Predicting adverse cardiovascular events in emergency department patients with bupropion overdose

Objectives: Bupropion toxicity can lead to adverse cardiovascular events (ACVE), but delayed onset of toxicity makes risk stratification difficult. This study aimed to validate previously defined predictors of ACVE and identify novel predictors among patients presenting to the emergency department (ED) after bupropion overdose. Methods: This secondary analysis of prospective data from the Toxicology Investigators Consortium Core Registry analyzed adult acute or acute-on-chronic bupropion exposures from 2015 to 2018. The primary outcome was ACVE (any of the following: myocardial injury, shock, ventricular dysrhythmia, or cardiac arrest). Potential predictors of ACVE included previously derived predictors in the overall drug overdose population (prior cardiac disease, initial serum bicarbonate < 20 mEq/L, and initial QTc ≥ 500 ms), exposure circumstances, and initial serum lactate value. Candidate predictors were evaluated using univariate analysis and multivariable regression modeling. Receiver operator characteristic curves were used to derive optimal cutoff points for novel predictors, and prognostic test characteristics were calculated. Results: Of 355 patients analyzed, ACVE occurred in 34 (9.6%) patients. Initial serum bicarbonate < 20 mEq/L (adjusted odds ratio [aOR] 4.42, 95% confidence interval [CI] 1.94–10.0) and initial QTc ≥ 500 ms (aOR 2.52, 95% CI 1.01–6.09) independently predicted ACVE. Exposure circumstances did not predict ACVE. Initial serum lactate > 5.2 mmol/L independently predicted ACVE (aOR 12.2, 95% CI 2.50–75.2) and was 90.7% specific with 80.3% negative predictive value. Conclusions: Metabolic acidosis and QTc prolongation were validated as predictors of ACVE in ED patients with bupropion overdose. Serum lactate elevation was strongly predictive of ACVE in this study and warrants further investigation.