The Effect of Extreme Alkalemia upon Presentation to the Emergency Department on Patient Outcomes

Abstract

Background/Objectives: The prognostic significance of alkalemia found in an initial emergency department (ED) evaluation has not been described thus far. Methods: We retrospectively reviewed the records of all patients aged 18 years or older evaluated in the ED of one large academic referral center during 2000–2023. Included patients were those with at least one measurement of pH ≥ 7.55 upon initial ED presentation. Alkalemia was deemed primarily metabolic (PM) if PCO2 was ≥35 mmHg and primarily respiratory (PR) if bicarbonate levels were ≤24 mEq/L. The primary outcome was survival 30 days from ED presentation. Results: Of 2440 patients included, 199 (8.1%) had PM and 1494 (61.2%) had PR. Alkalemia severity was not correlated with prognosis. Survival at 30 days was significantly (p < 0.001) lower in the PM group (78.9%) compared with that of either the PR (95.3%) or the combined etiology (92.2%) groups. Multivariate survival analysis after balancing potential observed confounders using propensity score matching revealed the type of alkalemia (PM vs. PR) to be a significant predictor of 30-day mortality (aHR 1.73; 95% C.I. = [1.07 to 2.82]; p = 0.026), irrespective of age, other laboratory values obtained on ED evaluation (including pH), past medical history, or vital signs on presentation. Conclusions: In patients presenting to the ED with significant alkalemia, the mechanism of alkalemia, i.e., primarily metabolic versus primarily respiratory, rather than the absolute degree of alkalemia, is associated with increased mortality.