Platelets

All platelet units within the Fairview system are single donor platelet (SDP) units obtained by apheresis and prestorage leukoreduced. An SDP unit is equivalent to 5 to 6 whole blood platelet concentrate units.

Each platelet pheresis has been tested for bacterial contamination, but a risk of bacterial contamination and sepsis remains. Approximately 1:75,000 platelet transfusions is associated with a clinically significant septic transfusion reaction. (See Infectious Risks.)

Contents:
A dose of single donor platelets (SDPs) contains at least 3.0 x 1011 platelets.  Volume varies from 180-550 mL.  
 
Dose:
For adults, one dose is one unit of SDPs.
For patients 45 kg or less, one dose is 5 mL per kg body weight.
 
Expected Results: One dose should increase the platelet count by 25,000 to 40,000 in the absence of comorbidities that accelerate platelet consumption.

Indications for Platelet Transfusion

The decision to transfuse should be supported by the need to relieve or prevent bleeding. A patient’s platelet count should not be the sole deciding factor in transfusing platelets. The following indications should be used to decide whether platelets are needed:

1. Platelet count less than 10 X 109/L

2. Platelet count less than 20 X 109/L with mucosal bleeding

3. Platelet count less than 50 X 109/L with: ◦Active bleeding

  • Surgery or other invasive procedure
  • Infant less than 1 month of age
  • Coagulopathy, including DIC, with bleeding
  • Severe infections and bleeding
  • Patients with Sickle Cell Anemia or with inborn errors of metabolism immediately following marrow transplant (due to increased risk of intracranial hemorrhage around transplant period)

4. Platelet count less than 100 X 109/L with: ◦Neuro- or ophthalmologic surgery

  • Following cardiopulmonary bypass, or use of intra-aortic balloon pump, or ventricular assist devices
  • Receiving extracorporeal membrane oxygenation (ECMO) 

5. Platelet dysfunction (drugs, congenital, other)

 CAUTION 
  • Do not transfuse platelets to patients with thrombotic thrombocytopenic purpura (TTP).
  • Do not transfuse platelets to patients with idiopathic thrombocytopenic purpura (ITP) unless there is bleeding.

Washed Platelets

Plasma can be removed from platelets by washing. This will reduce the risk of a transfusion reaction in key patient populations (see below). Washing reduces the platelet count by approximately 10-15%.

CAUTION
Coordination with the Blood Bank is required. Washing platelets requires extra time. Please plan ahead. Washed platelets expire 4 hours after washing. 

Platelets should be washed for the following patient conditions:
  1. Patients with IgA deficiency and antibodies to IgA
  2. Patients with repeated severe transfusion reactions to plasma proteins unresponsive to medications
  3. Patients with haptoglobin deficiency and antibodies to haptoglobin

Platelets Stored in Additive Solution

Platelets stored in additive solution (PAS) have had 65% of their plasma replaced with a buffered salt solution. The platelet function is not affected by this change. PAS platelets have been shown to reduce the rate of allergic and febrile non-hemolytic transfusion reactions. These platelets may be requested for patients with a history of severe allergic rransfusion reactions. PAS platelets will not prevent an anaphylactic reaction in patients with IgA or haptoglobin deficiency.

Leukocyte Reduced Blood Components

All UMMC components, except granulocytes, are leukoreduced. Leukoreduced cellular components are used because they reduce the:
  1. Rate of febrile non-hemolytic transfusion reactions,
  2. Risk of CMV transmission, and
  3. Leukocyte alloimmunization.
Leukoreduced components and CMV-seronegative components (tested for CMV antibodies and found negative) have a comparable risk of CMV transmission.

CMV-seronegative components are provided only for intrauterine transfusions and granulocyte transfusions when indicated.

Transfusions for More than One Dose of Platelets Per Day

1. In some patients more than one platelet transfusion daily may be warranted if the post-transfusion platelet count is less than the guidelines suggest and one of the following is present: a.Significant blood loss is documented (patient requires one or more units of RBCs daily).
  • A life threatening bleed (especially CNS or pulmonary)
  • The patient is undergoing an invasive procedure.
2. More than one platelet transfusion per day is NOT indicated if the patient is NOT bleeding or if petechiae or mild hematuria are the only signs of bleeding.
3. Patients refractory to platelet transfusions may have greater benefit if they receive the transfusion during rather than before the procedure.
4. Platelet drips are strongly discouraged; however, in severely bleeding patients refractory to platelet transfusions a continuous infusion of platelets (platelet drip) may be attempted (e.g., three doses split to allow six 4-hour transfusions per day).

