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Biomedical subjects

R D Hull

Publications and source records attributed to R D Hull.

At least 127 records · Page 7Linked to original sources
PubMed1986

A randomized controlled trial of a low-molecular-weight heparin (enoxaparin) to prevent deep-vein thrombosis in patients undergoing elective hip surgery.

There is experimental evidence that low-molecular-weight fractions of heparin are as effective as the standard form but cause less bleeding. We therefore performed a double-blind, randomized trial comparing PK10169 low-molecular-weight heparin with placebo for the prevention of venous thrombosis in patients undergoing elective hip surgery. Prophylactic treatment with a fixed dose was begun postoperatively and continued for 14 days. Fifty patients in each treatment group underwent surveillance with [125I]fibrinogen leg scanning and impedance plethysmography. In the first 24 patients, venography was performed only if either surveillance test was positive. Because the rate of venous thrombosis detected in those patients was unexpectedly low, venography was requested in the remaining 76 patients, even if the screening tests were negative. In this latter group, venous thrombosis occurred in 4 patients (10.8 percent) given PK10169 heparin and 20 patients (51.3 percent) given placebo (P = 0.0002); the corresponding rates for proximal-vein thrombosis were 5.4 percent and 23.1 percent, respectively (P = 0.029). In the entire group of 100 patients, venous thrombosis occurred in 12 percent of those given PK10169 heparin and 42 percent of those given placebo (P = 0.0007), and the corresponding rates for proximalvein thrombi were 4 percent and 20 percent, respectively (P = 0.014). The observed hemorrhagic rate was 4 percent in each treatment group. We conclude that prophylaxis with fixed-dose PK10169 heparin is effective and safe for patients undergoing elective hip replacement.

Aged↗
PubMed1986

Epidemiology and pathogenesis of venous thrombosis.

Venous thrombi are intravascular deposits composed predominantly of fibrin and red blood cells with a variable platelet and leukocyte component. They frequently arise in large venous sinuses in the calf, in valve cusp pockets either in the deep veins of the calf or thigh or in venous segments that have been exposed to direct trauma. Venous thrombosis can be produced experimentally by a combination of stasis and systemic hypercoagulability or by stasis and endothelial damage. Thrombosis is augmented if the fibrinolytic mechanism is inhibited or defective. A number of clinical conditions and laboratory abnormalities are associated with and predispose to venous thrombosis and, in many of these, it is possible to identify one or more of the thrombogenic factors discussed. Venous thromboembolism (venous thrombosis and pulmonary embolism) is a serious and potentially fatal disorder that usually complicates the course of sick hospitalized patients, but occasionally affects ambulant and otherwise healthy individuals. Screening studies with iodine-125 fibrinogen leg scanning, impedance plethysmography and perfusion lung scanning have shown that the majority of venous thrombi and pulmonary emboli that occur in hospitalized patients are small and asymptomatic, and it is likely that most are clinically insignificant. In bedridden patients, most thrombi commence in the calf and are asymptomatic. When a calf vein thrombus extends into the proximal venous segment, the risk of clinically significant pulmonary embolism increases. Less is known about the incidence and clinical significance in a nonhospital population; although asymptomatic disease occurs, its frequency is unknown. In contrast to the patients with asymptomatic venous thrombosis, symptomatic patients with venous thrombosis usually have large occulsive thrombi localized in their proximal veins.

Blood Circulation↗
PubMed1986

Clinical features and diagnosis of venous thrombosis.

The clinical diagnosis of venous thrombosis is inaccurate because the clinical findings are both insensitive and nonspecific. The sensitivity of clinical diagnosis is low because many potentially dangerous venous thrombi are clinically silent. The specificity of clinical diagnosis is low because the symptoms or signs of venous thrombosis all can be caused by nonthrombotic disorders. For these reasons, a practical approach for the diagnosis of venous thrombosis is important. A current approach to the diagnosis of clinically suspected venous thrombosis favors the use of impedance plethysmography over Doppler ultrasonography as the main test for this disorder. This is because impedance plethysmography is precise and objective, whereas the interpretation of Doppler ultrasonography is subjective and requires considerable skill and experience to form reliable diagnoses. The use of serial impedance plethysmography has been evaluated recently in a prospective study. The rationale of repeated impedance plethysmography evaluation is based on the premise that calf vein thrombi are only clinically important when they extend into the proximal veins, at which point detection with impedance plethysmography is possible. Therefore, by performing repeated examinations with impedance plethysmography in patients with clinically suspected venous thrombosis, it is possible to identify patients with extending calf vein thrombosis who can be treated appropriately. Impedance plethysmography is performed immediately on referral; if it is positive in the absence of clinical conditions that are known to produce falsely positive results, the diagnosis of venous thrombosis is established, and the patient is treated accordingly. If the result of the initial impedance plethysmography evaluation is negative, anticoagulant therapy is withheld, and impedance plethysmography is repeated the following day, again on day 5 to 7 and on day 10 to 14. If impedance plethysmography becomes positive during this time, a diagnosis of venous thrombosis is made and anticoagulant therapy is commenced. Positive impedance plethysmography in the presence of conditions known to produce a false positive result (for example, congestive cardiac failure) should be confirmed by venography. If noninvasive tests for the diagnosis of venous thrombosis are not available, a clinical suspicion of venous thrombosis should be objectively confirmed or excluded by performing ascending venography.

