This may lead to thrombus formation and impaired function or occlusion of medical devices. The normal procedure is to control coagulation by administering UF heparin, although recent developments, which may promise fewer bleeding problems, include the use of LMW heparins or the concept of using heparin-coated membranes.
Hemorrhage is the main complication associated with heparin therapy, particularly when full dose heparin is injected intravenously. The risk is greater in the elderly, in patients with hypertension after trauma or surgery, and in patients with additional hemostatic abnormalities. The effect is usually moderate and is reversible once heparin administration is discontinued.
Following long-term heparin therapy, the development of osteoporosis bone loss can occur, with vertebral fractures as the predominant clinical sign.
Most cases reported are in connection with pregnancy. The precise cause of these heparin-induced reactions is at present unclear. Heparin has been shown to cause a prehaemorrhagic tendency in patients undergoing aspirin salicylates therapy. Of particular note is the fact that heparin may be inhibited by concurrent intravenous nitroglycerin infusion during the treatment of patients with unstable angina or in the acute postmyocardial infarction period.
The role of laboratory monitoring in heparin treatment according to Abildgaard. Individual variation in response to heparin is the main reason for monitoring heparin therapy. The purpose of monitoring heparin therapy is primarily to minimize the risk of haemorrhage from overdosage and to optimize the antithrombotic effect by appropriate dose adjustments. However, relatively few studies have been performed that clearly evaluate the usefulness of laboratory monitoring.
The main reason is the complex pharmacokinetics of heparin and the relatively weak correlation between the antithrombotic effect in vivo and anticoagulant activity in vitro.
Nevertheless, it is generally accepted that high-dose intravenous therapy with UF heparin should be monitored because of the danger of haemorrhage.
For LMW heparins there is currently no definitive recommendation in favor of monitoring although, considering the comparable hemorrhagic risk of LMW heparins to UF heparins, as well as the risk of undertreatment, it may be useful to test the anti-Xa activity at least once at the beginning of treatment.
Low doses of UF heparin or LMW heparin, given subcutaneously for prophylaxis of DVT seldom require monitoring, although it may be useful to document the anti-Xa level in the case of unexpected hemorrhagic episodes. The risk of bleeding depends not only on the dose but also on the individual response.
A large number of variables influence the antithrombotic and anticoagulant effect of heparin, including sex, age, weight, drug interactions, associated disease, extent of fibrin, vascular surfaces and the levels of various heparinbinding proteins. Elevated levels of heparin-binding proteins may contribute to heparin resistance in patients with inflammatory and malignant disorders.
In the case of LMW heparin, which is cleared mainly through the kidneys, it has been reported that renal insufficiency lowers the clearance rate and may result in a dangerous accumulation. Thus, it may be advisable to check the anti-Xa activity at the beginning of therapy in such patients irrespective of the severity of the impaired renal function.
The large variation in response to heparin calls for an individualization of the heparin dose regimen, according to the characteristics of the thrombosis and the patient.
The determination of the anticoagulant activity of UFH and LMW heparin is performed using a wide variety of assay methods. The most frequently used tests are the activated partial thromboplastin time APTT and the specific anti-factor Xa assays, using either a clotting or a chromogenic substrate method. Activated partial thromboplastin time APTT is a conventional screening test that measures the prolonged clotting time of recalcified citrate-anticoagulated plasma in the presence of heparin, by using a phospholipid reagent and a surface activator, such as kaolin.
However, the therapeutic range measured as an APTT ratio differs between varius different commercial thromboplastin reagents. Therefore it is recommended to calibrate the therapeutic ratio for each APTT reagent, to be equivalent to a heparin level of 0. Since the APTT is a global test, it measures the overall coagulability of a blood sample and not the specific presence of heparin alone. Therefore this test has important limitations that must be taken into consideration.
A frequent clinical situation is the cross-over to oral warfarin therapy from intravenous heparin therapy. It takes about three days for warfarin to reach therapeutic effect and the drug is usually administered concurrently with heparin during this period.
Since warfarin prolongs APTT it may prompt the clinician to decrease heparin administration. Heparin is commonly included in the thrombolytic treatment of myocardial infarction. Because the APTT is prolonged during thrombolytic thearpy with t-PA, it is not a clear indicator of heparin anticoagulation.
If the APTT is not prolonged as expected in patients receiving intravenous heparin, this may be a result of altered levels of coagulation proteins.
There are four main situations in which this may occur: increased fibrinogen, increased factor VIII, increased platelet factor 4 and decreased antithrombin.
The lupus anticoagulants have been shown to react with anionic phospholipids and may therefore cause prolonged APTT. As a result, the usual therapeutic range for heparin is no longer valid. Unlike the APTT, the anti-factor Xa assays are more specific since they measure the ability of heparin-accelerated antithrombin to inhibit a single enzyme.
Either plasma or purified antithrombin can be used, and residual enzyme can be measured by its clotting activity or amidolytically by a chromogenic peptide substrate. The clotting assay introduced by Yin et al in is based on the heparin-accelerated inhibition of factor Xa.
During the initial phase of the reaction, the amount of neutralized factor Xa is proportional to the heparin concentration if antithrombin is present in excess. Residual factor Xa is then measured using a clotting technique. If we combine this information with your PHI, we will treat all of that information as PHI, and will only use or disclose that information as set forth in our notice of privacy practices.
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This content does not have an English version. By blocking the process early on, both warfarin and heparin ultimately help to reduce blood clots from forming in your body. Warfarin comes in tablet form, and heparin must be given as an injection. The amount of medication needed differs with each person and each situation, and individuals on these medications should be closely monitored by their doctors to ensure that they are being given the correct dose.
Warfarin Coumadin is not safe during pregnancy. It can cause birth defects and fetal bleeding. Women who take warfarin must switch to heparin or low molecular weight heparin before they become pregnant, since heparin or low molecular weight heparin Lovenox, Fragmin do not cross the placenta into the fetus.
Do not smoke or drink alcohol while taking anticoagulants. Smoking increases the risk of blood clots and cardiovascular disease, and cardiovascular disease is the number one cause of death in people with lupus. Alcohol can interfere with the effectiveness of anticoagulant medications, can be harmful to your liver, and can irritate your stomach gastritis , causing bleeding. Warfarin is the most widely used anticoagulant, but because everyone differs in their physiological make-up, dosage requirements differ from person to person.
Blood clotting is a natural protective mechanism employed by the body to seal off damaged blood vessels; any medication that alters this natural protective mechanism must be carefully monitored.
People taking warfarin must obtain a blood test every weeks to ensure that their blood is thinning to the correct degree without bleeding complications. This test the INR, discussed below may be requested several times a week at the beginning of your treatment to ensure that you are started on the correct dose. In actuality, Prothrombin time is the test used, and INR is simply a standardized way for medical institutions to report consistent values for Prothrombin times.
The INR ratio is calculated based on comparison of blood tests against a known standard, and your physician will monitor your warfarin levels based on this INR ratio. Generally, an INR of 2. Heparin works faster than warfarin, so it is usually given in situations where an immediate effect is desired. For example, this medication is often given in hospitals to prevent growth of a previously detected blood clot.
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