Dosing and uses of Platelets
Thrombocytopenia
Typical dosing for an adult is a pool of 6 whole blood derived (sometimes referred to as random donor) platelets or one apheresis platelet. This is expected to raise the platelet count by 30,000-60,000/uL in a 70 kg patient. Transfused platelets have a short life span and will need to be re-dosed within 3-4 days if given for prophylaxis. Suboptimal increases can be seen due to non-immune destruction or immune refractoriness. If suboptimal increases are suspected, the corrected count increment (CCI) can help determine if the response is truly suboptimal based on amount of platelets transfused compared to body surface area. The CCI can also assist in determining whether the response is due to immune refractoriness or non-immune causes. Please see the pharmacology section for CCI calculations.
Other Indications & Uses
Platelet transfusions may be given for thrombocytopenia or platelet dysfunction to treat active platelet-related bleeding or as prophylaxis in those at serious risk of bleeding.
Typical indications include leukemia, myelodysplasia, aplastic anemia, solid tumors, congenital or acquired/medication-induced platelet dysfunction, central nervous system trauma, and patients undergoing extracorporeal membrane oxygenation or cardiopulmonary bypass may also need platelet transfusion.
Thresholds for transfusion due to thrombocytopenia have been controversial. However it is generally accepted that a count of 50,000/uL is sufficient for most invasive procedures including most surgeries. Platelet counts of >100,000/uL are recommended for ophthalmic and neurosurgery. Higher transfusion thresholds may be appropriate for patients with platelet dysfunction.
Probably the most controversial threshold is for the clinically stable patient with an intact vascular system and normal platelet function. Prophylactic platelet transfusions may be appropriate at 5,000- 10,000/uL to prevent spontaneous bleeding. Patients with autoimmune destruction of platelets, such as ITP, may not receive therapeutic benefit from prophylactic transfusion, but may however benefit from transfusion if bleeding.
Pediatric dosage forms and strengths
Thrombocytopenia
Neonates and small children
- Transfusion of 5-10 mL/kg should raise the platelet count by 50,000-100,000/uL.
Children > 10kg
- Transfusion of 1 unit of whole blood derived platelets per 10kg should raise the platelet count by 50,000/uL
- Transfused platelets have a short life span and will need to be re-dosed within 3-4 days if given for prophylaxis. Suboptimal increases can be seen due to non-immune destruction or immune refractoriness. If suboptimal increases are suspected, the corrected count increment (CCI) can help determine if the response is truly suboptimal based on amount of platelets transfused compared to body surface area. The CCI can also assist in determining whether the response is due to immune refractoriness or non-immune causes. Please see the pharmacology section for CCI calculations.
Other Indications & Uses
Platelet transfusions may be given for thrombocytopenia or platelet dysfunction to treat active platelet-related bleeding or as prophylaxis in those at serious risk of bleeding.
Typical indications include leukemia, myelodysplasia, aplastic anemia, solid tumors, congenital or acquired/medication-induced platelet dysfunction, central nervous system trauma, and patients undergoing extracorporeal membrane oxygenation or cardiopulmonary bypass may also need platelet transfusion.
Thresholds for transfusion due to thrombocytopenia have been controversial. However it is generally accepted that a count of 50,000/uL is sufficient for most invasive procedures including most surgeries. Platelet counts of >100,000/uL are recommended for ophthalmic and neurosurgery. Higher transfusion thresholds may be appropriate for patients with platelet dysfunction.
Probably the most controversial threshold is for the clinically stable patient with an intact vascular system and normal platelet function. Prophylactic platelet transfusions may be appropriate at 5,000- 10,000/uL to prevent spontaneous bleeding. Patients with autoimmune destruction of platelets, such as ITP, may not receive therapeutic benefit from prophylactic transfusion, but may however benefit from transfusion if bleeding.
Platelets adverse (side) effects
Frequency not defined
Hemolytic Transfusion Reactions
Febrile Non-Hemolytic Reactions
Allergic Reactions ranging from urticaria to anaphylaxis
Septic Reactions
Transfusion Related Acute Lung Injury (TRALI)
Circulatory Overload
Transfusion Associated Graft Versus Host Disease
Post-transfusion Purpura
Warnings
Contraindications
Platelet transfusions are contraindicated in patients with thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), or heparin induced thrombocytopenia (HIT). Although these conditions can have marked thrombocytopenia, they are generally pro-thrombotic and transfusion of platelets may “fuel the fire” if transfused as prophylaxis in the absence of significant bleeding.
Platelet transfusions are controversial in patients with Post Transfusion Purpura, since platelet specific antibodies against high frequency platelet antigens are part of the pathophysiology of this potentially fatal disorder. IVIG is typically a first line therapy and immediate consultation with a hematologist and/or your institutions transfusion medicine physician is highly recommended.
Platelet transfusions in patients with autoimmune destruction of platelets such as ITP should not be transfused in the absence of bleeding because the transfused platelets will be quickly removed similarly to the patient’s own platelets without clinical benefit.
Cautions
If a transfusion reaction is suspected, the transfusion should be stopped, the patient assessed and stabilized, the blood bank notified, and a transfusion reaction investigation initiated. Massive or rapid transfusion may lead to arrhythmias, hypothermia, hyperkalemia, hypocalcemia, dyspnea, and/or heart failure.
