Bradycardia Risk Associated with Intravenous Dexmedetomidine: A Retrospective Study of Risk Factors and Clinical...

Dexmedetomidine is a selective α2-adrenergic agonist commonly used for sedation in intensive care units (ICUs). While effective, it is associated with cardiovascular side effects, particularly bradycardia that may limit its use. Concerns about bradycardia-related complications often influence clinical decision-making regarding dexmedetomidine dosing and monitoring, yet the true clinical significance of this side effect remains unclear. This study aimed to identify risk factors for dexmedetomidineassociated bradycardia and evaluate its impact on clinical outcomes.

We conducted a retrospective cohort study involving adult patients who were mechanically ventilated and received dexmedetomidine for sedation across 12 ICUs in 4 hospitals under one hospital system. Bradycardia was defined as a heart rate below 60 beats per minute within 24 hours after dexmedetomidine administration. Multivariable logistic regression was employed to identify independent risk factors and assess the association between bradycardia and clinical outcomes, including inpatient mortality.

Among 5,106 patients, 1,143 (22.4%) developed bradycardia. Independent risk factors for bradycardia included moderate/severe liver disease (OR 1.87, 95% CI 1.42-2.47), dementia (OR 1.67, 95% CI 1.21-2.31), cerebrovascular disease (OR 1.32, 95% CI 1.15-1.51), and cancer (OR 1.25, 95% CI 1.06-1.47). Lower risk of bradycardia included congestive heart failure (OR 0.71, 95% CI 0.63-0.80) and myocardial infarction (OR 0.73, 95% CI 0.63-0.85). Crude mortality rates were similar between groups (11.4% vs. 10.2%, p = 0.297), and after adjustment for age and illness severity, bradycardia was not independently associated with hospital mortality (adjusted OR 0.99, 95% CI 0.79-1.23, p = 0.915). Patients with bradycardia had shorter ICU length of stay compared to those without bradycardia (10.4 ± 10.1 vs. 10.8 ± 10.6 days, p = 0.012). A sensitivity analysis adjusting for minimum heart rate before dexmedetomidine initiation and using a stricter bradycardia definition of heart rate less than 50 bpm, resulted in similar findings.

Dexmedetomidine-associated bradycardia occurs in approximately one-quarter of ICU patients at out institution. Specific comorbidities significantly influence the risk of developing bradycardia, but dexmedetomidine-associated bradycardia itself may not associated with worse outcomes.