Heparin is a medication that is used in hospitals across the world to prevent blood clot formation. Heparin can be given either directly into the bloodstream, or as an injection under the skin. No oral form of heparin is available.
When is Heparin Used in the Hospital?Heparin has many uses, but nearly all of them aim to prevent the formation of blood clots. Below are some of the most common reasons heparin is used by physicians.
- To prevent the formation of dangerous blood clots in people who must stay in bed for prolonged periods of time. This can be accomplished with a low daily dose of this medication which is typically given under the skin, which is known to prevent the formation of deep venous thromboses, or DVTs in the deep veins of the legs, thighs, and pelvis. Such blood clots are known as DVTs for short, and are well known to cause strokes and pulmonary embolisms, (PEs) which can be lethal (see below).
- To treat pulmonary embolisms: Pulmonary embolisms are blood clots that migrate into the lungs from the heart, or from the deep venous system of the body. Once in the lungs, pulmonary embolisms can block blood flow to large portions of the lung and prevent oxygen-poor, venous blood from being repleted with oxygen. As stated previously, PEs can be lethal.
- To prevent the enlargement of high risk blood clots found inside the heart, and other parts of the body, as they can cause pulmonary embolisms or strokes.
- To prevent the formation of blood clots during heart surgery, or during surgery of the large arteries.
When is Heparin Used to Treat Stroke?Heparin is used to treat strokes that are caused by identifiable blood clots.
Strokes commonly associated with blood clots, and treated with heparin in the hospital include:
- Carotid or vertebral dissection
- Dural sinus thrombosis
- When an ultrasound of a stroke patient shows a Deep venous thrombosis
- When the EKG in a stroke patient shows atrial fibrillation
- When a carotid dopler test suggests that a blood clot is sitting inside the carotid artery, or an echocardiogram shows a blood clot inside the heart.
Intravenous Heparin DosageUnlike most medications, the dose of heparin must be chosen according to the results of a blood test called the partial thromboplastin time or PTT. Once an intravenous infusion of heparin is started, its dose is adjusted every 4 to 6 hours in order to ensure that blood does not become so thin that a person runs the risk of spontaneous bleeding.
On the average, most heparin treatment protocols call for a one-time "bolus injection" of heparin followed by a slow increase of the dose to a PTT that is roughly twice the normal value.
Because there is no oral form of this medication, heparin must be stopped before a person leaves the hospital. People who need long-term therapy with blood thinners are commonly prescribed coumadin, another powerful blood thinner which is available in a tablet form. Coumadin is started while patients are still receiving intravenous heparin, but once blood tests show that coumadin's blood thinning effect is adequate, heparin can be stopped. This is done because coumadin can take up to 72 hours before its desired effect is reached.
Heparin side effectsThe main side effect of heparin is bleeding. For this reason, it is important that physicians follow blood counts when people are being treated with intravenous heparin in order to ensure that blood counts remain stable during treatment. Spontaneous bleeding can occur from several places in the body including:
- Open wounds or surgical sites
- The stomach and intestines
- The uterus and ovaries
- The gums and mouth
In cases of profuse bleeding due to heparin treatment, a medication called protamine sulfate can be given intravenously to neutralize heparin's blood-thinning effect. In cases of severe bleeding blood transfusions are required to replace the blood lost.
Another important side effect of heparin is a condition known as heparin-induced thrombocytopenia (HIT). In this condition heparin induces the body's immune system to develop antibodies against its own platelets. Since a normal level of platelets is required by the body to prevent bleeding, a low level of platelets places people at risk of major bleeding. Paradoxically, this same condition can also cause the inappropriate and spontaneous formation of large blood clots, which can block blood flow through important blood vessels and damage the kidneys, the skin, and the brain, among other organs.
J Philip Kistler, MD, Karen L Furie, MD, MPH, Hakan Ay, MD, Treatment for specific causes of ischemic stroke and transient ischemic attack. In: UpToDate, Rose, BD (Ed), UpToDate, Waltham, MA, 2008.
Heparin: Drug information. In: UpToDate, Rose, BD (Ed), UpToDate, Waltham, MA, 2008.