How to use venous oxygen saturations and lactate in critically ill patients

Mixed venous oxygen saturation (SvO2) and central venous oxygen saturation (ScvO2) contain much information of the (patho-) physiologic balance between a patient’s oxygen delivery and oxygen consumption. Also, they are influenced by many factors, which makes them as appealing as complex: in contrast to low values, which may always be considered pathological, normal values may leave the clinician clueless. In critically ill patients the agreement between ScvO2 and SvO2 is unacceptably wide, but this does not mean that both should be abandoned from our clinical tool set. This is completely different for femoral venous oxygen saturation (SfvO2), which should not be used as surrogate for ScvO2 or SvO2. Furthermore there is no place for SfvO2 in (goal-directed) care of critically ill patients. Besides venous oxygen saturations as surrogates for global tissue hypoxia, blood lactate levels give important information too. In prehospital settings, i.e. ambulance services, hyperlactatemia may serve as an early warning sign for severe illness. In the intensive care unit (ICU), ongoing hyperlactatemia should encourage the clinician to reflect the adequacy of the current therapeutic regime