Abnormal platelet function can be inherited or acquired. A number of drugs interfere with platelet function including aspirin, non-steroidal anti-inflammatory drugs, and anti-platelet agents e.g. clopidogrel. Coronary artery bypass surgery and severe renal impairment may also interfere with platelet function. Platelet transfusions given on account of impaired platelet function should usually be discussed with a haematologist to ensure the transfusion is needed and that platelets of the appropriate specification are given.
Platelets should only be used when the benefits outweigh the risks. Most platelets are given to prevent rather than to treat bleeding. One adult pack of platelets is termed one Adult Therapeutic Dose (ATD). One ATD should increase the platelet count by at least 20 x 109/L.
Children under 15Kg should receive 10-20mL/kg body weight.
Children from the age of 1 year can receive standard platelets.
Prophylaxis:
Dose: for prophylaxis, do not routinely transfuse more than 1 adult therapeutic dose. A post-transfusion increment can be checked 10 minutes after the transfusion has finished to ensure the desired platelet count has been reached.
Compatibility
Platelets are suspended in plasma which contains anti-A and anti-B, thus platelet compatibility for ABO is considered similar to that of plasma. When ordering standard platelets for patients of any group, ABO and D matched platelets are the preferred option where available.
Remember ABO compatibility for platelets is different to red cells. Group A platelets should be given to patients whose blood group is unknown if transfusion is required before it can be tested. Where time permits, match components with the patient’s ABO group, rather than relying on group A platelets. Group AB components should be reserved for group AB patients.
| Patient's blood group | Choice priority | Platelets |
|---|---|---|
| O | 1st | O |
| 2nd | A/B | |
| 3rd | AB | |
| A | 1st | A |
| 2nd | AB | |
| 3rd | B* | |
| O (adult only)* | ||
| B | 1st | B |
| 2nd | AB | |
| 3rd | A* | |
| O (adult only)* | ||
| AB | 1st | AB |
| 2nd | A/B** | |
| 3rd | O (adult only)* |
Active bleeding
Offer platelet transfusions to patients with a platelet count of $<30 x 10^9$ with clinically significant bleeding (World Health organisation bleeding grade 2- e.g. haematemesis, melaena, prolonged epistaxis)
Platelet thresholds for transfusion are higher (maximum $<100 x 10^9$) for patients with severe bleeding (World Health organisation bleeding grades 3&4), or bleeding at critical sites, such as the CNS.
It should be noted that platelet transfusions have the highest risk of bacterial contamination compared to other types of blood product.