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Platelet Transfusions

Larry H. Bernstein, MD, FCAP, Curator

LPBI

Platelet Transfusion: A Clinical Practice Guideline From the AABB

Richard M. Kaufman, MD; Benjamin Djulbegovic, MD, PhD; Terry Gernsheimer, MD; Steven Kleinman, MD,
Alan T. Tinmouth, MD; Kelley E. Capocelli, MD; Mark D. Cipolle, MD, PhD; Claudia S. Cohn, MD, PhD; et al.

Ann Intern Med. 2015;162(3):205-213. http://dx.doi.org:/10.7326/M14-1589

Annals of Internal Medicine 3 February 2015, Vol 162, No. 3>

Approximately 2.2 million platelet doses are transfused annually in the United States (1). A high proportion of these platelet units are transfused prophylactically to reduce the risk for spontaneous bleeding in patients who are thrombocytopenic after chemotherapy or hematopoietic progenitor cell transplantation (HPCT) (13). Unlike other blood components, platelets must be stored at room temperature, limiting the shelf life of platelet units to only 5 days because of the risk for bacterial growth during storage. Therefore, maintaining hospital platelet inventories is logistically difficult and highly resource-intensive (45). Platelet transfusion is associated with several risks to the recipient (Table 1), including allergic reactions and febrile nonhemolytic reactions. Sepsis from a bacterially contaminated platelet unit represents the most frequent infectious complication from any blood product today (8). In any situation where platelet transfusion is being considered, these risks must be balanced against the potential clinical benefits.

Background: The AABB (formerly, the American Association of Blood Banks) developed this guideline on appropriate use of platelet transfusion in adult patients.

Methods: These guidelines are based on a systematic review of randomized, clinical trials and observational studies (1900 to September 2014) that reported clinical outcomes on patients receiving prophylactic or therapeutic platelet transfusions. An expert panel reviewed the data and developed recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.

Recommendation 1: The AABB recommends that platelets should be transfused prophylactically to reduce the risk for spontaneous bleeding in hospitalized adult patients with therapy-induced hypoproliferative thrombocytopenia. The AABB recommends transfusing hospitalized adult patients with a platelet count of 10 × 109 cells/L or less to reduce the risk for spontaneous bleeding. The AABB recommends transfusing up to a single apheresis unit or equivalent. Greater doses are not more effective, and lower doses equal to one half of a standard apheresis unit are equally effective. (Grade: strong recommendation; moderate-quality evidence)

Recommendation 2: The AABB suggests prophylactic platelet transfusion for patients having elective central venous catheter placement with a platelet count less than 20 × 109 cells/L. (Grade: weak recommendation; low-quality evidence)

Recommendation 3: The AABB suggests prophylactic platelet transfusion for patients having elective diagnostic lumbar puncture with a platelet count less than 50 × 109 cells/L. (Grade: weak recommendation; very-low-quality evidence)

Recommendation 4: The AABB suggests prophylactic platelet transfusion for patients having major elective nonneuraxial surgery with a platelet count less than 50 × 109 cells/L. (Grade: weak recommendation; very-low-quality evidence)

Recommendation 5: The AABB recommends against routine prophylactic platelet transfusion for patients who are nonthrombocytopenic and have cardiac surgery with cardiopulmonary bypass. The AABB suggests platelet transfusion for patients having bypass who exhibit perioperative bleeding with thrombocytopenia and/or evidence of platelet dysfunction. (Grade: weak recommendation; very-low-quality evidence)

Recommendation 6: The AABB cannot recommend for or against platelet transfusion for patients receiving antiplatelet therapy who have intracranial hemorrhage (traumatic or spontaneous). (Grade: uncertain recommendation; very-low-quality evidence)

Table 1. Approximate Per-Unit Risks for Platelet Transfusion in the United States

Approximate_Per-Unit_Risks_for_Platelet_Transfusion_in_the_United_States

Approximate_Per-Unit_Risks_for_Platelet_Transfusion_in_the_United_States

Clinical and laboratory aspects of platelet transfusion therapy
Literature review current through: Sep 2015. | This topic last updated: Jun 12, 2015.

