HOW I DO – Transfusion of Blood Products PART – 2

HOW I DO – Transfusion of Blood Products PART – 2

(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)

Question: In last part, we started a series about common hematology issues. First part was very relevant to current season i.e. dengue and thrombocytopenia. I was very surprised to know that SDP AND RDP ARE EQUAL IN TERMS OF RESPONSE. We also learned 1. Manual platelet count should not be used. It has extremely limited value in whole field of medicine. And no value in Dengue fever. 2. Once a day CBC is sufficient in large majority of hospitalized patients. 3. Clinical variety of dengue patients and that most do not bleed. And do not need platelet transfusion unless platelet is below about 10,000.

Does the same principle apply to SDP and RDP in non dengue conditions as well?

Answer: Yes. In almost all conditions practically, SDP and RDP are equal. Only in aplastic anemia, or patients likely to need transplant, we prefer SDP. Here the reason is to reduce exposure to number of donors. Response is not different. But more donors means more HLA antigens, and risk of more antibodies. These antibodies may lead to rejection of hematopoietic stem cell transplant (earlier known as Bone Marrow Transplant). This is a much smaller group of patients. Hence for all practical purposes, for any non hematologist, SDP and RDP are equal.

It is important to give the right dose of RDP however. For an average adult, 4-6 units of RDP are required in most cases. If you use lower number, response may be suboptimal.

Que: Thank you. Any other important points that we should know related to platelet transfusion?

Ans: Following are the most important practical points relevant for most practitioners:

1. Platelets are to be transfused as soon as possible, once sent from blood bank. Otherwise there is risk of microclots leading to lower response. Platelets are generally given as free flowe. average 6 units in about 30-60 minutes. Each RDP is about 50 ml.
2. Additionally, platelets have the highest risk of leading to bacterial transmission or endotoxic shock, among all blood products. Since they are kept at room temperature. Means if there is any contamination during blood collection from donor, or during processing, bacteria can proliferate in platelet product. Other blood products are kept at very low temperature, where bacteria cannot grow. Means during or immediately after platelet transfusion, if there is any high fever, or drop in blood pressure, or other signs of sepsis, treat empirically as septic shock. Send the bag for culture and inform blood bank.
3. Blood group does not matter for platelet transfusion in adults. Hence patient can receive platelet from any donor.
4. Platelet response is best measured up to one hour after transfusion. Very broadly, one RDP is supposed to raise platelet count by about 5000. And one SDP is equal to about 6 RDPs.

Thereafter, drop can be due to several reasons other than product quality or match. Response to platelet is highly variable in individuals due to rapid utilization during bleeding, breakdown due to sepsis or HLA antibodies, and other factors. Hypersplenism also reduces response to transfusion, highly significant in most cases.

5. There are no absolute contraindications for platelet transfusion. I have seen hesitation for platelet transfusion in conditions like ITP, TTP, HIT diagnosed or suspected. Response to platelet transfusion in ITP is mostly poor, and you do need to plan for other therapies. But a bleeding patient with ITP or before any emergency procedure, platelet can certainly be given. “platelets add fuel to fire” means formation of more antibodies is not the right understanding. Same way for TTP (thrombotic thrombocytopenic purpura) – these people rarely bleed. But yes, before putting a central line for plasmapheresis for example, it is recommended in our guidelines also to give platelets if necessary. In general, we recommend against frequent use of platelet transfusions, especially when given for thrombocytopenia without bleeding. However for bleeding patients, even if no diagnosis, it is ok to give platelet transfusions once or twice while awaiting expert opinion.
6. When we say bleeding as an indication, it does NOT mean skin bleedinge. NOT for petechiae, purpura, ecchymoses/bruises. It is for mucosal bleeding or obvious major bleeding.
7. Reason for avoiding platelet transfusion indiscriminately is mainly for safety. Risk of infection, TRALI, febrile reactions, cost, formation of alloantibodies leading to poor response in future.
8. Make sure to avoid any NSAIDS, aspirin, clopidogrel, other newer antiplatelet agents and of course all anticoagulation (warfarin or newer ones) in patients with severe thrombocytopenia. For cardiac patients, one may continue antiplatelet agents till platelet count is about 50,000. Between 30 to 50,000 one has to weigh risk benefit ratio and discuss risks with patient. For example, in a patient with a recent cardiac event, one may continue but with knowledge that bleeding risk will be higher. Whereas with an old cardiac event, risk benefit ratio may favor stopping for a while. Below 20-30,000 approximately, better to stop.
9. Antiplatelet agents do NOT reduce platelet number, only reduce their function. Means if patient is on antiplatelet agent and platelet counts reduce, they must be investigated for the etiology of low platelet.

July 14, 2024

Dr Chirag A. Shah; M.D. Oncology/Hematology (USA), 9998084001. Diplomate American Board of Oncology and Hematology. Ahmedabad. drchiragashah@gmail.com   www.shyamhemoncclinic.com