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Biomedical subjects

R I White

Publications and source records attributed to R I White.

At least 55 records · Page 3Linked to original sources
PubMed1989

Frequency and determinants of adverse reactions induced by high-osmolality contrast media.

To determine the frequency of and risk factors for adverse reactions to high-osmolality contrast media, the authors prospectively studied hospitalized patients undergoing cardiac catheterization. The authors also studied patients undergoing peripheral angiography and contrast material-enhanced computed tomography (CT) of the head or body who met at least one of the following criteria thought to increase the risk of adverse reactions: age of more than 60 years, diabetes, renal or liver disease, concurrent nephrotoxic drug use, or a history of allergic reactions (n = 795). Criteria were defined and used to group adverse reactions into three classes of clinical severity. Overall, class I (mild), class II (moderate), and class III (severe) reactions occurred in 362 (45%), 44 (5.5%), and three (0.4%) patients, respectively. Class II reactions were relatively common (25%) in patients undergoing cardiac catheterization yet were uncommon (2%) in patients undergoing the other three procedures. Nephrotoxicity occurred in 18 of 651 patients who had follow-up creatinine levels obtained at 48-72 hours. With multivariate regression analysis, the only risk factor (P less than .05) for combined class II and III reactions was diabetes. Diabetes, furosemide use, and a history of atopy (odds ratio = 2.8) were associated with nephrotoxicity (P less than .05). Underlying renal insufficiency was not a risk factor for nephrotoxicity.

Adult↗
PubMed1989

Etiologic factors in renovascular fibromuscular dysplasia. A case-control study.

The role of several factors that have been suggested as being of etiologic importance in renovascular fibromuscular dysplasia was examined in a case-control study of 33 patients with angiographically demonstrated fibromuscular dysplasia and 61 renal transplant donor control subjects with normal renal arteries. The factors studied included use of oral contraceptive agents or markers of sex hormone dysfunction, mechanical stress to the renal artery wall, human lymphocytic antigen (HLA) type, cigarette smoking, history of hypertension for more than 5 years, and family history of cardiovascular disease. The risk of fibromuscular dysplasia was significantly (p = 0.003) increased (odds ratio = 4.1, 95% confidence interval = 1.5-10.9) among cigarette smokers. A significant (p less than 0.001) dose-response relation was noted between cigarette use and the risk of fibromuscular dysplasia developing (odds ratio = 8.6 for those who had smoked more than 10 pack-years). Personal history of hypertension more than 5 years was also associated (odds ratio = 5.0, 95% confidence interval = 1.1-22.8) with a significantly (p = 0.036) increased risk for the development of fibromuscular dysplasia. HLA-DRw6 antigen was more common in the 33 fibromuscular dysplasia patients than in the 61 renal transplant donor control subjects (odds ratio = 3.00, p = 0.067) or a second group of 934 ambulatory control subjects (odds ratio = 2.51, p = 0.031). Adjustment for cigarette smoking increased the odds ratio to 5.0 (95% confidence interval = 1.3-19.6). There was a positive though not statistically significant (odds ratio = 1.7, p = 0.175) association noted between family history of cardiovascular disease and fibromuscular dysplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Percutaneous laser probe femoropopliteal angioplasty: a preliminary experience.

Percutaneous laser probe "hot tip" angioplasty procedures were performed on 47 occluded femoropopliteal artery segments in 27 men and 10 women ranging in age from 31 to 92 (mean, 64.7) years. Indications for the procedure included claudication in 29 (78%) segments, and the occlusion lased was greater than 7 cm in length in 51% of the procedures. Failure to recanalize the occlusion occurred in 14 (30%) segments, and recanalization followed by in-hospital reocclusion occurred in seven (15%) segments, yielding an initial failure rate of 45%. Initial failures were noted in 40% of the less than 3 cm occlusions, 33% of the 4 to 7 cm occlusions, and 54% of the greater than 7 cm occlusions. In nine (43%) instances in these 21 failures there was extension of the occluded segment or decline of the ankle/brachial index or both, precipitating the need for surgery in three (18%) of these 17 patients. Among the successfully treated group, 17 (65%) of these vessels in 15 patients reoccluded from 1 to 14 (mean, 3 1/2) months after the procedure. Cumulative patency among the successfully lased vessels was 69% at 1-month, 38% at 6 months', 29% at 12 months', and 14% at 15 months' follow-up. Fifteen-month patency was 7% of the entire series of 47 vessels treated. Eighteen complications occurred after 15 (32%) of these 47 procedures. Based on these results, the widespread application of laser probe angioplasty cannot be justified without further clinical and laboratory investigation.

