Hypophosphataemia is common in patients with aneurysmal subarachnoid haemorrhage.

Introduction: Hypophosphataemia is common in critically ill patients, but neither its prevalence nor its association with outcome have been investigated specifically in patients with aneurysmal subarachnoid haemorrhage (aSAH).

Methods: Patients with aSAH and at least one phosphate measurement were included from two independent cohorts; an American cohort extracted from two open-access databases (Medical Information Mart for Intensive Care-III and eICU Collaborative Research Database v. 2.0) and a Danish cohort consisting of patients with aSAH admitted to Rigshospitalet, Denmark over a 4-year period. In each cohort, we calculated the prevalence of mild (0.32-0.80 mmol/L) and severe (<0.32 mmol/L) hypophosphataemia and their association with in-hospital mortality before and after propensity-score matching.

Results: Hypophosphataemia occurred in 72.4% (95% CI: 68.1-76.3) of patients in the American cohort (n = 471) and 54.9% (50.0-59.7) in the Danish cohort (n = 419). However, it was not associated with mortality in neither full (American: Mild, Odds ratio (OR) 0.99 (0.91-1.07), Severe OR 1.20 (0.95-1.51); Danish: Mild, OR 1.01 (0.95-1.08), Severe OR 1.20 (0.95-1.51)) nor propensity-score matched cohorts (American (n = 168): Mild, OR 1.06 (0.88-1.28), Severe OR 1.46 (0.96-2.12); Danish (n = 44): Mild, OR 1.16 (0.82-1.65), Severe OR 0.45 (0.13-1.55)).

Conclusion: In this retrospective study of patients with aSAH, hypophosphataemia was common.