Platelet Concentrates

Platelet concentrates are suspensions of donor platelets in plasma or additive solution, given to prevent or treat bleeding caused by low platelet number or poor platelet function. They do not correct bleeding from surgical causes, coagulation factor deficiency or fibrinogen deficiency.

Types.

• Whole blood derived platelets, from the buffy coat or platelet rich plasma of four to six donations pooled into one adult dose.

• Apheresis platelets, collected from a single donor by a cell separator, giving one adult dose from one donor.

Content. An adult dose contains at least about 3 x 10¹¹ platelets in about 150 to 350 mL (usually 200 to 300 mL) of plasma or plasma and additive solution. Leucodepletion is by filtration or at collection.

Storage and shelf life. 20 to 24 degrees Celsius with continuous gentle agitation. Shelf life is usually 5 days, extended to 7 days where bacterial testing or pathogen reduction is used. Platelets must never be refrigerated, because cold storage causes rapid clearance after transfusion.

Bacterial risk. Room temperature storage allows bacterial growth, so platelets carry the highest bacterial contamination risk of any component. Visual inspection for swirling, clumps, discolouration and leaks is required.

ABO and RhD. ABO identical products are preferred, with options for non-identical use set out by the blood bank. RhD negative recipients, especially girls and women of childbearing potential, should receive RhD negative platelets where possible.

Special groups. Neonates and children need smaller doses and low titre or plasma reduced products. In East Africa, platelets may be scarce, short dated and available only in larger centres, so transfer and planning matter.

Indications. Bleeding with thrombocytopenia or platelet dysfunction, prophylaxis in hypoproliferative thrombocytopenia at defined counts, and cover for invasive procedures at defined counts. Thresholds depend on the setting and are never universal.

Non-indications.

• Immune thrombocytopenia without life-threatening bleeding.

• Thrombotic thrombocytopenic purpura and heparin induced thrombocytopenia, unless there is life-threatening bleeding.

• A low count without bleeding in stable chronic thrombocytopenia (for example liver disease, hypersplenism).

• Bleeding from a surgical source with a normal count.

Contraindications and cautions. Previous severe allergic or febrile reactions (premedication has weak evidence, and washed or plasma reduced platelets may be needed), IgA deficiency with anti-IgA, known antibodies against platelet antigens, and sepsis (low increments).

Special products. Irradiated for defined immunosuppression and for HLA matched donors; cytomegalovirus safe for pregnancy, neonates and transplant candidates; HLA matched or crossmatched for immune refractoriness; washed or plasma reduced for severe reactions.

Dose.

• Adult: one adult therapeutic dose, with an expected increment of about 20 to 40 x 10⁹/L measured 10 minutes to 1 hour after transfusion.

• Children: 10 to 20 mL/kg, not over one adult dose.

• Neonates: 10 to 15 mL/kg, with the volume set by the neonatal service.

• Larger doses are not more effective in stable patients. In active major bleeding, a larger dose or repeated doses are used.

Compatibility and testing. ABO identical products are preferred, and RhD negative products for girls and women of childbearing potential. A crossmatch is not needed except for immune refractoriness.

Timing and rate. Request in advance, because stock is limited and short dated. Start within 30 minutes of arrival, and infuse over about 30 to 60 minutes (about 20 to 30 minutes for each pool in adults), faster in active bleeding. Do not delay a dose for a laboratory result in life-threatening bleeding.

Equipment. Platelet or blood giving set with a 170 to 200 micrometre filter, and a new set for each product where hospital practice requires. Do not use a filter designed to remove leucocytes at the bedside, because it removes platelets. Do not use a blood warmer.

Compatible fluids. Only 0.9% sodium chloride in the same line. No drugs, dextrose or calcium containing solutions.

Observations. Temperature, pulse, blood pressure, respiratory rate and oxygen saturation before, at 15 minutes and at completion.

Anti-D cover. When RhD positive platelets are given to an RhD negative girl or woman of childbearing potential, anti-D immunoglobulin is given within 72 hours, and the dose is set by the blood bank.

Special groups.

• Neonates and children: weight based dose, plasma reduced products where possible.

• Pregnancy: RhD negative products and cytomegalovirus safe products.

• Older adults and cardiac failure: watch volume, because platelet concentrates are plasma rich.

Expected effects. Rise in platelet count and cessation of bleeding where platelet deficiency was the cause.

Serious reactions. Febrile non-haemolytic reactions, allergic reactions and anaphylaxis, bacterial sepsis (fever, rigors, hypotension, often within minutes to hours), transfusion related acute lung injury, circulatory overload, passive haemolysis with non-identical group O platelets, alloimmunisation (HLA and platelet antigens), transfusion associated graft versus host disease in unirradiated products and post transfusion purpura.

Immediate interruption criteria. Fever with rigors, hypotension, dyspnoea, urticaria with systemic signs, chest pain or unexplained deterioration. Stop the transfusion, assess the patient, keep intravenous access, recheck identity of patient and unit, and inform the blood bank. Do not restart without authorised clinical evaluation. In suspected bacterial contamination, culture the patient and the product and start broad spectrum antibiotics early.

Follow up. Platelet count 10 minutes to 1 hour after transfusion, and again at 18 to 24 hours when assessing response. A poor increment needs a repeat with an ABO identical fresh unit and assessment for refractoriness.

Referral and escalation. Haematology and the blood bank for refractoriness, recurrent reactions, immune causes and suspected contamination. Report every serious reaction.