Immune Cells Characteristics and Their Prognostic Effects in Exertional Heatstroke Patients: A Retrospective Cohort Study

BACKGROUND: Exertional heatstroke (EHS) remains a major problem for those who take strenuous physical activity. Inflammation and immune dysfunction were thought to be crucial to the pathophysiological process of heatstroke. The present study was aimed to investigate the dynamic changes of the immune cells in patients with EHS and determine their prognostic effects to provide the clinical evidence of the above process. METHODS: This single-center retrospective cohort study collected all patients with EHS admitted to the intensive care unit (ICU) of the General Hospital of Southern Theater Command of PLA from October 2008 to May 2019. The dynamic changes of the main immune cell count and ratio were collected, including white blood cell (WBC), neutrophil, monocyte, and lymphocyte. The neutrophil-to-lymphocyte ratios (NLR) were calculated by the neutrophil count/lymphocyte count × 100%. The main outcome was 90-day mortality. RESULTS: A total of 189 patients were enrolled. For survivors, after 24 h, the WBC and neutrophil counts began to decrease, and they were back to normal in 72 h. In addition, the lymphocyte counts were within normal limits all the time. For non-survivors, the WBC and neutrophil counts were continuous over the normal range, while the lymphocyte count and the ratio began to decrease after 24 h and were continuously low in the following days. Receiver operating characteristic (ROC) curves analysis showed that increased neutrophils and decreased lymphocytes were associated with the poor prognosis of the patients. A prediction model based on immune cell counts and ratios was constructed, and the lymphocyte count was accounted for the maximum weight. CONCLUSIONS: In patients with EHS, increased neutrophils and decreased lymphocytes were associated with the poor prognosis. The lymphocyte count at 72 h after admission was the most important prognostic factor.