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Biomedical subjects

R D Hull

Publications and source records attributed to R D Hull.

At least 73 records · Page 4Linked to original sources
PubMed1996

Aging and heparin-related bleeding.

BACKGROUND: Many studies have suggested that elderly patients are at increased risk of bleeding during heparin therapy. OBJECTIVE: To establish whether the risk of bleeding in the elderly results from concomitant risk factors or is associated with the aging process itself. METHODS: One hundred ninety-nine patients who presented with proximal deep vein thrombosis were treated with a standard intravenous heparin protocol in a double-blind, randomized, prospective study. Bleeding complications were monitored. Activated partial thromboplastin times and heparin levels were assessed 4 to 6 hours after a standard intravenous heparin bolus and infusion. Heparin doses and heparin levels were also assessed after stable therapeutic heparin infusion rates were established. RESULTS: There was an increase in total and major bleeding complications with aging (P < .05) that was not accounted for by standard risk factors for bleeding. Aging was associated with an increase in heparin levels (r = .239, P = .003) and a tendency for an increase in activated partial thromboplastin time (r = .134, P = .07) after standard heparin doses. Aging was also associated with lower heparin dose requirements (r = .267, P = .003) after therapeutic activated partial thromboplastin times were achieved. CONCLUSION: Aging is a risk for heparin-related bleeding that may be explicable by age-related changes in the pharmacologic characteristics of heparin.

Adult↗
PubMed1996

Cost-effectiveness of pulmonary embolism diagnosis.

BACKGROUND: In recent years, improvements in the methods of clinical trials and the use of objective tests to detect venous thrombosis have enhanced the clinician's ability to diagnose pulmonary embolism. OBJECTIVE: To perform a cost-effectiveness analysis of the commonly recommended strategies for pulmonary embolism diagnosis and management. METHODS: Two criteria of effectiveness were used: correct identification of pulmonary embolism and correct identification of patients in whom treatment was unnecessary. The cost of each diagnostic alternative was defined as the direct cost of administering the diagnostic test plus the treatment cost associated with a positive test result. Data derived from a decision analysis published separately on 662 patients were used for this study. RESULTS: A strategy based on the use of ventilation-perfusion lung scans, serial impedance plethysmography, and pulmonary angiography was the most cost-effective. It remained so under all possible variations within the sensitivity analysis. CONCLUSIONS: The strategy that requires pulmonary angiography in the fewest patients is a combination of ventilation-perfusion lung scans and serial impedance plethysmography. This strategy also proved to be the most cost-effective.

Angiography↗
PubMed1996

Prevention and treatment of venous thromboembolism.

All patients at moderate to high risk for the development of venous thromboembolism should receive prophylaxis. The approaches of proven value include low dose heparin, low molecular weight heparin, oral anticoagulants and intermittent pneumatic compression. The use of one of the cited heparin nomograms will ensure that all patients are rapidly brought within the therapeutic range. Because of the varying sensitivities of thromboplastins, each laboratory should establish a therapeutic range using the activated partial thromboplastin time (APTT) which will correspond to 0.2 to 0.4 U/ml of heparin. Constant vigilance and a high level of suspicion are necessary to establish the clinical diagnosis of heparin-induced thrombocytopenia, and to institute appropriate therapy. Physicians should be aware of the sensitivity of the thromboplastin being used in the performance of the International Normalised Ratio (INR). Care must be taken to ensure that patients are maintained within the target therapeutic range for INR (in most cases 2 to 3) by frequent determination of the INR and appropriate adjustments of warfarin dosage. Low molecular weight heparin is the recommended approach to the initial management of venous thromboembolism where these agents are available. Patients with an acute episode of venous thromboembolism should receive warfarin therapy for at least 3 months. At the present time it is reasonable to treat the first recurrence with oral anticoagulants for a period of 12 months and indefinitely for more than 1 recurrence. For selected patients with acute massive pulmonary embolism, thrombolytic therapy with one of the available agents is recommended. However, the role of thrombolytic therapy in patients with proximal venous thrombosis remains unclear. In selected patients with acute venous thromboembolism who have contraindications to anticoagulant therapy or who-have objectively documented recurrent disease while on adequate therapy, the insertion of an inferior vena cava filter is recommended.

Anticoagulants↗
PubMed1995

Strategy that includes serial noninvasive leg tests for diagnosis of thromboembolic disease in patients with suspected acute pulmonary embolism based on data from PIOPED. Prospective Investigation of Pulmonary Embolism Diagnosis.

