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Biomedical subjects

A C Hayes

Publications and source records attributed to A C Hayes.

At least 19 recordsLinked to original sources
PubMed2003

Neutrino-12C scattering in the Ab initio shell model with a realistic three-body interaction.

We investigate cross sections for neutrino-12C exclusive scattering and for muon capture on 12C using wave functions obtained in the ab initio no-core shell model. In our parameter-free calculations with basis spaces up to the 6 variant Planck's over 2pi Omega we show that realistic nucleon-nucleon interactions, like, e.g., the CD-Bonn, underpredict the experimental cross sections by more than a factor of 2. By including a realistic three-body interaction, Tucson-Melbourne TM'(99), the cross sections are enhanced significantly and a much better agreement with experiment is achieved. At the same time, the TM'(99) interaction improves the calculated level ordering in 12C. The comparison between the CD-Bonn and the three-body calculations provides strong confirmation for the need to include a realistic three-body interaction to account for the spin-orbit strength in p-shell nuclei.

Journal Article↗
PubMed1988

The effect of contralateral disease on carotid Doppler frequency.

Continuous-wave Doppler frequency analysis is one standard of noninvasive evaluation for stenotic carotid disease. Interpretation is most commonly based on frequency recorded at the site of stenosis. If flow velocity is increased because of contralateral disease, this criterion may overstate the degree of stenosis. To investigate this, three centers contributed 167 patients to a study of carotid Doppler frequency analysis. Each patient underwent bilateral carotid studies by a standard protocol with use of continuous-wave 5 MHz Doppler probe. There were 309 patent and 25 occluded internal carotids seen on subsequent angiographs. Each patient side was categorized by the severity of ipsilateral disease (less than 45%, 45% to 70%, 71% to 99%, occlusion) and then subgrouped by contralateral disease. For all carotid arteries, the optimal peak frequency to detect 45% or more stenosis was 5500 Hz, with an overall accuracy of 92.2%. Within the three classifications of ipsilateral stenosis, a trend was noted that related increasing peak frequency to greater degrees of contralateral disease. This was most apparent when the contralateral internal carotid artery was occluded. Of all false-positive errors, 43% were accounted for by this subset that represented 15% of the total population. For the 25 patients with occlusion opposite a stenosis, the 5500 Hz cutoff of Doppler peak frequency yielded only 76% accuracy; an ROC curve showed that a cutoff value of 8500 Hz improved overall accuracy to 92% for these patients. By applying two cutoff criteria--5500 Hz for those with patent contralateral internal carotids and 8500 Hz for those in whom a contralateral Doppler signal was not detected--the overall accuracy for all patients improved to 93.3%. It is concluded that contralateral occlusion affects Doppler peak frequency by increasing the velocity in the companion carotid artery, whereas severe contralateral stenosis did not result in a consistent pattern of increased velocity.

Carotid Artery Diseases↗
PubMed1987

Reproducibility of transcutaneous continuous-wave Doppler testing of the carotid arteries.

Hand-held, continuous-wave Doppler probes, coupled with sound spectral analysis, can successfully predict carotid artery stenosis. Changing either the emitting frequency of the probe, the beam/artery angle of the carotid flow velocity (e.g. cardiac output) may alter the recorded frequency shifts. These effects raise questions as to the efficacy of this technique to serially follow carotid atheroma for progressive stenosis. To test the inherent problems with this methodology, a study of reproducibility was conducted. Two Doppler probes (5 MHz and 8 MHz) were compared at the same sitting in 24 patients; 12 were restudied on two subsequent occasions. Peak systolic frequency was 135% higher with the 8 MHz probe; this was lower than the 160% calculated by substitution for emitting frequency in the Doppler formula. The linear correlation coefficient of the two probes was 0.88. In relationship to established laboratory criteria of a greater than 75% area stenosis, no errors were noted with the 5 MHz probe while four errors were noted with the 8 MHz probe. A serial study variation of peak systolic frequency was noted for both probes; these variations did not cross established criteria levels of a severe stenosis when the 5 MHz probe was used, but did with the 8 MHz probe for two carotids. A standard examining probe is recommended. Angle and cardiac output changes do result in peak systolic frequency variation from test to test, but these were not clinically significant with the 5 MHz probe. Thus, significant changes during follow-up testing should provide an index of evolving carotid stenosis.

Arterial Occlusive Diseases↗
PubMed1986

Pneumatic compression devices for prophylaxis of deep venous thrombosis (DVT).

A pneumatic compression device was applied to 155 patients with a normal Doppler venous examination who underwent a general surgical procedure of at least 1 hr in duration. One hundred fifty-three patients had neither PE nor DVT clinically or by Doppler studies, one patient had a venographically proven DVT, and one patient had a clinical pulmonary embolism verified by lung scanning. Using clinical and Doppler criteria, the device was effective in the prophylaxis of thromboembolic complications.