INTRODUCTION — Hemostasis depends on an adequate number of functional platelets, together with an intact coagulation (clotting factor) system. This topic covers the logistics of platelet use and the indications for platelet transfusion in adults. The approach to the bleeding patient, refractoriness to platelet transfusion, and platelet transfusion in neonates are discussed elsewhere.

(See “Approach to the adult patient with a bleeding diathesis”.)

(See “Refractoriness to platelet transfusion therapy”.)

(See “Clinical manifestations, evaluation, and management of neonatal thrombocytopenia”, section on ‘Platelet transfusion’.)

PLATELET COLLECTION — There are two ways that platelets can be collected: by isolation from a unit of donated blood, or by apheresis from a donor in the blood bank.

Pooled platelets – A single unit of platelets can be isolated from every unit of donated blood, by centrifuging the blood within the closed collection system to separate the platelets from the red blood cells (RBC). The number of platelets per unit varies according to the platelet count of the donor; a yield of 7 x 1010platelets is typical [1]. Since this number is inadequate to raise the platelet count in an adult recipient, four to six units are pooled to allow transfusion of 3 to 4 x 1011 platelets per transfusion [2]. These are called whole blood-derived or random donor pooled platelets.

Advantages of pooled platelets include lower cost and ease of collection and processing (a separate donation procedure and pheresis equipment are not required). The major disadvantage is recipient exposure to multiple donors in a single transfusion and logistic issues related to bacterial testing.

Apheresis (single donor) platelets – Platelets can also be collected from volunteer donors in the blood bank, in a one- to two-hour pheresis procedure. Platelets and some white blood cells are removed, and red blood cells and plasma are returned to the donor. A typical apheresis platelet unit provides the equivalent of six or more units of platelets from whole blood (ie, 3 to 6 x 1011platelets) [2]. In larger donors with high platelet counts, up to three units can be collected in one session. These are called apheresis or single donor platelets.

Advantages of single donor platelets are exposure of the recipient to a single donor rather than multiple donors, and the ability to match donor and recipient characteristics such as HLA type, cytomegalovirus (CMV) status, and blood type for certain recipients. (See ‘Ordering platelets’ below.)

Issues related to the effects of platelet pheresis on the donor are covered elsewhere. (See “Blood donor screening: Procedures and processes to enhance safety for the blood recipient and the blood donor”, section on ‘Apheresis platelet donors’.)

Both pooled and apheresis platelets contain some white blood cells (WBC) that were collected along with the platelets. These WBC can cause febrile non-hemolytic transfusion reactions (FNHTR), alloimmunization, and transfusion-associated graft-versus-host disease (ta-GVHD) in some patients.

Platelet products also contain plasma, which can be implicated in adverse reactions including transfusion-related acute lung injury (TRALI) and anaphylaxis. (See‘Complications of platelet transfusion’ below.)

Several strategies are used to prevent the complications associated with WBC and plasma contamination of platelets. (See ‘Ordering platelets’ below.)

Platelets concentrates also contain a small number of red blood cells (RBCs) that express Rh antigens on their surface (platelets do not express Rh antigens). The small numbers of RBCs in apheresis platelets negates the issue of Rh alloimmunization in most patients. However, blood banks avoid giving platelets from Rh+ donors to Rh female patients because of the potential risk of Rh alloimmunization and subsequent hemolytic disease of the newborn. (See “Overview of Rhesus D alloimmunization in pregnancy”.)

PLATELET STORAGE AND PATHOGEN REDUCTION — Platelets are stored at room temperature, because cold induces clustering of von Willebrand factor receptors on the platelet surface and morphological changes of the platelets, leading to enhanced clearance by hepatic macrophages and reduced platelet survival in the recipient [3-6].

All cells are more metabolically active at room temperature, so platelets are stored in bags that allow oxygen and carbon dioxide gas exchange. Citrate is included to prevent clotting and maintain proper pH, and dextrose is added as an energy source [2].

A disadvantage of room temperature storage is the increased growth of bacteria compared with blood products stored in the refrigerator or freezer. (See‘Complications of platelet transfusion’ below.)

