Things to note when drawing blood for culture

Many people don't know much about blood culture. This is a method of blood culture that can perform good examinations for certain diseases. However, when doing blood culture, you need to be aware of some precautions, such as the best time to draw blood and some better blood collection methods before you can perform blood culture. Let’s take a brief look at this aspect below.

Things to note when drawing blood for culture

1. The best time to collect blood: before the use of antibiotics, and 30 minutes to 1 hour before the onset of chills and fever. The blood collection environment should be relatively clean.

2. Venous puncture disinfection: Strictly follow the skin disinfection steps (chlorhexidine is recommended).

Blood culture must be strictly disinfected to avoid contamination from bacteria on the skin or in the environment.

3. Disinfection of culture bottles: discard the plastic cap on the top of the bottle, disinfect the rubber stopper on the top of the bottle with a 75% ethanol cotton ball, and wait for it to dry for 60 seconds.

4. The collected blood should first be injected into the aerobic bottle and then into the anaerobic culture bottle, which is conducive to better separation of fungi, Pseudomonas aeruginosa and Stenotrophomonas maltophilia.

5. Blood collection device and minimum blood collection volume:

How to perform blood culture

The first is the timing of blood collection. To maximize the chance of obtaining a positive blood culture, blood cultures should be obtained when the patient is shivering or when the temperature is just beginning to rise. Once the body temperature reaches its peak, most of the bacteria have been cleared from the blood, and the culture positivity rate will naturally be low.

Secondly, the quantity of specimens submitted for inspection must be sufficient. In clinical practice, some doctors perform blood culture on patients, but usually only send the blood for testing once. In most cases, the correct operation should be to collect two sets of blood cultures from different parts almost at the same time, about 40 ml of blood. In this way, the positive rate of blood culture can be as high as about 80%. On this basis, the positive rate increases by approximately 1.3% for every additional 1 ml of blood. However, the practice of sending 5 to 10 ml of blood for culture once has a positive detection rate of pathogens of only 7% to 10%. Certain infectious diseases, such as endocarditis, have pathogens that appear intermittently in the blood of patients and are difficult to capture. In this case, it is also necessary to provide three or more sets of blood specimens, with an interval of about one hour, to increase the positive detection rate.

Again, blood samples should be drawn for culture before the patient uses antibiotics, otherwise the accuracy of blood culture may be affected. If the patient has used antibiotics before seeing a doctor, a culture bottle containing resin should be selected for the operation to neutralize and adsorb the antibiotics and increase the positive detection rate of pathogens.

Finally, don’t give up on the test just because blood culture takes a long time. Some doctors are reluctant to choose blood culture because of factors such as the rotation rate of hospital beds. In fact, with the improvement of testing technology, most pathogens can now be detected within 48 hours. Targeted medication after identifying the pathogen can not only avoid the embarrassment of changing medications after blind medication fails, save precious treatment time, but also save patients a lot of treatment costs.