A standard heparin nomogram for the management of heparin therapy

Article Abstract:

Heparin is used to prevent blood clots in patients who have had heart attacks, thrombophlebitis (clots in the veins), or other conditions caused by blood clots, but care must be taken because heparin may also lead to hemorrhage. Patient response to heparin varies greatly, so normally the effect is monitored by laboratory tests to maintain the activated partial thromboplastin time (APTT) (an index of blood clotting time) within defined limits. The sooner the optimum effect of heparin is reached, the smaller the risk of further clotting, but the risk of bleeding increases if the APTT is prolonged. Usually heparin is administered by injection, and then intravenously, during which period it is monitored at least once a day. A nomogram (plot of a relationship between variables) was developed to adjust the heparin dosage to standardize therapy, avoid delays, and prevent inadequate anticoagulation or overanticoagulation during heparin administration. Fifty patients with acute venous thromboembolism (clots in veins) had their dosage regulated according to the nomogram, and these patients were compared with 53 previously treated patients. By using the nomogram, 66 percent of the patients reached therapeutic levels at 24 hours, and 81 percent at 48 hours. Among the control group, the numbers were 37 percent and 58 percent, respectively. There was also more rapid correction of APTT values outside the therapeutic range by means of the nomogram. The nomogram has proved useful in adjusting the dosage of heparin to maximize its anticlotting effect while minimizing side effects. (Consumer Summary produced by Reliance Medical Information, Inc.)

Models, Usage, Drug therapy, Thrombophlebitis, Dosage and administration, Dose-response relationship (Biochemistry), Dose-response relationship, Nomography (Mathematics)

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Prevention of deep vein thrombosis after elective hip surgery: a randomized trial comparing low molecular weight heparin with standard unfractionated heparin

Article Abstract:

Heparin is an anticoagulant or anticlotting drug composed of multiple subunits of varying weights. In animal studies, low molecular weight (LMW) heparin has been shown to have an anticlot, or antithrombotic, effect with fewer bleeding complications than standard heparin, but human trials have not yet shown the same results. One surgical procedure with a high risk of postoperative clotting complications is hip replacement, but orthopedic surgeons are generally reluctant to institute heparin therapy because of a concern for bleeding complications. Nearly 700 patients undergoing elective hip surgery were randomly assigned to a postoperative regimen if either standard heparin or LMW heparin, and followed with several tests for evidence of thrombosis (clot formation) in their legs. Thrombosis was identified in 50 patients in the LMW group and 61 patients in the standard heparin group. This difference was not statistically significant. Bleeding complications were noted in 31 patients (9.3 percent) in the standard heparin group and 17 (5.1 percent) of the LMW group patients, yielding a relative risk reduction of 42 percent, which was found to be statistically significant. As up to 50 percent of patients having elective hip surgery will develop a blood clot, with up to 4 percent mortality, use of antithrombotic therapy seems indicated. The lower rate of bleeding complications associated with LMW heparin might make antithrombotic therapy more acceptable to surgeons, but for now LMW heparin is still an investigational drug. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Prevention, Risk factors, Surgery, Hip

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Limitations of impedance plethysmography in the diagnosis of clinically suspected deep-vein thrombosis

Article Abstract:

Impedance plethysmography (IPG) may not be an effective method for diagnosis of deep-vein thrombosis (DVT), or blood clot formation in a major vein. A plethysmograph is an instrument that measures variations in the amount of blood present or passing through an organ, limb or other type of body part. Among 142 patients who underwent venography for suspected DVT, 57 had abnormal results from impedance plethysmography and 85 had normal results. Sixty-six percent of the patients diagnosed with DVT after venography had had an abnormal IPG. Sixty-three percent of the patients with DVT who were missed using impedance plethysmography had large blood clots that blocked a blood vessel. Sixty-five percent of the patients with abnormal results on impedance plethysmography were diagnosed with DVT after undergoing venography.

Diagnosis, Impedance plethysmography

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