Strategies for reducing exposure to contaminating pathogens include:

Donor screening for bloodborne pathogens (see “Blood donor screening: Laboratory testing”, section on ‘Infectious disease screening’ and “Blood donor screening: Procedures and processes to enhance safety for the blood recipient and the blood donor”, section on ‘Protection of the recipient’)

Proper skin sterilization techniques during collection, and discarding the first 15 to 30 mL of blood collected, which is most likely to be contaminated by skin bacteria

Performing tests to screen for bacterial contamination, such as automated culture-based assays, and rapid point-of-issue tests (see “Transfusion-transmitted bacterial infection”, section on ‘Detection of contamination’)

Using blood products that have been subjected to pathogen inactivation or reduction treatment (not available in the United States) (see “Pathogen inactivation of blood products”, section on ‘Pathogen inactivation of platelets’and “Preparation of blood components”, section on ‘Pathogen reduction’)

The shelf life of platelets stored at room temperature is five days because of the bacterial infection risk that increases in relationship to the storage duration. This short shelf life contributes to the greater sensitivity of platelet inventory to shortages.

INDICATIONS FOR PLATELET TRANSFUSION — Platelets can be transfused therapeutically (ie, to treat active bleeding or in preparation for an invasive procedure that would cause bleeding), or prophylactically (ie, to prevent spontaneous bleeding).

Actively bleeding patient — Actively bleeding patients with thrombocytopenia should be transfused with platelets immediately to keep platelet counts above50,000/microL in most bleeding situations, and above 100,000/microL if there is disseminated intravascular coagulation or central nervous system bleeding. (See“Clinical features, diagnosis, and treatment of disseminated intravascular coagulation in adults”, section on ‘Treatment’ and “Spontaneous intracerebral hemorrhage: Treatment and prognosis”, section on ‘Initial treatment’.).

Other factors contributing to bleeding should also be addressed. These include:

Surgical or anatomic defect

Fever

Infection or inflammation

Coagulopathy

Acquired or inherited platelet function defect

The dose and frequency of platelet transfusions will depend on the platelet count and the severity of bleeding. (See ‘Dose’ below.)

Preparation for an invasive procedure — Platelets are transfused in preparation for an invasive procedure if the thrombocytopenia is severe and the risks of bleeding are deemed high. Most of the data used to determine bleeding risk come from retrospective studies of patients who are afebrile and have thrombocytopenia but not coagulopathy [7]. Typical platelet count thresholds that are used for some common procedures are as follows:

Neurosurgery or ocular surgery – 100,000/microL

Most other major surgery – 50,000/microL

Endoscopic procedures – 50,000/microL for therapeutic procedures;20,000/microL for low risk diagnostic procedures (see “Endoscopic procedures in patients with disorders of hemostasis”, section on ‘Procedure-related bleeding risk’)

Central line placement – 20,000/microL [8]

Lumbar puncture – 10,000 to 20,000/microL in patients with hematologic malignancies and greater than 40,000 to 50,000 in patients without hematologic malignancies, but lower in patients with immune thrombocytopenia (ITP) [9-11]

Epidural anesthesia – 80,000/microL [11]

Bone marrow aspiration/biopsy20,000/microL

Prevention of spontaneous bleeding — Prophylactic transfusion is used to prevent spontaneous bleeding in patients at high risk of bleeding. The threshold for prophylactic transfusion varies depending on the patient and on the clinical scenario. (See ‘Specific clinical scenarios’ below.)

Predicting spontaneous bleeding — There are no ideal tests for predicting who will bleed spontaneously [12]. Studies of patients with thrombocytopenia suggest that patients can bleed even with platelet counts greater than 50,000/microL [13]. However, bleeding is much more likely at platelet counts less than 5000/microL. Among individuals with platelet counts between 5000/microL and 50,000/microL,clinical findings can be helpful in decision-making regarding platelet transfusion.

The platelet count at which a patient bled previously can be a good predictor of future bleeding.

Petechial bleeding and ecchymoses are generally not thought to be predictive of serious bleeding, whereas mucosal bleeding and epistaxis (so-called “wet” bleeding) are thought to be predictive.

Coexisting inflammation, infection, and fever also increase bleeding risk.

The underlying condition responsible for a patient’s thrombocytopenia also may help in estimating the bleeding risk. As an example, some patients with ITP often tolerate very low platelet counts without bleeding, while patients with some acute leukemias that are associated with coagulopathy (eg, acute promyelocytic leukemia) can have bleeding at higher platelet counts (eg, 30,000 to 50,000/microL). (See ‘Specific clinical scenarios’ below.)

