Measurement of blood lactate

Analysers are available to allow rapid measurement of blood or plasma lactate on small samples, using enzyme-based methods. The enzymatic conversion of lactate to pyruvate is an oxygen utilising reaction. The extraction of oxygen from the sample can be detected by a sensitive oxygen fuel cell sensor and is directly proportional to the sample lactate concentration. A whole blood sample (venous or arterial since there is no practical difference) is collected into a heparin fluoride tube to prevent coagulation and glycolysis (lactate producing). Nitrite may be used in the sample tube to convert haemoglobin to the met form, thus avoiding uptake of oxygen during the enzyme reaction. The enzymatic method is specific for the L-isomer and will not, therefore, detect D-lactate (e.g. in short bowel syndrome). Normal arterial whole blood lactate concentration is <1.5mmol/l. Lactate may also be measured from regional sites as an aid to the assessment of regional perfusion (e.g. arterial-jugular bulb difference).

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