A transfusion medicine physician or transfusion safety officer may evaluate orders for more than one platelet transfusion per patient per day.

Patients Refractory to Platelet Transfusions

For most patients with thrombocytopenia, the effects of a single platelet transfusion will last 2-3 days. Refractory patients fail to obtain the expected post-transfusion increment. In the majority of cases, the cause of refractoriness is non-immune rather than immune-mediated. The platelet lifespan may be shorter in patients with fever, infection, hypersplenism, or disseminated intravascular coagulation (DIC). Some drugs such as antibiotics (e.g., amphotericin, vancomycin, ciprofloxacin), heparin, and others can result in a reduced post-transfusion increment. In rare cases a patient may have a drug-dependent antibody causing increased platelet destruction.

Alloimmunization can also cause refractoriness. Alloimmunization is the development of antibodies that are directed against HLA (human leukocyte antigens) or HPA (human platelet antigens) antigens on the platelets. These antibodies are formed due to previous pregnancies, transfusions, or organ, tissue or stem cell transplantation. Testing may determine whether these antibodies are present. When refractoriness is due to alloimmunization, a trial of matched platelets is warranted. Matched platelets are selected by crossmatching or donated by an HLA-matched blood donor. Testing for drug-related immune thrombocytopenia can also be considered.

Alloimmunized patients who do not respond to crossmatch-compatible platelets or HLA-or HPA-matched platelets should be carefully re-evaluated for the presence of non-immune causes of refractoriness. As a last resort, a trial of platelets donated by family members or the stem cell donor could be considered.

Causes of Refractoriness to Platelet Transfusion

Non-immune causes:
  • Fever, infection, sepsis
  • Diffuse endothelial injury
  • Medications
  • Hypersplenism
  • Microangiopathy 
  • Disseminated intravascular coagulation
Immune causes:
  • Alloimmunization: HLA and HPA antibodies
  • Autoimmune: ITP
  • Drug-dependent antibodies

CAUTION
Coordination between the clinical team and the Blood Bank is required to obtain crossmatched and/or HLA matched platelets. Re-evaluation is required on a daily basis. A transfusion medicine physician should be consulted Monday-Friday, 8 am - 5 pm at pager (612) 899-8938; on nights and weekends call the East Bank Blood Bank at (612) 273-5367 or the West Bank Blood Bank at (612) 273-4011. 

Evaluation of Patients Refractory to Platelet Transfusion

1. Determine if the post-transfusion increment is satisfactory using the corrected count increment (CCI):


CCI = [(post-platelet count - pre-platelet count/uL) X body surface area (m2) X 1011] / 4 X 1011
  • Post Platelet Count = 10-60 minutes post-transfusion
  • Pre Platelet Count = Less than 4 hours before transfusion
  • 4 X 1011 is theaverage number of platelets in an adult dose.
  • For patients 10-45 kg use 2 X 1011
Note: Two consecutive CCIs less than 5000 suggest immune refractoriness.

2. Make a clinical judgment whether non-immune factors (e.g., sepsis, fever, antibiotics, bleeding, splenomegaly, etc.) are the major factors causing reduced platelet survival and refractoriness.

3. If a specific drug is suspected of contributing to refractoriness, discontinue the drug if clinically appropriate.

4. If immune factors are thought to contribute, contact the Blood Bank and order the following:

•platelet incompatibility screen (platelet crossmatch)
•platelet antibody screen

Mobile-Caution
IVIG may interfere with these tests!

5. A Blood Bank physician will interpret the platelet incompatibility screen. If appropriate, a trial of crossmatch compatible platelets may be tried.

6. If the platelet incompatibility screen is negative, there are likely to be no HPA or HLA antibodies and random platelet pheresis can be used.

7. If the patient fails to respond to a trial of crossmatched platelets, a trial of HLA matched platelets may be tried. For this to occur:

  • A Class I HLA panel reactive antibody (PRA) test is required to define antibody specificities. 
  • The patient’s HLA type is helpful but not required.
Mobile-Caution
For many patients, finding HLA matched platelets is difficult and may take several days. In addition, a very limited supply is usually available.

8. Directed donation of platelets from family members or from the stem cell donor may also be considered if all above measures fail.

9. Pre- and Post-platelet counts must be obtained to follow the patient’s CCI to assess the efficacy of these treatments.

10. Coordination with the Blood Bank is required to obtain these specialty products.

Platelet Transfusion Algorithm for Refractory Patients

Platelet-Transfusion-Algorithm