Compared with adults, children with bone marrow suppression may be more likely to experience bleeding at the same degree of thrombocytopenia. In a secondary subgroup analysis of the PLADO trial, in which patients were randomly assigned to different platelet doses, children had more days of bleeding, more severe bleeding, and required more platelet transfusions than adults with similar platelet counts [14]. However, these findings do not suggest a different threshold for platelet transfusion in children, as the increased risk of bleeding was distributed across a wide range of platelet counts.

Tests for platelet-dependent hemostasis (ie, bleeding time, thromboelastography, and other point of care tests) are generally not used to predict bleeding in thrombocytopenic patients. (See “Platelet function testing”, section on ‘The in vivo bleeding time’ and “Platelet function testing”, section on ‘Instruments that simulate platelet function in vitro’.)

Therapeutic versus prophylactic transfusion — By convention, most authors use the term “therapeutic transfusion” to refer both to transfusion of platelets to treat active bleeding and transfusion of platelets in preparation for an invasive procedure that could cause bleeding. The term “prophylactic transfusion” is used to refer to platelet transfusion given to prevent spontaneous bleeding.

We use prophylactic platelet transfusion to prevent spontaneous bleeding in most afebrile patients with platelet counts below 10,000/microL due to bone marrow suppression. We use higher thresholds (ie, 30,000/microL) in patients who are febrile or septic. Patients with acute promyelocytic leukemia (APL) have a coexisting coagulopathy, and we use a platelet transfusion threshold of 30,000 to 50,000/microLfor them. (See ‘Leukemia and chemotherapy’ below.)

Patients with platelet consumption disorders (eg, immune thrombocytopenia [ITP], disseminated intravascular coagulation) and platelet function disorders are typically transfused only for bleeding or, in some cases, invasive procedures. Platelets should not be withheld in bleeding patients with these conditions due to fear of “fueling the fire” of thrombus formation. (See ‘Immune thrombocytopenia (ITP)’ below and ‘TTP or HIT’ below and ‘Platelet function defects’ below.)

Given the need to balance the risk of spontaneous bleeding with the potential complications of unnecessary platelet transfusion, the decision of whether to transfuse platelets based upon a clinical event (ie, for active bleeding or invasive procedures) or at a particular threshold (ie, to prevent spontaneous bleeding) is challenging. Standard practice has evolved to transfusion of platelets at a threshold platelet count of 10,000 to 20,000/microL for most patients with severe hypoproliferative thrombocytopenia due to hematologic malignancies, cytotoxic chemotherapy, and hematopoietic cell transplant (HCT) [15]. However, the risks and benefits of reserving platelet transfusion for active bleeding episodes in these patients continue to be evaluated [7,16-19].

In a randomized trial, 400 patients with acute myeloid leukemia (AML; patients with APL were excluded) and patients undergoing autologous HCT for hematologic malignancies were assigned to receive platelet transfusions when morning platelet counts were ≤10,000/microL or only for active bleeding [20]. Patients transfused only for active bleeding received fewer platelet transfusions during the 14-day period after induction or consolidation chemotherapy (1.63 versus 2.44 per patient, a 33.5 percent reduction). However, among patients with AML who were transfused only for active bleeding, there were more episodes of major bleeding (six cerebral, four retinal, and one vaginal) and there were two fatal intracranial hemorrhages compared with four retinal hemorrhages among patients transfused for a platelet count ≤10,000/microL. Patients undergoing HCT also experienced more bleeding episodes when transfused only for active bleeding, but most of these were minor.

In another randomized trial, 600 patients with hematologic malignancies receiving chemotherapy, autologous, or allogeneic HCT were assigned to receive platelet transfusion for a platelet count ≤10,000/microL or only for active bleeding (the Trial of Prophylactic Platelets [TOPPS]) [21-23]. Compared with those who received prophylactic transfusions, patients transfused only for active bleeding received fewer platelet transfusions during the 30-day period after randomization, but had a higher incidence of major bleeding (50 versus 43 percent) and a shorter time to first bleed (1.2 versus 1.7 days) [24]. There were no differences in the duration of hospitalization, and no deaths due to bleeding. In a predefined subgroup analysis, patients undergoing autologous HCT had similar rates of major bleeding whether they were transfused for a platelet count≤10,000/microL or only for active bleeding (45 and 47 percent).

