Femoral blood gas analysis, another tool to assess hemorrhage severity following trauma: an exploratory prospective study

BACKGROUND: Veno-arterial carbon dioxide tension difference (ΔPCO(2)) and mixed venous oxygen saturation (SvO(2)) have been shown to be markers of the adequacy between cardiac output and metabolic needs in critical care patients. However, they have hardly been assessed in trauma patients. We hypothesized that femoral ΔPCO(2) (ΔPCO(2 fem)) and SvO(2) (SvO(2 fem)) could predict the need for red blood cell (RBC) transfusion following severe trauma. METHODS: We conducted a prospective and observational study in a French level I trauma center. Patients admitted to the trauma room following severe trauma with an Injury Severity Score (ISS) > 15, who had arterial and venous femoral catheters inserted were included. ΔPCO(2 fem,) SvO(2 fem) and arterial blood lactate were measured over the first 24 h of admission. Their abilities to predict the transfusion of at least one pack of RBC (pRBC(H6)) or hemostatic procedure during the first six hours of admission were assessed using receiver operating characteristics curve. RESULTS: 59 trauma patients were included in the study. Median ISS was 26 (22–32). 28 patients (47%) received at least one pRBC(H6) and 21 patients (35,6%) had a hemostatic procedure performed during the first six hours of admission. At admission, ΔPCO(2 fem) was 9.1 ± 6.0 mmHg, SvO(2 fem) 61.5 ± 21.6% and blood lactate was 2.7 ± 1.9 mmol/l. ΔPCO(2 fem) was significantly higher (11.6 ± 7.1 mmHg vs. 6.8 ± 3.7 mmHg, P = 0.003) and SvO(2 fem) was significantly lower (50 ± 23 mmHg vs. 71.8 ± 14.1 mmHg, P < 0.001) in patients who were transfused than in those who were not transfused. Best thresholds to predict pRBC(H6) were 8.1 mmHg for ΔPCO(2 fem) and 63% for SvO(2 fem). Best thresholds to predict the need for a hemostatic procedure were 5.9 mmHg for ΔPCO(2 fem) and 63% for SvO(2 fem). Blood lactate was not predictive of pRBC(H6) or the need for a hemostatic procedure. CONCLUSION: In severe trauma patients, ΔPCO(2 fem) and SvO(2 fem) at admission were predictive for the need of RBC transfusion and hemostatic procedures during the first six hours of management while admission lactate was not. ΔPCO(2 fem) and SvO(2 fem) appear thus to be more sensitive to blood loss than blood lactate in trauma patients, which might be of importance to early assess the adequation of tissue blood flow with metabolic needs. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13049-023-01095-9.