Adult↗
PubMed1988

Treatment of a case of thromboembolism resulting from thoracic outlet syndrome with intra-arterial urokinase infusion.

A 36-year-old man with thoracic outlet syndrome, admitted to the hospital with digital ischemia from subclavian artery thrombosis and distal embolization, was given intra-arterial urokinase. Thrombus in the subclavian artery was lysed successfully and peripheral emboli were partially cleared, resulting in relief of digital symptoms. Although surgical decompression and vascular reconstruction at the thoracic outlet may be necessary, this technique provides a means of recanalizing small distal vessels.

Adult↗
PubMed1988

Blue toe syndrome: treatment with anticoagulants and delayed percutaneous transluminal angioplasty.

The spontaneous onset of a painful unilateral blue toe is usually caused by fibrinoplatelet microemboli arising from an upstream stenotic or occlusive lesion of the iliac or femoral artery. This constellation of findings is referred to as the blue toe syndrome (BTS). In 12 patients who experienced 14 spontaneous episodes of BTS, angiography demonstrated 15 proximal atherosclerotic arterial lesions, which were presumed to be the source of the microemboli. Fourteen of the 15 lesions were short-segment stenoses or occlusions distal to the aortic bifurcation. Six lesions were treated with antiplatelet or anticoagulant drugs followed by delayed percutaneous transluminal angioplasty (PTA) 6-12 weeks later. Three lesions were treated with surgical bypass, three with long-term anticoagulation, and one with transcatheter clot aspiration and immediate PTA. Two were treated with immediate thrombolytic therapy and had embolic complications. Antiplatelet and anticoagulant therapy followed by delayed PTA may be an effective alternative to surgery for treating BTS.

Adult↗
PubMed1988

Streamlining operation of an admitting service for interventional radiology.

The authors describe how operations of an inpatient admitting service for interventional radiology were improved by developing a clinic and hiring a physician's assistant. The service, begun in 1982, was managed by a senior radiologist and fellows. Because of increasing admissions (from a mean of 52 per year in 1982-1985 to 110 per year in 1985-1987), a 1/2-day, twice-weekly clinic was created in 1985 to evaluate new patients and perform follow-up examinations. In 1986 a physician's assistant was hired to assist in the clinic and during patient admissions. Use of the clinic and physician's assistant streamlined patient flow and management during hospitalization. This resulted in a decrease in mean length of stay for patients undergoing angioplasty (from 3.74 days in 1982-1983 to 2.41 days in 1986-1987). This decrease means cost savings for the hospital under the prospective payment system. Other benefits include improved physician-patient relationships and follow-up, new patients for colleagues (15% of patients had anatomy unsuitable for interventional procedures and were referred to staff surgeons), and increased professional fees.

Angioplasty, Balloon↗
PubMed1988

Contrast medium-induced adverse reactions: economic outcome.

Because the cost of managing an expected greater number of adverse reactions when high-osmolality contrast media (HOM) are used could offset the higher material cost of low-osmolality contrast media (LOM), a prospective study was done of 795 inpatients undergoing any of four procedures involving intravascular injection of HOM: cardiac catheterization, peripheral angiography, head computed tomography (CT), or body CT. The resources used in managing HOM-induced adverse reactions were measured, and the costs of these resources were estimated. Four hundred five patients (51%) had adverse reactions. Reactions were grouped into three classes according to their severity. Class 1 (mild) reactions occurred in 358 patients (45%), class 2 (moderate) reactions occurred in 44 patients (6%), and class 3 (severe) reactions occurred in three patients (0.4%). Ninety-nine patients (12%) consumed resources as a result of an adverse reaction. The average cost of these resources per patient undergoing examination was $1.07 to the radiology department, $5.83 to the hospital, and $12.93 to a charge-paying insurer. Mean (+/- standard deviation) cost to the hospital for managing class 1, class 2, and class 3 reactions were $2.52 +/- $5.33, $24 +/- $54, and $910 +/- $749, respectively. By comparison, the difference in material cost of HOM versus LOM ranged from $93 for body CT to $179 for cardiac catheterization. Even if LOM were to induce no adverse reactions, the increased material cost associated with universal substitution of LOM for HOM would be greater than the expected cost of managing adverse reactions when HOM are used.

Adult↗
PubMed1988

Congenital arteriovenous malformations: tailored embolotherapy.

