The safety of high-dose dexmedetomidine after cardiac surgery: a historical cohort study.

PURPOSE: The off-label use of dexmedetomidine beyond the monograph-recommended maximum dose of 0.7 µg·kg-1 ·hr-1 is common in postoperative cardiac surgical units; however, limited data exist on the association of higher doses and adverse hemodynamic effects. We sought to compare the rate of hypotension or bradycardia in cardiac surgery patients receiving peak infusion doses below and above 0.7 µg·kg-1 ·hr-1 for any indication or duration.

METHODS: In this historical cohort study, we reviewed all patients who received dexmedetomidine infusion after cardiac surgery between June 2013 and July 2017 at a single centre. Regardless of the duration of exposure at the peak infusion dose, patients were categorized into high- or standard-dose groups using 0.7 µg·kg-1 ·hr-1 as the cutoff value. We compared rates of the primary composite outcome of hypotension or bradycardia, and secondary outcomes (i.e., arrhythmia and hyperglycemia) between groups using the two-proportion z test. Exploratory regression models were fitted to adjust for potential confounders.

RESULTS: The median [interquartile range (IQR)] peak infusion dose was 1.0 [1.0-1.4] µg·kg-1 ·hr-1 in the high-dose group (N = 121) and 0.5 [0.4-0.7] µg·kg-1 ·hr-1 in the standard-dose group (N = 124). The rates of the primary composite outcome were 73% and 65%, respectively (absolute risk difference, 8%; 95% confidence interval, -3 to 20; P = 0.17). There was no significant difference in primary or secondary outcomes between groups.

CONCLUSION: There was a high overall rate of hypotension or bradycardia in patients receiving dexmedetomidine after cardiac surgery; infusion rates below or above 0.7 µg·kg-1 ·hr-1 had similar rates of adverse hemodynamic events.