Article: Prognostic Utility of Initial Lactate in Patients with Acute Drug Overdose: A Validation Cohort
This is an observational prospective cohort study that analyzed 1406 patients in 2 urban teaching hospitals with acute drug overdose to determine if initial lactate concentration was a useful biomarker for early clinical decision making and a predictor of inpatient mortality. Secondary outcome was the presence of shock, which was defined as the use of vasopressors (not defined by vitals). Inclusion criteria included acute presentation within 24 hours of exposure and suspected overdose (drug dose sufficient to cause symptoms or any prescription drug exposure greater than its therapeutic dose).
The study found that the optimal lactate cut point to predict death was 5.0 mmol/L which performed best for salicylates, sympathomimetics, APAP, and opioids. However, digoxin, diuretics and b-adrenergic antagonists and calcium channel blockers combined were significantly associated with fatality. Of the 1406 patients included in the study, there were 24 deaths (1.7%). Mean initial lactate concentration was 8.1 mmol/L in fatalities and 2.21 mmol/L for survivors. The optimal cut point for the occurrence of both primary and secondary outcomes combined (shock or death) was 2.7 mmol/L. An initial lactate concentration of 7.5 mmol/L or greater had 23.8% positive predictive value and less than 2.0 mmol/L had 99.5% negative predictive value. The utility of a lactate concentration could not be assessed for lithium, metformin, and statin drugs because of absence of deaths in the cohort. The authors of the study suggest that a lactate > 5.0 mmol/L identifies patients for whom ICU admission is warranted or should at least be considered whereas lactate <2.0 mmol/L may identify a low-risk subset of patients for medical clearance.
Limitations of the study include: 1) sample size – many patients were excluded as no ED serum lactate was drawn, 2) multiple drugs were involved in each fatality case and overdose from which specific drug was not addressed, 3) time to obtaining initial lactate varied, 4) how shock was defined.
Major Take-home: Lactate can be a useful marker in determining severity of acute drug overdose — but ultimately remember to treat the patient, not the number!
This article was reviewed, presented and summarized by Sophia Umphress, MD – PGY-2
Despite the fact that this is my #1 reason for sending a lactate willingly, this study does not support the use of lactate as an independent prognostic factor (if everyone who made lactate had a sBP of 70, then who cares about the lactate?). They didn’t do the correct analysis, and the journal should be ashamed of itself.
The take-home point is that you can publish anything once everyone jumps on the band wagon.