The findings from these trials support continued use of prophylactic transfusion for patients with hematologic malignancies and HCT until further data become available. Although the findings suggest that reserving platelet transfusion for active bleeding may be safe for some adults undergoing autologous HCT, such a strategy requires intensive monitoring and the ability to perform immediate imaging for suspected CNS or ocular bleeding. We do not recommend reserving platelet transfusion for active bleeding in patients with HCT outside of highly specialized centers with the ability to support this level of vigilance.

SPECIFIC CLINICAL SCENARIOS — There are several common clinical scenarios that raise the questions of whether to transfuse patients prophylactically to prevent bleeding, and, if prophylactic transfusion is used, of what platelet count is the best threshold for transfusion.

Leukemia and chemotherapy — Patients with leukemia, hematopoietic cell transplant (HCT), or those being treated with cytotoxic chemotherapy have a suppressed bone marrow that cannot produce adequate platelets. We use prophylactic transfusion in these settings. The thresholds suggested below apply to patients with thrombocytopenia who are afebrile and without active infection. If fever or sepsis is present, higher thresholds may be needed.

Acute myeloid leukemia (AML) – Patients with AML can have suppressed bone marrow from AML, chemotherapy, or HCT. We use standard dose prophylactic transfusion of these patients at a threshold platelet count of10,000/microL, and transfusion for any bleeding greater than petechial bleeding. (See ‘Dose’ below.)

This approach is in line with the 2001 American Society for Clinical Oncology (ASCO) guidelines (table 1) and a practice guideline from the AABB [25]. It is supported by randomized trials comparing prophylactic (ie, threshold-based) and therapeutic platelet transfusion, in which patients who did not receive prophylactic transfusion had more severe bleeding [20,24,26]. (See ‘Therapeutic versus prophylactic transfusion’ above and “Overview of the complications of acute myeloid leukemia”, section on ‘Bleeding’.)

Acute promyelocytic leukemia (APL) – Patients with APL differ from other patients with AML because they often have an associated coagulopathy that puts them at high risk for disseminated intravascular coagulation and bleeding. We prophylactically transfuse these patients at a platelet count of 30,000 to50,000/microL, and treat any sign of bleeding, especially central nervous system bleeding, with immediate platelet transfusion. (See “Clinical manifestations, pathologic features, and diagnosis of acute promyelocytic leukemia in adults”, section on ‘Disseminated intravascular coagulation’ and“Initial treatment of acute promyelocytic leukemia in adults”, section on ‘Control of coagulopathy’.)

Acute lymphoblastic leukemia (ALL) – Patients with ALL have thrombocytopenia from bone marrow suppression. In addition, these patients are often treated with L-asparaginase, which causes severe hypofibrinogenemia. However, the risk of life-threatening bleeding is low. As an example, in over 2500 children with ALL, only two intracranial hemorrhages occurred, and they were associated with hyperleukocytosis in one case and intracerebral fungal infection in the other [9]. We transfuse adults with ALL at a threshold platelet count of 10,000/microL. The use of platelet transfusion in children with ALL is discussed separately. (See “Overview of the treatment of acute lymphoblastic leukemia in children and adolescents”, section on ‘Bleeding’.)

Chemotherapy for solid tumors – Cancer chemotherapy often makes patients thrombocytopenic from bone marrow suppression. Randomized trials of platelet transfusion threshold in this population have not been performed. Observational studies support a prophylactic platelet transfusion threshold of 10,000/microL[26]. A threshold of 20,000/microL may be appropriate for patients with necrotic tumors. These recommendations are generally consistent with the ASCO 2001 Guidelines (table 1) [26].

Hematopoietic cell transplant (HCT) – Chemotherapy and radiation therapy administered as part of the conditioning regimen for HCT can be highly bone marrow suppressive, depending on the doses used. We use standard dose prophylactic transfusion of these patients at a threshold platelet count of10,000/microL, and therapeutic transfusion for any bleeding greater than petechial bleeding. (See “Hematopoietic support after hematopoietic cell transplantation”, section on ‘Platelet transfusion’.)

