Purpose: Although a moderate proportion of cardiac arrest (CA) patients achieve return of spontaneous circulation (ROSC), few survive to discharge with mainly poor neurological development. Existing prognostication parameters at index to forecast the outcome are imprecise. As serum phosphate levels were described as elevated after CPR, we asked whether these elevations would predict a higher chance of mortality and impaired neurological outcome in CPR patients following ROSC.

Methods: We analyzed the relationship between initial serum phosphate levels, survival, and neurologic status at discharge in 488 non-traumatic CA patients treated at the University Clinic of Duesseldorf after achieving ROSC. By receiver operator characteristic (ROC) curve, we determined the cut-off value of phosphate for mortality prediction and divided patients accordingly for comparison. We validated the initial prognostication power on survival from a single-center cohort in a multi-centric collective of 3299 CA patients from the United States.

Results: In the German collective, ROC analysis showed a 90% specificity for phosphate levels > 2.7 mmol/L to predict mortality. Patients with initial phosphate levels > 2.7 mmol/L showed significantly increased mortality in both analyzed collectives. The Odds-Ratio (OR) of phosphate level elevations on in-hospital mortality was after adjustment for Creatinine 2.867 (95% CI, 2.18 to 3.86). When patients initially had higher phosphate levels, they also showed a higher proportion of impaired neurological status at discharge, morphological signs of brain injury, and higher peak neuron-specific enolase values.

Conclusion: In CA patients following ROSC, initial serum phosphate levels > 2.7 mmol/L predict higher mortality and impaired neurological outcome. Phosphate determination might add to the preciseness of the overall and neurologic prognostication in patients after CPR following ROSC.