OBJECTIVE: To estimate the percentage of patients with suspected acute pulmonary embolism in whom a noninvasive diagnosis or exclusion of thromboembolic disease might be safely made on the basis of ventilation-perfusion (VQ) lung scans, single noninvasive tests of the lower extremities, and, in patients with adequate cardiorespiratory reserve, serial noninvasive tests of the lower extremities. METHODS: Calculations were made among 662 patients who participated in the collaborative study Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) and who had blood gas values measured while breathing room air and who underwent pulmonary angiography. The diagnostic strategy recommends treatment in all patients with a high-probability VQ scan and no treatment in patients with nearly normal VQ scans. In patients with nondiagnostic VQ scans (intermediate- or low-probability scans), a single noninvasive leg test is recommended. It was assumed that 50% of patients with pulmonary embolism would show deep venous thrombosis with a single noninvasive leg test. If results are abnormal, treatment is indicated. If normal, serial noninvasive leg tests are recommended. Treatment can be withheld if results of serial tests are normal. In patients with poor cardiorespiratory reserve, pulmonary angiography is indicated. RESULTS: A single noninvasive leg test in patients with nondiagnostic VQ scans would show deep venous thrombosis and, therefore, eliminate the need for pulmonary angiography in 53 (11%) of 468 patients (95% confidence interval [CI], 9% to 15%) who otherwise would require angiography. Serial noninvasive leg tests in patients with adequate cardiorespiratory reserve who had a normal result of a single leg test would either show deep venous thrombosis or exclude it in 222 (47%) of 468 patients (95% CI, 43% to 52%). The need for pulmonary angiography, therefore, would be reduced from 468 (71%) of 662 (95% CI, 67% to 74%) if no noninvasive leg tests were performed to 415 (63%) of 662 (95% CI, 59% to 66%) if only a single noninvasive leg test were performed, and further reduced to 193 (29%) of 662 (95% CI, 26% to 33%) if serial noninvasive leg tests were used where appropriate. CONCLUSION: A noninvasive strategy that includes VQ scans, single noninvasive leg tests, and serial noninvasive leg tests would permit a diagnosis of thromboembolic disease or a safe exclusion of thromboembolic disease in 71% of patients with suspected acute pulmonary embolism.

Acute Disease↗
PubMed1995

The low-probability lung scan. A need for change in nomenclature.

BACKGROUND: The prognosis in patients with suspected pulmonary embolism who have a low-probability lung scan has been the focus of much clinical debate. This is particularly so in patients with underlying cardiac and pulmonary disease, because these disorders frequently cause low-probability lung scans in the absence of pulmonary embolism. Historically, the clinical response has been to exclude pulmonary embolism and withhold treatment on the basis of a low-probability lung scan, which has been regarded as synonymous with a good prognosis. METHODS: A prospective cohort-analytic study to evaluate prognosis, using long-term follow-up, in patients with inadequate cardiorespiratory reserve who have presented with suspected pulmonary embolism (inadequate cardiorespiratory reserve, ie, pulmonary edema, right-ventricular failure, hypotension, syncope, acute tachyarrhythmia, abnormal spirometry [forced expiratory volume in 1 second, < 1.0, or vital capacity, < 1.5 L], or abnormal arterial blood gases [PO2, < 50 mm Hg, or PCO2, > 45 mm Hg]). RESULTS: The outcomes of the 77 consecutive patients with low-probability lung scans, suspected pulmonary embolism, and inadequate cardiorespiratory reserve were compared with those in 711 consecutive patients with good cardiorespiratory reserve and nondiagnostic lung scans who were entered into the study over the same period of time. Six (7.8%) of the 77 patients died within days of entry with autopsy-proven pulmonary embolism compared with one (0.14%) of the 711 patients with nondiagnostic lung scans (P < .0001). CONCLUSIONS: Our findings indicate that the term low-probability lung scan should be abandoned in reference to patients with inadequate cardiorespiratory reserve, because it is not synonymous with a good prognosis and is, indeed, misleading.

Adult↗
PubMed1995

Hirudin and hirudin analogues as new anticoagulant agents.

Recombinant hirudin and hirudin analogues constitute interesting new antithrombotic agents that have distinct advantages over heparin. These agents specifically inhibit thrombin and all of its actions and also suppress further thrombin generation. As opposed to unfractionated heparin, hirudin and hirulog effectively suppress clot-bound thrombin, making these agents of particular interest in the treatment of arterial thrombosis, for example, following thrombolysis or percutaneous transthoracic angioplasty. The recent data derived from clinical trials supporting the use of hirudin and hirulog in the prevention and treatment of thrombotic diseases are reviewed here.

