Preparation and storage of the product
The source for obtaining platelet concentrate is preserved donor blood plasma. A crucial condition is that the blood must be fresh: its storage period prior to platelet separation must not exceed 24 hours. The separation process itself is carried out using light centrifugation.
In clinical practice, it is most appropriate to use freshly prepared concentrate, as the cells rapidly lose their functional activity. If immediate transfusion is not possible, the product is placed in storage, which has strict temperature limits:
- At room temperature (22 °C), the cells remain viable for up to 72 hours.
- When cooled to 4 °C, the shelf life drops sharply to just 6–8 hours.
Antigenic composition and properties of platelets
After transfusion, donor cells circulate and perform their functions in the patient's body for an average of 7–9 days. During the harvesting process by centrifugation, a small number of red blood cells often end up in the final product, which dictates special safety rules during transfusion.
Platelets themselves have a complex antigenic structure. They contain:
- Erythrocyte and leukocyte antigens (including HLA, AB0 system antigens, Rh factor, as well as NA-NB).
- Specific platelet systems, such as Zw, Ko and P1.
Despite the variety of specific systems (Zw, Ko, P1), in real transfusiology and transplantology practice, they have no clinical significance. The main role is played by standard blood group and Rh antigens.
Indications for transfusion
Platelet transfusion is prescribed for a critical decrease in the platelet count in the patient's blood, which poses a risk of dangerous bleeding. The main clinical situations include:
- Thrombocytopenia of various origins. This includes primary blood system disorders as well as secondary conditions — for example, severe consequences of radiation therapy or chemotherapy courses.
- Acute massive blood loss. During massive blood transfusions to restore blood volume, thrombocytopenia can develop, accompanied by pronounced hemorrhagic syndrome. In this case, platelet administration is necessary to stop the bleeding.
Key transfusion rules
The procedure for transfusing platelet concentrate is equated to a surgery and requires the strictest adherence to safety algorithms. The physician must verify the immunological compatibility of the donor and recipient.
- Accounting for group compatibility. The product is selected strictly according to the AB0 system.
- Accounting for the Rh factor. Compatibility for the Rh factor is just as mandatory as during red blood cell transfusion.
- Mandatory biological test. Even if the blood group and Rh factor match, a biological test is performed before starting the main transfusion. This requirement is due to the fact that the product always has a potential admixture of donor red blood cells capable of causing an acute reaction.
Briefly: answers to topical questions
What dose of platelet concentrate is required to stop thrombocytopenic bleeding, and how is the effective transfused dose calculated?
- By body weight — 50–70 $ imes 10^9$ platelets per 10 kg of the recipient's body weight.
- By body surface area — 200–250 $ imes 10^9$ platelets per 1 m² of the recipient's body surface area.
- Optimal dose — according to general consensus, therapeutic transfusions should increase the platelet count to a level that ensures adequate hemostasis.
Remembering the specific platelet systems that are not considered in clinical practice can be aided by the mnemonic: "Zvuk Pervy" (Zw, Ko, P1).
Class and exam questions
Why is the shelf life of platelets shorter when stored in a refrigerator (4 °C) than at room temperature?
Unlike red blood cells, platelets rapidly lose their functional properties and break down at low temperatures; therefore, at 4 °C they can only be stored for 6–8 hours.
What is the purpose of the biological test during platelet transfusion?
The light centrifugation method does not allow 100% purification of the product, which is why an admixture of red blood cells is always present. The test protects the patient from hemolytic complications.
Do Zw, Ko, and P1 system antigens matter in donor selection?
No, in practical transfusiology and transplantation, these specific platelet antigen systems have no clinical significance.
What else to study on this topic
- Methodology for performing the biological test
- Pathogenesis of hemorrhagic syndrome in massive blood transfusions
- The impact of chemo- and radiation therapy on the megakaryocytic lineage
- The HLA system and its role in transplantology
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