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

Abstract

Background: Veno-arterial carbon dioxide tension difference (ΔPCO₂) and mixed venous oxygen saturation (SvO₂) 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 ΔPCO₂ (ΔPCO_{2 fem}) and SvO₂ (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.

Keywords: Hemorrhagic shock; Lactate; Severe trauma; Tissue hypoxia; Veno-arterial carbon dioxide tension difference; Venous oxygen saturation.

Fig. 1

Volumes of red blood cells transfused during the first six hours of admission. Volumes are shown according to quartile distribution of A ΔPCO_{2 fem}. B SvO_{2 fem} and C lactate. All data are reported as mean ± SD. ΔPCO_{2 fem} femoral venous-arterial difference in carbon dioxide pressure. SvO_{2 fem} femoral venous oxygen saturation

Fig. 2

Evolution during the first 24 h of hemodynamic variables in transfused and non-transfused patients. A ΔPCO_{2 fem}. B SvO_{2 fem} and C lactate. All data are reported as mean ± SD. *P < 0.05; **P < 0.005; ***P < 0.001. Parameters were measured at hospital admission and over the first 24 h. ΔPCO_{2 fem} femoral venous-arterial difference in carbon dioxide pressure. SvO_{2 fem} femoral venous oxygen saturation

Fig. 3

ROC curves for prediction of RBC transfusion and hemostatic procedure by ΔPCO_2fem and SvO_2fem. A ROC curve for prediction of pRBC_H6 by ΔPCO_{2 fem} at admission. B ROC curve for prediction of pRBC_H6 by SvO_{2 fem} at admission. C ROC curve for prediction of hemostatic procedure during the first 6 h of admission by ΔPCO_{2 fem} at admission. D ROC curve for prediction of hemostatic procedure during the first 6 h of admission by SvO_{2 fem} at admission. AUC area under the curve. ΔPCO_{2 fem} femoral venous-arterial difference in carbon dioxide pressure. pRBC_H6 transfusion of at least 1 pack of red blood cell during the first 6 h of admission. ROC Receiver operating characteristics. SvO_{2 fem} femoral venous oxygen saturation