Other Components

The general principles set out in paragraphs 1 to 6 above also apply to transfusions of other blood components.

Platelets^10,11

Platelet concentrates are now derived from whole blood donation by the "buffy coat" method and undergo pre-storage filtration to produce a leukocyte-depleted product. This is intended to reduce febrile reactions and allo-immunization. These are pooled prior to issue by CBS into 4 unit doses, typically containing
> 240 x 10⁹platelets in 300 mL of plasma. This is considered a standard adult dose.

One unit of apheresis platelets is derived from a single donor by an apheresis procedure and is approximately equivalent to 4 unit pool of whole blood derived platelets. The unit undergoes pre-storage filtration to produce a leukocyte-depleted product.

a. Apheresis platelets are recommended for patients with the standard indications for platelet transfusion. HLA matched apheresis platelets may be indicated for patients who have demonstrated HLA antibodies and are refractory to regular platelet transfusions..

b. It is recommended that HLA typing be performed before treatment is initiated in patients who are potential candidates for apheresis platelets (e.g. those with acute leukemia).

The decision to transfuse platelets depends on several factors besides the platelet count and clinical judgement must be exercised when applying the following guidelines to a specific clinical situation.

1. Platelets less than 10 x 10⁹/L due to poor platelet production. A higher threshold is recommended in neonates.

2. Platelets less than 20 x 10⁹/L due to poor platelet production in a bleeding or febrile patient.

3. Platelets less than 50 x 10⁹/L in bleeding patient with documented disseminated intravascular coagulation.

4. Platelets less than 50 x 10⁹/L in massively transfused (>1 blood volume in 24 hours) patient with continued bleeding.

5. Platelets less than 50 x 10⁹/L and impending surgery or invasive procedure.

6. Platelets less than 100 x 10⁹/L in patient with diffuse microvascular bleeding following cardiovascular bypass or with intra-aortic balloon pump.

7. Platelets less than 100 x 10⁹/L in patients undergoing ophthalmic or neurosurgery.

8. Platelet dysfunction with bleeding or prophylactically before invasive procedure.

For adult transfusion, platelets will be ordered by dose. One dose of platelets will be a 4 unit pool of "buffy coat" platelets. Note that this is considered functionally equivalent to the former 5 unit pools of whole blood derived platelets due to a greater degree of platelet activation in the latter.

The recommended pediatric dose is 5- 10 mL/ kg body weight.

Check platelet count within 10 minutes to 1 hour post-transfusion to determine if an increment has been obtained. The expected increment per dose of platelets should be at least 15 x 10⁹/ L.

Cryoprecipitate⁸

Cryoprecipitate transfusion guidelines:

Bleeding patient with hypofibrinogenemia (< 1.0 g/L) or dysfibrinogenemia. (Usual pediatric or adult dose is 1 unit / 10 kg body weight).

Note that virus inactivated concentrates or recombinant products are preferred for those with congenital forms (see section on factor concentrates.)

Cryoprecipitate is no longer considered appropriate therapy for the treatment of von Willebrand disease or Hemophilia A. Von Willebrand disease should be treated with DDAVP or Humate-P. Hemophilia A should be treated with Factor VIII concentrate.

Specialized Components

Washed RBC

Washed RBC can be used in patients at risk for allergic reactions (typically IgA deficient patients with antibodies).

Leukodepleted Products

All cellular blood components have undergone pre-storage leuko-depletion.

Irradiated/CMV Negative Components

In order to prevent transfusion associated graft versus host disease and CMV infection, irradiated CMV negative cellular components are recommended in the following situations:

Irradiated and CMV Negative:

Neonates
Intra-uterine transfusions
Allogeneic Hematopoietic Progenitor Cell transplant recipient
Solid organ transplant recipient
Congenital immunodeficiencies (e.g. SCID, Di George syndrome)

Irradiated:

Autologous Hematopoietic Progenitor Cell transplant recipient
Patients treated with Fludarabine or Cladribine.
Directed donations from relatives of recipients

CMV Negative:

HIV infected patients who are CMV negative.

Techniques that reduce the number of leukocytes to fewer than 5 x 10⁶ per unit have been shown to provide substantial protection against CMV infection. This degree of leukodepletion is achieved by the current practice used by CBS to produce platelet concentrates and red cells. No data are currently available to show whether there is an additional level of safety when the donor unit is both CMV negative and leukodepleted. A recent Canadian Consensus Conference¹⁷ recommended that CMV negative leukoreduced units be transfused to those at greatest risk.