After the advent of voluntary blood donation, some people felt dizzy. What is the reason?

Author: Ye Huifen

Author unit: Dongguan Central Blood Station

Today, when I was chatting with a friend, she said: "I went to donate blood two days ago. I felt a little dizzy after donating blood, but I was fine after resting for a while. What was the reason? Was it caused by poor physical condition? Can I go again in the future?" Looking at my friend's serious expression, I couldn't help laughing.

Let me first introduce my friend's situation: 22 years old, female, weighs 47 kilograms, is 1.6 meters tall, has a typical tall and thin body shape, and this is her first time donating blood.

I took this opportunity to give her some scientific knowledge about donation-related vasovagal reaction (DRVR): a systemic adverse reaction to blood donation. Most symptoms are mild, manifested by general discomfort, weakness, pale complexion, sweating, anxiety, dizziness, and nausea.

A few are more serious, and may cause transient loss of consciousness (syncope), convulsions or incontinence. If syncope and falls occur, accidental injuries may occur. Why is she the only one who feels dizzy? She has 4 characteristics of the population prone to blood donation-related vasovagal reaction (DRVR) (young, female, first-time blood donor, blood volume <3300ml), and the probability of adverse reactions to blood donation is of course higher than that of ordinary people. The characteristics of the susceptible population have the following characteristics, especially those who have two or more of the following characteristics at the same time: a) young (age <23 years old, especially age <20 years old); b) female (clinical research data show that women are more likely to have adverse reactions than men); c) first-time blood donor (first-time blood donors are often emotionally nervous); d) blood volume <3 300 mL (blood volume refers to the sum of blood in the human body, accounting for about 7% to 8% of body weight); e) have certain psychological or physiological characteristics (such as fear or anxiety of blood donation, orthostatic hypotension, history of syncope and other inducing factors). Predisposing factors (predisposing factors may exist before, during and after blood donation) a) Change of body position (from lying to sitting or standing, from squatting or sitting to standing) or standing for a long time; b) Emotional tension, anxiety or fear (for example: first time blood donation); c) Fasting, fatigue, drinking, lack of sleep, long-term lack of water; d) Use of drugs with vasodilator or diuretic effects; e) Overheated environment (for example: hot shower and hot bath) or sudden increase in ambient temperature (for example: in summer, blood donors walk from an indoor blood donation site with air conditioning to a hot outdoor environment) or stuffy environment; f) Painful or uncomfortable stimulation (such as venipuncture, especially when the venipuncture is not smooth or when seeing others have adverse reactions to blood donation); g) Blood collection time is too long (for example: whole blood collection time >10 min).

When my friend heard these words, he suddenly realized something and immediately responded, "I couldn't sleep the night before and drank a little. How can I prevent it?"

The following preventive measures can be taken for the above-mentioned susceptible groups and predisposing factors:

Blood bank staff

1. Strengthen the publicity of voluntary blood donation so that blood donors can fully understand the knowledge and process of blood donation, precautions before and after blood donation, and the significance of blood donation.

2. Provide a safe and comfortable blood donation service environment and facilities, ensure air circulation, and moderate temperature and humidity; set up materials and places to deal with adverse reactions to blood donation.

3. Cultivate blood donation service staff with strong professional skills, including physical examination doctors, blood collection nurses, initial screening test personnel and logistics personnel, who have a high sense of responsibility, good communication skills and rich experience in blood donation service.

4. Assessment before blood donation: (1) Avoid selecting donors who are nervous, fasting, or underweight; (2) Select skin without damage, inflammation, rash, dermatitis, or scars as the puncture site; (3) Select veins at the elbow of the upper limb that are clearly visible, large, elastic, full, and not prone to sliding; (4) Before collecting blood components, fully estimate the extracorporeal blood volume and give the donor 10% calcium gluconate orally as a preventive measure to prevent citrate anticoagulant poisoning reactions; (5) It is recommended that people who are prone to motion sickness should not donate blood on the blood donation vehicle, but should donate at a fixed blood collection point. (6) Control the donation volume of whole blood and the extracorporeal blood volume during the apheresis process. According to the Guidelines for the Prevention and Management of Vasovagal Reactions Related to Blood Donation, the donation volume of whole blood should not exceed 15% of the donor's blood volume. For female first-time blood donors aged <23 years with a blood volume <3,300 mL, caution should be exercised when choosing a whole blood donation volume of 400 mL. During the apheresis process, the extracorporeal blood volume should not exceed 15% of the donor's own blood volume. If it is estimated that the extracorporeal blood volume will exceed 15% of the donor's own blood volume during the apheresis process, intravenous supplementation with normal saline should be given.

