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Thursday the 28th of March 2024 02:24:29 PM

July 1, 2006

Stumble It!Platelets

Filed under: Health,Science and Technology — Eric Ptak @ 8:50 pm

Today, I donated platelets. It was the first time I’ve ever had apheresis (ay-fur-ee-sis), and it wasn’t that bad, actually. I’ll probably wind up doing it often. What is apheresis, you might ask? It’s a process where they draw blood from you, separate it into its components via a centrifuge, remove the part that’s needed, and return the other components to your body. For me, it’s pretty basic science.

If you are not up on blood science, here’s the basics: your blood, even though it looks like a red fluid, is made up of different components: plasma, and cells which include red blood cells, white blood cells and platelets. The red cells are the heaviest, the white cells are the next heavy, platelets are lighter, and plasma, the yellowish fluid they all float around in, is the lightest of them all. What happens inside the machine is the blood is spun around, and from the spinning, the components separate into layers. Individual pumps set for the different layers are activated and the desired component is removed. The rest of the blood is allowed to return to your body, undamaged by the whole affair.

Who would need platelets? From Wikipedia,

Platelet transfusions are traditionally given to those undergoing chemotherapy for leukemia, those with aplastic anemia, AIDS, hypersplenism, ITP, sepsis, DIC, or surgeries such as cardiopulmonary bypass. Platelet transfusions should be avoided in those with TTP-HUS because it can worsen neurologic symptoms and acute renal failure, presumably due to creation of new thrombi as the platelets are consumed. It should also be avoided in those with heparin-induced thrombocytopenia (HIT).

Thrombocytopenia due to underproduction. Patients in this category falls under those undergoing chemotherapy, those with myelophthisic marrow, AIDS, or with aplastic anemia. If indicated, transfusions (one plateletphresis concentrate) should be given until recovery of platelet function, generally approximately twice weekly. Surgical bleeding due solely to thrombocytopenia occurs when platelets < 50,000/uL while spontaneous bleeding occurs when platelets < 10,000/uL. Thrombocytopenic patients can develop "dry" bleeding, that is, petechiae and ecchymoses only. They will not suffer fatal hemorrhagic events unless they first have extensive mucosal bleeding, or "wet" bleeding. Therefore, in those with no bleeding or only "dry" bleeding, the threshold for transfusion should be between 5,000 to 10,000/uL. A more conservative threshold of 20,000/uL should be used in those with a fever or other risk factors for bleeding. Those with active bleeding or prior to surgery should have a threshold of 50,000/uL. An unconfirmed, but helpful, way to determine whether a patient is recovering from chemotherapy-induced thrombocytopenia is to measure "reticulated" platelets, or young RNA-containing platelets, which signifies that the patient is starting to make new platelets.

Immune thrombocytopenia. Patients in this category include those with ITP or drug-induced thrombocytopenia. Platelet transfusions are generally not recommended for this group of patients because the underlying cause involves antibodies that destroy platelets, therefore any newly transfused platelets will also be destroyed. More studies need to be done.

Altered platelet functions. Disorders of platelet function can be congenital or acquired. Most of these disorders are mild and may respond to therapy with desmopressin (dDAVP). Transfusion is not necessarily required. However, with some more severe disorders such as Glanzmann thrombasthenia, transfusions with large amount of platelets may be needed. The number of transfusions may be reduced if these patients are given recombinant human factor VIIa since the underlying cause are antibodies to platelet glycoproteins IIb/IIIa.

Cardiopulmonary bypass surgery. This surgery can result in destruction of a large proportion of the patient’s platelets and may render the remaining viable platelets to be dysfunctional. The indications for transfusion in such patients is controversial. General guidelines recommends not transfusing patients prophylactically but only when they are bleeding excessively, while also giving desmopressin.

Drug-induced platelet dysfunction. The most common of these is aspirin, and its similar drug class, the NSAIDs. Other antiplatelet drugs are commonly prescribed for patients with acute coronary syndromes such as clopidogrel and ticlopidine. When surgery is undertaken following the administration of these drugs, bleeding can be serious. Transfusion under these circumstances is not clear-cut and one has to use clinical judgment in these cases.

That’s a good amount of conditions and people in need.

Since this was the first time I underwent plateletpheresis, they just let me stay on the machine for only 40 minutes. They have to get a count to make sure you have a high enough level of platelets in your system, typically 150×105/mm3 of blood. You don’t want to give too many – the most you can give is three units, or about 9×1011 platelets, or the number of platelets from six liters of blood. Of course, if you have higher platelet levels, you don[‘t have to use as much blood to donate the maximum amount. Platelets are the part of your blood that cause clotting, and it would be a bad thing if you didn’t have enough. Thankfully, if the levels drop too low, your liver will produce thrombopoietin which induces you bone marrow to produce more platelets. Typically after donation, platelet levels return to normal after about 2 days.

There are a couple of things you have to be careful of when donating platelets. First of all, there are the normal precautions taken when donating blood: the 150,000 questions they ask about diseases, sex, drugs, antibiotics, tattoos, and travel. Importantly, you can’t have taken aspirin in the last three days. Aspirin by its nature interferes with the platelets and and their function, rendering them useless. There’s also a bit of calcium depletion in your bloodstream caused by the procedure. This is from the anticoagulant used, which binds to the calcium in the blood. Since calcium is important in nervous system function, when it is depleted it causes tingling sensations. In the lips this is noticed quickly, as they are nerve-dense. All I felt was a slight numbness in my upper lip, as I had a feta cheese omelet for breakfast, drank some milk earlier, and took a calcium supplement this morning. I didn’t need to chew TUMS during the procedure.

The one thing that’s nice about platelet donation is that when you are found to be compatible with someone who is in need, you can have the satisfaction of knowing that you are helping a specific person. The Red Cross will notify you if a person with a specific need for your platelet type (similar to blood type) is in need. You can then set an appointment to donate platlets for him/her. I doubt that you would find out who that person is, but it’s still nice to know that you are actually helping one specific person.

I figure, one a month, I’ll either be donating platelets or blood. Since the recovery time from donating platelets is so short, it won’t interfere with my regular donation regimen of six times yearly. Going downtown to donate once a month is good enough for me.

1 Comment »

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    a great deal more attention. I’ll probably be back again to read through more, thanks for the advice!

    Comment by Antonio — March 19, 2015 @ 7:10 am

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