Lactate, pH, and blood gas analysis in critically ill patients

To obtain information about the relationship between different types of circulatory insufficiency, a series of oxygen parameters and plasma lactate, we have performed a pilot study comprising five patients with circulatory insufficiency. Plasma lactate was measured on a Stat Profile 7 (NOVA Biomedical, USA) and pH/blood gases on an ABL 520 (Radiometer Medical A/S, Denmark). Plasma lactate seems to be inversely related to base excess (BE), whereas no relationship to venous oxygen tension pO2(v) of the vein draining the inadequately perfused region seemed to exist. In one patient we made simultaneous measurements from v. cava inferior., v. cava superior., a. pulmonalis and a. radialis. Simultaneously sampled plasma lactate from different sites differed up to 0.6 mmol/L with the highest value obtained from v. cava inferior. This pilot study indicates that the increase of plasma lactate may vary with the type of circulatory disturbance and the sampling site.