Understand the whole process of blood collection in one article and say goodbye to tension and misunderstandings

Written by: Chief Technician Xu Yinyin and Chief Technician Zhang Xiaoli of Yongchuan Hospital Affiliated to Chongqing Medical University, and Chief Technician Zou Jingbo of Mr. Zou's Science Garden

"Nurse, I feel dizzy when I see blood being drawn. Am I afraid of needles? What's the use of drawing so much blood from me? Are you going to sell it? Will it hurt?" There are also children and even adults who panic and cry at the blood drawing window. Even the best-tempered nurses will inevitably feel annoyed when facing these almost identical questions and noisy scenes of loud crying every day. In fact, blood drawing is not as scary as you think. It is just the starting point of the safest minimally invasive auxiliary examination method to help doctors understand your physical condition.

1. Tips on blood collection: Why is venous blood drawn?

Hospitals often choose venous blood for blood collection. The human body's blood circulates under the impetus of the heart, a "power pump". The vein wall is thin and the pressure is low, so it is easy to puncture and has a low risk of bleeding, just like walking on a flat path. In addition, the composition of venous blood is stable, which can provide doctors with accurate diagnosis basis. By collecting venous blood, doctors can obtain key information for diagnosing diseases or evaluating health status.

2. Before blood collection, don’t forget these preparations!

Preparation before blood collection is very important. For patients, it is important to get enough sleep the night before to avoid stress and anxiety that may affect blood composition. If blood sugar, liver function, etc. are to be checked, fasting for 8 to 12 hours is required. In addition, avoid strenuous exercise before blood collection, otherwise it will affect the accuracy of the test results [1].

In hospitals, medical staff should prepare various supplies. Skin disinfectant is used for disinfection and can kill bacteria on the skin surface in a short time. Different colored blood collection tubes have different uses due to different internal additives. Tourniquets can fill blood vessels and facilitate puncture. Gloves, labels, etc. are also indispensable. The blood collection environment should be clean, bright and well ventilated to provide patients with comfortable and safe blood collection conditions.

3. The blood collection process is actually not that scary!

When drawing blood, medical staff will carefully check the patient information to ensure that the sample accurately corresponds to the patient to avoid confusion. Generally, blood is drawn from the median vein of the elbow or the basilic vein. After being tied with a tourniquet, the blood vessels are more obvious and easier to puncture.

Disinfection is an important part of ensuring safety. First, spray the skin of the intended blood collection site with skin disinfectant. After it dries slightly, wipe the skin from the inside out with a sterile cotton swab to reduce the risk of infection. Then quickly and accurately insert the blood collection needle into the blood vessel, and the blood flows into the blood collection tube. During the whole process, the patient should stay relaxed and cooperate with the medical staff, and it will be completed quickly.

After the blood is collected, the medical staff will press the puncture site with a sterile cotton ball, cotton swab or gauze. The patient needs to press for a few minutes to prevent bleeding and bruising. After that, the blood sample will be labeled and sent to the laboratory for testing.

4. Before and after blood collection, keep these precautions in mind!

Before blood collection, patients should inform medical staff of their health conditions, allergy history, and medications they are taking so that they can assess the risks. In particular, patients who are extremely allergic to ethanol should inform the blood collection nurse in advance so that special non-ethanol skin disinfectants can be used, because most skin disinfectants contain ethanol. Try to relax during blood collection. You can relieve tension by taking deep breaths, distracting your attention, etc., to reduce the difficulty and pain of puncture [2].

After blood collection, patients should not leave immediately but should be observed in the hospital for a while. If they experience discomfort such as dizziness or fatigue, it may be needle phobia or hypoglycemia, and they should inform the medical staff in time. After returning home, avoid getting the blood collection site wet to prevent infection, and do not engage in strenuous exercise or heavy physical labor to give the body time to recover.

5. Common misunderstandings in blood drawing must be avoided!

Myth 1: You can’t drink water before blood collection ✘

It is OK to drink boiled water before blood collection. Generally, drinking a small amount of water (no more than 200 ml) will not have a significant impact on the blood test results. Especially for projects that require fasting blood collection, drinking water can prevent the blood from being too concentrated, which will help the blood collection operation. However, be careful not to drink sugary drinks, coffee, strong tea, etc., so as not to affect the test indicators.

Myth 2: Finger pricking and venous blood drawing have the same effect✘

There are big differences between finger prick blood and venous blood draw in terms of test items and accuracy. Finger prick blood is generally used for some simple blood routine tests, with a small amount of blood and limited test items. Venous blood can test more comprehensive items, and the composition of venous blood is relatively stable, so the test results are more accurate. For the detection of important indicators such as blood sugar, liver function, and kidney function, venous blood must be used to obtain reliable results.

Myth 3: Too many blood draws will harm your body ✘

In fact, the amount of blood drawn each time is generally only a few milliliters to tens of milliliters. The impact of a small amount of blood on the body is minimal, and the body can quickly replenish the lost blood through mechanisms such as the differentiation of hematopoietic stem cells [3]. Moreover, blood tests are designed to detect potential health problems in a timely manner. Early diagnosis and early treatment are more beneficial to health.

Although blood sampling seems simple, it plays a huge role in medical treatment. Finally, let's answer the questions at the beginning of the article:

I get dizzy when I see blood being drawn. It is true that I may be afraid of the needle, but in most cases, if I meet a nurse who is skilled in the technique, I won’t feel anything even after the blood is drawn. The maximum amount of blood drawn at one time is 10 to 20 ml, and in extreme cases it may be a little more, but it is all required for disease examinations. Because different blood collection tubes contain different anticoagulants, and most of them come from clinical patients, the blood may contain known and unknown bacteria and viruses, and it is absolutely impossible to transfuse it to others. Selling blood and making mao xuewang are purely jokes, just to make everyone happy. Different people have different pain thresholds, because there are indeed nerve endings at the blood collection site, which may be a little painful, but if you meet a nurse who is skilled in the technique, sometimes you may not feel any pain and that's OK!

After understanding this knowledge, you will be able to deal with it calmly next time you have your blood drawn!

References:

[1] Xu Yupei. What are the precautions for blood collection? [J]. Family Knowledge, 2024, (12): 28-29.

[2] Li Zhixiang. Common blood test items and blood collection precautions [J]. Health Guide, 2024, 30(04): 65-66.

[3] Lu Jingfang. What are the precautions and common misunderstandings for blood tests? [J]. Family Life Guide, 2024, 40(07): 111-112.