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Biomedical subjects

R B Dilley

Publications and source records attributed to R B Dilley.

At least 37 records · Page 2Linked to original sources
PubMed1989

Intraoperative transcranial Doppler: limitations of the method.

To test the hypothesis that the transcranial Doppler is a useful technique for intraoperative neuromonitoring, we prospectively used it to study 83 patients undergoing carotid end-arterectomy. A 2 MHz pulsed-wave, range-gated transcranial Doppler was positioned at the transtemporal window after induction of general anesthesia. Mean middle cerebral artery velocity, intraarterial blood pressure, end-tidal PCO2, heart rate, and a spectral array of electroencephalographic activity were recorded continuously throughout the operation. Internal carotid artery back pressure was measured routinely. On completion of the endarterectomy, duplex ultrasound examinations and arteriograms were uniformly obtained to assess technical adequacy. Forty-nine of the 83 patients (60%) had complete preoperative and intraoperative transcranial Doppler examinations. Eleven (13%) had incomplete assessments because of small or absent transtemporal windows. Twenty-three (27%) had unsuccessful monitoring because of technical difficulties, primarily because of inability to maintain probe position--with loss of mean middle cerebral artery velocity recording. In the patients with complete studies, transcranial Doppler failed to provide information that altered surgical therapy. All monitoring modalities were normal in the one patient (1.2%) who sustained an operative stroke. We conclude that at this time, transcranial Doppler has not been useful to routinely monitor the intraoperative events during carotid endarterectomy.

Aged↗
PubMed1988

The improving long-term outlook for patients over 70 years of age with abdominal aortic aneurysms.

During the past decade, selective criteria for elective surgery for abdominal aortic aneurysms have been refined based on natural history and aneurysm expansion information. Using these criteria, contemporary preoperative preparation and newer intraoperative technical adjuncts, 123 consecutive patients underwent elective resection with 1 death (mortality rate: 0.8%). These include all patients operated on with both elective and urgent aneurysms at this institution since 1978, with the exception of those with frank rupture. Most importantly, however, the 5-year life-table survival of all of these patients (average age: 71.3 years, range 46-96 yr) was 72%, including both hospital and late mortality rates. More than half of the patients were over 70 years old (78 cases), with no hospital deaths and a 5-year life-table survival probability of 67%. For those under 70 years of age at the time of operation, the 5-year life-table probability of survival was 79%. We believe that these accomplishments were a direct result of an aggressive policy of screening for and selectively treating coronary disease and carotid stenosis preoperatively and the utilization of such intraoperative adjuncts as routine Swan-Ganz monitoring, autologous blood transfusion, the cell saver, and the frequent use of the tube grafting (50%). Thus, with proper selection, the outlook for the patient over 70 years old with an elective abdominal aortic aneurysm resection now approaches that of the normal population (67% vs. 69%).

Age Factors↗
PubMed1988

Importance of cerebral collateral pathways during carotid endarterectomy.

Before surgery, we evaluated major intracranial collateral pathways using transcranial Doppler ultrasonography (TCD) in 50 patients who then underwent carotid endarterectomy with concurrent multimodality cerebral monitoring. Patients were grouped with respect to collateral pathways demonstrated preoperatively by TCD: Group 1, good collateralization with an anterior and/or posterior communicating artery ipsilateral to the operative carotid lesion (29 patients, 58%); Group 2, collateral pathways present but impeded by other proximal stenoses (nine patients, 18%); and Group 3, no collateralization identified (nine patients, 18%). Three patients (6%) could not be classified. TCD identified major collateral pathways with a sensitivity of 89% and a specificity of 80% when compared with arteriography. During carotid endarterectomy mean middle cerebral artery velocity, pulsatility index, and stump pressure were higher and the decrease in middle cerebral artery velocity with extracranial carotid artery cross clamping was significantly less among Group 1 patients than among Group 2 and 3 patients (p less than 0.05 for both groups). Group 1 patients required fewer intraoperative carotid artery shunts and developed fewer ischemic electroencephalographic abnormalities than did patients in Groups 2 and 3 (p less than 0.05 for both groups). TCD assessment of cerebral collateralization helps predict hemodynamic consequences of cross clamping during carotid endarterectomy.

Aged↗
PubMed1987

Evaluation of a new classification of cerebrovascular disease: CHAT.

A new scheme that classifies cerebrovascular disease on the basis of current and prior clinical symptoms, arteriographic findings, and target organ abnormalities has been evaluated. The scheme proved to be easy to learn and to use. Its utility was demonstrated by the previously unreported distinctions that became apparent when various patient subsets were analyzed according to the CHAT classification. These included an improved probability of stroke-free survival in patients operated on for brief strokes (transient ischemic attack) as opposed to temporary strokes (reversible ischemic neurologic deficit), and similarly improved survival probability in patients operated on for amaurosis fugax in comparison to those with carotid territory hemispheric transient ischemic attacks. The impact of multiple arterial lesions and positive computerized tomography scan findings appeared to be minimal with respect to both late stroke and survival in our preliminary observations. The simplicity and utility of the CHAT scheme make it a useful method to evaluate and report clinical experience with cerebrovascular disease.

