Detection of Exhaled Methane Levels in Hemorrhagic Shock

To measure methane concentrations, a near-infrared laser technique-based photoacoustic apparatus will be attached to the exhalation outlet of the ventilator upon arrival of severely injured patients. Exhaled methane levels will be monitored continuously during the first 72 in-hospital hours and will be recorded at pre-determined time points (directly upon arrival, 6 hours post-admission, 12 hours post-admission, 24 hours post-admission, 48 hours post-admission and 72 hours post-admission).

Orthogonal polarization spectral imaging technique (Cytoscan A/R, Cytometrics) will be used to visualize the microcirculation of the sublingual mucosa of the patients. The OPS technique utilizes reflected, polarized light at the wavelength of the isobestic point of oxyhemoglobin and deoxyhemoglobin (548 nm). The diminution of sublingual microcirculation can refer to circulatory redistribution due to hemorrhage. Sublingual microcirculation of the patients will be visualized and evaluated at pre-determined time points (directly upon arrival, 6 hours post-admission, 12 hours post-admission, 24 hours post-admission, 48 hours post-admission and 72 hours post-admission) during the first 72 in-hospital hours.

Arterial blood gas analysis and laboratory testing of venous blood are routine examinations in clinical practice. Base deficit and lactate are considered as global markers of blood loss and shock, and can be obtained rapidly with blood gas analysis. Hemoglobin and hematocrit values can correspond to the severity of blood loss, and are measured routinely both from arterial and venous blood. Sampling of arterial and venous blood for blood gas and laboratory analyses will be performed at pre-determined time points (directly upon arrival, 24 hours post-admission, 48 hours post-admission and 72 hours post-admission) during the first 72 in-hospital hours.

Hemodynamic monitoring is an essential part of emergency trauma care. Non-invasive monitoring of blood pressure, heart rate and respiratory rate of patients will be started immediately upon arrival. After patients are stabilized, invasive arterial blood pressure (IABP) monitoring can be started. IABP is considered as the gold standard of blood pressure measurement in critical care as it reflects the fluctuations of blood pressure in real time. Blood pressure and heart rate values will be recorded at pre-determined time points (directly upon arrival, 6 hours post-admission, 12 hours post-admission, 24 hours post-admission, 48 hours post-admission and 72 hours post-admission) during the first 72 in-hospital hours.