World Blood Donor Day | How to donate blood more safely?

June 14 is World Blood Donor Day. This year marks the 20th anniversary of World Blood Donor Day. The slogan for World Blood Donor Day in 2024 is: "In celebration of the 20th anniversary of World Blood Donor Day: Thank you, blood donors!"

Blood donation is no trivial matter. While promoting the spirit of dedication, how to donate blood correctly, safely and effectively is crucial for both patients and blood donors. Let us listen to the professional answers from transfusion doctors.

Blood type matters

◆ The history of the discovery of blood types

Blood type refers to the specific antigen type on the red blood cell membrane. The well-known blood types are: red blood cell ABO blood type system and Rh blood type system. So how was blood type discovered? This is thanks to Karl Landsteiner, a pathologist in Vienna. In 1900, he took blood samples from himself and five colleagues, mixed them, and conducted observations and studies.

He found that some samples could be successfully mixed, but some agglutinated (stuck together): two samples had a substance called "Anti-gen" (antigen) on their red blood cells, which he marked with "A"; the other two samples had another antigen, which was marked with "B" in alphabetical order. The plasma marked as group A could cause the red blood cells marked as group B to agglutinate, and the plasma of group B could cause the red blood cells of group A to agglutinate; only one person, including Landsteiner himself, had no A antigen or B antigen in his red blood cells, but his plasma had two antibodies, that is, the red blood cells did not agglutinate after mixing with the plasma marked with groups A and B, but the plasma could agglutinate the red blood cells of groups A and B. At first he called this type C, and later changed it to O, and marked it with "O" (for no antigen).

Two years later, Landsteiner's colleagues discovered the AB type in a larger crossover experiment, and thus all four blood types of the ABO blood type system, A, B, O, and AB, were discovered. After that, a series of other red blood cell blood type systems were discovered, including MN, P, etc.

In 1940, Landsteiner and Wiener used rhesus monkey red blood cells to immunize guinea pigs and rabbits. The immune serum obtained could agglutinate 85% of white people's red blood cells, and the remaining 15% were negative. It was named after the first two letters of the monkey Rhesus. This was the beginning of the establishment of the complex Rh blood type system.

(Contributed by Ma Haimei, Blood Transfusion Department, Beijing Tsinghua Chang Gung Hospital)

◆ Is O-type blood really universal blood ?

In daily life, we often hear such a saying: O-type blood is universal blood and can be transfused to anyone. So, is O-type blood really so magical? Let's take a look at the professional answer from doctors.

The reason why human blood types are different is because there are different antigens on the red blood cell membrane. The specific classification is shown in the figure below:

As can be seen from the above figure, since O-type red blood cells do not have A and B antigens, O-type red blood cells can be transfused to patients with A, B, and AB types when the primary side matches. However, O-type blood plasma contains A antibodies and B antibodies. If red blood cell preparations containing O-type plasma are transfused into A, B, and AB type patients, it will cause varying degrees of immune hemolytic transfusion adverse reactions, which is detrimental to the patient's health and may even be life-threatening. The "Technical Specifications for Clinical Blood Transfusion" issued by the Ministry of Health clearly stipulates: "Red blood cell preparations containing O-type plasma must undergo cross-matching tests before transfusion."

Secondly, blood types A, B, O, and AB can also be divided into Rh positive and Rh negative. If an Rh negative patient has already produced Rh positive antibodies, then O type Rh positive blood cannot be transfused to the Rh negative patient. In addition, if the recipient's blood contains irregular antibodies against other antigens of a bag of O type red blood cells, this bag of O type blood cannot be transfused to the recipient.

From this we can see that O-type blood is not universal blood. The claim that O-type blood is universal blood is unscientific. During blood donation and blood transfusion, blood matching tests must be done and the doctor's advice must be followed.

