in the intervention arm in all the studies. In the control arm, the sedation assessment tools for CA included the Sedation-Agitation Scale (SAS), Ramsay Sedation Scale (RSS) or subjective CA utilizing traditional clinical signs (heart rate, blood pressure, conscious level and pupillary size). Only one study was classified as low risk of bias, the other three studies were classified as high risk. There was no evidence of a difference in one study (N = 50) that measured ICU LOS (Median (Interquartile Range IQR) 8 (4 to 14) in the CA group; 12 (6 to 18) in the BIS group; low-quality evidence).There was little or no effect on the duration of mechanical ventilation (MD -0.02 days (95% CI -0.13 to 0.09; 2 studies; N = 155; I2 = 0%; low-quality evidence)). Adverse events were reported in one study (N = 105) and the effects on restlessness after suction, endotracheal tube resistance, pain tolerance during sedation or delirium after extubation were uncertain due to very low-quality evidence. Clinically relevant adverse events such as self-extubation were not reported in any study. Three studies reported the amount of sedative agents used. We could not measure combined difference in the amount of sedative agents used because of different sedation protocols and sedative agents used in the studies. GRADE quality of evidence was very low. No study reported other secondary outcomes of interest for the review. We found insufficient evidence about the effects of BIS monitoring for sedation in critically ill mechanically ventilated adults on clinical outcomes or resource utilization. The findings are uncertain due to the low- and very low-quality evidence derived from a limited number of studies.

Plain-language summary: The evidence identified from our literature search is current to May 2017. Four randomized controlled studies met the inclusion criteria for this review (involving 256 adults). One more study is awaiting classification. These studies were conducted in adult surgical and mixed medical-surgical ICUs, and compared BIS monitoring with various measures for CA. For one study, the BIS monitoring devices manufacturer provided equipment. The company had no role in the conduct of the study. Another study was funded as part of a scientific and technological project. No funding information was available for the other two studies. With BIS monitoring, we found no significant differences in ICU length of stay (one study, 50 adults), duration of ventilation (two studies, 155 adults) and the risk of adverse events (one study, 105 adults) compared with CA. Clinically relevant adverse events, for example, accidental self-removal of the breathing tube, were not reported. We could not measure combined difference in amount of sedative use because of the different sedation protocols and sedatives used. None of the other outcomes of interest for the review, for example, death, ventilator-associated pneumonia, quality of life etc. were reported in any of the studies. The findings of our review are from a limited number of studies which provided 'low to very low' GRADE quality of evidence. The authors of this review conclude that we found insufficient evidence about the effects of BIS monitoring compared with CA of sedation in critically ill adults who were on a ventilator.