Lactic acid is an intermediate in sugar metabolism in the body. In certain pathological conditions (such as respiratory failure or circulatory failure), tissue hypoxia can be caused, and lactic acid elevation can be caused by hypoxia. In addition, in the process of glucose metabolism in the body, such as increased glycolysis rate, strenuous exercise, dehydration, can also cause elevated lactic acid in the body. Elevated lactic acid in the body can cause lactic acidosis. Checking blood lactate levels can indicate the severity of the underlying disease.

Basic Information

Specialist classification: Digestive examination classification: blood examination

Applicable gender: whether men and women apply fasting: fasting

Tips: Blood should be taken on an empty stomach and at rest. Do not use a tourniquet, do not use force to make a fist. If a tourniquet is used, the tourniquet should be removed after puncture for 2 minutes before blood is drawn. Normal value

1. Determination of whole blood lactic acid (spectrophotometry) Whole blood lactic acid 0.5 to 1.7 mmol/L (5 to 15 mg/dl). Urine lactic acid is 5.5 to 22 mmol / 24 h.
2, plasma lactic acid determination (colorimetric method) is less than 2.4mmol / L (22.0mg / dl, a positive skew distribution, 95% percentile upper limit).

Clinical significance

1. Irreversible high lactic acid: severe hypoxia of the tissue can lead to aerobic oxidation of pyruvate in the Krebs cycle. The enzymatic action of pyruvate to lactic acid is enhanced, the ratio of lactic acid to pyruvate in the blood is increased, and lactic acid is increased. Up to 25mmol / L. The appearance of this extreme value marks the deterioration of the cellular oxidation process and is associated with significant respiratory enhancement, weakness, fatigue, paralysis and eventual coma. Even though acidosis and hypoxemia have been treated, such hyperlactemia is often irreversible. Seen in the irreversible period of shock, diabetic coma without ketotoxicosis and the end stage of various diseases.

2, reversible high lactic acid: in shock, cardiac decompensation, blood disease and pulmonary insufficiency, common hypoxemia and high lactateemia, often reversible after hypoxemia and primary conditions of. In cases where liver perfusion is reduced, lactic acid is significantly reduced by liver removal and lactic acidosis can occur.

High results may be diseases: mitochondrial myopathy, lactic acidosis in the elderly, mitochondrial disease, lactic acidosis in diabetes, dystrophic myocardium in children, acute lymphoblastic leukemia in the elderly, lactic acidosis, pediatric Lai syndrome, Children with glycogen storage disease type V, elderly septic shock considerations

1. Determination of whole blood lactate (spectrophotometry):

1 Blood should be drawn on an empty stomach and at rest. Do not use a tourniquet, do not use force to make a fist. If a tourniquet is used, the tourniquet should be removed after puncture for 2 minutes before blood is drawn. It is best to draw blood with a heparinized syringe and immediately inject it into a pre-weighed tube containing ice-cold protein precipitant. If measured by plasma, anti-coagulation was performed with 10 mg of sodium fluoride and 2 mg of potassium oxalate per ml of blood, and the specimen was immediately cooled and centrifuged within 15 min.

The tube number before blood draw, weighed (Wt) and recorded. Add 6ml of MPA (50g / L), weighed (Wm) and placed in an ice bath, each sample is best for double tube analysis. Immediately after the blood was drawn, it was injected into the above test tube, 2 ml per tube. Mix 3 times in reverse and do not create bubbles. After the tube temperature is equilibrated with room temperature, weigh it again (Wb). After standing for at least 15 min, the pellet was centrifuged (400 r/min, 15 min). The supernatant must be clarified. Calculate the dilution factor D:


2 Metaphosphoric acid forms a polymer (HPO3) in an aqueous solution and hydrates to orthophosphoric acid (HPO3+H2O→H3PO4). The orthophosphoric acid does not precipitate the protein, and the ability of the metaphosphoric acid solution to precipitate the protein can only be maintained for about 1 week at 4 °C.

3 The linear range of this method is 5.6mmol/L (50mg/dl).

4 This method does not use perchloric acid as a protein precipitant.

5 Generally, lithium lactate is not labeled with L- or DL-, both are DL-type, and L-type lithium lactate is expensive.

2, plasma lactate determination (colorimetric method):

1 Under the condition of this method, the NBT reduction product is very stable in the reaction liquid, no turbidity and precipitation, and the absorbance is unchanged for a long time.

2 Heparin anticoagulated plasma, blood bank ACD maintenance solution anticoagulated plasma, cerebrospinal fluid, urine, gastric juice, etc. can be determined by this method.

3 The addition of protein is necessary for the stabilization of the reaction and product solution. Adding protein and surfactant at the same time improves sensitivity and stability. Brij-35 and TritonX-100 have the same effect. The concentration of lactic acid in human serum albumin is high and is not applicable. The color intensity of human serum albumin is 1.06 times higher than that of bovine serum albumin. For example, when bovine serum albumin is used and it is only added to a standard tube, the standard tube absorbance must be multiplied by this number.

4 The lactic acid-free protein solution can be pre-mixed with the buffer and then added to 1 ml instead of separately in Table 2.

5 The linear range of this method is 8.0mmol/L (73mg/dl).

6 Absorbance increases with increasing incubation time and must be accurate for 10 min. The absorbance did not change after adding 0.1 mol/L hydrochloric acid.

7 Heparin-sodium fluoride is preferred for the anticoagulant (1 mg heparin, 6 mg sodium fluoride can be anticoagulated 5 ml blood). After the blood is drawn out, the blood sample tube is placed in an ice bath for examination, the plasma is separated as soon as possible, and the ice chamber is stored for testing. Potassium oxalate has a certain inhibitory effect on LDH, especially when blood is drawn less and potassium oxalate is relatively more.

Inspection process

Immediately after venous blood collection, the test method:

1. Determination of whole blood lactic acid (spectrophotometry): According to Table 1.

2. Determination of plasma lactic acid (colorimetric method): according to Table 2.

After mixing, the absorbance of each tube was read with a spectrophotometer at a wavelength of 530 nm, a 10 mm optical diameter comparison cup, and zero with distilled water.

Not suitable for the crowd

Inappropriate people: Generally there are no people who are not suitable.

Adverse reactions and risks

1, local subcutaneous hemorrhage: after the blood collection should be pressed for a sufficient time, especially those with bleeding tendency, so as not to cause subcutaneous oozing and bruising due to no blood coagulation.

2, infection: attention to aseptic operation during venous blood collection, so as not to cause local infection.