Lactic acid is produced as a result of anaerobic metabolism when Do2 to the tissues is low or inadequate. Currently, blood lactate is measured by bedside analyzers using an enzymatic technique, and a level of 1.5 mmol/l is generally accepted as the upper limit of normal. Lactate levels may be elevated when vital signs and oxygen transport variables appear satisfactory, indicating Do2 values that are insufficient for the clinical circumstances involved or inability to consume oxygen. It has been suggested that lactate levels may be invalidated by the presence of liver disease. However, even with advanced cirrhosis, patients in shock with a high lactate have a poorer prognosis, and in acute hepatic encephalopathy a high blood lactate is associated with mortality and inadequate oxygen transport patterns.
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