Diagnosis, Differential↗
PubMed1986

Diagnosis of pulmonary embolism.

The clinical diagnosis of pulmonary embolism is highly nonspecific because none of the symptoms or signs of pulmonary embolism is unique and all may be caused by other cardiorespiratory disorders. Thus, objective testing is mandatory to either confirm or exclude a diagnosis of pulmonary embolism. Based on current available information, a diagnostic approach for the management of clinically suspected pulmonary embolism is proposed. After a history and physical examination, electrocardiogram and chest X-ray film, all patients should undergo perfusion lung scanning. The finding of a normal perfusion lung scan rules out clinically significant pulmonary embolism, and anticoagulant therapy is withheld. The management of patients with an abnormal perfusion lung scan is more complex. If this scan demonstrates one or more segmental (or greater) perfusion defects, ventilation lung scanning should be performed because the probability of pulmonary embolism is markedly increased if a mismatch is found, with a high probability scan (positive predictive value 86%) providing an end point for commencing anticoagulant therapy in the majority of patients. In an abnormal ventilation-perfusion study, the presence of a ventilation-perfusion match does not rule out the possibility of pulmonary embolism, and further objective testing is required in these patients with nonhigh probability scans. Similarly, in patients with small perfusion defects (one or more subsegmental defects) or indeterminate lung scan findings (in which the perfusion scan defects correspond to a defect on a chest X-ray film), the predictive values obtained from these ventilation-perfusion scan patterns are not sufficiently high or low to confirm or exclude the presence of pulmonary embolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis, Differential↗
PubMed1986

Evaluation of the Du Pont Pro-Tek Formaldehyde Badge and the 3M Formaldehyde Monitor.

The 3M Formaldehyde Monitor and the DuPont Pro-Tek Formaldehyde Badge were evaluated for performance and reliability. This evaluation revealed that the 3M monitor results were variable and lower than reference concentrations determined independently. When the monitors were humidified before use and then exposed in humid (ca. 80% RH) formaldehyde-containing atmosphere, the monitors did give accurate results. Results of additional experiments led to the conclusion that quantitative reaction between formaldehyde generated in our chamber and the absorbent pad in the 3M monitor required the presence of a minimum level of absorbed water. The DuPont badges gave good agreement with the reference concentrations determined independently under the following conditions: sampling period of 1 to 12 hr with a minimum integrated sample loading of 4 ppm-hr; at least 3 m/min (10 ft/min) face velocity; correction for blank badges; and correction for loss of reagent from the samples. The evaluation indicated that the DuPont badge was not well suited to short term sampling and was subject to evaporation of liquid from the absorbing liquid blister. Blank values also were found to be variable, necessitating the analysis of several blanks to be used for blank correction with each set of samples. This blank variability also contributed to high variability found when short term measurements were made. The badge also had a negative interference from phenol at high phenol-to-formaldehyde ratios. Some of the major problems observed with both passive monitors were found only after devices which had been aged under storage conditions were analyzed and these results interpreted. If all testing had been done with fresh sampling devices, many of the problems would not have been noticed. Based on the results of this study, this factor of diffusive monitor aging needs to be addressed in any further work on passive monitor evaluation.

Air Pollutants, Occupational↗
PubMed1985

Performance of sulfur dioxide passive monitors.

The following four commercial sulfur dioxide passive monitors were tested for performance and realiability: DuPont Pro-Tek C-20 air monitoring badges; MSA Vaporgard Dosimeter tubes; REAL BioBadges; and 3M Sulfur Dioxide Nutshell monitors. The experiments conducted were designed to test factors critical to the operation of passive samplers: accuracy and precision; capacity; stability; analytical recovery; and the effects of exposure time, concentration, humidity, face velocity, orientation, chemical interference, and temperature. The DuPont Pro-Tek badges performed satisfactorily for all the factors tested, and the REAL BioBadges performed satisfactorily except for the instability of the SO2/tetrachloromercurate complex when stored. An alternate monitoring system, REAL BioBadges containing deionized water absorbent had a limited capacity. Only the MSA dosimeters exhibited unsatisfactory performance. The 3M Nutshell monitor was withdrawn by the manufacturer after only partial evaluation.

