In this episode, I’ll discuss which overdose patients with prolonged QTc are most likely to experience ventricular dysrhythmia.
Among overdose patients who present to the emergency department, those with a severely prolonged QTc of over 500 milliseconds represent a cohort that is at an elevated risk of a poor clinical outcome, such as ventricular dysrhythmia. However, the vast majority of patients, even with a QTc above 500 msec, will have an uneventful clinical course in the ED. Therefore it would be useful to be able to predict which patients with severe QTc prolongation after overdose will actually manifest ventricular dysrhythmias. In order to accomplish this, a group of authors published in Academic Emergency Medicine a secondary analysis of Toxicology Investigators Consortium Core Registry data looking at Clinical Factors Associated With Ventricular Dysrhythmia in Emergency Department Patients With Severe QTc Prolongation After Drug Overdose.
The authors analyzed data from over 1200 patients 13 years old or greater with acute or acute-on-chronic overdose, a toxicology consultation in the inpatient or ED setting, and initial ED electrocardiogram QTc of at least 500 ms.
Only 3.79% of this cohort went on to develop a ventricular dysrhythmia, highlighting the rarity of this occurrence even within a cohort of patients most at risk.
There were 3 predictors that were independently associated with an increased risk of ventricular dysrhythmia:
Bradycardia (defined as a heart rate less than 50 beats per minute), with an adjusted odds ratio of 3.12
Acidosis (defined as a serum pH less than 7.2), with an adjusted odds ratio of 3.02
Shock (defined as a systolic blood pressure less than 80 mm mercury treated with vasopressors), with an adjusted odds ratio of 4.54
Each of these predictors was also associated with the secondary outcomes, which included death, cardiac arrest, the need for rhythm control, and the need for extracorporeal membrane oxygenation.
These three predictors were also more helpful in identifying patients at risk for ventricular dysrhythmia than specific suspected drug exposures, overdose characteristics like intent for self-harm, or patient demographics, including prior cardiac disease.
The absence of bradycardia, acidosis, and shock had a negative predictive value of 98.2% for the development of ventricular dysrhythmia.
These findings allow for early identification of the patients most at risk for a negative clinical event after drug overdose. This information can be used by ED pharmacists to prioritize care and monitoring for the overdose patients that are most likely to need it.
The article in this episode is a selection from my Hospital Pharmacy Academy’s weekly literature digest. Have you ever felt like your physician colleagues are one step ahead of you with new literature developments? Every week, Academy members are provided a summary curated and explained by me of the top hospital pharmacy-related articles published that week from over 20 major journals and sources to save you time and keep you up to date with the literature. To get immediate access, go to pharmacyjoe.com/academy.
If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.
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