Diagnostic Value of End-Tidal Carbon Dioxide Combined With Lactate for Early Detection of Sepsis in Prehospital Patients: A Prospective Cohort Study.

BACKGROUND Sepsis is a critical condition requiring prompt identification and intervention, especially in prehospital settings where diagnostic uncertainty is high. This study investigated the effectiveness of a dual-marker approach using end-tidal carbon dioxide (ETCO2) and lactate levels for early sepsis detection. MATERIAL AND METHODS In this single-center prospective cohort study, we enrolled 327 patients with suspected sepsis admitted through prehospital emergency care from January 2023 to January 2025. We evaluated the diagnostic performance of ETCO₂ and lactate, using thresholds of ETCO₂ ≤25 mmHg and ≤30 mmHg, and hyperlactatemia defined as ≥2 mmol/L. Primary outcomes were sepsis and septic shock diagnosis, while secondary outcomes included ICU admission and in-hospital mortality. Receiver operating characteristic (ROC) curves were used to assess diagnostic accuracy. RESULTS Our findings revealed that lower prehospital ETCO₂ and elevated lactate levels were significantly associated with increased risks of septic shock and in-hospital mortality. ETCO₂ ≤25 mmHg alone showed an AUC of 0.781 (95% CI 0.738-0.846) for sepsis, with a sensitivity of 82.9% and specificity of 81.7%. The combined model of ETCO₂ ≤25 mmHg and hyperlactatemia significantly enhanced diagnostic accuracy, achieving a sensitivity of 89.9% and specificity of 91.7%. CONCLUSIONS The integration of ETCO₂ and lactate as a dual-marker decision rule significantly enhances early sepsis detection in prehospital settings, surpassing the limitations of single-biomarker or symptom-based approaches. This dual-marker approach offers a robust, objective tool for improving sepsis risk stratification, potentially leading to better patient outcomes through timely intervention.