Air Pollutants, Occupational↗
PubMed1985

Diagnostic value of ventilation-perfusion lung scanning in patients with suspected pulmonary embolism.

Differing opinions about the value of ventilation-perfusion lung scanning have created controversy concerning the correct approach to the diagnosis of pulmonary embolism. In a prospective study of 305 consecutive patients with clinically suspected pulmonary embolism and abnormal perfusion lung scans, we evaluated the role of ventilation-perfusion lung scanning, pulmonary angiography, and objective testing for venous thrombosis in the diagnostic process. Segmental or greater perfusion defects with ventilation mismatch have a high probability (86 percent) of pulmonary embolism. Contrary to current clinical practice, however, the approach of ruling against pulmonary embolism by a "low probability" scan pattern is incorrect, even with an improved technique for ventilation imaging; the frequency of pulmonary embolism in these patients ranged from 25 to 40 percent. Objective testing for venous thrombosis provides a practical alternative to performing pulmonary angiography in the diagnostic work-up; by providing an endpoint for commencing anticoagulant therapy, a positive result obviates the need for further testing in 20 to 30 percent of patients.

Adolescent↗
PubMed1985

Diagnostic efficacy of impedance plethysmography for clinically suspected deep-vein thrombosis. A randomized trial.

Impedance plethysmography is an accurate noninvasive method to test for proximal vein thrombosis, but it is insensitive to calf-vein thrombi. We randomly assigned patients on referral with clinically suspected deep-vein thrombosis and normal impedance plethysmographic findings to either serial impedance plethysmography alone or combined impedance plethysmography and leg scanning (which has been shown to be essentially as sensitive as venography) and compared the long-term outcomes. During the initial surveillance, deep-vein thrombosis was detected in 6 of 311 patients (1.9%) tested by serial impedance plethysmography alone and in 30 of 323 patients (9.3%) (most with calf-vein thrombi) tested by the combined approach (p less than 0.001). During long-term follow-up, no patient died from pulmonary embolism; but 6 patients (1.9%; 95% confidence limits, 0.7% to 4.2%) tested by serial impedance plethysmography developed deep-vein thrombosis compared with 7 patients (2.2%; 95% confidence limits, 0.9% to 4.4%) tested by the combined approach. Serial impedance plethysmography used alone is an effective strategy to evaluate such symptomatic patients.

Adult↗
PubMed1984

A cost-effectiveness analysis of alternative approaches for long-term treatment of proximal venous thrombosis.

Recent data from randomized trials have provided a clear understanding of the effectiveness and safety of differing long-term anticoagulant therapies for proximal vein thrombosis. An issue that has not been addressed is their cost-effectiveness. We have performed a cost-effectiveness analysis to rank alternative approaches for long-term therapy. Less intense oral anticoagulant therapy using warfarin sodium is the most cost-effective approach and is preferred in the majority of patients.

Canada↗
PubMed1984

Lidocaine and the reduction of post-venographic pain.

Venography remains the standard method for the diagnosis of deep venous thrombosis but it is invasive and frequently causes discomfort. A randomised double-blind study was performed to determine the efficacy of lidocaine in reducing pain and discomfort associated with venography. Sixty patients undergoing ascending venography received 40 mg of lidocaine (2 ml of 2% lidocaine mixed with 50 ml of contrast medium) in one leg and saline in the other. Assessment of pain was by a standard questionnaire administered by an investigator unaware of the sequence of administration of lidocaine or saline placebo. Twenty-four patients reported no difference in pain or discomfort between the two limbs. Of the 36 patients experiencing an overall difference in pain between the two legs, 12 reported more pain in the leg receiving lidocaine and 24 reported more pain in the leg receiving saline (p = 0.023). There were no significant side effects attributable to lidocaine. These results indicate that lidocaine is beneficial in reducing pain and discomfort associated with venography.

Aged↗
PubMed1984

The diagnosis of clinically suspected venous thrombosis.

The clinical diagnosis of venous thrombosis is highly non-specific. The reason for this is that none of the symptoms or signs of venous thrombosis is unique to this condition--that is, each can be caused by nonthrombotic disorders. Objective testing to confirm or exclude the diagnosis of venous thrombosis, then, is mandatory in patients with clinically suspected deep vein thrombosis.

Cost-Benefit Analysis↗