(Contributed by Shi Fangfang, Department of Blood Transfusion, Tsinghua Chang Gung Memorial Hospital, Beijing)

◆Rare " panda blood type " - RH negative blood

Rh-negative trait is the most clinically significant blood type system after ABO blood type, and is also the most complex red blood cell blood type system in humans. The Rh blood type system includes more than 50 antigens, among which D antigen has the strongest antigenicity and can cause transfusion reactions and severe hemolytic disease of the newborn (HDN). When a person's red blood cell surface has D antigen, it is called RhD positive, represented by RhD(+); when the red blood cell surface lacks D antigen, it is RhD negative, represented by RhD(-).

The distribution of RhD(-) varies greatly among different races, and the proportion among Caucasians is relatively high, about 15%. Among the people of all ethnic groups in my country, Rh-negative people only account for about 0.1%~0.5%, which is extremely rare. In some ethnic groups, there are more Rh-negative people, such as 15.8% of the Tatars, 12.3% of the Miao, and 8.7% of the Buyi and Uzbeks. If the ABO and Rh blood type systems are considered at the same time, the number of people with AB type Rh(-) in the Han population is less than 0.03%, which is very rare, so Rh(-) blood is also called "panda blood".

Generally, Rh(-) people cannot accept Rh(+) blood, because the antigens in Rh-positive blood will stimulate the Rh-negative body to produce Rh antibodies. If Rh(+) blood is transfused again, it may cause hemolytic transfusion reactions. In addition to blood transfusion, people with Rh(-) blood type who have anti-D antibodies due to other immune reasons such as miscarriage and childbirth may also have hemolytic transfusion reactions when they are transfused with Rh(+) blood again. Therefore, patients with Rh-negative blood can generally only use Rh-negative blood. However, in emergency situations to save lives, if Rh(-) blood is not available, Rh-positive blood can be used as an emergency. In this case, the patient may become sensitized to RhD, but the risk of an immediate hemolytic reaction is very small. Fortunately, Rh-positive people can accept blood from Rh-negative people.

(Contributed by Zhao Hui, Blood Transfusion Department, Beijing Tsinghua Chang Gung Hospital)

Is fainting from blood caused by fear ?

Some people faint when they see scary scenes, some faint due to lack of oxygen, and some faint when they see blood, which is what we often call "hemophobia". Hemophobia is also called "blood phobia", which is a mental disorder in a special situation. This disease is the same as "object phobia" such as fear of insects and hairy objects, and "social phobia" such as fear of strangers and the opposite sex, and is not necessarily related to timidity. Hemophobia is also different from motion sickness and seasickness. The former is similar to acrophobia and is a psychological problem; the latter is a physiological problem of the inner ear balance organ. Except for the inability to see blood, people who phobia blood are no different from ordinary people.

When people with hemophobia see blood, their blood pressure and heart rate will first increase and then decrease, while most other phobias only increase the heart rate. John Sanford of Stanford Medicine has made a major breakthrough in this area, and the study pointed out that the manifestation of hemophobia is a vasovagal reaction. The vagus nerve/sympathetic nerve is part of the parasympathetic nervous system, winding from the brainstem to the neck, chest and abdomen, helping to control the autonomic "rest and digest" function, such as lowering the heart rate and promoting gastric secretion. But if it overreacts, such as due to hunger, dehydration, standing up quickly, standing for too long, sudden fright, and other specific triggers - blood, it will cause an overreaction of the vasovagal nerve, which is not usually seen in other phobias.

Phobia is a relatively widespread psychological disorder. Many experts are committed to helping people get rid of phobias. In the treatment of hemophobia, some doctors use a treatment method similar to "systematic desensitization": gradually show the patient objects that are closer and closer to blood, starting from a dot, to a red dot, and then to a photo of blood... until the patient can look directly at the blood without fainting. At present, this treatment method has a good clinical effect. If you are a person who is enthusiastic about donating blood but unfortunately suffers from hemophobia, you might as well try this method.

Blood transfusion is risky and should be performed with caution

The discovery of blood types provides a basis for safe blood transfusion. If red blood cells of a certain blood type are mixed with serum containing its antibodies, the red blood cells will clump together, causing a series of adverse reactions to blood transfusion, such as blood circulation disorders, hemolysis, renal damage, and even death. Therefore, when transfusing blood, attention must be paid to the choice of blood type, and the principle should be to transfuse blood of the same type.

