Warfarin dosage requirements: prospective clinical trial of a method for prediction from the response to a single dose

We have previously described a model for predicting individual daily maintenance dosage (MD) requirements of warfarin 24 h after the administration of a single dose. This model relies on measurement of the initial anticoagulant response as the 24 h percentage fall in plasma clotting factor VII activity. It permits prediction of the individual MD given the size of the initial dose, a baseline and desired maintenance value of the prothrombin ratio, and a baseline and 24 h plasma level of factor VII activity. We now present the results of a prospective clinical trial of the method. Data from 65 patients were suitable for analysis. The mean daily MD of warfarin was 4.0 mg (range 1-10 mg). There was a moderately strong linear relationship between predicted and actual MDs of warfarin (r = 0.66, P less than 0.001). Actual vs predicted MDs in individual patients were not significantly different. The mean difference was 0.39 mg. The results of this prospective trial suggest that our model predicts warfarin MD requirements with reasonable accuracy. Nevertheless, the accuracy of the model is not sufficient to replace careful clinical and haematological monitoring of each patient commencing warfarin therapy.

Depth-dose curves for 90Sr and natural and depleted uranium in Mylar

Strontium and uranium are common sources used to calibrate personal dosimeters and survey meters for beta radiation. Since the absorbed dose rate of low-penetrating beta radiation decreases significantly with increased depth in tissue or dosimeters, it is necessary to describe the dose rate accurately as a function of depth. Complete depth dose information from zero to 1000 mg/cm2 is currently unavailable for strontium and uranium. This paper describes the generation of accurate depth-dose curves in Mylar for 90Sr and slabs of natural and depleted uranium from 0 to 1000 mg/cm2, utilizing an extrapolation chamber. The absorbed dose rate produced by natural uranium was found to decrease from 235 mrad/hr at a depth of 7 mg/cm2 to 43 mrad/hr at 300 mg/cm2 to 4.8 mrad/hr at 1000 mg/cm2. The dose rate produced by depleted uranium was found to decrease from 205 mrad/hr at 7 mg/cm2 to 34 mrad/hr at 300 mg/cm2 to 2.3 mrad/hr at 1000 mg/cm2. A 1-mCi extended area 90Sr source (encapsulated in 50 mg/cm2 AG) was found to produce an absorbed dose rate of 16,997 mrad/hr at 57 mg/cm2, 5000 mrad/hr at 300 mg/cm2, and 27.1 mrad/hr at 1050 mg/cm2. Doses to deep organs have been determined historically at depths ranging from 300 to 1000 mg/cm2. The results of this study show that 90Sr and uranium produce significant absorbed dose rates at a depth of 300 mg/cm2. Thus, if doses for deep depths are determined at 300 mg/cm2 for mixed beta-gamma exposures, the dose will be overestimated due to the presence of the beta component. The depth-dose curves generated in this study can be used by dosimeter processors to normalize the response of their dosimeters to the shallow (7 mg/cm2) and deep (1000 mg/cm2) depths defined by the U.S. Nuclear Regulatory Commission.

Enhancement of fibrinolysis in rabbits exposed to low and moderate levels of carbon monoxide inhibited by epsilon amino caproic acid

The first (control) group of rabbits breathed ambient air whereas the second was exposed to low level carbon monoxide (CO, 50 ppm by volume) for 24 hr continuously for 8 weeks. The third group was exposed to 300 ppm CO for 4 weeks. The fourth group was exposed to 300 ppm CO for the same period of time as the third group but in addition they were also given epsilon amino caproic acid (EACA) orally, and the results compared to Group III. Per cent oxyhemoglobin (HbO2), per cent hemoglobin (Hb) and per cent carboxyhemoglobin (HbCO) were monitored in all groups. Tests of fibrinolysis were monitored and showed acceleration of the whole blood clot lysis and euglobulin lysis times (ELT). A fibrin plate test confirmed the increased lysis and serum fibrin and/or fibrinogen degradation products (FDP) were elevated in the CO exposed animals. No changes were observed in the same tests in the rabbits exposed to ambient air. The fourth group of animals receiving EACA showed inhibition of lysis and decrease in serum FDP. Alpha-1-antitrypsin and alpha-2-macroglobulin assays in all groups showed no change. Microscopic examination of the large vessels in these test groups showed endothelial damage which indicates a possible source for a plasminogen activator release, or lead to action of Hageman factor and activated plasma plasminogen proactivator.

Endrin induced alterations in bound carbohydrates in rat serum

Endrin (1 mg per kg body weight) was daily administered intraperitoneally to rats which were sacrificed in groups of 10 after 5, 12 and 19 days and analyses of blood serums were conpared to appropriate controls. No alterations were found in the concentrations of general serum protein or paper electrophoretically separated serum lipoproteins, albumin, alpha1, alpha2, beta or gamma globulins. Protein bound sialic acid and methyl pentose had increased by the 5th day, remained elevated through the 12th day and appeared to be decreasing back toward control values by the 19th day although these values were still above normal. Bound hexose demonstrated no changes for the first 12 days but had increased significantly by 19 days. Bound hexosamine was significantly decreased by the end of 5 days and remained at this depressed level for the 19 days.