Test Talk: Lactate

Lactate, also referred to as lactic acid, is produced by muscles, red blood cells, in the brain, and in other tissues when oxygen levels are insufficient. Lactate levels are ordered when physicians suspect their patient is not getting sufficient oxygen (hypoxia) or other conditions for which high lactate levels are symptoms. Such conditions include sepsis, congestive heart failure, shock, liver disease, chronic alcoholism, Reye's syndrome, uncontrolled diabetes, and kidney disease.

An elevated lactate level is not diagnostic by itself, but contributes to a diagnosis with other supportive indicators. 

Lactates should be collected in heparin tubes (green stopper) and placed on ice immediately.  If kept at room temperature, levels within the sample increase dramatically within minutes. Some studies limit room-temperature stability to two hours.

Significant confusion exists in regards to the effect of tourniquet constriction on lactate levels. A thorough review of the literature is inconclusive. No study shows lactates are affected when the tourniquet is applied and released within one minute, as required by industry standards, however, one study found lactate increases when the tourniquet is constricted for five minutes. The current CLSI venipuncture standard suggests lactate increases with venous stasis, but provides no reference. Follow facility policy. 

Bibliography

1. LabTestsOnline. American Association for Clinical Chemistry. AACC. 
2. CLSI. Collection of Diagnostic Venous Blood Specimens; Approved Standard—Seventh Edition. Clinical and Laboratory Standards Institute. Document GP41-A7 Wayne, Pennsylvania 2017.
3. CLSI. Procedures for the Handling and Processing of Blood Specimens for Common Laboratory Tests; Approved Guideline—Fourth Edition. GP44-A4. Clinical and Laboratory Standards Institute. Document H18-A4 Wayne, Pennsylvania 2010.
4. Wu A. Tietz Clinical Guide to Laboratory Tests---Fourth Edition. Elsevier. St. Louis, Missouri. 2006.
5.  World Health Organization. Use of Anticoagulants in Diagnostic Laboratory Investigations. WHO. Geneva, Switzerland. 2002.