Aged↗
PubMed1986

Quantitative analysis of continuous-wave Doppler spectral broadening for the diagnosis of carotid disease: results of a multicenter study.

This article reports the results of a multicenter study that compares 333 frequency analysis studies with the continuous-wave Doppler method with angiography. With receiver operating characteristic curves, the study documents the accuracy of the Doppler technique for the diagnosis of extracranial carotid arterial stenosis greater than 45% diameter reduction. It confirms the accuracy of the measurement of the maximal peak Doppler frequency and, in addition, shows that quantitative analysis of the instantaneous Doppler spectrum at peak systole by the measurement of the spectral broadening index is of diagnostic value. Likelihood ratios have been calculated with the use of curve-fitting techniques and it has been demonstrated how both the peak frequency and the spectral broadening index can be used together to improve the certainty of diagnosis. It is concluded that the probability that an individual patient has significant carotid arterial disease can be determined with the measurements of peak frequency and spectral broadening index from the continuous-wave Doppler spectral waveform.

Carotid Arteries↗
PubMed1984

Carotid endarterectomy without a shunt: the control series.

Nine hundred forty carotid endarterectomies were performed without the use of a temporary indwelling shunt. Six patients (0.6%) died, all from stroke; 17 other patients (1.8%) had another stroke, and 21 patients (2.2%) had temporary neurologic symptoms. Complete x-ray films detailing the opposite internal carotid artery and carotid artery back pressure were available for 783 operations. Correlation of stroke to back pressure, status of the contralateral internal carotid artery, preoperative neurologic deficit, and carotid clamp time was examined. Statistical analysis demonstrated significantly increased neurologic complications only if the systolic carotid back pressure was less than or equal to 50 mm Hg or the contralateral internal carotid artery was occluded. Analysis to determine if these factors were dependently related showed that when both a contralateral carotid occlusion and a carotid back pressure of less than or equal to 50 mm Hg coexisted (82 patients), the rate of permanent deficit was 11.0% compared with 2.8% when either factor was singly present and 0.9% when neither factor was present. No statistical difference exists between the group with only a single factor and those with neither factor. When a temporary shunt is not used during carotid endarterectomy, the risk of neurologic complication is increased if both a contralateral internal carotid artery occlusion and a carotid back pressure of less than or equal to 50 mm Hg coexist. The use of a shunt in this patient population may be beneficial.

Adult↗
PubMed1984

Factors influencing morbidity of carotid endarterectomy without a shunt.

A retrospective analysis of 156 unshunted carotid endarterectomies in 124 patients indicates that at least three factors may influence the surgeon to consider using an indwelling shunt. Contralateral internal carotid artery occlusion, prolonged cross-clamp time, and possibly stump pressures less than 25 mm Hg torr were associated with increased rate of permanent neurologic deficit. Selective shunting would not be based on stump pressures less than 50 mm Hg torr, previous ipsilateral stroke, or abnormal intraoperative electroencephalogram.

Adult↗
PubMed1983

The normal Doppler venous examination.

The clinical diagnosis of acute deep vein thrombosis (DVT) is but 50% accurate when compared to the results of contrast venography. This clinical inaccuracy had led to the dependence of the physician upon laboratory diagnosis. Whereas contrast venography is the gold standard of diagnosis, its expense, special equipment, personnel, and discomfort make it unsuitable for evaluating large numbers of patients. For this reason, numerous noninvasive tests utilizing plethysmographic and Doppler techniques have been developed to evaluate patients with suspected venous disease, and when expertly performed have a degree of accuracy of approximately 90%. This degree of accuracy coincides with the experience of our peripheral vascular laboratory using the Doppler venous examination. Based on these statistics, our current practice is to evaluate patients suspected of having DVT with a Doppler venous examination (Figure 1). If the test is abnormal or equivocal, contrast venography is usually obtained and anticoagulation recommended. Contrariwise, if the Doppler venous examination is normal, venography is not obtained, and anticoagulation treatment is not recommended. This practice should reduce the number of venograms in a patient population that is not at an increased risk of pulmonary embolism or repeated deep venous thrombosis. To evaluate the validity and safety of this practice, one hundred eighty-six patients with normal Doppler venous examinations in whom contrast venography was not obtained were evaluated and form the basis of this report.

Angiography↗
PubMed1983

Durability of carotid endarterectomy.