Congenital arteriovenous malformations (AVMs) involving the pelvis or an extremity were occluded in 16 symptomatic patients, who subsequently underwent tailored embolotherapy. An additional 11 patients did not undergo embolization due to unfavorable vascular anatomy or lack of significant symptoms. Permanent occlusive agents including isobutyl cyanoacrylate, particles of polyvinyl alcohol foam, and coils were used to embolize the multiple feeding vessels and, when possible, the nidus of the AVM. All patients experienced dramatic reduction in pain and resolution of ulceration and bleeding, with a mean follow-up period of 41 months. Symptoms recurred in four patients but again resolved with repeat embolization. The authors conclude that selective and repetitive embolization is highly effective in palliation of symptomatic congenital AVMs.

Adult↗
PubMed1988

Pulmonary arteriovenous malformations: techniques and long-term outcome of embolotherapy.

Over a 10-year period, 276 pulmonary arteriovenous malformations (PAVMs) were occluded with balloon embolotherapy in 76 patients, 67 (88%) of whom had hereditary hemorrhagic telangiectasia. Eleven patients (14%) were discovered by means of family screening with measurement of arterial blood gases and chest radiography. Epistaxis, dyspnea, hemoptysis, and hemothorax occurred in 79%, 71%, 13%, and 9% of patients, respectively. Clinical histories of strokes and transient ischemic attacks were present in 18% and 37% of patients, respectively. Computed tomographic scans of 59 patients showed stroke in 36%. Sixty-five percent of PAVMs were located in the lower lobes, which correlated with the finding of more pronounced hypoxemia in the upright position. After embolotherapy, symptomatic hypoxemia was corrected, and serial values have remained constant for 5 years. Complications were minimal, and no patient required surgery. Balloon embolotherapy is effective long-term therapy for PAVMs, and family screening should be pursued because of the possibility of a higher frequency of paradoxical embolization (stroke) than previously recognized.

Adolescent↗
PubMed1988

Changes in myocardial repolarization in patients undergoing balloon valvuloplasty for congenital pulmonary stenosis: evidence for contraction-excitation feedback in humans.

Alterations in ventricular loading conditions lead to changes in action potential duration and arrhythmias via contraction-excitation feedback; a decrease in load leads to prolongation of repolarization. To determine whether changes in right ventricular load alter ventricular repolarization in man, the corrected QT interval, a measure of overall ventricular repolarization, was measured in 32 patients before and after valvuloplasty for pulmonary stenosis. Right ventricular systolic pressure decreased (82.5 +/- 30.7 to 40.5 +/- 9.5 mm Hg, p less than .001) and the QTc increased concurrently (409.1 +/- 24.3 to 440.7 +/- 28.0 msec, p less than .001) after successful valvuloplasty. The increase in QTc was most marked for those patients with a greater than 30 mm Hg decrease in right ventricular pressure (40.0 +/- 23.3 vs 16.3 +/- 21.3 msec, p = .006). In a subset of seven patients in whom monophasic action potentials were recorded, monophasic action potential duration, a measure of local repolarization, was prolonged (230.0 +/- 24.3 vs 216.9 +/- 21.9, p less than .001) after successful valvuloplasty, confirming that the QTc prolongation reflected changes in local ventricular repolarization. In addition, during nine acute right ventricular outflow tract occlusions in a subset of six patients, monophasic action potential duration shortened (206.6 +/- 17.6 vs 221.7 +/- 20.9 msec, p less than .01) and early afterdepolarizations developed consistent with contraction-excitation feedback. These data suggest that, in humans, changes in mechanical load are associated with changes in ventricular repolarization consistent with contraction-excitation feedback.

Action Potentials↗
PubMed1988

Use of low-osmolality contrast media in a price-sensitive environment.

Over the past 3 years, three radiographic contrast media that are lower in osmolality than traditional contrast media have become available in the United States. These lower osmolality media have been reported to produce fewer adverse reactions than the higher osmolality media, but they cost 10 to 20 times more than higher osmolality media. To explore hospital and physician decision-making regarding the use of lower osmolality media in the increasingly price-sensitive health-care environment, we surveyed the 40 hospitals in the United States that received the most funding from the National Institutes of Health in 1985. Radiologists in 27 (68%) of the hospitals responded. Of these, 93% believed lower osmolality media improve the quality of patient care. However, nearly half of responding institutions limited the use of lower osmolality media. On average, in 1986 lower osmolality media were used in 9% of procedures in which contrast media were injected intravascularly. The decision to limit use was made primarily by radiologists, rather than hospital administrators, and was based on concerns regarding the high price of lower osmolality media. Twelve respondents had developed guidelines for appropriate use of lower osmolality media, but only 25% of these had developed mechanisms to ensure or increase compliance with those guidelines. Only one respondent (4%) reported that he routinely informs patients of the issues and tradeoffs involved in deciding whether to use lower or higher osmolality media. We conclude that cost is an important factor in physicians' and hospitals' choices of contrast media and that increased attention should be given to defining appropriate procedures to follow when informed consent is obtained for the use of contrast material.

