Venous blood drawing steps

When we have a physical examination or go to the hospital for a disease checkup, we usually need a blood test. The blood test is done by drawing blood from our veins, and doctors generally recommend that patients fast for eight hours, because the blood collection effect will be better and the results will be more accurate. Most people will choose to draw blood from the wrist, so what are the steps for venous blood drawing?

Correct collection of blood samples is the key to obtaining accurate and reliable experimental results. Before sample collection, the blood collection method, required blood volume and applicable anticoagulant should be determined according to the experimental requirements. During the experiment, for any test that requires a large amount of blood (>0.2 ml), such as multiple blood cell analyses, hematocrit determination, blood rheology, biochemical tests, etc., samples can be obtained by venous blood sampling; some special tests, such as blood gas analysis, require the collection of arterial blood. Blood collection site: Venous blood collection mostly uses superficial veins located on the body surface, usually the elbow vein, the back of the hand vein, the medial ankle vein or the femoral vein. In children, blood can be drawn from the external jugular vein. Different types of syringes can be selected according to the amount of blood collected, equipped with corresponding needles. For some special examinations, plastic syringes and siliconized or plastic test tubes should be used to avoid platelet activation.

Steps:

(1) Patient preparation: Before blood collection, the procedure should be explained patiently to the patient to eliminate any doubts or fears. If individual patients experience dizziness during needle insertion or after blood drawing, they should lie down and rest. If necessary, you can sniff aromatic ammonia tincture, or apply acupuncture (or finger pressure) to the Zhonghe and Hegu acupoints. If dizziness is caused by hypoglycemia, glucose can be immediately injected intravenously or the patient can be given sugar water orally. If there are other situations, you should consult a doctor.

(2) Check the syringe: Before drawing blood from a vein, carefully check whether the needle is firmly installed and whether there is air or moisture in the syringe. The needle used should be sharp, smooth, and breathable, and the syringe should not leak.

(3) Disinfection: First, use a 30g/L iodine tincture cotton swab to disinfect the skin from the inside to the outside and in a clockwise direction at the selected venous puncture site. After the iodine tincture evaporates, use a 75% ethanol cotton swab to wipe off the iodine traces in the same way.

(4) Puncture: Use the left thumb to fix the lower end of the intravenous puncture site, use the right thumb and middle finger to hold the syringe barrel, and use the index finger to fix the lower seat of the needle, so that the bevel of the needle and the scale of the syringe face upward, and keep the needle at a 30-degree angle to the skin along the direction of the vein. The skin is pierced quickly and diagonally, and then at 5. The horn penetrates the venous wall forward and enters the venous cavity. After seeing the blood returning, push the needle in a little bit to prevent the needle from slipping out during blood collection; but do not pierce too deep to avoid causing hematoma, and remove the blood pressure cuff immediately.

(5) Bleeding and mixing: Remove the syringe needle and slowly inject the blood into the anticoagulant tube along the wall of the test tube to prevent hemolysis and foaming. After the blood coagulates and shrinks on its own, the light yellow transparent serum can be separated. If whole blood or plasma is needed, inject the blood into the anticoagulant tube (bottle) prepared in advance and mix gently to prevent coagulation. This is anticoagulated whole blood.