Carbon monoxide (CO) is a colorless gas with a weak odor. CO is a common asphyxiating chemical poison that seriously endangers human health. It is mainly caused by its combination with hemoglobin (Hb) in the blood to form carboxyhemoglobin (COHb), which causes Hb to lose oxygen. In severe CO poisoning, death can result from hypoxia in the tissue. Therefore, the monitoring of COHb concentration in blood is of great significance in health monitoring.

Basic Information

Specialist classification: neurological examination classification: blood examination

Applicable gender: whether men and women apply fasting: fasting

Analysis results:

Below normal:
Normal people have no or little content.

Normal value:
Non-smoker: 0-0.023
Smoker: 0.021-0.042

Above normal:
Elevation is seen in carbon monoxide poisoning (CoHb > 50% lethal).



Tips: The observations must be timely, otherwise the cherry red will gradually fade away and it is difficult to distinguish. Normal value

Qualitative: negative.

Quantification: 0 to 0.023 (0 to 2.3%) for non-smokers and 0.021 to 0.042 (2.4% to 4.2%, <6.5%) for smokers.

Clinical significance

Elevation is seen in carbon monoxide poisoning (CoHb > 50% lethal).

High results may be diseases: carbon monoxide poisoning, carbon monoxide poisoning in children, delayed encephalopathy after carbon monoxide poisoning

1. Carbon oxide hemoglobin qualitative test:

1 The observations must be timely, otherwise the cherry red gradually fades and is difficult to distinguish.

2 The sensitivity of this test is poor, and the carbon monoxide content in the blood is only positive when it reaches a certain level. If the patient has previously taken ventilation measures, the blood carbon monoxide content will decrease and the test may be negative. However, clinical symptoms and signs may still exist.

2, carbon oxide hemoglobin dual wavelength quantitative determination:

In the quantitative determination of 1COHb, there is no standard. The value of F1, F2 and F3 in the formula is the premise of accurate quantification of COHb. Although the literature provides F value, the equipment conditions of each laboratory are not completely consistent, such as spectrophotometer. The wavelength width of the monochromatic light, the wavelength error, etc., so it is not appropriate to directly apply the F value of the literature, and the F value should be determined according to the spectrophotometer used. After the F value is determined, as long as the instrument conditions are not changed, it can be used all the time, so the workload of the conventional sample measurement is not increased.

2 In the preparation of 100% saturation COHb (for the determination of F value), if there is no civil gas, CO can also be prepared by chemical method: 100 ml of formic acid and 150 ml of sulfuric acid are mixed, and the generated gas is sequentially passed into NaOH (5 mol/L). Purified in water and CaCl2 (0.5mol/L) and then used in latex gloves for later use.

3 Methodological evaluation results of this method: After color development of the sample, the color is stable within 30 min; repeated test results (n=20): 10.41%, s=0.21, CV3.7%; recovery: 92.7%-106.3% .

Inspection process

1, carbon oxide hemoglobin hemoglobin qualitative test:

1 Take 2 tubes, add 3 to 5 ml of distilled water, add 3 drops of blood to the patient, and add 3 drops of normal control blood to the other tube and mix. at this time. If the patient has carbon monoxide in his blood, the blood is cherry red.

2 add 50g/L NaOH 1 drop to each tube and mix gently. The normal control tube is greenish brown. If there is carboxyred blood red hemoglobin in the blood of the patient, the dissolved blood is still cherry red, which is positive; if it is consistent with the normal control color negative.

2, carbon oxide hemoglobin hemoglobin dual wavelength quantitative determination:

1F value formulation: Preparation of Hb solution (without COHb) and saturated COHb solution (COHb content of 100%). Take 50 μl of whole blood without smoking and no history of CO exposure in the near future, add 6.0 ml of reagent II, and let it stand for 5 min to fully hemolyze. Another two 25.0ml volumetric flasks were used. Each bottle was accurately added with 2.0 ml of the above dissolved blood. In a fume hood, one of the bottles was ventilated for 5 min; the other bottle was purged with gas (CO) for 1 min, and then nitrogen was introduced for 2 min. Add 250 mg of Na2S2O4 per bottle, add reagent I to the mark, and add 3 to 5 times to dissolve. After 10 min, □b420, AHb432, ACOHb420, ACOHb432 were recorded by colorimetric two-wavelength 420 nm and 432 nm with reagent II. According to Beer's law: A=a·b·c, because both Hb and COHb are from the same sample, hemoglobin has the same iron molar concentration (c) and the same colorimetric conditions (b), so:

Using the above method, the measured F values ​​were F1 = 1.3041; F2 = 0.5742; F3 = 1.8627.

2 sample determination: take a small test tube, add reagent 1.2ml, add 10μl of finger blood, mix it for 5min to make it hemolyze, take another tube with plug, take the above dissolved blood 0.2ml and 2.3ml reagent I The phases were mixed, Na2S2O425mg was added, and the mixture was dissolved by cascading. After 10 minutes, the reagent II was used for zero adjustment, and the A420 and A432 were recorded on the narrow bandwidth type spectrophotometer with two wavelengths of 420 nm and 432 nm.

Not suitable for the crowd

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

Adverse reactions and risks

1. Infection: Pay attention to aseptic operation when collecting blood, avoid contamination of water and other parts at the blood collection site to avoid local infection.

2, bleeding: after the blood is given a full compression time, especially coagulopathy, bleeding tendency, to avoid local subcutaneous oozing, bruising and swelling.