Aplastic anemia – Patients with aplastic anemia do not have a malignancy, but they may have severe thrombocytopenia, and they may be candidates for HCT. Issues related to platelet transfusion in these patients are discussed separately. (See “Treatment of aplastic anemia in adults”.)

Prophylactic platelet transfusion for a platelet count ≤10,000/microL in hospitalized patients with thrombocytopenia from therapy-induced bone marrow suppression is consistent with a practice guideline from the AABB [25].

Immune thrombocytopenia (ITP) — Individuals with immune thrombocytopenia produce anti-platelet antibodies that destroy circulating platelets and megakaryocytes in the bone marrow. Circulating platelets in patients with ITP tend to be highly functional, and platelet counts tend to be well above 30,000/microL. Bleeding is rare even in patients with severe thrombocytopenia (ie, platelet count <30,000/microL). (See “Immune thrombocytopenia (ITP) in adults: Clinical manifestations and diagnosis”, section on ‘Pathogenesis’.)

Our general approach to platelet transfusion in patients with ITP is to transfuse for bleeding rather than at a specific platelet count. (See “Immune thrombocytopenia (ITP) in adults: Initial treatment and prognosis”, section on ‘Indications for treatment’.)

TTP or HIT — Thrombotic thrombocytopenic purpura (TTP) and heparin-induced thrombocytopenia (HIT) are disorders in which platelet consumption causes thrombocytopenia and an increased risk of bleeding; but the underlying platelet activation in these conditions also increases the risk of thrombosis.

Platelet transfusions can be helpful or even life-saving in patients with these conditions who are bleeding and/or have anticipated bleeding due to a required invasive procedure (eg, placement of a central venous catheter), and platelet transfusion should not be withheld from a bleeding patient due to concerns that platelet transfusion will exacerbate thrombotic risk. However, platelet transfusions may cause a slightly increased risk of thrombosis in patients with these conditions; thus, we do not use prophylactic platelet transfusions routinely in patients with TTP or HIT in the absence of bleeding or a required invasive procedure.

Support for this approach comes from a large retrospective review of hospitalized patients with TTP and HIT, in which platelet transfusion was associated with a very slight increased risk of arterial thrombosis but not venous thromboembolism [27]. In contrast, the review found that patients with immune thrombocytopenia (ITP) had no increased risk of arterial or venous thrombosis with platelet transfusion. Of note, this was a retrospective study in which sicker patients were more likely to have received platelets, and the temporal relationships between platelet transfusions and thromboses were not assessed.

TTP – Of 10,624 patients with TTP in the large review mentioned above, approximately 10 percent received a platelet transfusion [27]. Arterial thrombosis occurred in 1.8 percent of patients who received platelets, versus 0.4 percent of patients who did not (absolute increase, 1.4 percent; adjusted odds ratio [OR], 5.8; 95% CI, 1.3-26.6). The rate of venous thrombosis was not different in those who received platelets and those who did not (adjusted OR 1.1; 95% CI 0.5-2.2).

In contrast, a systematic review of patients with TTP who received platelet transfusions, which included retrospective data for 358 patients and prospective data for 54 patients, did not find clear evidence that platelet transfusions were associated with adverse outcomes [28].

HIT – Of 6332 patients with HIT in the large review mentioned above, approximately 7 percent received a platelet transfusion [27]. Arterial thrombosis occurred in 6.9 percent of patients who received platelets, versus 3.1 percent of patients who did not (absolute increase, 3.8 percent; adjusted OR, 3.4; 95% CI, 1.2-9.5). The rate of venous thrombosis was not different in those who received platelets and those who did not (adjusted OR 0.8; 95% CI 0.4-1.7).

In a series of four patients with HIT who received platelet transfusions, two of three with active bleeding had cessation of bleeding following platelet transfusion, and no thromboses occurred; a literature review was not able to identify any complications clearly attributable to platelet transfusion [29].

Management of TTP and HIT is discussed in detail separately. (See “Acquired TTP: Initial treatment” and “Management of heparin-induced thrombocytopenia”.)

