Background: Sodium bicarbonate therapy (SBT) has a variety of ED indications but its use is controversial. Some authors recommend SBT for drug overdoses involving salicylates and sodium channel antagonists such as tricyclics (TCA). Due to its effect on serum potassium, we hypothesized that SBT may prolong the QTc and increase risk for adverse cardiovascular events (ACVE). Our purpose was to evaluate SBT dose and duration in ED patients with drug overdose for an association with ACVE.
Methods: We prospectively analyzed consecutive ED patients with acute drug overdose who were given SBT at two urban teaching hospitals from 2015-present. Data included SBT indication, dose, duration, and QTc (initial/peak from computer generated Bazett correction) during hospital stay. We used median values to dichotomize total dose (high/low) and total duration (long/short) of SBT. Patients were prospectively followed to hospital discharge for the occurrence of the primary outcome: ACVE and/or mortality. The previously validated definition of ACVE was used for in-hospital occurrence of any of these: ventricular dysrhythmia, myocardial infarction, shock requiring vasopressors, and cardiac arrest. Severe QTc prolongation was defined using the validated cutoff ≥500ms. Ventricular dysrhythmias were adjudicated by a blinded cardiologist.
Results: Indications for SBT in 30 patients analyzed were: salicylism (5), sodium channel antagonist (6 TCA, 5 other), wide QRS in absence of known drug (9), acidosis or cardiac arrest (3), and unknown (2). After SBT, severe QTc prolongation occurred in 6 (20%), ACVE in 17 (57%), and 6 (20%) died. There was a significant association between severe QTc prolongation in-hospital for both high dose and long duration groups (p<0.05 for both). There was a significant correlation between both SBT dose (83% high, 38% low, p < .05) and SBT duration (100% long, 25% short, p < .05) with the primary outcome.
Conclusion: ED patients with acute drug overdose receiving SBT had very high rates of mortality and ACVE, which were strongly associated with higher dose and longer duration of SBT. Severity of overdose was a limitation to interpretation as a potential confounder. Overall, these results are consistent with the hypothesis that SBT prolongs the QTc and increases risk for ACVE, validating previous safety concerns regarding the administration of SBT for drug overdose.