Lactic Acid

Performed in Chemistry

LA

Lactic Acid, Arterial (LAA)

Gray NaF, Plasma

• After separation from cells:
  • Room temperature: 8 hours
  • Refrigerated: 2 weeks
  • Frozen: 38 days
• Whole blood stability (before separation):
  • Room temperature: 90 minutes

Collected in an outdated/expired tube
Hemolyzed, icteric or lipemic
Contaminated

Daily, Sunday through Saturday

Less than 4 hours

Anaerobic glycolysis markedly increases blood lactate and causes some increase in pyruvate levels, especially with prolonged exercise. The common cause for increased blood lactate and pyruvate is anoxia resulting from such conditions as shock, pneumonia and congestive heart failure. Lactic acidosis may also occur in renal failure and leukemia. Thiamine deficiency and diabetic ketoacidosis are associated with increased levels of lactate and pyruvate. Lactate levels in cerebrospinal fluid are increased in bacterial meningitis. Increased CSF levels also occur in hypocapnia, hydrocephalus, brain abscesses, cerebral ischemia and any clinical condition associated with reduced oxygenation of the brain and/or increased intracranial pressure. Lactate measurements that evaluate the acid-base status are used in the diagnosis and treatment of lactic acidosis (abnormally high acidity in the blood). In recent years, enzymatic methods for the determination of lactate have gained favor over colorimetric and titrimetric methods. Enzymatic methods are generally simple and provide greater specificity, accuracy, and reproducibility. The first enzymatic method described for the determination of lactate was based on the transfer of hydrogen from lactate to potassium ferricyanide by lactate dehydrogenase. However, the procedure was cumbersome and did not receive wide acceptance. Subsequent methods involved the UV measurement of the formation of NADH. In 1974, Gutmann and Wahlefeld described a lactate procedure that measures the NADH formed by the oxidation of lactate catalyzed by LD, using hydrazine as a trapping agent for pyruvate. A method described by Noll is also based on the catalytic action of LD but includes ALT in the reaction mixture to more rapidly remove the pyruvate formed form the conversion of lactate. The method presented here uses an enzymatic reaction to convert lactate to pyruvate. The hydrogen peroxide produced by this reaction is then used in an enzymatic reaction to generate a colored dye. This method offers longer reagent stability than the previous UV enzymatic methods.