5. Nursing during blood collection: (1) Keep an eye on all directions, listen carefully, talk enthusiastically with blood donors, and create a relaxed and pleasant atmosphere; (2) Perform venous puncture quickly, accurately, and gently to avoid damaging the vein; (3) Closely observe the blood donor's complexion and facial expression, accurately determine the occurrence of adverse reactions to blood donation and deal with them in a timely manner to ensure the safety of blood donors and blood. 6. Observation after blood donation: (1) Closely observe the blood donor's condition after blood donation; (2) Issue blood donation certificates and souvenirs, and focus on explaining the precautions after blood donation; (3) Leave the blood donor with the contact information of the blood station and doctor, so that the blood donor can communicate with the blood station at any time.

Cooperation of blood donors

1. Before donating blood (1) Do not fast: Do not fast before donating blood. Drink water and eat light food in moderation, such as porridge, bread, steamed buns, etc., to prevent dizziness, palpitations, sweating and other hypoglycemia symptoms during blood donation. (2) Low-fat diet: Do not eat high-fat, high-protein foods, such as meat, fish, eggs, milk, soy products and greasy foods before donating blood. Because lipid substances enter the blood, it is easy to cause fatty blood. (3) Get enough sleep and do not drink alcohol: Lack of sleep and drinking alcohol increase the burden on the liver and easily cause high ALT values; fatigue and poor mental state can easily cause systemic adverse reactions to blood donation. (4) Understand blood knowledge and eliminate nervousness: Free blood donation propaganda has been very widespread. Before donating blood, you can learn about blood knowledge through the blood station official website, WeChat public account, and authoritative media; you can call the blood station service hotline to consult relevant knowledge about blood donation; communicate with relatives and friends who have donated blood experience to establish a scientific concept of blood donation without harming health.

2. After donating blood (1) Take a rest After donating blood, take a rest at the scene, press the needle hole for 10 minutes, and leave only when you feel no discomfort; keep the bandage/dressing for at least 4 hours; do not do strenuous exercise within 24 hours, avoid working at heights, and get enough sleep; do not overexert your arm on the day of donating blood. (2) Replenish body fluids After donating blood, drink plenty of water, juice or soup is also acceptable; do not drink alcohol. (3) Maintain a normal diet, including fresh fruits, vegetables, soy products, dairy products, fresh fish and shrimp, meat and eggs, etc. No special nutrition is required.

The friend then asked: "If there is a reaction, how do you deal with it?"

1. Stop blood collection immediately;

2. The blood donor lies flat on his back with his head low and feet high, and his head tilted to one side;

3. Loosen your collar or tight clothes to keep breathing unobstructed;

4. Monitor pulse and blood pressure;

5. Provide psychological care and oral administration of warm glucose water;

6. If necessary, pinch the Renzhong and Hegu points with your fingers and apply wind-repelling oil. After taking on-site treatment measures, the patient can generally recover quickly. If the patient still has not recovered or improved, we will send the blood donor to the hospital for further diagnosis and treatment. I also taught my friend a "skill" - preventive "muscle contraction and relaxation activity (AMT)", which is very important for reducing the occurrence of DRVR. It can be done before, during and after blood donation.

Friends who are interested can also learn:

1. When doing AMT in a lying or sitting position, cross your legs and forcefully contract your legs, buttocks, and abdominal muscles. Hold for 5 to 10 seconds, relax for 5 to 10 seconds, alternate between contraction and relaxation, and repeat 20 to 30 times. Keep breathing normally during contraction to avoid holding your breath.

2. Do the tiptoe exercise when standing, lift your heels with force, then relax, and repeat 20 to 30 times. AMT should be performed in the following situations: a) before standing up from a lying, squatting or sitting position; b) when you experience symptoms such as dizziness or cold sweats; c) when blood collection is about to end; d) before leaving the blood donation chair; e) before leaving the blood donation site; f) when you experience discomfort such as dizziness after leaving the blood donation site.

Remember the following tips and you won’t feel dizzy when donating blood.

Donating blood for free is not scary, just make a plan before donating blood;

Don’t drink alcohol or stay up late, drink more water and less fat;

The blood donation process is not stressful, as medical staff are by your side;

After donating blood, it is most important to rest and eat normally;

Saving lives is not easy, leaving a lasting fragrance will earn you praise.

Author: Ye Huifen

Author unit: Dongguan Central Blood Station