Introduction to Lactate in Veterinary Practice

How are blood lactate measurements useful?

Whilst lactate is not diagnostic of any particular disease state when taken in isolation as a single reading, it is a useful triage tool in the overall treatment decision making pathway. It can be used as a guide to morbidity and/or the need to further investigate and monitor more closely specific patients. However, it should also be noted that trends in lactate levels provide better prognostic information than a single measure [REF[SP1] ].

Lactate is a normal by-product of energy use in the body produced largely during anaerobic metabolism[AM2] [GD3]  (see Figure 1) and typical levels are typically under  approximately [GD4] 2.0 mmol l^-1. Elevated lactate levels (hyperlactatemia and lactic acidosis) are an indication of stress which will require further clinical investigation, as lactate is produced when cells are not getting sufficient oxygen to support normal aerobic energy production. This is usually due to tissue hypoperfusion and hypoxia when there is decreased blood flow to cells, either systemically or locally.

Measurements of blood lactate can, therefore, indicate the degree to which oxygen is being transported adequately around the body. As an increase in lactate levels occurs before changes in heart rate, blood pressure, or urine output, so this makes it a sensitive indicator of hypoperfusion [REF[SP5] ]. Thus offering ways of assessing the severity of pulmonary or cardiovascular disease, how the body responds to treatment, and the ability to predict health outcomes and influence decisions regarding the improvement of survival prospects [REFS[SP6] ].

Crucially, it should be noted that when considering treatment options for hyperlactatemia, the underlying cause of such elevated blood lactate concentration must first be established. Although poor perfusion is the most common reason, other factors can come into play. Such factors that can artificially raise lactate levels include: improper sample handling, excessive patient struggling and restraint and  prolonged venous occlusion when drawing a sample [REF[SP7] ].