An enthusiastic person almost fainted after donating blood! Don't do these things before and after donating blood!

Recently, there was a news report: a certain enthusiastic citizen did not forget to donate blood while traveling; unexpectedly, she became pale, weak all over, and almost fainted after donating blood. Fortunately, the police found her in time and sent her to the hospital.

Source: Weibo screenshot

So, is there a connection between donating blood and symptoms like fainting? If so, how can it be prevented?

Adverse reactions to blood donation

Will there be adverse reactions to blood donation? Yes, but the probability is very low. Domestic data shows that the incidence of adverse reactions to blood donation is 1.3%. In other words, it only occurs in one out of a hundred people. This is not only the case in China, but also in the world. The rate of adverse reactions to blood donation is not high. Overall, blood donation is very safe.

Source: Tuchong Creative

Those adverse reactions can be divided into three categories according to the causes: related to puncture, related to blood donation supplies, and related to the patient's general condition.

Adverse reactions related to puncture

Donating blood definitely requires "insertion". Specifically, the staff will insert the needle at an angle, first piercing the skin with the needle, then piercing the blood vessel wall, until the blood is introduced into the blood bag. This leads to a question: there is a little distance between the puncture point on the skin and the puncture point on the blood vessel wall.

If blood is not compressed correctly after donation, blood may flow out of the puncture site in the blood vessel wall. This blood may flow out of the puncture site in the skin, causing bleeding in the donor (i.e., delayed bleeding); or it may pool under the skin. A small amount of blood pooling may appear as a subcutaneous bruise, but if there is a large amount of blood, it may form a hematoma; a hematoma may also cause pain if it presses on a nerve.

This type of adverse reaction is the most common in blood donation. The solution is simple: after donating blood, do not ignore the puncture point . Specifically, first, press the puncture point accurately and in time; second, do not let the wound get wet within one day after blood donation, and do not rush to use this arm for heavy work. If subcutaneous bruises appear, cold compresses can be applied within one day to shrink the subcutaneous bleeding points; after one day, hot compresses should be applied to accelerate the spread of bruises.

What is correct pressing? (Chart by the author)

Adverse reactions related to blood donation supplies

Blood donation is divided into two categories: one is to donate whole blood, and the other is to donate blood components, such as platelets. The former requires needles and tape, while the latter is more complicated and requires drugs such as citrate.

These devices and drugs may cause adverse reactions. For example, the donor may be allergic to the tape, or citrate may cause hypomagnesemia, hypocalcemia, facial numbness, or even nausea and vomiting.

This type of adverse reaction is relatively rare and the prevention method is also very simple. Before donating blood, the staff of the blood station will hand out some materials. Do not rush through them , but fill them out according to your own situation, for example, whether you have ever had drug allergies in the past .

Adverse reactions related to systemic conditions

It is winter now. When doctors encounter patients with high blood pressure, they usually advise: Don't be too anxious to get up in the morning, take your time. Because if you get up too quickly or change your body position too quickly, your blood pressure may rise suddenly, which may lead to life-threatening conditions. In fact, there are many factors that affect blood pressure, such as the total amount of blood, psychological state, and the state of the vagus nerve. When the vagus nerve is excited, blood vessels dilate, the heartbeat slows down, and blood pressure drops accordingly. If the drop is too large and too fast, the brain will not get enough blood, which will cause fainting.

During the blood donation process, the donor's blood volume will inevitably decrease; staring at the needle and blood bag all the time may make people more and more nervous; if you are tired before and after blood donation, the vagus nerve will be in an excited state. This type of adverse reaction has a special name: donation-related vasovagal reaction (DRVR) .

The enthusiastic people mentioned in the previous news belong to this kind of situation. Due to the change of blood pressure, mild cases may cause dizziness, sweating, and pale face; severe cases may directly faint and cause falls.

According to statistics from domestic scholars, the overall incidence of vasovagal reactions related to blood donation is not high, and severe cases are even less, about one in a thousand. Even if you encounter it, don't worry too much. Just squat or lie down in time and take a good rest, and you will recover soon.

Reducing adverse reactions to blood donation (author’s illustration)

So, how to prevent such adverse reactions?

Adjust the state of the whole body and try not to stimulate the vagus nerve. For example, drink enough water before and after donating blood and avoid overexerting yourself. During the blood donation process, try to divert your attention and keep a good mood. For another example, you can do muscle contraction and relaxation (applied muscle tension, AMT) before and after donating blood to use muscle activities to avoid rapid changes in blood pressure .

How to perform muscle contraction and relaxation activities? (Chart by the author)

Conclusion

In short, donating blood is a good thing. China has also introduced many policies for voluntary blood donors, including honorary rewards and convenience when donors and their relatives need blood. However, you need to pay attention to some things before and after donating blood to reduce adverse reactions.

Little-known facts about blood donation (drawn by the author)

References

[1] TAHERI SOODEJANI M, HAGHDOOST AA, OKHOVATI M, et al. Incidence of adverse reaction in blood donation: a systematic review[J]. American Journal of Blood Research, 2020, 10(5): 145-150.

[2] KA, AV, GL, et al. Adverse events and safety issues in blood donation--a comprehensive review[J/OL]. Blood reviews, 2012, 26(1)[2023-11-25].

[3] China Blood Transfusion Association. Requirements for health examination of blood donors: GB 18467-2011[S/OL]. (2011)[2023-11-25].

[4] Chinese Blood Transfusion Association. Guidelines for the prevention and management of vasovagal reactions associated with blood donation: WS/T 595-2018[S/OL]. (2018)[2023-11-25].

[5] Chinese Blood Transfusion Association. Classification Guidelines for Adverse Reactions to Blood Donation: WS/T551-2017[S/OL]. (2017)[2023-11-25].

[6] Yang JH, Chen M, He T, et al. Meta-analysis of the incidence of adverse reactions to blood donation among whole blood donors in my country[J/OL]. Chinese Journal of Blood Transfusion, 2021, 34(4): 376-381.

[7] Xie Dongfu. A brief discussion on vasovagal response after blood donation [EB/OL]//Shanghai Blood Center. (2018-01-19)[2023-11-25].

Author: Zhao Yanchang, a popular science author

Reviewer: Liu Zhengxin, Chief Physician, Beijing Chaoyang Hospital, Capital Medical University

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.