As a branch of modern medicine, blood transfusion has gradually become an independent comprehensive discipline, involving blood, immunity, infectious diseases, microorganisms, viruses, epidemiology, molecular biology and other disciplines, and has become one of the important means of clinical treatment. However, due to current technical limitations, blood transfusion, like other clinical treatment methods, has many risk factors: such as transfusion reactions, blood donors may be infected by pathogens, and blood recipients may be infected with diseases due to transfusion. In order to minimize the risks of clinical blood transfusion and make effective and timely predictions and management of risks, the following relevant knowledge should be understood:

1. Blood transfusion risks can induce immune and non-immune reactive diseases. Immune diseases include: fever reaction, allergic reaction, hemolytic reaction, graft-versus-host disease, post-transfusion purpura, etc. Non-immune diseases include: bacterial infection, bleeding, citrate poisoning, electrolyte imbalance, etc.

2. There is a possibility that there are viruses that may be missed in the blood of blood donors. Hepatitis B, hepatitis C, AIDS, syphilis, etc. are infection detection items stipulated by my country's blood centers, but due to the limitations of detection technology and the fact that blood donors may be in the "window period", some viral infections cannot be detected. In addition, new viruses have continued to emerge in recent years, and blood transfusion cannot guarantee "zero" risk. The risk of transfusion-transmitted diseases still exists.

3. Blood transfusion can cause infection with other types of pathogenic diseases, such as toxoplasmosis, mad cow disease, etc. These diseases are difficult to diagnose and treat.

(Contributed by Yang Yinan, Department of Blood Transfusion, Beijing Tsinghua Chang Gung Hospital)

Are you afraid of donating blood ?

Every year, many enthusiastic citizens in our country voluntarily donate blood to contribute to medical and charity causes. So what is the process of blood donation? How can blood donation be healthy and effective? Let's first understand the basic process of blood donation.

● Things to note before donating blood

1. Learn about blood donation and eliminate tension.

2. Do not eat too greasy food for the two meals before donating blood, but do not go on an empty stomach either. You can eat lighter food.

3. Do not take any medication before donating blood.

4. Do not drink alcohol, especially strong liquor.

5. Take a shower before donating blood to keep the puncture site clean, get enough sleep, and avoid strenuous exercise.

● Precautions for blood donation

1. Blood donation registration: Please bring your valid ID (ID card, social security card, driver's license, officer ID, soldier ID, passport, etc.) to register for blood donation.

2. Fill in the form: First, carefully read the "Health Status Inquiry Form", and then fill in each item of the registration form in detail.

3. Physical examination: blood pressure, hepatitis B surface antigen, hemoglobin, etc.

4. Clean and disinfect your arm: If your arm is not clean, it is easy to cause infection and blood contamination at the puncture site of your arm. Please be sure to clean it carefully in advance. Please do not touch the disinfected area after the medical staff disinfects it with iodine.

5. Qualified blood collection: Please lie on the blood collection chair, clench your fist before puncture, and once the blood collection needle enters the vein, clench and relax your fist continuously until the blood collection is completed.

6. Stop bleeding: When standing after blood collection, do not be too aggressive. Please press the needle hole with three fingers for 5-10 minutes to prevent subcutaneous hematoma.

7. Collecting blood donation certificate: Please carefully check the name, ID number and blood type of the blood donor on the blood donation certificate. If there is any error, please contact the staff of the issuing office in time for timely correction.

● Precautions after blood donation

1. Protect the venous puncture site and do not wash it with water within 24 hours.

2. Please do not engage in high-altitude work, high-temperature work, long-distance driving, sports competitions, overnight entertainment and other activities on the day after donating blood.

3. Drink plenty of water and take proper nutrition on the same day. You can eat fresh vegetables, fruits, soy products, dairy products, fresh fish, shrimp, meat and eggs, etc. Please do not eat greasy food and avoid overeating.

(Contributed by Shang Weiwei from the Blood Transfusion Department of Beijing Tsinghua Chang Gung Memorial Hospital)