Attitude of Health Personnel↗
PubMed1987

Evaluation of balloon angioplasty of coarctation restenosis by magnetic resonance imaging.

Eight patients treated by balloon angioplasty for coarctation restenosis have been followed for 4 to 54 months (mean 40) by physical examination using Doppler pressures and by magnetic resonance imaging in a superconducting magnet operating at 0.6 tesla. Image analysis was performed by inspection and by measurement of the aorta, with particular attention to the angioplasty site and its relation to the ascending aorta at the same axial level. Similar measurements were made from immediate postangioplasty angiograms. Residual pressure gradients were 0 to 12 mm (mean 2), reflecting persistent absence of a gradient in 1 patient and further gradient reduction in 7. Images showed no aneurysm formation, mild residual or recurrent stenosis in 4 patients, minimal focal periaortic soft tissue thickening in 1 patient and an interval increase in the ratio of ballooned segment diameter to ascending aortic diameter in the 7 patients in whom it could be measured. Thus, intermediate-term results of balloon dilatation of coarctation restenosis are excellent and magnetic resonance imaging is well suited to the serial studies required in these patients.

Angioplasty, Balloon↗
PubMed1987

The role of CT in the management of pelvic arteriovenous malformations.

Four cases of pelvic arteriovenous malformations (AVM) were diagnosed and managed by CT, angiography, and embolotherapy. CT was used to determine the size, extent, and vascularity of each AVM and the involvement of adjacent organs. Thus CT was pivotal in the choice between surgical extirpation or embolotherapy. CT was also useful in monitoring patients following therapy.

Adult↗
PubMed1987

Thermodynamic correlates of hot tip laser angioplasty.

Surface temperatures of normal human cadaver arteries and polytetrofluoroethylene grafts were measured in vitro using thermography to assess vascular wall heating from the metal-capped ("hot tip") laser probe. Laser pulse duration, vessel diameter, blood flow, and saline infusion were varied; power from an Argon laser was constant at 10 watts. The surface temperatures resulting in perforation were 76.2 +/- 2.2 degrees C for arteries and 90.4 +/- 2.1 degrees C for grafts. Blood flow provided an effective heat sink reducing artery and graft wall peak temperatures from 10 watt/5 sec pulses by 12.2 +/- 1.7 and 14.1 +/- 6.1 degrees C at 100 mL/min, and by 16.3 +/- 2.4 and 22.4 +/- 4.9 degrees C at 500 mL/min, respectively. In the occluded conduit, inflow of saline proximal to the probe tip reduced peak temperatures (degrees C) from 10 watt/5 sec pulses as follows: 14.0 +/- 3.2 (artery) and 23.2 +/- 8.5 (graft) at 50 mL/min, and 19.0 +/- 0.6 (artery) and 26.6 +/- 8.5 (graft) at 100 mL/min. Radial heating by the hot tip probe can cause thermal perforation. Blood flow or saline infusion modifies nontarget heating and may offer significant protection to the vasculature.

Arteriosclerosis↗
PubMed1987

Long-segment femoropopliteal stenoses: is angioplasty a boon or a bust?

Analysis of 193 femoropopliteal angioplasties demonstrated patency rates in the stenotic group of 75.5% at 6 months and 54.4% at 54 months. The patency rates for the occlusive group were 93.7% at 6 months and 72.9% at 54 months; these rates were significantly better than those in patients with stenoses. A group of 14 patients with long-segment (greater than 7 cm) stenosis had the highest risk of early failure, with a 6-month patency of 23.1%. After removal of the long-segment stenosis group from the results, there were no significant differences between the long-term patencies for stenotic and occlusive lesions. If angioplasty of long stenoses is attempted, a high initial success rate but early failure should be anticipated.

Angioplasty, Balloon↗
PubMed1987

Interventional radiology: reflections and expectations. The 1985 Eugene P. Pendergrass new horizons lecture.

The history and current practice of interventional radiology are reviewed. Interventional radiology is considered a subspecialty of diagnostic radiology that involves the use of a variety of percutaneous techniques to treat a spectrum of vascular and nonvascular diseases. It is physician intensive and requires a commitment to patient care analogous to that in surgery. Still considered in its infancy, interventional radiology should prosper and undergo continued growth over the next several decades.

Angioplasty, Balloon↗