Thrombocytopenia in cancer and platelet transfusion

Thrombocytopenia occurs in cancer patients quite often, the main reasons for its development are presented in the table.

Causes of thrombocytopenia

The mechanism of development	Specific reasons	Contingent of patients
Insufficient platelet formation	Cytostatic / cytotoxic effects	Patients receiving radiation or chemotherapy
	Replacement of normal hematopoiesis	Patients with leukemia (beyond remission and treatment), or metastatic bone marrow disease
Increased destruction	Autoantibodies	Patients with chronic lymphocytic leukemia
	Splenomegaly	-
Increased consumption	DIC-syndrome, massive hemorrhage, the syndrome of massive transfusions using AIC or a cell-saver	Severe infection of shock of various etiologies, surgical interventions
Thrombocyte function disorder	Relationship with pathological protein, internal defect	Acute myeloid leukemia, myeloma, Waldenstrom macroglobulinemia

The main risk of thrombocytopenia is the risk of developing hemorrhages to vital organs (the brain, etc.) and severe uncontrolled bleeding. Transfusions of donor platelets allow preventing (preventive transfusion) or controlling (therapeutic transfusion) hemorrhagic syndrome in patients with thrombocytopenia due to lack of education or increased platelet consumption. With increased destruction of platelets, substitutional transfusions are usually ineffective, although the haemostatic effect can be achieved with a significant increase in the dose of transfused platelets.

[1], [2], [3], [4], [5], [6], [7], [8]

Healing Transfusions

Specific indications for transfusion of donor platelets are set by the attending physician depending on the clinical picture, the causes of thrombocytopenia, the degree of its severity and the localization of bleeding, but there are a number of guidelines that need to be remembered.

• Platelet level in the blood> 50x10 ⁹ / l is usually sufficient for hemostasis even when performing cavitary surgical interventions (bleeding time within the norm is 2-8 min) and does not require transfusion. The presence of hemorrhagic syndrome in these patients is associated with other causes (impaired platelet function, vascular injury, DIC syndrome, overdose of anticoagulants, etc.).
• With a decrease in platelet counts (up to 20x10 ⁹ / L or less), manifestations of hemorrhagic syndrome (hemorrhages and petechiae on the skin and mucous membranes, appearing spontaneously or with insignificant contact, spontaneous bleeding of the oral mucosa, nasal bleeding) are most likely associated with thrombocytopenia. In case of spontaneous hemorrhagic syndrome against a background of thrombocytopenia <20x10 ⁹ / L, transfusion of donor platelets is necessary. At a platelet level of 20-50х10 ⁹ / l the decision is made depending on the clinical situation (risk of profuse bleeding, additional risk factors for bleeding or hemorrhage, etc.).
• Puncture hemorrhages on the upper half of the trunk, hemorrhage in the conjunctiva, eye fundus (harbingers of cerebral hemorrhage) or clinically significant local bleeding (uterine, gastrointestinal, renal) oblige the doctor to emergency platelet transfusion.
• Transfusion of platelet concentrate with increased destruction of platelets of immune genesis (antiplatelet antibodies) is not shown, as the antibodies circulating in the recipient rapidly lyse donor platelets. However, in severe haemorrhagic complications, a number of patients with alloimmunization manage to achieve a haemostatic effect when transfusing large volumes of platelets from HLA-matched donors.

Prophylactic transfusion

Prophylactic transfusion of donor platelets to patients who do not show signs of hemorrhagic syndrome is shown when:

• a decrease in the level of platelets <10x10 ⁹ / l (in any case),
• decrease in platelet count <20-30х10 ⁹ / l and the presence of infection or fever,
• DIC-syndrome,
• planned invasive manipulations (catheterization of vessels, intubation, lumbar puncture, etc.),
• a decrease in the platelet count <50x10 ⁹ / l in the process or immediately before the cavitary operation.

In general, the prophylactic appointment of transfusions of platelet concentrate requires an even stricter relationship than the therapeutic purpose of replacement transfusion of donor platelets with minimal bleeding.

Transfusion technique and evaluation of efficacy

Therapeutic dose is a dose with a high degree of probability able to stop the hemorrhagic syndrome or prevent its development, 0.5-0.7x10 ¹¹ donor platelets per 10 kg of body weight or 2-2.5x10 ¹¹ / m ^{2 of} the body surface (3-5x10 ¹¹ thrombocytes per adult patient). Such an amount of platelets is contained in 6-10 doses of thromboconcentrate (platelet polydonor concentrate, thromboplasm, thrombosis) obtained by centrifuging one dose of donor blood. An alternative is a TK obtained on a blood cell separator from a single donor. One dose of such a concentrate usually contains at least 3x10 ¹¹ platelets. Clinical efficacy depends on the number of platelets administered, and not on the method of preparation, but the use of polydonor thromboconcentrate increases the number of donors with which the patient "contacts". To prevent transfusion reactions and alloimmunization, it is recommended to use leukocyte filters.

Clinical criteria for the effectiveness of therapeutic transfusion of donor platelets termination of spontaneous bleeding and the absence of fresh hemorrhages on the skin and visible mucous membranes, even if there is no calculated and expected increase in the number of platelets in circulation.

Laboratory evidence of the effectiveness of substitution therapy is the increase in the number of circulating platelets, a day later with a positive result, their amount should exceed the critical level of 20x10 ⁹ / l or be higher than the original pre-transfusion amount. In some clinical situations (splenomegaly, DIC syndrome, alloimmunization, etc.), the need for platelet count increases.

The donor-recipient pair with transfusion of thromboconcentrate should be compatible with ABO antigens and Rhesus factor, however, in everyday clinical practice it is permissible to transfuse platelets 0 (1) of the group to recipients of other blood groups. It is important to observe the rules for storing platelets (store at room temperature), since at a lower temperature, they aggregate with a decrease in the effectiveness of transfusions.