Biomedical subjects
Brent G Petty
Publications and source records attributed to Brent G Petty.
Limitations of D-dimer testing in unselected inpatients with suspected venous thromboembolism.
PURPOSE: To determine the utility and limitations of D-dimer testing for the evaluation of venous thromboembolism in hospitalized patients. METHODS: We performed D-dimer testing by four different methods in unselected inpatients undergoing radiologic evaluation for possible venous thromboembolism. We included patients with a history of malignancy, recent surgery, thrombosis, and anticoagulation treatment. C-reactive protein levels were assayed as a measure of inflammation. RESULTS: Of 45 patients with radiographically proven proximal deep venous thrombosis or pulmonary embolism, 43 had elevated D-dimer levels by enzyme-linked immunosorbent assay (ELISA) (sensitivity, 96%); the specificity of the test was 23% (36/157). The qualitative non-ELISA tests had higher specificities, but their sensitivities were <70%. Nineteen patients (42%) with thrombosis had false-negative D-dimer tests by at least one assay. The specificity of the tests decreased with increasing duration of hospitalization, increasing age, and increasing C-reactive protein levels. D-dimer testing had little or no utility in distinguishing patients with thrombosis from those without in patients who had been hospitalized for more than 3 days, were older than 60 years, or had C-reactive protein levels in the highest quartile. CONCLUSION: In unselected inpatients, D-dimer testing has limited clinical utility because of its poor specificity. This is particularly true for older patients, those who have undergone prolonged hospitalization, and those with markedly elevated C-reactive protein levels. In some patient subsets, a negative non-ELISA D-dimer test cannot discriminate between inpatients with and without thrombosis.
Perioperative medication management.
One of the consultant's roles is to make recommendations regarding the use of medications in the perioperative period. Unfortunately, the data in this area are often insufficient to provide evidence-based recommendations. In this article, we have provided advice considering the pharmacokinetics of the drug, the effect on the primary disease of stopping medications, and the effect of the medication on perioperative risk, including potential drug interactions with anesthetic agents.
Risks and benefits of anticoagulant and antiplatelet medication use before cataract surgery.
OBJECTIVE: To estimate the risks and benefits associated with continuation of anticoagulants or antiplatelet medication use before cataract surgery. DESIGN: Prospective cohort study. PARTICIPANTS: Patients 50 and older scheduled for 19,283 cataract surgeries at nine centers in the United States and Canada between June 1995 and June 1997. INTERVENTION: None. MAIN OUTCOME MEASURES: Intraoperative and postoperative (within 7 days) retrobulbar hemorrhage, vitreous or choroidal hemorrhage, hyphema, transient ischemic attack (TIA), stroke, deep vein thrombosis, myocardial ischemia, and myocardial infarction. RESULTS: Before cataract surgery 24.2% and 4.0% of patients routinely used aspirin and warfarin, respectively. Among routine users, 22.5% of aspirin users and 28.3% of warfarin users discontinued these medications before surgery. The rates of stroke, TIA, or deep vein thrombosis were 1.5/1000 among those who did not use aspirin or warfarin and 3.8/1000 surgeries among routine users of aspirin and warfarin who continued their medication before surgery. The rate was 1 event per 1000 surgeries among those who discontinued aspirin use (relative risk = 0.7, 95% confidence interval = 0.1-5.9). There were no events among warfarin users who discontinued use. The rates of myocardial infarction or ischemia were 5.1/1000 surgeries (aspirin) and 7.6/1000 surgeries (warfarin) among routine continuous users and no different from those of routine users who discontinued use. CONCLUSIONS: The risks of medical and ophthalmic events surrounding cataract surgery were so low that absolute differences in risk associated with changes in routine anticoagulant or antiplatelet use were minimal.
A methacholine challenge dose-response study for development of a pharmacodynamic bioequivalence methodology for albuterol metered- dose inhalers.
BACKGROUND: With the expiration of the patent on albuterol metered-dose inhalers (MDIs) in 1989, methods to assess in vivo bioequivalence of generic formulations required investigation. OBJECTIVE: In an effort to develop a sensitive method to document bioequivalence, bronchoprovocation with methacholine chloride was used to assess the dose-response relationship of albuterol as delivered by MDI. Sensitivity was assessed in terms of magnitudes of ED(50), the estimated albuterol dose required to achieve 50 % of the fitted maximal value of the pharmacodynamic effect above baseline, and change in response as a function of dose, with emphasis on 1 and 2 actuations. METHODS: On separate study days, 15 nonsmokers with mild asthma received randomized nominal albuterol doses of 0 to 576 microg by using specially manufactured MDI canisters. FEV(1) was measured 15 minutes after MDI dosing. Serially increasing doses of methacholine were administered, and FEV(1) was measured after each methacholine dose until a 20 % decrease in FEV(1) (PD(20)) was achieved. RESULTS: Mean PD(20) values after use of each of the albuterol-containing MDIs were significantly greater than either mean screening or mean placebo PD(20) values (P <.05). Mean responses and most individual subject responses to 1 and 2 actuations (90 and 180 microg) of albuterol MDI were within the sensitive region of the dose- response curve. The mean estimated ED(50) value on the basis of nonlinear mixed effect modeling was 119.2 microg (range, 33.3-337.1 microg), with an intersubject percentage coefficient of variation of 69.0 %. CONCLUSIONS: The methacholine bronchoprovocation model is safe and useful in the study of albuterol MDI dose-response in asthmatic subjects. Bronchoprovocation studies may be used for determination of bioequivalence of multisource albuterol MDI products.