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Biomedical subjects

William H Wehrmacher

Publications and source records attributed to William H Wehrmacher.

11 recordsLinked to original sources
PubMed2006

Thromboembolism in cancer patients: pathogenesis and treatment.

In this review we summarize the causes of cancer related thrombosis as well as modern treatment approaches. Malignancy as a risk factor for thromboembolism is becoming increasingly recognized by clinicians caring for these patients. The probability of thrombosis occurring in an individual patient is dependent on several factors, including accompanying medical problems, the type of cancer, the clinical stage, performance status, and the treatment modalities employed. Thrombophilia with a history of thromboembolism is important as well. The overall risk of thrombosis is sevenfold that of noncancer patients. Though much has been learned about the pathogenesis of cancer-related thrombosis, we are in fact just beginning to understand the cross-talk between cancer cells and their related microenvironment, and such investigations are likely to increase our knowledge of cancer-related thrombosis mechanisms. Research in these areas may also suggest new strategies for cancer prevention, metastasis suppression, and new treatments. Drugs used in cancer therapy are increasingly recognized to directly contribute to the thrombotic tendency. Few studies provide data on the optimal management of cancer patients with thrombosis. It has been learned that retreating with the same drug can be very hazardous. In general the approach to prevention of thrombosis is the same as for noncancer patients, recognizing that specific cancer types and stage can place a patient in a high-risk category. Initial coumadin therapy fails in a significant number of patients with cancer. Recognition of the cancer patients at highest risk for coumadin failure is challenging. Low-molecular-weight heparins appear to be more effective in such situations where coumadin is likely to fail or has failed, but these drugs are thought to be costlier. Newer agents such as Factor Xa inhibitors and TF inhibitors are currently under investigation and may be found useful in the management of cancer-related thrombosis.

Anticoagulants↗
PubMed2004

Unstable angina.

Properly treated unstable angina and non-Q wave myocardial infarction have low hospital mortality, but untreated, mortality is high. Symptoms and labs usually suffice for diagnosis. Abnormal physical findings are rarely helpful and often absent. Careful surveillance and management substantially reduce long-term risks.

Angina, Unstable↗
PubMed2004

Heparin to pentasaccharide and beyond: the end is not in sight.

The 87-year history of heparin began in 1916 when a 26-year-old medical student named Jay McLean startled his mentor William Howell, Professor of Physiology at Johns Hopkins University, by proclaiming that he had discovered "antithrombin." This discovery was so surprising to Howell because he had expected McLean to isolate thromboplastin, a clot-promoting substance from animal tissue. In 1928, Charles Best, M.D., in Toronto, Canada, organized a team of chemists, physiologists, and surgeons to focus on the development of heparin. This group determined which animal tissues were the best source, had performed purification and identification, and had determined pharmacologic properties in vitro. By 1935, they were ready for human trials. By 1941, the group reported a series of 700 patients treated with the glycosaminoglycan called heparin. Meanwhile a critical cofactor, antithrombin, had been discovered at the University of Iowa (Brinkhous, et al). Introduction of newer tests for laboratory monitoring enabled refinement of dosages during the 1960s and 1970s. Its use permitted the development of hemodialysis and cardiopulmonary bypass surgery, and the prophylaxis of deep vein thrombosis in surgical patients. The concept of low-molecular-weight heparin occurred to Dr. Choay and others in France in the late 1970s. During the 1980s and 1990s, the development of low-molecular-weight heparins evolved for both prophylaxis and therapy. The first synthetic product was called the pentasaccharide, named for the five critical sugar units in heparin that bind to antithrombin (1983). Since then, this drug has been studied extensively to prove its clinical efficacy and safety.

Heparin↗
PubMed2003

Differential effects of DX-9065a, argatroban, and synthetic pentasaccharide on tissue thromboplastin inhibition test and dilute Russell's viper venom test.

