Detection of Exhaled Methane Levels for the Recognition and Monitoring of Hemorrhagic Shock - Study Protocol for a Prospective Observational Study

This prospective observational study aims to test the efficacy of the continuous measurement of exhaled methane levels in monitoring the hemodynamic state of severely injured, bleeding trauma patients. Our inclusion criteria require an age of 18 years or greater, an Injury Severity Score (ISS) of 16 or greater, transport directly from scene, intubation on scene or upon arrival, hemorrhage confirmed with eFAST or CT, and signed consent from patient surrogates. Exhaled methane concentrations and indicators of blood loss and shock (vital signs: systolic blood pressure, heart rate; blood gas and laboratory markers: base deficit, lactate, hemoglobin, hematocrit; videomicroscopic image of sublingual microcirculation) will be recorded in pre-determined time points during the first 72 in-hospital hours. The relation between exhaled methane levels and indicators of shock will constitute our primary outcome measures. The association of methane concentrations with clinical outcomes (transfusion need, mortality) will serve as secondary outcomes.