Platelets are indicated in treatment or prevention of bleeding in patients with a low platelet count (thrombocytopenia) or platelet function defect. An adult therapeutic dose (ATD) of platelets is >240×109 per transfusion.
Platelets are produced in two ways
- whole blood donations are centrifuged and the buffy coats (between the red cell and plasma layers) from four donations are pooled in the plasma of one of the donors
- an ATD of platelets is obtained from a single donor by apheresis (donors may give two or three ATDs at a single session) (1)
NICE guidelines recommendations on platelet transfusion are as follows:
- offer platelet transfusions to patients with thrombocytopenia who have clinically significant bleeding (WHO grade 2) and a platelet count below30x109 per litre.
- use higher platelet thresholds (up to a maximum of 100x109 per litre) for patients with thrombocytopenia and either of the following:
- severe bleeding (WHO grades 3 and 4)
- bleeding in critical sites, such as the central nervous system (including eyes).
- offer prophylactic platelet transfusions to patients with a platelet count below10x109 per litre who are not bleeding or having invasive procedures or surgery, and who do not have any of the following conditions:
- chronic bone marrow failure
- autoimmune thrombocytopenia
- heparin-induced thrombocytopenia
- thrombotic thrombocytopenic purpura
- consider prophylactic platelet transfusions to raise the platelet count above50x109 per litre in patients who are having invasive procedures or surgery
- consider a higher threshold (for example 50–75x109 per litre) for patients with a high risk of bleeding who are having invasive procedures or surgery, after taking into account:
- the specific procedure the patient is having
- the cause of the thrombocytopenia
- whether the patient's platelet count is falling
- any coexisting causes of abnormal haemostasis.
- consider prophylactic platelet transfusions to raise the platelet count above100x109 per litre in patients having surgery in critical sites, such as the central nervous system (including the posterior segment of the eyes).
- do not routinely transfuse more than a single dose of platelets
- only consider giving more than a single dose of platelets in a transfusion for patients with severe thrombocytopenia and bleeding in a critical site, such as the central nervous system (including eyes).
- reassess the patient's clinical condition and check their platelet count after each platelet transfusion, and give further doses if needed.
Platelets are invariably contaminated with red cells so that ABO and rhesus compatability should be ensured.
Febrile reactions following platelet transfusions are related to the substances IL1-beta and IL6 in the supernatant; the latter should ideally be removed before use.
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