Blood tests are one of the important examination items in modern medicine, which can help doctors diagnose diseases. Before the blood draw, nurses often ask questions such as "Did you eat and drink before the blood draw?" and "Have you been staying up late lately?" Let's learn about the things involved in blood draws.
1、 Precautions before blood draw
(1) It is best to clean the skin one day before blood draw, which can improve the disinfection effect during blood draw and prevent wound infection.
（2） 1-3 days before blood draw, try to have a light diet, avoid drinking alcohol, staying up late, and do not engage in strenuous sports or heavy physical labor.
（3） On the day of blood draw, clothing should be as loose as possible, especially the sleeves should not be too tight, to prevent compression of the veins and the formation of subcutaneous hematoma.
（4） If there is a history of alcohol/iodine allergy or dizziness with needles and blood, the nurse should be informed before blood collection.
（5） When drawing blood, one should try to relax as much as possible to avoid mental tension that may cause vasoconstriction.
（6） If symptoms such as abdominal pain, palpitations, chest tightness, dizziness, etc. occur during blood collection, the blood collection nurse should be informed immediately so that the nurse can take measures to handle them.
（7） If there are any special circumstances before blood collection, the nurse should be informed in advance, such as having received blood transfusion treatment within the past 10 days, having undergone enhanced CT or MRI examination in the last 7 days, having just completed arteriovenous fistula surgery or undergoing hemodialysis treatment, etc.
（8） If medication is taken before a blood draw, it may affect the accuracy of the test results. If medication is not necessary, such as supplements, vitamins, birth control pills, antibiotics, etc., it should be suspended. If medication is necessary, it should be taken according to the doctor's instructions after consulting a doctor. For chronic diseases such as heart disease, hypertension, asthma, etc. that require long-term medication, medication should be taken under the doctor's advice, and medication should not be stopped without authorization to prevent the concentration of medication in the blood from decreasing and causing serious consequences.
2、 Which projects require fasting?
In general, blood routine tests do not require fasting, but blood biochemical tests such as kidney function, liver function, immune related items, etc. often require fasting. The examination of blood lipids also requires fasting, and a light diet should be maintained for 3 days before the examination. In addition, fasting insulin, fasting blood glucose, fasting C-peptide, etc. also require fasting examination. If you are unsure whether the item you are examining requires fasting, you should consult with the department doctor. The so-called fasting refers to fasting for 8-12 hours, usually not exceeding 16 hours. During this period, you can drink a small amount of water, not exceeding 50ml, but be sure not to drink beverages, coffee, and strong tea. If you are concerned about insufficient physical strength during the examination, you can bring some convenient food and consume it after the blood collection is completed.
3、 Precautions after blood draw
(1) Correct compression
When taking blood from a vein, it is often necessary to use a needle to penetrate the skin surface and enter the vein, and the needle is usually tilted at 15-30 °. In this case, the needle points on the skin surface and the blood vessel wall often do not overlap. After blood draw, correct compression is necessary to achieve hemostasis and avoid adverse events such as subcutaneous hematoma and bleeding caused by incorrect compression. The correct method of pressing is to keep the arm straight after blood collection, and then press the puncture point with the thumb for 3-5 minutes to compress and stop bleeding. It is worth noting that when pressing, attention should be paid to the force, not too much or too little, to prevent poor hemostasis or local blood blockage, which may cause bleeding or bruising. If coagulation problems occur due to anticoagulant therapy or other reasons, the compression time should be appropriately extended until complete hemostasis is achieved before releasing. During the pressing process, do not rub the puncture site to prevent bacteria from entering and causing infection.
（2） Handling of adverse conditions
If subcutaneous hematoma, bruising, or other conditions occur at the puncture site, they can be relieved by cold compress within 24 hours after blood draw, and then switched to hot compress after 24 hours to eliminate local swelling and pain.
（3） After drawing blood, you should wait for a moment in the blood collection hall. If there are no abnormalities, then leave. After 24 hours of blood draw, try not to take a shower or dirty or wet the puncture site to prevent bacteria from entering the body and causing infection. At the same time, try not to use the blood drawing limb to lift heavy objects or engage in sports such as playing ball or swimming, to prevent local blood pressure from rising and causing the wound to bleed again.
4、 What should I do if I feel dizzy with blood or needles?
Some people may experience palpitations, shortness of breath, pale complexion, dizziness, nausea, vomiting, blood pressure drop, and even fainting during blood draws due to mental stress, excessive fatigue, physical weakness, hunger, and other reasons. For such individuals, psychological counseling should be provided in advance to help them relax as much as possible before blood draws can be performed. During the blood draw process, attention should be paid to observing their demeanor and reminding them to inform medical staff in a timely manner if they experience any discomfort, so that medical staff can handle it.
Conclusion: Blood drawing is not about taking a small amount of blood with a needle. It is important to understand the precautions involved to prevent a decrease in the accuracy of the test results.