Heparin

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                                          Anticoagulants Part 2:Heparin

On our first look at anticoagulants part 1, we looked at coumadin, the most commonly used oral anticoagulant. Now we will look at heparin, a commonly used injectable anticoagulant.

Heparin is a pharmaceutical preparation of the naturally occurring anticoagulant produced by white blood cells in various body tissues, obtained from pig intestines or the lungs of cattle. It is an injectable blood thinner used to treat & prevent the formation of clots and the extension of existing clots within the blood. It does not break down clots that have already formed, but it allows the body’s natural clot lysis mechanisms to work normally to break down clots that have formed.

It is normally given for deep vein thrombosis (DVT), pulmonary embolism, acute coronary syndrome, atrial fibrillation, and in the treatment of heart attacks & unstable angina.

Heparin acts immediately after IV injection and within 20-30 minutes after subcutaneous injection.

The activated partial thromboplastin time (aPTT) is a sensitive version of the PTT and is the most commonly used blood test to monitor heparin therapy. The aPTT evaluates the function of the intrinsic clotting system (as you can see on the coagulation cascade). It measures the clotting time of plasma, with a reference range of 30-40 seconds. The therapeutic range while on heparin therapy would be 45-75 seconds (or 1.5 – 2.5 times the mean normal value).

When an IV bolus of heparin is given, followed by a continuous IV infusion, the aPTT is evaluated every 6 hours during the first day of heparin therapy & 6 hours after any dosage change. If the aPTT is in the therapeutic range, it can be checked once daily while the patient is on heparin.

During the course of Heparin therapy, periodic platelet counts, hematocrits, and tests for blood in the stool are recommended.

The aPTT is NOT recommended for monitoring low molecular weight heparin (which we’ll discuss more later).

When an IV bolus of heparin is given, followed by a continuous IV infusion, the aPTT is evaluated every 6 hours during the first day of heparin therapy & 6 hours after any dosage change. If the aPTT is in the therapeutic range, it can be checked once daily while the patient is on heparin.

During the course of Heparin therapy, periodic platelet counts, hematocrits, and tests for blood in the stool are recommended.

The aPTT is NOT recommended for monitoring low molecular weight heparin.

The most common adverse effect of heparin is bleeding – hemorrhage can occur at virtually any site in patients receiving heparin.

Therefore, an unexplained fall in hematocrit, fall in blood pressure, or any other unexplained symptom should lead to further investigation of possible bleeding. The first sign of bleeding is usually seen as easy bruising, nosebleeds, blood in urine or tarry stools. There is also a decrease in blood platelets.

Other side effects of heparin therapy include elevation of liver enzymes, ALT & AST (in 80% of patients) and hyperkalemia, elevated potassium (in 5-10% of patients). More rarely, alopecia (hair loss) or osteoporosis may also be a side effect.

Most common adverse effect of Heparin: Bleeding
Investigate further if there is:
   Unexplained fall in hematocrit
   Fall in blood pressure
   Any other unexplained symptom 

First sign of bleeding seen as:
    Easy bruising
    Nosebleeds
    Blood in urine
    Tarry stools

Other side effects of heparin therapy:
    Elevation of liver enzymes, ALT & AST (in 80% of patients)
    Hyperkalemia, elevated potassium (in 5-10% of patients)
    Alopecia (hair loss) or osteoporosis

Similar to warfarin, heparin should NOT be given to patients with:
GI ulcerations                            Severe kidney or Liver disease 
Intracranial bleeding                 Severe hypertension 
Dissecting aortic aneurysm      Polycythemia vera 
Blood dyscrasias                       Recent surgery of the eye, spinal cord, or brain 


Heparin should be used cautiously in patients with:
Hypertension Drainage tubes (NG tube or urinary Catheter Renal or hepatic disease Threatened abortion Alcoholism Endocarditis History of GI ulcerations Any occupation with high risks of traumatic injury

Heparin-induced thrombocytopenia is a serious adverse effect of heparin and may occur in up to 30% of patients on heparin.

Heparin-induced thrombocytopenia (HIT) is caused by an immunological reaction that results in the development of antibodies that activate platelets. HIT may progress to the development of blood clots in the veins & arteries, a condition known as Heparin-induced thrombocytopenia and thrombosis.

HIT is a vicious cycle of platelet activation & coagulation, leading to thrombosis, embolism, and even death. The patient usually presents with a blood clot such as a DVT, pulmonary embolism, cerebral vein thrombosis, limb ischemia, stroke, heart attack, skin necrosis, gangrene of the extremities that may lead to amputation, and possibly death.

All patients exposed to any heparin are at risk. If the platelet count falls below 100,000/mm3 or if recurrent blood clots develop, Heparin should be discontinued immediately. HIT can even occur several weeks after stopping Heparin therapy.

If there has been an overdosage of heparin, the heparin effect can be neutralized by administering protamine sulfate injection, infused very slowly. Fatal reactions have been reported, so resuscitation techniques need to be readily available.

So far, we’ve been talking about standard heparin, which is a mixture of heparins of variable molecular weights. Low molecular weight heparin (LMWH) contains only the low weight heparins and was developed to obtain more effective & safer blood thinning treatment with fewer side effects. It is as effective as IV heparin in the treatment of blood clots. It is given SQ and does not require close monitoring of blood coagulation tests, allowing for outpatient anticoagulation therapy. The risk of heparin-induced thrombocytopenia and osteoporosis is decreased.

A commonly used LMWH is Lovenox (enoxaparin), which is given to prevent DVT in knee replacement surgery, hip replacement surgery, & abdominal surgery. It is also given for the treatment of DVT with or without pulmonary embolism, unstable angina, & heart attack.

Nursing tips for the patient on heparin therapy:
– Educate the patient regarding the reason they are taking heparin – for prevention, treatment, or both.
– Identify the correct dosage, frequency & duration.
– Demonstrate & have the patient return demonstrate the proper SQ administration of the LMWH (Lovenox) that will be taken at home.
– Review rotation of SQ injection sites.
– Do not skip, double up or change the dosage of the heparin – take exactly as prescribed by the health care provider.
– Do not use OTC medications or herbal products along with anticoagulants without discussing with the health care provider, as they may alter bleeding times.
– Assess the patient for falls or potential for injury, so as to prevent trauma & bleeding.


Anticoagulant Review
– Anticoagulant drugs are given to prevent the formation of new clots & the extension of clots already present.
– Coumadin (warfarin) is the most commonly used oral anticoagulant drug.
– Heparin is a commonly used injectable anticoagulant, given IV or SQ.
– Both are given to prevent or treat thromboembolic disorders such as DVT and pulmonary embolism.
– The PT and INR are used to monitor Coumadin therapy; the aPTT is used to monitor Heparin therapy.
– The main adverse effect of both is bleeding.

 

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