New synthetic direct and indirect factor Xa or factor IIa inhibitors are increasingly used for the prevention and treatment of thrombotic disorders, including patients suffering from antiphospholipid syndrome. In this study, the effects of the synthetic direct factor Xa inhibitor DX-9065a, the indirect synthetic heparinomimetic pentasaccharide, and the direct factor IIa inhibitor Argatroban were studied. These two widely used assays for the detection of lupus anticoagulant, namely the tissue thromboplastin inhibition (TTIT) and the dilute Russell viper venom tests (DRWT) proved useful. The drugs were added to a normal human plasma pool ranging in concentration from 0.04 to 10 microg/mL. Using the two tests named above, DX-9065a and Argatroban showed a dose-related prolongation of TTIT and DRWT in the concentration range from 0.04 to 5 micromol/mL, but the pentasaccharide only slightly prolonged the clotting times of these assays even at high concentrations. Argatroban had the more pronounced effect on both tests when compared with DX-9065a (p < 0.001). The most responsive assay for DX-9065a up to a concentration of 2.5 micromol/mL was the DRWT. For Argatroban both TTIT and DRWT were equally responsive. Patients whose plasma was tested for suspected lupus anticoagulant and who have been given DX-9065a or Argatroban may have false-positive results with the TTIT tests and DRWT. This effect should be considered during patient management. These results indicate that these assays could be used for the effective quantitation of the direct factor Xa or factor IIa inhibitors when suitable controls are used.

Anticoagulants↗
PubMed2002

Reference ranges of the dilute tissue thromboplastin inhibition and dilute Russell's viper venom tests revisited.

Reference ranges for two well-recognized tests for the lupus anticoagulant were determined utilizing 98 healthy subjects. The purpose of the study was to compare the reference ranges for the dilute tissue thromboplastin inhibition test on this group of healthy subjects calculated by parametric and nonparametric statistical methods, and to compare these results with results obtained on subsets of 20 and 40 randomly selected individuals from the group of 98. The same procedures were followed for the dilute Russell's viper venom test. Results were recorded in seconds of clotting times and in ratios (subject/mean of that set or subset). Statistical analysis revealed Gaussian distribution of the results in the large group as well as in each subset for both tests. The results showed more variation between sets of the dilute tissue thromboplastin inhibition test than of the dilute Russell's viper venom test. Nonparametrically calculated reference ranges were wider than those determined by a parametric method, especially if confidence intervals are provided for both reference ranges in the group of 94 controls or in a subset of 40 subjects. The nonparametric technique utilizes all data for the calculation of reference ranges of such sample sizes no matter how wide the results are spread. There was no significant difference between the reference ranges of subsets and the whole group (p > 0.05) calculated by both statistical techniques.

Adolescent↗
PubMed2002

Reference intervals of the dilute tissue thromboplastin inhibition and dilute Russell's viper venom tests revisited.

Reference intervals for two well-recognized tests for the lupus anticoagulant were determined using 98 healthy subjects. The purpose of the study was to compare the reference intervals for the dilute tissue thromboplastin inhibition test on this group of healthy subjects calculated by parametric and nonparametric statistical methods, and to compare these results with results obtained on subsets of 20 and 40 randomly selected individuals from the group of 98. The same procedures were followed for the dilute Russell's viper venom test. Results were recorded in seconds of clotting times and in ratios (subject/mean of that set or subset). Statistical analysis revealed Gaussian distribution of the results in the large group as well as in each subset for both tests. The results showed more variation between sets of the dilute tissue thromboplastin inhibition test than of the dilute Russell's viper venom test. Nonparametrically calculated reference intervals were wider than those determined by the parametric method, especially if confidence intervals are provided for both reference limits in a group of 94 controls or in a subset of 40 subjects. The nonparametric technique uses all data for the calculation of reference interval of such sample sizes no matter how widely spread the results are. There was no significant difference between the reference intervals of subsets and the whole group (p > 0.05) calculated by both statistical techniques. Very few outliers were observed among these subjects in both tests.

Blood Coagulation Tests↗