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.