Platelet products have an increased risk of significant bacterial contamination/sepsis compared to other blood products because platelets must be stored at room temperature since they rapidly lose function when refrigerated. The risk of sepsis with platelet transfusion is thought to be at least 1:75,000 and the risk of fatal septic platelet transfusion reactions is thought to be at least 1:500,000. Bacterial contamination is more commonly caused by Gram-positive skin flora such as Staphylococcus spp but septic reactions can be due to either Gram-positive or Gram-negative organism contamination. Gram-negative organisms are usually associated with more severe reactions, but broad spectrum antibiotics should be initiated until the causative organism is identified.
Due to the short shelf-life of platelets (5 days from collection), it is not uncommon for blood banks to experience platelet shortages which can delay transfusion for those who have urgent need of transfusion.
If ABO identical platelets are not available, platelets from donors who are ABO plasma compatible may be used. This may occasionally result in suboptimal responses since platelets have a variable amount of ABO antigens, but will not cause clinically significant problems. In large children and adults, ABO incompatible platelets may be issued with only minimal risk of hemolysis, unless large doses of ABO incompatible platelets are transfused. If platelets that are ABO identical or from ABO plasma compatible donors are not available, then efforts to volume reduce or wash the platelets may be considered for neonates if the platelets are not needed urgently. Washing and volume reducing will require significant delays in transfusion and may alter the quantity and quality of the platelet product.
Because all platelet products contain a small amount of RBCs, Rh-compatible platelets should be used if possible to prevent the formation of anti-D in Rh negative individuals. This is particularly important for females that are pregnant or may become pregnant in the future because of the risk of hemolytic disease of the fetus and newborn due to anti-D. Risk of anti-D formation, particularly in this population, can be minimized by providing RhIG within 72 hours of exposure. RhIG is often offered in both intramuscular (IM) and intravenous (IV) suspensions. Use of IV RhIG may be considered if the amount of RhIG needed is large or the patient is at increased risk of injury from IM injections, but is not available in all institutions. One full standard dose of RhIG will be sufficient to cover at least 5 adult doses of pooled whole blood derived platelets or 7 doses of apheresis platelets. Repeat dosing depends on number of Rh-positive platelet doses received and the half-life of RhIG and may need to be considered if it has been greater than 21 days since the last dose of RhIG and additional Rh-positive platelets are to be transfused.
Platelet transfusions may induce formation of HLA antibodies and rarely platelet specific antibodies that may cause immune refractoriness for future transfusions, particularly for patients that require numerous platelet transfusions. The CCI may help determine if the patient has immune refractoriness and its calculation is described in the pharmacology section. Leukocyte reduction may help decrease HLA sensitization. Please see the leukocyte reduced blood products monograph for more complete indications of leukocyte reduced products. Patients with HLA or platelet specific antibodies (HPA-1a) may benefit from HLA matched or HPA-1a negative apheresis platelet transfusions if available. Please see their respective monographs for complete transfusion information.
Patients at increased risk of TA-GVHD should receive irradiated platelet products. For more information regarding indications for irradiation to prevent TA-GVHD, please see the irradiated blood products monograph.
Patients that are CMV seronegative or whose CMV status is unknown and are at increased risk of symptomatic CMV infection should receive CMV reduced risk platelets. Please see the CMV seronegative and leukocyte reduced blood product monographs for more information.
All transfusions must be given via blood administration sets containing 170- to 260-micron filters or 20- to 40-micron microaggregate filters unless transfusion is given via a bedside leukocyte reduction filter. No other medications or fluids other than normal saline should be simultaneously given through the same line without prior consultation with the medical director of the blood bank.
Patient’s should be monitored for signs of a transfusion reaction including vitals pre, during, and post transfusion.
Non-septic infectious risks include transmission of HIV (~1:2 mill), HCV (~1:1.5 mill), HBV (1:300k), HTLV, WNV, CMV, parvovirus B19, Lyme disease, babesiosis, malaria, Chaga’s disease, vCJD.
Consult with blood bank medical director or hematologist if you have questions regarding special transfusion requirements.
Pregnancy and lactation
CMV-seronegative or CMV reduced risk (leukocyte reduced) platelets should be used in pregnant women who are CMV-seronegative or whose CMV status is unknown.
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Platelets
Whole blood derived platelets should contain a minimum of 5.5 x 1010 platelets per unit with an overall volume of around 50 mL. Apheresis platelets should contain a minimum of 3 x 1011 platelets per unit with an overall volume around 300 mL.
Transfused platelets have an expected life-span of 3-4 days. This may be significantly reduced due to immune refractoriness, consumption, or sequestration. Common causes of suboptimal platelet count increments include ongoing bleeding, DIC, sepsis, fever, and hypersplenism. If suboptimal platelet counts are suspected, post transfusion platelet counts should be obtained within 1 hour of transfusion and again at 24 hours of transfusion to calculate the CCI. CCI calculations may be helpful for these patients to determine their cause of platelet refractoriness.
CCI = [post count (per uL) – pre count (per uL)] x BSA (m2) / Number of administered platelets (x1011)
A CCI greater than 7500 at 1 hour and greater than 4500 at 24 hours post transfusion indicate adequate platelet responses.
A CCI less than 5000 at 1 hour indicates possible immune refractoriness.
A CCI less than 4500 at 24 hours indicates probable non-immune refractoriness.
Consultation with a hematologist or transfusion medicine physician is recommended for providing platelet therapy to patients with platelet refractoriness.
Mechanism of action
Platelets are major contributors to primary hemostasis.
