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To Bleed or not to Bleed, that is the Question: Platelets

By Carl Davidson

Republish: EasyPublish™
Published: 14Jun2010
Word count: 624
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Two things are needed to stop bleeding. One is a platelet plug and the second is a fibrin clot. These need to be thought of as completely separate entities even though the end product is hemostasis. Let’s talk about the platelet plug.

Now, there are two main problems with platelets, either 1) a decreased number or 2) bad (broken) platelets that have poor function. There are two tests that we need to evaluate for platelet function.

One is the platelet count as seen on the red blood cell count. So, we are looking at the absolute number, or we are looking at a test called the bleeding time. When a platelet count is decreased, this is known as thrombocytopenia. This is seen if there is a problem in the bone marrow such as decreased production of platelets which you can see in some malignancies, most commonly seen in chemotherapy that suppresses bone marrow, increased destruction such as a hyperactive spleen where the only potential solution to this is to have a splenectomy, or from idiopathic thrombocytopenia which is typically a child after a viral syndrome where the treatment is steroid removal immunoglobulin or spleen removal. When I was in my pediatric rotation, I remember seeing a young child for a well child visit, and this was actually my first rotation as a physician assistant student. When the physician came in, the child clearly responded adversely to the pediatrician who was a bit older with a beard, and the mom said that he looked kind of like his father. The child was really kind of frightful of the physician. When he looked over the child, the child had a number of bruises especially on his lower legs. I was quite upset by this thinking this was a very clear case of child abuse and that the father was beating the child. The doctor sent him off for blood work, and I was quite upset with the physician which I talked about wondering how he could not see how apparent abuse was. Well, when the blood work came back, this child had idiopathic thrombocytopenia, and it was not child abuse.

A red flag is to think sepsis when you have unexplained thrombo-cytopenia, especially with children. Platelet counts lower than 50,000, you can get increased bleeding status post trauma. If you have platelet counts of less than 20,000, you can have increased spontaneous bleeding. When I used to cover the hematology/ oncology floor, we would transfuse patients when they got below 10,000.

To test platelet function, we need a bleeding time. The bleeding time is basically a small incision in the skin that by spring-loaded apparatus, it gives us a very uniform little abrasion, and the lab will blot that area until the bleeding stops. I have maybe ordered the test once or twice in my career. It is pretty rare. The most common reason why platelets would not clot well is aspirin, someone who takes aspirin, their blood is a little bit thin. Or uremia. Hypothermia can do this as well.

Remember that a platelet lives in the body for seven days, and when you take an aspirin this completely deactivates all platelets that are in the body. I will not discuss coagulopathies here such as Von Willebrand’s or hemophilia. But, I do want to talk about medications that affect the platelets. The most common one by far is aspirin. The dose can vary between 81 mg to 1,000 mg daily. Plavix is typically 75 mg once per day, and has been used with success in people with known coronary artery disease or atherosclerotic disease such as a past myocardial infarction or stroke. Glycoprotein 2B and 3A inhibitors are used for unstable angina. It is kind of like a fancy IV aspirin.

If you care for acute presenting patients, you need to understand laboratory analysis at a very hight level.

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