High Potassium Levels Tied to Higher Short-Term Risks in ER Patients

Higher initial serum potassium levels in emergency department patients are tied to an increased short-term risk of cardiac arrest, dangerous heart rhythms, intensive care unit admission, and death within 48 hours, Medscape reported.

A large retrospective cohort study published on September 16, 2026, in The American Journal of Emergency Medicine examined data from the TriNetX Research Network on adults visiting United States emergency departments between 2010 and 2024. Researchers analyzed 140,288 patients with potassium levels of 5.5 mmol/L or higher after propensity score matching, comparing them against normokalemic control individuals who had potassium levels between 3.5 and 5.0 mmol/L.

Emergency Department Risks Tied to Elevated Potassium

The primary outcome tracked a composite of cardiac arrest, ventricular tachycardia, or ventricular fibrillation within 48 hours of the initial potassium measurement. Among patients with potassium levels ranging from 5.5 to 5.99 mmol/L, this composite outcome occurred in 3.05% of individuals. That figure climbed to 6.68% for patients with potassium levels of 7.0 mmol/L or higher. By comparison, matched control individuals experienced these cardiac events at rates between 0.77% and 0.90%, yielding relative risks ranging from 3.97 to 8.08.

Secondary outcomes demonstrated similar escalations across multiple tiers of hyperkalemia severity. Mortality within 48 hours rose from 2.04% in the 5.5 to 5.99 mmol/L tier to 5.79% in the highest tier of 7.0 mmol/L and above, compared with 0.18% to 0.21% in control patients. Intensive care unit admissions ranged from 8.46% in the lowest hyperkalemia bracket up to 13.28% in the 6.5 to 6.99 mmol/L tier, versus roughly 4% for controls. Intubation or mechanical ventilation followed a comparable pattern, affecting between 5.00% and 7.85% of patients across the hyperkalemia tiers.

Borderline Potassium Findings and Hypoglycemia Rates

An exploratory analysis examined 1,249,213 patients with borderline potassium elevations between 5.01 and 5.49 mmol/L. In this borderline group, the primary composite outcome occurred in 1.52% of patients compared with 0.85% of matched controls, producing a relative risk of 1.79. However, the rates of isolated ventricular tachycardia and ventricular fibrillation did not increase in this borderline category.

Hypoglycemia within 24 hours appeared more frequently across all hyperkalemia groups, with relative risks spanning from 3.32 to 6.55, though researchers noted no consistent gradient linking the severity of potassium elevation directly to the frequency of low blood sugar.

Study Limitations and Author Perspectives

The research was led by Joseph O’Brien of Denver Health Medical Center in Denver, Colorado. Study authors acknowledged several limitations in their retrospective design, noting potential residual confounding by acute illness severity. The analysis did not account for presenting complaints, mental status, electrocardiographic abnormalities, sepsis severity, lactate levels, or validated illness severity scores. Furthermore, residual imbalances in creatinine and bicarbonate persisted after matching, particularly within the 6.0 to 6.49 mmol/L stratum.

These findings support the use of potassium as a readily available risk marker in acute care, but they do not establish potassium-specific causality or demonstrate that more aggressive treatment would reduce adverse outcomes.

Joseph O’Brien et al.

The study received no funding, and the authors reported no conflicts of interest. The 48-hour outcome window may have captured events occurring after significant shifts in potassium levels or following treatments directed at lowering potassium, while serial measurements and exact treatment timing were unavailable.

Future Research Directions in Acute Care

Future studies incorporating vital signs, electrocardiographic data, serial potassium measurements, and treatment timing are needed to clarify the independent contribution of hyperkalemia to early ED outcomes.

Study Authors