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Biomedical subjects

R W Barnes

Publications and source records attributed to R W Barnes.

At least 109 records · Page 6Linked to original sources
PubMed1984

Renal artery flow velocity analysis: a sensitive measure of experimental and clinical renovascular resistance.

Renal artery flow velocity analysis has recently been shown to be an indicator of renal parenchymal resistance. Noninvasive measurement of graded renovascular resistance is investigated with experimental models of canine gel microsphere embolization (n = 15), canine renal allografts (n = 4), and clinical renal allografts (n = 6). Intraoperative pulsed Doppler recordings were made on the canine renal artery simultaneous to pressure and flow measurements with sequentially increasing resistance. Transcutaneous echo-Doppler (Duplex) measurements were made on acute patient renal allografts following chemical estimation of renal function. Noninvasive prediction of renovascular resistance in the experimental canine gel microsphere and allograft models correlates with invasive recordings of volume flow (pressure nearly constant), r = 0.93 and r = 0.90, respectively. Duplex estimation of clinical renal allograft resistance and chemical prediction of renal function are similarly interdependent, r = 0.81. Directional arterial flow analysis may be a useful indicator of native and acute allograft renovascular resistance.

Animals↗
PubMed1984

An approach to the noninvasive periodic assessment of arterial elasticity in the young.

The detailed variation of the lumen diameter of common carotid arteries throughout the cardiac cycle was noninvasively measured using a pulse-echo ultrasonic technique in a population of 100 free-living, unrelated, human subjects between the ages of 6 and 25 years. The fractional diameter change (mean +/- SEM) during the cardiac cycle in the 50 male subjects (0.122 +/- 0.004) was found to be significantly (P less than 0.001) greater than the corresponding diameter change in the 50 female subjects (0.106 +/- 0.003). The pressure-strain elastic modulus, Ep, for the carotid arteries was also computed for these subjects by dividing the blood pulse pressure measured in the brachial artery by the fractional diameter change of the carotid. The male elastic modulus (67 +/- 3 kPa) was not significantly (P approximately 0.17) different from the female elastic modulus (62 +/- 2 kPa). Subject age and systolic blood pressure were able to explain approximately one-third of the variability in Ep. Reproductibility studies clearly demonstrated that only a small fraction of the remaining variability could be attributed to experimental technique or intrasubject variability. The results suggest that studies can now be safely performed on young human subjects to assess the effects of a variety of developmental, behavioral, and environmental factors on arterial elasticity. Such results could help to establish an important data base on arterial mechanics which might help in evaluating health promotion recommendations to societies.

Adolescent↗
PubMed1984

The early evaluation of survivors after extracorporeal membrane oxygenation for neonatal pulmonary failure.

Excluding mortality data, there is little information regarding patients' development after extra corporeal membrane oxygenation (ECMO). In six of nine neonates surviving ECMO for predictably fatal pulmonary failure, examination 15 to 21 months afterward showed (1) physical growth and development, normal in six; (2) chest x-ray, normal pulmonary parenchyma; (3) average arterial blood gases, PO2 80, Pco2 35, pH 7.35; (4) echocardiogram, normal, without evidence of pulmonary hypertension; (5) cerebrovascular dopplers, normal ophthalmic artery flow in five patients, retrograde in one; (6) CT scan, EEG, neurologic survey, normal in five, cerebral atrophy in one patient who had an air embolus during decannulation; (7) psychologic examination, normal in all. This early evaluation of ECMO survivors should encourage its further application in those newborns who would otherwise die.

Child Development↗
PubMed1984

Complications of TUR of the bladder neck in the female. A study of 238 procedures.

Transurethral resection of the bladder neck in the female is unpopular because of complications and indifferent results. This retrospective study of 238 procedures (carried out over the period 1940-72) documents the various complications and shows that the fears generally held are exaggerated. Most complications are of moderate incidence and can be easily and satisfactorily managed. The incontinence rate (4.7% in this study) can be further reduced by selection of cases after careful urodynamic evaluation and avoiding certain types of cases. It is related more to the type of patient than to the procedure itself.

Adolescent↗
PubMed1984

Noninvasive evaluation of renal artery stenosis and renovascular resistance. Experimental and clinical studies.

Doppler ultrasound was used to detect experimental and clinical renal artery stenosis (RAS) and increased renovascular resistance (RVR). Parameters assessing RAS included elevated systolic frequency and spectral broadening, while diastolic/systolic frequency ratios predicted elevated RVR. In canine models these parameters detected graded RAS before reduction in renal blood flow. Index values were 88% sensitive and 100% specific in identifying RAS with gradients greater than or equal to 25 mm Hg. Diastolic/systolic frequency correlated well with increased RVR induced by microsphere injections (p less than 0.05). Duplex scanning noninvasively detected bilateral renal artery velocity in 113 of 120 patients. Index values were 83% sensitive and 97% specific in identifying greater than or equal to 60% RAS in 86 vessels visualized by angiography. Estimated RVR was significantly higher in age-matched hypertensive and atherosclerotic patients than in controls (p less than 0.01). Ultrasound may be useful to screen patients for RAS and increased RVR.

