Clinical Characteristics, Complications, and Outcomes of Heat Stroke Among Pilgrims During the Hajj Mass Gathering: A Prospective Cohort Study.

Background: Heat stroke is a leading cause of mortality during the Hajj season, yet data on its clinical progression remain limited. Objective: This study evaluates the clinical characteristics, complications, and outcomes of heat stroke among pilgrims. Methods: This prospective exploratory cohort study included adult pilgrims (≥18 years) who were admitted with a confirmed diagnosis of heat stroke, defined as a core temperature ≥40°C and central nervous system dysfunction, across nine hospitals. The primary endpoint measure is the frequency of at least one heat stroke-related complication. Patients were stratified into those discharged from the treating ICU and those transferred to an advanced referral center, with transfer used as a pragmatic surrogate for greater clinical severity within the Hajj healthcare system. Results: Twenty-three patients were included (mean age 65.1 ± 10.5 years; 56.5% male). Fifteen (65.2%) were discharged from the treating ICU, whereas eight (34.8%) were transferred to an advanced referral center. Compared with discharged patients, the transferred group showed higher ccreatinine upon admission (165.50 (146.00-185.50) vs. 130.50 (114.25-152.25); P=0.02), Peak creatinine values (275.90 (223.32-328.80) vs. 143.00 (126.00-160.50); p = 0.001), peak Urea values (17.40 (13.70-23.95) vs. 11.00 (8.70-13.00); p = 0.01); and the highest AST during admission was also higher in the transferred group (P=0.015). The lowest platelet counts during the patient's admission were significantly reduced in the transferred group (p = 0.007). Mechanical ventilation was required more often in the transferred group (75.0% vs. 26.7%; p = 0.026), and its duration was longer (p = 0.019). Given the small sample size, these findings should be considered exploratory. Conclusion: In this small, exploratory cohort, patients requiring transfer to an advanced referral center generally had a greater burden of organ dysfunction and required more critical care interventions. These observations should not be interpreted as establishing predictors of severe heat stroke because transfer status may also reflect healthcare system factors. Larger prospective multicentre studies are required to determine whether these observed differences are reproducible and clinically meaningful.