Platelets, or thrombocytes, are small, colorless cell fragments in our blood that form clots and stop or prevent bleeding. Platelets are made in our bone marrow, the sponge-like tissue inside our bones. Bone marrow contains stem cells that develop into red blood cells, white blood cells, and platelets.
Platelets are the tiny packages in the bloodstream that make up the body’s first response to bleeding. When we scratch or cut ourselves, platelets rapidly congregate in the area of injured blood vessels and initiate a series of events that effectively controls most bleeding. The platelets stick to each other and the vessel walls to form a platelet plug that blocks further blood loss. They also release chemicals that cause constriction of blood vessels and reduce blood flow to the bleeding area.
In addition, they stimulate the clotting cascade, a series of chemical reactions that help to form a longer-lasting and stronger clot that prevents blood loss until new tissue can grow to heal the injured area with scar tissue or regrown vascular cells.
Platelets can also be triggered to clump in areas where there is no dangerous bleeding. The most important of these is inside blood vessels where damage to the vessel’s lining occurs, sometimes by the rupture of an unstable cholesterol plaque. When this happens in a critical area like the coronary blood vessels of the brain, myocardial infarction or stroke can occur.
A low platelet count occurs when:
- A person’s bone marrow is damaged and unable to make enough of its own platelets. This can be caused by certain cancers, such as Leukemia – and it can also be caused by cancer treatments.
- Platelets have been lost due to severe bleeding, such as following a traumatic injury or during surgery.
- Platelets have been destroyed by autoimmune diseases, certain medicines, infections, or other conditions.
- The patient’s spleen, which filters the bloodstream, removes too many platelets.
Cancer and Platelets
Low platelet count is a major side effect of cancer treatment. Some types of chemotherapy can damage bone marrow, reducing platelet production. (This damage is usually temporary.) Other times, the cancer itself causes the problem. Leukemia and lymphoma can invade the bone marrow and prevent the patient’s body from producing the platelets it needs.
Without a platelet transfusion, these cancer patients face life-threatening bleeding.
Symptoms of low platelets include bruising easily and unusual bleeding, such as excessive bleeding from a small cut or blood in urine or stool.
Several medications have been found to interfere with platelet function. Aspirin was the first of these to be understood and remains an important medication used to inhibit platelet function and reduce the incidence of heart attack and stroke in patients at risk. Other medications used to inhibit platelet function include Plavix and others. These medications have been very important in reducing the incidence of early thrombosis in patients with endovascular procedures like stents for coronary artery disease, as well as in preventing second events in patients who have had a stroke or transient ischemic attack.
Some adults are felt to be at high enough risk to take a low dose of aspirin daily to reduce their risk of MI or stroke, whereas in others at lower risk of vascular events, the slightly increased risk of bleeding problems can neutralize or even out-weight the potential benefits. Ask your physician if taking low-dose aspirin is appropriate for you.