Venous blood for the analysis of acid-base status in a model of septic shock

Objective To determine the relationship between arterial and venous acid-base status in a model of septic shock. Methods Paired samples (n = 435) of arterial and femoral venous blood from 57 sheep (47 septic, 10 non-septic) managed with protocol-guided ventilation, sedation, parenteral fluids and inotropic support. Results The arterial-venous difference in acid-base parameters was similar with and without sepsis. There was a consistent arterio-venous relationship for metabolic (pH, lactate, bicarbonate, base excess), but not respiratory parameters (partial pressures of oxygen, carbon dioxide, and haemoglobin-oxygen saturation), independent of sepsis. Conclusions Venous blood provides a reliable measure of metabolic but not respiratory disturbance.