Adult↗
PubMed1984

Percutaneous transluminal angioplasty following endarterectomy.

Recurrent occlusive disease was found by noninvasive methods and confirmed arteriographically in 7 patients who had undergone endarterectomy for stenosis of one [5] or both iliac arteries [1] or the subclavian artery [1]. Three patients with iliac artery stenosis had percutaneous transluminal angioplasty (PTA) 1 to 5 years after endarterectomy. One patient with stenosis of the external iliac artery had PTA 4 years after endarterectomy, and dilatation was repeated 7 months later because of recurrence. One patient had 2 endarterectomies and 2 PTAs within 8 years for stenosis of the right common iliac artery. One patient had recanalization of the left common iliac artery 6 years after endarterectomy with low-dose streptokinase followed by PTA. Another patient underwent endarterectomy of the left subclavian artery 3 months after PTA and required further dilatation at 5 and 10 months because of recurrence. The authors conclude that endarterectomy does not preclude PTA (or vice versa) in patients with recurrent arterial occlusive disease.

Adult↗
PubMed1984

Noninvasive quantification of ambulatory venous hemodynamics during elastic compressive therapy.

Quantifying the hemodynamic results of elastic compression requires invasive and cumbersome techniques. Twenty lower extremities (normal, primary, acute and chronic post-thrombotic varicosities) were evaluated with quantitative photoplethysmography (PPG) prior and subsequent to initiating graded compression. The PPG transducer is placed against the stockings and the in vivo method of calibration is used to predict the results of compressive therapy on ambulatory venous pressure (AVP). (table see text) Noninvasive evaluation of patients with quantitative PPG techniques following compressive therapy may provide a better understanding of venous hemodynamics and a rational approach to selection of therapy.

Adult↗
PubMed1984

Intraoperative assessment of in situ saphenous vein bypass grafts with continuous-wave Doppler probe.

A 5 MHz continuous-wave Doppler probe was used intraoperatively to evaluate 25 in situ saphenous vein bypass grafts. At least one arteriovenous fistula per case and five retained competent posterior valvular leaflets were identified before completion angiography. The Doppler was able to distinguish a retained valve from an arteriovenous fistula on clinical grounds but not by waveform analysis. Intraoperative assessment of in situ saphenous vein bypass grafts with the continuous-wave Doppler can identify retained valves that might be missed by angiography. It can reduce the number of angiograms needed to demonstrate a technically perfect result, thus saving operative time and contrast agent load to the patient.

Arterial Occlusive Diseases↗
PubMed1984

Advocates in vascular controversies.

The cardiovascular surgeon may find bibliographic support for his or her particular therapeutic bias for almost any controversial clinical problem. Such management dilemmas are not unique to vascular surgery in particular or surgery in general but reflect much of the field of medicine. Therapeutic controversies usually represent our ignorance of the natural history of disease or the deficiencies in our knowledge of the efficacy of medical or surgical therapy. While prospective epidemiologic studies or randomized blind clinical trials should be the optimal basis for our therapeutic decisions, how much of medical practice can lay claim to such a foundation? This panel debate represents a programmatic attempt to accomplish what each of us should, but often fails to, do in reaching a clinical therapeutic decision in the face of controversial alternatives: namely, objectively search one's experience and the available literature, pro and con. This approach proved very popular to those attending the meeting of the Southern Association for Vascular Surgery. The audience was greeted with the fruits of labor of the panelists who had taken their charge seriously. As advocates of their particular position in the therapeutic arguments, each panelist had carefully reviewed the pertinent literature, much of which is subject to the deficiencies and bias that are reflected in our clinical approach to these problems. Indeed, some of the advocates used the same literature references to support their opposing sides of the argument. Nevertheless, the eloquence and intensity of each presentation heightened the interest and understanding of the audience to these controversies. The annotated bibliography left a tangible document of the effort that had been expended in this debate. One hopes that out of our increased recognition of the fallibility of some of our therapeutic approaches to vascular controversies will come future efforts to base our clinical decisions on the results of epidemiologic studies or properly designed clinical trials.

Age Factors↗
PubMed1983

Evaluation of transplant renal artery blood flow by Doppler sound-spectrum analysis.

