Macroscopic assessment of suitability
Before blood transfusion, the physician checks the integrity of the packaging, expiration dates, and compliance with the temperature regime (no signs of overheating or freezing). It is most advisable to use components with a shelf life of no more than 5–7 days, since prolongation leads to morphological and biochemical changes that reduce the quality of the medium.
Normal settled blood clearly divides into three layers:
- Lower: red erythrocytes.
- Middle: thin leukocyte layer.
- Upper: transparent, slightly yellowish plasma.
Signs of medium unsuitability:
- Hemolysis: plasma acquires a pink or red coloration.
- Contamination: plasma turbidity is observed, flakes or a film appear on the surface.
- Clotting: presence of visible clots.
If an urgent transfusion of unsettled blood is imminent, part of the contents is poured into a test tube and centrifuged to assess the plasma. Frozen components are pre-warmed rapidly to 38 °C and washed free of cryoprotectants.
Control determination and AB0 system test
The control blood group determination is carried out at the patient's bedside immediately before the procedure, regardless of the records in the medical history or on the container label. Performing the test in advance or delegating it to another physician is strictly prohibited.
Methodology of the individual compatibility test (AB0):
- 3–5 ml of blood is taken from the patient's vein, and serum is obtained (by settling or centrifugation).
- A large drop of the recipient's serum and a drop of donor blood are applied to a tile or plate (ratio from 5:1 to 10:1).
- The drops are gently mixed with a glass rod or the corner of a glass slide.
- The reaction is observed for 5 minutes, after which a drop of isotonic sodium chloride solution is added.
The absence of agglutination indicates compatibility. It is important to remember that the test is performed with every container or ampoule of transfused blood. In practice, priority is always given to same-group blood, despite the theoretical rule of the universal donor (group I) and universal recipient (group IV).
Compatibility test with 33% dextran
Rh compatibility testing is indicated in burdened anamnesis (prior blood transfusions, Rh-incompatible pregnancies, miscarriages), as well as in critical situations where the patient's Rh factor is unknown. The test is universal for detecting isoimmune sensitization, including antibodies of the Kell, Lutheran, Kidd systems.
A glass test tube with a volume of at least 10 ml is required. The use of plastic tubes or small-volume containers severely complicates the evaluation of results. The tube is strictly labeled (full name and blood groups of the recipient and donor, container number).
Procedure algorithm:
- Apply 2 drops of the recipient's serum, 1 drop of donor blood, and 1 drop of 33% dextran solution (with a molecular weight of 50,000–70,000) to the wall of the test tube.
- Tilt the test tube almost horizontally and rotate it slowly for 3 minutes. The contents should spread along the walls to enhance the reaction.
- Add 2–3 ml of 0.9% sodium chloride solution.
- Smoothly invert the test tube 2–3 times to a horizontal level. Shaking is strictly prohibited!
Evaluation is performed against the light (daylight lamp is used). If the liquid is evenly colored, slight opalescence is observed, and there are no clumps, the blood is compatible (isoimmune antibodies are absent). If agglutination (a suspension of clumps) is visible against a clarified or completely discolored background, transfusion is prohibited.
Tactic in case of incompatibility detection
If true agglutination is detected during tests in a planned situation, individual blood selection at the blood transfusion center (BTC) is required.
In emergency transfusions for vital indications, media are selected from the available stock (same group and Rh factor). The physician performs tests with blood from each container. If at least one container is compatible, the transfusion is started with a biological test. However, if agglutination occurs in all containers, the available blood must not be transfused. Physicians are obliged to wait for individually matched blood from the BTC.
Briefly: answers to topical questions
How exactly is the biological compatibility test performed immediately before starting a blood transfusion?
The biological test in direct blood transfusion is performed using the syringe method at the very beginning of the procedure.
- Preparation of syringes — the first three syringes are filled with 2 ml of 4% sodium citrate solution each to prevent clotting.
- Blood collection — donor venous blood is drawn into the prepared syringes.
- Administration to the recipient — blood from the first syringes is administered slowly, at a rate of one syringe per 2 minutes.
What methods exist for performing the individual Rh compatibility test?
The sources describe one method for evaluating individual Rh compatibility — the test using 33% polyglucin (dextran) solution.
- Addition of components — 2 drops of the recipient's serum, 1 drop of donor blood, and 1 drop of 33% dextran are added to a glass test tube.
- Incubation — the test tube is tilted almost horizontally and rotated slowly for 3 minutes.
- Dilution — 2–3 ml of isotonic sodium chloride solution is added and mixed gently.
The absence of agglutination when viewed against the light indicates compatibility.
What factors can lead to false agglutination (pseudoagglutination) when evaluating compatibility tests?
Two main factors can lead to false agglutination (pseudoagglutination) when evaluating compatibility tests.
- Drying of the drop — causes the formation of erythrocyte "rouleaux", creating the appearance of a reaction.
- Low temperature — leads to cold agglutination when the study is performed at temperatures below 15 °C.
To prevent false-positive results, it is recommended to add a drop of isotonic sodium chloride solution and perform the evaluation at temperatures above 15 °C.
To memorize the layers of normal settled blood, use the bottom-up abbreviation ELP: Erythrocytes (lower red layer) — Leukocytes (middle thin layer) — Plasma (upper transparent yellowish layer).
Class and exam questions
Can the performance of compatibility tests be delegated to the on-duty male nurse?
No, the control blood group determination and tests are performed exclusively by the physician conducting the transfusion. Delegating this task or performing it in advance is prohibited.
Why are glass test tubes required for the dextran test?
The use of plastic test tubes or small-volume containers (less than 10 ml) distorts the distribution of liquid along the walls and significantly complicates the visual assessment of agglutination results.
What should be done if, during an emergency transfusion, blood from all vials shows agglutination?
Transfusing such blood is strictly prohibited even for vital indications. It is necessary to wait for individual blood selection at the blood transfusion center (BTC).
Why are frozen blood components washed before transfusion?
After rapid warming to 38 °C, the components must be freed from cryoprotectants. Erythrocytes are washed free of glycerol, and leukocytes and platelets are washed free of dimethyl sulfoxide.
What else to study on this topic
- Biochemical and morphological changes in conserved blood with prolonged storage periods.
- Mechanism of action of cryoprotectants (glycerol and dimethyl sulfoxide) on blood cells.
- Kell, Lutheran, and Kidd blood group antigen systems and their clinical significance.
- Causes and types of post-transfusion reactions during incompatible blood transfusion.
- Rules and algorithm for performing the biological test before starting a blood transfusion.
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Other topics in the section "CHAPTER 6. BLOOD TRANSFUSION"
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