Dexmedetomidine Versus Placebo in Cardiac Surgery: A Meta-Analysis of Randomized Trials

Background: Cardiac surgery is associated with substantial perioperative morbidity encompassing haemodynamic instability, postoperative delirium, organ dysfunction, and mortality. Dexmedetomidine, a highly selective alpha-2 adrenoreceptor agonist with sympatholytic, sedative, analgesic, and organ protective properties, has attracted interest as a perioperative adjunct. This meta-analysis synthesises RCT evidence comparing dexmedetomidine with placebo in cardiac surgery. Methods: This systematic review and meta-analysis were conducted per PRISMA 2020, registered on PROSPERO. PubMed/MEDLINE, Embase, Scopus, and CENTRAL were searched until April 2026. Eligible studies were RCTs comparing intravenous dexmedetomidine with placebo or standard care in cardiac surgery. Primary outcome: postoperative delirium. Secondary outcomes: all-cause mortality, hospital and ICU LOS, duration of mechanical ventilation, atrial fibrillation, bradycardia, hypotension, stroke, myocardial infarction, acute kidney injury, respiratory failure, and infection. Random effects models and GRADE were applied. Results: Twenty RCTs (5,519 patients; 2,779 dexmedetomidine; 2,740 placebo). Dexmedetomidine reduced all-cause mortality (RR 0.60, 95% CI 0.40-0.91; p=0.02; I 2 =0%; moderate certainty), postoperative delirium (RR 0.71, 95% CI 0.54-0.93; p=0.01; I 2 =50%; low certainty), and hospital LOS (MD –0.60 days, 95% CI –1.06 to –0.13; p=0.01; I 2 =97%; moderate certainty). No significant differences in atrial fibrillation, stroke, myocardial infarction, acute kidney injury, bradycardia, infection, or respiratory failure; a non-significant trend toward increased hypotension was observed (RR 1.37; 95% CI 0.97-1.94; p=0.07). ICU LOS (I 2 =99%) was uninterpretable. The largest trial (DECADE; Turan et al. 2020) showed higher delirium with dexmedetomidine (17% vs 12%; not significant). Conclusions: Dexmedetomidine is associated with reduced all-cause mortality (moderate certainty), postoperative delirium (low certainty), and hospital LOS (moderate certainty) versus placebo, without increased major adverse events. The delirium finding and ICU LOS heterogeneity warrant caution, with appropriate haemodynamic monitoring. Multicentre RCTs with standardised outcome reporting remain essential.