Doppler ultrasonography sound-spectrum analysis (SSA) was used to evaluate blood flow in the transplanted kidney and its renal artery. Seven patients with posttransplant hypertension and a bruit over the transplanted kidney were screened for renal artery stenosis (RAS). In five patients, RAS was diagnosed by SSA, and in two it was not. These findings were confirmed by subsequent angiography in all patients. Three patients studied after surgical correction of their RAS had improvement in their SSA patterns. Fourteen hypertensive patients with a cause other than RAS were evaluated by SSA. None of them had SSA findings suggestive of RAS. Doppler ultrasonography with SSA is an effective, noninvasive technique of monitoring transplant renal blood flow, especially in the screening of hypertensive transplant recipients for transplant RAS.

Auscultation↗
PubMed1983

Deep vein thrombosis and prostatectomy.

A research protocol to evaluate the prevention of deep vein thrombosis in sequential patients undergoing prostatectomy is presented. There is an overall incidence of deep vein thrombosis in 8 per cent of patients. There was no advantage with intermittent leg compression when compared with elastic stockings.

Clothing↗
PubMed1983

The FDA report on intraocular lenses.

Clinical studies of intraocular lenses (IOLs) as investigational devices have been regulated in the United States by the Food and Drug Administration (FDA) since February 9, 1978. As of August 1982, data have been collected on more than one million IOLs implanted. During the last 12 months of the study, 409,000 IOLs were implanted. Visual acuity of 20/40 or better at one year after surgery was present in 85% of over 45,000 cases reviewed. Increasing patient age, surgical problems, postoperative complications, and adverse reactions were factors that reduced the visual acuity. The current trend in the USA is for implantation of the posterior chamber and anterior chamber IOLs.

Aged↗
PubMed1983

Quantitative photoplethysmography in chronic venous insufficiency: a new method of noninvasive estimation of ambulatory venous pressure.

We estimated ambulatory venous pressure (AVP) noninvasively with a new technique of quantitative photoplethysmography (PPG). Postural changes of hydrostatic pressure permitted in vivo calibration of the PPG. We recorded quantitative PPG and AVP in 14 normal subjects and 14 patients with postthrombotic chronic venous insufficiency. The results were contrasted with qualitative PPG recordings on 41 consecutive patients with chronic venous insufficiency. All but one of the latter patients demonstrated a decrement in skin blood content with exercise of the calf muscle, and shortened recovery time ws the only significant indicator of venous disease. Quantitative PPG correlated closely with AVP with respect to both estimated drop in superficial venous pressure (r = 0.97, P less than 0.001) and recovery time (r = 0.98, P less than 0.001). PPG estimates of intravenous pressure in normal and postthrombosis patients, 42 +/- 10 and 62 +/- 18 mm Hg, respectively, agreed with AVP measurements, 39 +/- 9 and 61 +/- 18 mm Hg, respectively. Quantitative PPG may prove to be an accurate estimate of AVP in patients with suspected chronic venous insufficiency.

Chronic Disease↗
PubMed1982

Real-time Doppler spectrum analysis: predictive value in defining operable carotid artery disease.

A prospective study compared the sensitivity, specificity, and predictive value of indirect periorbital Doppler screening and direct carotid Doppler interrogation using real-time sound spectrum analysis to detect operable extracranial carotid occlusive disease. The results of noninvasive studies were compared with independently assessed contrast arteriograms of carotid arteries of patients studied for symptomatic cerebrovascular disease. Periorbital Doppler ultrasound was insensitive to carotid stenosis of less than 75% and did not distinguish operable stenosis from inoperable occlusion of the internal carotid artery. Carotid Doppler spectrum analysis was sensitive to 98% of hemodynamically significant disease and correctly discriminated 77% of carotid occlusions, 96% of stenoses larger than 50%, and 70% of stenoses of less than 50%. The predictive value for direct carotid interrogation in identifying carotid occlusion or operable stenosis was 94% and 86%, respectively. Real-time spectrum analysis of direct carotid Doppler signals substantially improves the diagnostic accuracy of noninvasive identification of operable carotid artery disease.

Arterial Occlusive Diseases↗
PubMed1982

Transurethral resection of the prostate for chronic bacterial prostatitis.

Forty-nine patients with chronic bacterial prostatitis causing symptoms and receiving routine accepted treatment for many months or years, without permanent relief, were treated by transurethral prostatic resection (TURP). The purpose of the surgery was to remove the gland down to the true capsule (radical TURP). The patients' own appraisal of the results, the absence of symptoms and of infection, indicate 67% had a good result when assessed 1 year following surgery; 21% were improved and 12% received no benefit. Transurethral resection is recommended in selected cases and when the surgeon is able to remove all of the glandular tissue without causing large perforations through the true capsule. Acceptable results have been achieved in two-thirds of cases. There was no mortality and insignificant morbidity. Patients experiencing no benefit and those who were only improved but not cured were either poorly selected or infected prostatic tissue was not removed.

Adult↗