Carotid Arteries↗
PubMed1987

Late results after carotid endarterectomy for amaurosis fugax.

Amaurosis fugax is considered an ocular transient ischemic attack with an ominous prognosis. One hundred twenty-eight patients with amaurosis fugax as the presenting symptom underwent carotid endarterectomy at the University of California, San Diego (UCSD) and Scripps Clinic between 1970 and 1985 with one death (0.8%) and one postoperative permanent stroke (0.8%). Subsequently, these patients were followed up for 6 to 160 months (mean 45.3 months). Only two subsequent late strokes were documented (at 2 and 5 years after operation). These results were significantly better (p less than 0.01) by life-table analysis than the late stroke rate after carotid endarterectomy performed to treat anterior motor transient ischemic attacks at both UCSD and Scripps Clinic, as well as the reported late follow-up for all transient ischemic attacks after carotid endarterectomy in the literature (1.8% per year, 17 publications, 1980 operations). Thus amaurosis fugax appears to be a particularly favorable indication for carotid endarterectomy. Left untreated, this event carries a high risk of stroke; after carotid endarterectomy, which has a low operative risk, there is a very low postoperative stroke rate (two strokes in 448 patient-years of follow-up).

Actuarial Analysis↗
PubMed1986

A comparison of B-mode real-time imaging and arteriography in the intraoperative assessment of carotid endarterectomy.

In this study we compare intraoperative B-mode imaging with arteriography in the same patient for intraoperative assessment after carotid endarterectomy. Since April 1983, 158 patients have been studied with both techniques. After a routine intraoperative arteriogram, the vessel was examined in multiple planes with a B-mode imager, and the impression of the operating surgeon was recorded before review of the arteriogram. Thirteen studies were unsatisfactory because the design of the probe did not allow examination of the high carotid bifurcation. Twelve patients had significant abnormalities (8.3%) in the internal carotid artery. Results were false negative in three intraoperative arteriograms (2.1%) and five B-mode imaging studies (3.4%). In each of the 12 cases the vessel was reopened and the abnormality confirmed and corrected. Fifty-seven patients had abnormalities (37%) in the external carotid artery. Results were false negative in eight arteriograms (5.3%) and in 12 B-mode imaging studies (7.9%). Fourteen of the 57 patients with abnormalities of the external carotid artery underwent repeat operation to correct the technical problem. Although not conclusive, the incidence of postoperative neurologic deficit as well as that of recurrent carotid stenosis seems decreased since both modalities for intraoperative assessment were used. The data suggest that neither intraoperative angiography nor B-mode imaging, when used alone, accurately detects all postoperative abnormalities. The results also suggest that a heightened sensitivity to technical details may improve both early and late postoperative morbidity.

Carotid Arteries↗
PubMed1985

The contribution of spectral analysis to the diagnosis of carotid artery disease.

Pulsed and continuous-wave Doppler examinations with spectral analysis were performed on 258 carotid arteries in 220 patients and compared with multiplane contrast angiography. Each artery was examined for stenosis and assigned to one of four groups: normal to 19%, 20% to 49%, 50% to 99%, and occlusion. The incidence of disease was 70%. Diagnostic sensitivity with all noninvasive techniques varied from 76% to 90% depending on the degree of stenosis, with an overall accuracy rate of 86%. In an attempt to evaluate the diagnostic contribution of spectral analysis, stenosis classification by peak frequency alone was compared with that of the full laboratory profile, including spectral analysis. In the 147 carotid arteries in which such data were available, diagnostic sensitivity was improved with spectral analysis by 8% to 29% depending on the degree of stenosis. Detection of occlusions was unchanged. The major contribution of spectral analysis was in detecting non-flow-limiting stenoses of 20% to 49%. Spectral analysis added little to the diagnostic ability of peak frequency to detect lesions with greater than 50% stenosis. Spectral analysis of either pulsed Doppler or continuous-wave Doppler signals is an accurate noninvasive method for evaluating carotid bifurcation disease, which particularly improves the detection of non-flow-limiting stenoses.

Arterial Occlusive Diseases↗
PubMed1984

Posterior communicating artery visualization in predicting results of carotid endarterectomy for vertebrobasilar insufficiency.

