Prognostic value of serum phosphate level in adult patients resuscitated from cardiac arrest

Background: Several studies have reported increased levels of phosphate after cardiac arrest. Given the relationship between phosphate level and the severity of ischaemic injury reported in previous studies, higher phosphate levels may be associated with worse outcomes. We investigated the prognostic value of phosphate level after the restoration of spontaneous circulation (ROSC) in adult cardiac arrest patients. Methods: This study was a retrospective observational study including adult cardiac arrest survivors treated at the Chonnam National University Hospital between January 2014 and June 2017. From medical records, data regarding clinical characteristics, outcome at hospital discharge, and laboratory parameters including phosphate levels after ROSC were collected. The primary outcome was poor outcome at hospital discharge, defined as Cerebral Performance Categories 3–5. Results: Of the 674 included patients, 465 had poor outcome at hospital discharge. Serum phosphate level was significantly higher in patients with poor outcome than in those with good outcome (p < 0.001). Phosphate level was correlated with time to ROSC (r = 0.350, p < 0.001). Receiver operating characteristic curve analysis revealed an area under the curve of 0.805 (95% confidence interval [CI], 0.777–0.838) for phosphate level. In multivariate analysis, a higher phosphate level was independently associated with poor outcome at hospital discharge (odds ratio, 1.432; 95% CI, 1.245–1.626; p < 0.001). Conclusions: A higher phosphate level after ROSC was independently associated with poor outcome at hospital discharge in adult cardiac arrest patients. However, given its modest prognostic performance, phosphate level should be used in combination with other prognostic indicators.