Despite the drawbacks, blood lactate levels remain a useful means of assessing tissue oxygenation. The importance of tissue hypoxia in the development of multiple organ failure makes any such measure of tissue oxygenation valuable. A normal value can be considered to be about 1 mmol/l, and levels above 1.5 to 2 mmol/l should alert the clinician to the possibility of reduced tissue oxygenation. Raised levels must be interpreted cautiously in the light of clinical patient assessment and other available indices. Changes in blood lactate levels occur too slowly to guide therapy directly and therefore can never replace established hemodynamic variables. Evaluation of blood lactate levels over time are of most use in following the course of hypoxia and enabling the effects of treatment to be monitored. A combination of blood lactate with a more regional measure of tissue perfusion, such as gastric pHi, may give a more valuable assessment of the overall situation.
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