Carotid endarterectomy is the preferred treatment for patients with transient ischemic attacks and carotid stenosis. Although clinically these patients do well, the long-term fate of the operated carotid artery has not been well documented. To address this question, repeated noninvasive testing has been employed to follow our carotid endarterectomy patients since 1976. Supraorbital Doppler examination, oculoplethysmography-Kartchner, carotid phonoangiography and, later in this series, spectral analysis of the carotid Doppler velocities were performed after 193 endarterectomies. One hundred fifty-eight patients were initially tested within 3 months of operation, and 35 were initially tested 3 or more months after operation. Twenty-four arteries, four of which were symptomatic, had an initial abnormal test and are excluded from this study of carotid artery durability. Of the 169 patients with normal carotid tests, 36 had no further evaluation. Among the 133 patients who returned for serial testing from 1 to 60 months (mean 20 months), 115 carotid arteries continued to test normal at late follow-up but 18 subsequently developed test abnormalities. Ten had more than 75% stenosis, eight had 50% to 75% stenosis. Eight of these patients had contrast studies: three had normal findings; the five that had abnormal findings underwent reoperation. Interestingly, only two patients presented with symptoms appropriate to the abnormal test. The findings suggest that carotid endarterectomy is a reasonably durable operation. Recurrent stenosis was presumed or proven in 10% of 133 serially tested carotid arteries. This threat of restenosis makes long-term follow-up of these patients mandatory.

Arterial Occlusive Diseases↗
PubMed1978

Diagnosis of peripheral occlusive disease: comparison of clinical evaluation and noninvasive laboratory.

One hundred and two patients with peripheral vascular disease were evaluated by the attending surgeon, residents and students, and the vascular laboratory prior to arteriography to test their ability to make a correct anatomic diagnosis. The attending surgeons made a correct anatomic diagnosis in 98 patients and were at least partially correct in the other four. Surgical housestaff and students were 62% totally correct, 35% partially correct, and 3% totally wrong. The vascular laboratory results were almost identical with the attending surgeon, but two patients could not be evaluated because of calcified arteries. The operation that was eventually performed was suggested initially by the laboratory and the attending surgeon in 98% of the patients.

Arterial Occlusive Diseases↗
PubMed1978

Value of arterial pressure measurements in the proximal and distal part of the thigh in arterial occlusive disease.

A prospective study was carried out comparing two techniques of segmental arterial pressure measurements of the leg to detect, localize and quantify regional arterial occlusive disease. The measurement of pressures of the proximal and distal parts of the thigh with the narrow cuff technique permitted correct anatomic localization of aortoiliac, femoropopliteal or combined disease in 78 per cent of diseased extremities, including all limbs with isolated aortoiliac or femoropopliteal disease. A single wide cuff arterial pressure measurement of the thigh correctly localized arterial obstructions in only 19 per cent of diseased extremities. Although a wide cuff is associated with less artifactual elevation in measured arterial pressure at the thigh, this advantage is outweighed by the limitation of diagnostic accuracy in localizing segmental arterial occlusive disease. We recommend that segmental arterial pressure measurements of the limb be made at four levels on the lower extremity, including arterial pressures of the proximal and distal parts of the thigh to achieve maximal diagnostic accuracy.

Angiography↗
PubMed1977

Value of concomitant sympathectomy in aortoiliac reconstruction. Results of a prospective, randomized study.

The efficacy of concomitant lumbar sympathectomy in improving results of aortoiliac reconstruction was assessed by a prospective, randomized study of 51 patients undergoing operation for occlusive or aneurysmal disease. Sympathectomy was performed on 50 limbs, while 52 extremities served as controls. Sympathectomy resulted in a significant reduction in foot vascular resistance determined by plethysmography. However, the procedure had no effect on leg circulation, assessed by ankle/arm pressure indices determined by Doppler ultrasound. In the sympathectomy group, there were three early postoperative amputations for ischemia, despite patent grafts. In the control group, there was one late graft occlusion, caused by progressive atherosclerotic disease. Although sympathectomy may improve pedal circulation, the procedure does not appear to improve the results of aortoiliac reconstruction.

Adult↗
PubMed1977

Xenon-133 determination of muscle blood flow in electrical injury.

Xe-133 washout determination of muscle blood flow (MBF) was used to detect muscle ischemia in electrical injury of an experimental animal model and three patients. The control MBF of rabbit hindlimbs, which averaged 11.29 +/- 1.07 cc/min/100 gm, was significantly reduced by electrical injury, to 5.82 +/- 1.49 cc/min/100 gm (p less than 0.001). An electrical injury of 4,000 watt-seconds or greater was associated with uniform MBF less than 1.00 cc/min/100 gm and with histopathologic alterations of muscle necrosis. Thenar MBF less than 1.00 cc/min/100 gm in two patients was associated with muscle necrosis requiring distal arm amputation. The remaining patient with sequential muscle blood flows above this level had uneventful healing of hand electrical injuries. Xe-133 determination of MBF may be a useful objective technique to determine the extent of electrical injury in muscle.

Adult↗