Liver disease and DIC — Patients with liver disease and DIC have a complex mixture of procoagulant and anticoagulant defects along with thrombocytopenia, and therefore they are at risk for thrombosis and bleeding. There is no evidence to support the administration of platelets in these patients if they are not bleeding. However, platelet transfusion is justified in patients who have serious bleeding, are at high risk for bleeding (eg, after surgery), or require invasive procedures. (See “Clinical features, diagnosis, and treatment of disseminated intravascular coagulation in adults”, section on ‘Prevention/treatment of bleeding’ and “Hemostatic abnormalities in patients with liver disease”, section on ‘Bleeding’.)

Platelet function defects — Platelet function defects can be inherited or acquired, and may be associated with thrombocytopenia or a normal platelet count. Platelet transfusion in these settings is typically reserved for bleeding.

Inherited diseases Platelet function is impaired in Wiskott-Aldrich syndrome, Glanzmann thrombasthenia, and Bernard-Soulier syndrome. Bleeding in patients with these conditions is treated with platelet transfusion, along with other hemostatic agents discussed below. (See “Congenital and acquired disorders of platelet function”, section on ‘Inherited disorders of platelet function’ and‘Alternatives to platelet transfusion’ below.)

Acquired conditions – Uremia, diabetes mellitus, myeloproliferative disorders, and other medical conditions can impair platelet function. Bleeding risk can be reduced by treating the underlying condition. Platelet transfusion is typically reserved for major bleeding in these conditions. (See “Congenital and acquired disorders of platelet function”, section on ‘Acquired platelet functional disorders’.)

Patients who are febrile or septic can have impaired platelet function. We transfuse these patients for bleeding. We also use a higher threshold for when fever or sepsis coexist with thrombocytopenia (eg, in patients with leukemia). (See ‘Leukemia and chemotherapy’ above.)

Antiplatelet agentsAspirin, nonsteroidal antiinflammatory drugs (NSAIDs),dipyridamole, ADP receptor (P2Y12) inhibitors (eg, clopidogrel, ticlopidine), andGPIIb/IIIa antagonists (eg, abciximab, eptifibatide) are used to prevent thrombosis by interfering with normal platelet function. The antiplatelet effects of these agents are weakest with aspirin and more potent with the P2Y12inhibitors. (See “Platelet biology”, section on ‘Drugs with antiplatelet actions’.)

Typically, the approach to treating mild bleeding in a patient taking an antiplatelet agent is to discontinue the drug, assuming a favorable risk-benefit ratio. Although data are limited, platelet transfusion appears to be the best option in patients taking antiplatelet agents who experience severe bleeding [30].

Patients taking these agents may also require urgent surgical procedures (eg, coronary artery bypass grafting, neurosurgical interventions, and others). The role of platelet transfusion in this setting is not well defined. Some clinicians give prophylactic platelet transfusions to patients taking antiplatelet drugs who require major surgery, while other clinicians use platelet transfusion only to treat excessive surgical bleeding [30,31]. These cases can be complex, and we favor an individualized approach based on the complete clinical picture.

Other medications – Other medications may impair platelet function. As an example, the Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib inhibits platelet aggregation by interfering with activation signals. The role of platelet transfusion in patients with ibrutinab-associated bleeding despite a sufficient platelet count is unknown, and decisions are individualized according to the platelet count and the severity and site of bleeding.

Massive blood loss — Patients with massive blood loss from surgery or trauma are transfused with red blood cells (RBC), resulting in partial replacement of the blood volume with a product lacking platelets and clotting factors. In this setting, we transfuse RBC, fresh frozen plasma (FFP), and random donor platelet units in a 1:1:1 ratio. As an example, a patient transfused with six units of RBC would also receive six units of pooled platelets or one apheresis unit (both of which provide approximately 5 x 1011 platelets) and six units of FFP. (See “Initial evaluation and management of shock in adult trauma”, section on ‘Transfusion of blood products’.).

Cardiopulmonary bypass — Patients who undergo prolonged cardiopulmonary bypass can have thrombocytopenia and impaired platelet function. The use of platelet transfusion in the cardiopulmonary bypass setting is discussed separately. (See“Congenital and acquired disorders of platelet function”, section on ‘Cardiopulmonary bypass’ and “Early noncardiac complications of coronary artery bypass graft surgery”, section on ‘Bleeding’.)

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