Heparin-induced thrombocytopenia is a condition that can occur after the administration of heparin. In this condition, the number of platelets in the blood drops below 50 percent of normal.
What is heparin-induced thrombocytopenia?
Heparin-induced thrombocytopenia (HIT) is a complication of treatment with heparin. Heparin is a standard medical drug used for anticoagulation (inhibition of blood clotting). The administration of the active substance is intended to counteract thrombosis (blood clots). As a rule, therapy with heparin is considered to be quite useful. In some cases, however, a paradoxical effect of the drug may occur a few days after administration. This means that the thrombocytes (blood platelets) clump together, resulting in a decrease in the amount of thrombocytes in the blood. As the condition progresses, a heparin-induced platelet deficiency, also called thrombocytopenia or thrombocytopenia, occurs. Affected individuals are at increased risk of developing a blood clot. Overall, approximately ten percent of all treated patients suffer from heparin-induced thrombocytopenia.
Causes
In medicine, two different forms of heparin-induced thrombocytopenia are differentiated. They are called HIT type I and HIT type II and have different causes. In both cases, thrombocytopenia occurs only after administration of the heparin. The trigger for heparin-induced thrombocytopenia is an interaction between the platelets and the heparin. It is believed that the heparin is responsible for inhibiting an important enzyme, causing platelets to activate and aggregate more rapidly, which in turn results in more rapid consumption. However, HIT type I is considered harmless because only a minor platelet deficiency occurs and the complication resolves on its own after a few days. Because platelets do not normally fall below a level of 80,000/µl, no treatment is needed. Heparin-induced thrombocytopenia type II is due to a defense mechanism. Thus, antibodies are formed by the human immune system against the heparin in the blood, which in turn leads to clumping. There is a risk that the platelet count will drop to less than 50 percent of normal. If blood vessels become clogged as a result, there is a risk of serious health problems such as pulmonary embolism, stroke or heart attack. The risk of HIT type II increases with the duration of heparin treatment. If the physician administers the heparin for no longer than five days, complications rarely occur. The amount of heparin dose also plays a significant role in the development of HIT type II.
Symptoms, complaints, and signs
The symptoms that occur with heparin-induced thrombocytopenia depend on whether it is HIT type I or HIT type II, because the two forms take on different proportions. For example, most patients with HIT type I do not notice anything. After a few days, the disorder is resolved. In heparin-induced thrombocytopenia type II, on the other hand, the number of platelets decreases significantly, which becomes noticeable about 5 to 14 days after the start of treatment. If heparin is administered repeatedly, the antibodies form more quickly, so that they become apparent after only one to two days. The sharp drop in the number of platelets can lead to the formation of blood clots, which in the form of an embolism can cause a heart attack, among other things. The leg veins are also severely affected because the thromboses damage the tissue supplied by arteries. In extreme cases, amputation of the affected limb may even be necessary. Furthermore, pulmonary embolism, in which a pulmonary artery is displaced, is possible with pain, shortness of breath and fainting. Stroke is considered another life-threatening complication. Sometimes the tissue near the heparin injection site also dies.
Diagnosis and course
Suspicion of heparin-induced thrombocytopenia usually arises when the platelet count drops after heparin therapy, which occurs particularly in HIT type II. One of the most important diagnostic methods is a blood test to detect the lack of platelets. The blood test can also be used to detect heparin-specific antibodies, often using the ELISA method.Another test method is the HIPA method. Here, heparin is administered to the patient’s platelets to check for any clumping. Because some blood diseases have similar symptoms to heparin-induced thrombocytopenia, a differential diagnosis is also important. Here, it is important to exclude diseases such as diesseminated intravascular coagulation. The course depends on the type of heparin-induced thrombocytopenia that occurs. While HIT type I is mostly harmless, HIT type II often triggers venous thrombosis, which results in further serious complications.
Complications
This disease can lead to various symptoms and complications. In most cases, however, it goes unnoticed by the patient, with no particular symptoms occurring afterwards. The disease usually disappears on its own after only a few days. However, if there is a sharp decrease in platelets, symptoms may appear about a week later. This leads to blood clots, and the risk of a heart attack increases considerably. A heart attack can also cause the affected person to die in the worst case. Likewise, tissue throughout the body is damaged, which also affects the extremities. Extremities may die completely, and amputation may be necessary. It is not uncommon for respiratory distress and loss of consciousness to occur, and the patient may also suffer injuries or a fall in the process. The heart attack can also cause irreversible damage if it is not treated immediately. The treatment is carried out with the help of medication and usually leads to a quick relief of the symptoms. In most cases, life expectancy is not reduced if early treatment occurs.
When should you see a doctor?
