The prognostic significance of the mechanism of mild to moderate alkalemia at emergency department admission.

BACKGROUND

Paucity of evidence exists as to the prognostic significance of mild to moderate alkalemia upon presentation to the emergency department (ED).

METHODS

Patients presenting to the ED of one tertiary hospital over the last 24 years were included in this retrospective cohort study if the serum pH drawn within 3 h of the initial presentation was 7.45–7.55. Alkalemia was defined as primarily metabolic (PM) if PCO2≥35mmHg, and primarily respiratory (PR) if HCO3≤24mEq/L - otherwise, the etiology was considered to be mixed and the case was excluded from this analysis. The primary outcome was 30 days mortality, analysed by Cox’s regression.

RESULTS

Of 25,884 patients included in the final analysis, 14,802 (47.4%) were PM and 11,082 (35.4%) PR. Adjusted for age, comorbidities, severity scores, potassium derangements, and year of admission, PR was associated with increased 30-day mortality (aHR 1.21, 95% CI [1.12–1.32]). The association of higher degree of alkalemia with increased mortality was significant only in the PM group (p < 0.001).

CONCLUSIONS

The etiology of alkalemia (PR vs. PM) could provide important prognostication in the ED, even in mild to moderate cases.