Prognostic value of serum phosphate level in elderly post-cardiac arrest patients

Prognosticating the neurological outcomes of cardiac arrest is important. A recent study has shown that serum phosphate (SP) may be a prognostic indicator for poor neurological outcomes in cardiac arrest patients. Due to advancements in medicine, more elderly patients survive cardiac arrest than ever before, and prognostication of the markers in this population has not been studied previously. We aimed to confirm the hypothesis that a higher SP level predicts a poor neurological outcome of cardiac arrest, even in elderly patients. This retrospective observational study included post-cardiac arrest elderly patients (aged >= 65 years) who were admitted to three hospitals in urban areas in South Korea from December 2013 to February 2020. Data regarding patient characteristics, laboratory values, and neurological outcomes at 28 days were collected from patients' medical records. The primary outcome was poor neurological outcome (Cerebral Performance Category scores 3-5) at 28 days. Of the 389 eligible patients, 334/389 had poor neurological outcomes at 28 days. SP levels were significantly higher in those with poor neurological outcomes than in those with good neurological outcomes (7.32 vs. 5.01, p < 0.001). Multivariate logistic regression analysis also showed that SP levels were independently associated with neurological outcomes. Receiver operating characteristic curve analysis of SP levels showed an area under the curve of 0.772. Higher SP levels are associated with poor neurological outcomes after cardiac arrest in the elderly population.