If a diffuse feeling of illness persists, a physician should be consulted. If there are changes in blood circulation, heart problems or abnormalities in blood flow, a visit to the doctor is necessary. Pain in the body that appears or continues to spread without an apparent reason should be examined and treated. Consultation with a doctor is necessary as soon as the patient wants to take a medication because of the pain. Side effects often occur and must be clarified in advance and in good time. Increased vigilance is required in the event of respiratory disturbances. Respiratory distress should always be examined by a physician. If breathing stops or the heartbeat changes as a result, a doctor is needed. If the person suffers from anxiety or panic attacks, he or she should see a doctor. A disturbance of consciousness should also be investigated. If there is a failure to respond, an emergency physician must be called. Numbness on the skin or sensory disturbances must be clarified by a doctor. If sensory disturbances occur in the extremities or if there is unsteadiness of gait as well as problems with mobility, a doctor should be consulted. If there is an increased experience of stress, a decrease in usual performance or problems with concentration, a doctor should be consulted. Further investigation is necessary so that a cause can be found.
Treatment and therapy
If the suspicion of heparin-induced thrombocytopenia is confirmed, prompt medical treatment is necessary. Thus, it may be necessary not to wait for all laboratory tests until the start of therapy to gain valuable time. The most important part of the therapy is the discontinuation of heparin and the administration of another drug with a similar effect. This is usually the drug Argatroban. This drug reduces blood clotting but does not cause thrombocytopenia. Other drugs that may be considered are lepirudin and danaparoid. In addition, heparin must not enter the patient’s organism by other means. Thus, the drug may also be present in irrigations, ointments, or catheters.
Outlook and prognosis
The prognosis of heparin-induced thrombocytopenia depends on which type it is. Basically, there are two types of the disease. Type I heparin-induced thrombocytopenia is harmless and characterized only by a small decrease in platelet count. It usually runs without symptoms and also heals on its own. Treatment is therefore not necessary.In contrast, the outlook for heparin-induced thrombocytopenia type II is much worse. Here, the decrease in platelet count occurs very rapidly because antibodies against the heparin-protein complexes are formed. While the platelet count rarely falls below 100,000/µl in type I, it can fall extremely below this value in type II. In very rare cases, even lower values than 20,000/µl are possible. However, despite low platelet counts, there is usually no major bleeding and even increased thrombus formation because the antibodies lead to platelet activation. This is an acute life-threatening condition that requires immediate emergency medical attention. The administration of heparin must be immediately discontinued and replaced with other anticoagulants. The complications that occur in heparin-induced thrombocytopenia are almost entirely due to the secondary effects of the thrombi. Death can be caused by pulmonary embolism or myocardial infarction. Approximately 30 percent of all heparin-induced type II thrombocytopenias are lethal.
Prevention
To prevent heparin-induced thrombocytopenia, it is possible to administer low-molecular-weight heparin instead of conventional heparin. In this way, the risk of HIT is significantly reduced. In addition, the duration of therapy should be as short as possible.
Follow-up
In this disease, the affected person should first and foremost see a doctor as soon as possible to avoid further complications or other complaints. At the same time, the measures and the possibilities of aftercare in this disease are usually severely limited, so that the early detection and treatment of the disease is in the foreground. The earlier the affected person consults a doctor, the better the further course of the disease usually is, so that a doctor should be contacted already at the first symptoms and signs of the disease. In most cases, the disease is treated by discontinuing the triggering medication. However, the affected person should always discontinue this medication and take another medication only according to the doctor’s instructions. When taking medication, care should always be taken to ensure that the correct dosage is taken and that it is taken regularly in order to provide lasting relief from the symptoms. Furthermore, most sufferers are dependent on the help and support of their own family and friends in their everyday lives. In this context, loving and intensive conversations also have a positive effect on the course of the disease and can prevent psychological upsets or depression.
What you can do yourself
If heparin-induced thrombocytopenia is suspected, the most important action is to see a doctor. This is a medical emergency that requires medical intervention. First, the triggering drug must be discontinued and another drug with a similar effect must be prescribed. Most often, the drug Argatroban is prescribed, which lowers blood clotting and regulates blood pressure. The patient must ensure that heparin does not enter the organism by any other means. Thus, rinses, ointments or creams must be tested before use. Catheters may also contain the substance and should be checked before use. If further complaints occur, the doctor must be informed immediately. The same applies to side effects and interactions caused by the prescribed drugs. Other self-help measures are limited to taking care of the body and in particular the cardiovascular system. This can be achieved by avoiding strenuous physical activities in the first few weeks after the incident. The patient should also avoid stress and ensure a healthy night’s sleep. A balanced diet also contributes to a rapid recovery after heparin-induced thrombocytopenia.
