Abstract: Seven studies, covering 1624 participants, met the inclusion criteria. All included studies investigated adults and compared dexmedetomidine with traditional sedatives, including propofol, midazolam and lorazepam. Compared with traditional sedatives, dexmedetomidine reduced the geometric mean duration of mechanical ventilation by 22% (95% CI 10% to 33%; four studies, 1120 participants, low quality evidence), and consequently the length of stay in the intensive care unit (ICU) by 14% (95% CI 1% to 24%; five studies, 1223 participants, very low quality evidence). There was no evidence that dexmedetomidine decreased the risk of delirium (RR 0.85; 95% CI 0.63 to 1.14; seven studies, 1624 participants, very low quality evidence) as results were consistent with both no effect and appreciable benefit. Only one study assessed the risk of coma, but lacked methodological reliability (RR 0.69; 95% CI 0.55 to 0.86, very low quality evidence). Of all the adverse events included, the most commonly reported one was bradycardia, and we observed a doubled (111%) increase in the incidence of bradycardia (RR 2.11; 95% CI 1.39 to 3.20; six studies, 1587 participants, very low quality evidence). Our meta-analysis provided no evidence that dexmedetomidine had any impact on mortality (RR 0.99; 95% CI 0.79 to 1.24; six studies, 1584 participants, very low quality evidence). We observed high levels of heterogeneity in risk of delirium (I² = 70%), but due to the limited number of studies we were unable to determine the source of heterogeneity through subgroup analyses or meta-regression. We judged six of the seven studies to be at high risk of bias. In this review, we found no eligible studies for children or for clonidine. Compared with traditional sedatives, long-term sedation using dexmedetomidine in critically ill adults reduced the duration of mechanical ventilation and ICU length of stay. There was no evidence for a beneficial effect on risk of delirium and the heterogeneity was high. The evidence for risk of coma was inadequate. The most common adverse event was bradycardia. No evidence indicated that dexmedetomidine changed mortality. The general quality of evidence ranged from very low to low, due to high risks of bias, serious inconsistency and imprecision, and strongly suspected publication bias. Future studies could pay more attention to children and to using clonidine.

Plain-language summary: We searched the databases until October 2014. We included seven randomized controlled trials, with a total of 1624 participants, comparing dexmedetomidine versus traditional sedatives. All the studies required participants to have an anticipated need for sedation of more than 24 hours. The alternative sedatives included propofol, midazolam and lorazepam. We found no eligible studies in children or for clonidine. Of the seven studies, six were funded by the drug manufacturer, and one did not state any conflict of interest. Compared with traditional sedatives, dexmedetomidine reduced the breathing support time by approximately one-fifth, and the length of stay time in ICU by one-seventh. Dexmedetomidine was at least as effective as traditional sedatives for producing sedation and maintaining a light sedation level. There was no clear evidence in support of dexmedetomidine reducing the risk of delirium (a kind of acute confusion state), as results were consistent with both no effect and appreciable benefit. We had insufficient information to draw conclusions about reducing the risk of coma. Dexmedetomidine doubled the incidence of slow heartbeat, which was the most commonly reported adverse event. Our review provides no evidence that dexmedetomidine changed the overall death rate. The general quality of evidence ranged from very low to low, as most of the studies were at high risk of bias, serious inconsistency and imprecision, or strongly suspected publication bias.