Angina, Unstable↗
PubMed1995

Current concepts of anticoagulation therapy.

The use of heparin and warfarin in the treatment of venous thromboembolism has been revolutionized by the findings of clinical trials performed over the past decade. This article addresses some unanswered questions regarding the treatment of venous thromboembolism that are the subjects of current clinical trials, such as the optimum duration of oral anticoagulant therapy in patients with idiopathic or recurrent deep vein thrombosis and the role of low-molecular-weight heparin in the short-term and long-term treatment of venous thrombosis.

Heparin↗
PubMed1995

Management of venous thromboembolic disease. The impact of low-molecular-weight heparin.

Prophylaxis for DVT unequivocally is beneficial in patients identified to be at high risk. Heparin prophylaxis with subcutaneous low-dose UFH is adequate in some clinical settings but less effective in others. LMWH preparations are effective and safe as prophylaxis in certain medical patients as well as in general surgery and elective hip replacement. Efficacy and safety are demonstrated in the therapy of established venous thromboembolism. Subcutaneous administration of LMWH once or twice daily may prove more convenient from both the patient and nursing viewpoint, particularly in the treatment of established DVT. Monitoring is not necessary when using LMWH preparations as prophylaxis, and a fixed-dose without weight adjustment has been used in most prophylaxis trials. When treating established DVT, less monitoring is likely to be required than currently is the case with UFH. Although the cost of LMWH preparations is greater than that of UFH, the decrease in the occurrence or recurrence of thromboses that has been demonstrated in some trials might prove an effective balance. Future avenues to explore include discovery of better means to standardize the LMWH preparations and determination of the efficacy and safety of LMWH in specific populations, such as those in intensive care units, cancer patients, nursing home patients, and outpatients in general. Although cost-benefit is favorable thus far, meticulous assessment in other settings may enhance the acceptance of these agents. Long-term follow-up could be helpful in determining the relative effect of different heparin preparations on the frequency of postphlebitic syndrome. Comparison of different LMWH fractions may follow, as well as further investigations of newer ultra-low-molecular-weight agents. One LMWH preparation (enoxaparin) already has been approved in the United States for prophylaxis in the setting of elective hip replacement; and dalteparin has been approved here for use as DVT prophylaxis in patients undergoing abdominal surgery when there appears to be a significant risk of thromboembolism. It is likely that LMWH preparations will become even more widely used in North America and that the approved indications will expand to include prophylaxis in numerous settings and the treatment of established venous thromboembolism.

Clinical Trials as Topic↗
PubMed1995

Cost effectiveness of diagnosis of deep vein thrombosis in symptomatic patients.

BACKGROUND: The most widely used noninvasive test for deep vein thrombosis is Doppler ultrasonographic imaging of the lower extremities. The best evaluated of the noninvasive approaches are ascending contrast venography, impedance plethysmography, Doppler ultrasonography with B-mode imaging. Economic evaluation is aimed at helping decision makers to reach their goal of maximizing the health of the population served, subject to the available resources. METHODS: The data that provided the basis for this cost effectiveness analysis were derived from a prospective study of approximately 500 patients referred to a regional thromboembolism program with a first episode of clinically suspected deep vein thrombosis. The application of cost effectiveness analysis to the diagnosis of deep vein thrombosis is readily accomplished using cost minimization. This cost effectiveness technique makes it possible to rank the diagnostic approaches from "worst" to "best", with the best approach defined as that which accomplishes the desired health effect at minimum cost. Effectiveness (health benefit) may be defined in this context as the number or proportion of patients with deep vein thrombosis correctly identified by objective testing or, the number or proportion in whom treatment was correctly withheld. RESULTS: Clinical diagnosis is cost ineffective; $1,590,784 Canadian, $2,624,220 US. Outpatient diagnosis using noninvasive testing was the most cost effective. Serial Doppler ultrasonography is more costly ($618,265 Canadian, $1,326,180 US) than serial impedance plethysmography ($527,165 Canadian, $1,052,880 US). Combined Doppler ultrasonography and serial impedance plethysmography offers a less costly strategy ($551,065 Canadian, $1,124,580 US) than serial ultrasonography alone. DISCUSSION: Objective testing is mandatory. Outpatient testing is preferred, avoiding unnecessary hospital admissions. Noninvasive testing is the most cost effective. The most widely used test, serial Doppler ultrasonography, is less cost effective than serial impedance plethysmography. The combined approach of initial Doppler ultrasonography followed by serial impedance plethysmography combines the advantage of an initial ultrasound image with less costly serial impedance plethysmography.

Adolescent↗