Retrospectively, 51 patients who related two or more signs or symptoms of vertebrobasilar insufficiency and possessed concomitant carotid arterial disease were identified. The patient population was separated into two groups based on the presence or absence of an angiographically visualized posterior communicating artery during selective carotid artery injection. All patients had undergone unilateral or staged bilateral carotid endarterectomy. Comparison of postoperative clinical outcome with intracerebral angiographic findings exhibited statistically significant improvement in favor of those patients with at least one visualized posterior communicating artery. There was a greater likelihood of severe vertebral artery stenosis in those patients whose symptoms were not relieved by carotid endarterectomy.

Aged↗
PubMed1984

Recurrent carotid artery stenosis following endarterectomy.

Spectral analysis was used to examine 257 carotid arteries in 227 patients who had undergone carotid endarterectomy at 1, 3, 6, and 12 months after surgery and annually thereafter. Routine intraoperative completion angiography ensured that the operations were technically satisfactory. Postoperative restenoses were identified in 38 patients (15%). In 23 arteries (9%), the restenosis exceeded a 50% diameter reduction while in 15 arteries (6%) the stenosis was less than 50% of the diameter. Restenosis developed in 24/96 women (25%) and 14/161 men (9%). Twenty-nine (70%) stenotic lesions occurred within 12 months. In three patients early lesions regressed. Reoperation with patch angio-plasty was required in six patients. When the 219 carotid arteries that remained widely patent were compared to the 38 that restenosed , no differences were noted for age, diabetes mellitus, hypertension, smoking, or degree of preoperative stenosis. Early stenotic lesions appear to be due to myointimal hyperplasia, which is probably platelet mediated. The predominant female sex distribution may be explained by differences in platelet responsiveness in men and women.

Arterial Occlusive Diseases↗
PubMed1983

Life expectancy and late stroke following carotid endarterectomy.

A review of the UCSD experience with 456 consecutive carotid endarterectomy procedures confirms the acceptably low operative mortality and morbidity associated with this operation. Immediate complications were not different when routine or selective shunting was performed, but the patients with a low internal carotid artery back pressure had higher operative complication rates. The coexistence of atherosclerosis in other parts of the body severe-enough to warrant surgery for them was not associated with either higher early or late carotid surgery complication rates. Following both coronary bypass and carotid procedures, the late mortality was decreased, and the late incidence of stroke was particularly low in comparison to the remainder of the patient group. Late follow-up emphasized the high continuing attrition rate from all causes in these patients. Late strokes continued to occur, particularly in patients with prior strokes and severe preoperative bilateral carotid disease. The late course of patients with posterior circulation transient ischemic attacks treated by carotid endarterectomy was quite similar to that of patients treated for anterior circulation transient ischemia attacks (TIAs). Newer postoperative screening procedures may decrease the incidence of late postoperative stroke by identifying recurrent carotid stenosis while it is still in the asymptomatic stage.

Aged↗
PubMed1983

Selective streptokinase infusion: clinical and laboratory correlates.

Selective intra-arterial infusions of streptokinase (SK) were made in 50 arteries of 45 patients with a variety of acute thromboembolic conditions. The most common regimen was 5,000 units of SK/hour for 24 to 48 hours with a simultaneous heparin infusion of 250 to 500 units/hour. Significant lysis occurred in 80% of cases, with 74% of the patients benefiting clinically. Minor bleeding, usually from puncture sites, occurred in 30% of the patients. Major hemorrhages, requiring transfusion or surgery, developed in four patients (8%). No hemorrhagic strokes or fatalities were directly attributable to SK infusion. Coagulation parameters were determined before infusion, 4 and 24 hours after infusion, and every 24 hours thereafter. Significant alterations of coagulation parameters developed promptly, but were not very useful in predicting either clinical response or hemorrhage. Selective intra-arterial infusion of SK is a moderately effective and safe therapeutic technique in acute peripheral arterial thromboembolic disease. A comparison with prior reports suggests that selective low-dose infusion provides a moderate gain in benefit-risk ratio over systemic infusion.

Angiography↗
PubMed1982

Is carotid endarterectomy beneficial in prevention of recurrent stroke?

Of 456 consecutive carotid endarterectomies performed at the University of California, San Diego, 127 were in patients who had sustained a previous completed stroke and had recovered with minimal but permanent neurologic deficits (PNDs). Operative mortality for the entire series was 0.9%, but it was 3.1% for the stroke group. A postoperative PND was observed in 2.1% of patients without neurologic deficits but occurred in 3.9% of the patients after stroke. A 97% one-to-ten-year follow-up was obtained. The total early and late serious morbidity and mortality in this surgically treated series of patients after stroke was 24% at five years. We conclude that carotid endarterectomy for the prevention of recurrent stroke carries a high risk and may not be superior to nonoperative treatment.

Adult↗
PubMed1981

Acute physiologic effects of arteriovenous anastomosis and fistula in revascularizing the ischemic canine hind limb.

In a severe, diffuse arterial occlusion model of canine hind-limb ischemia, both distal arteriovenous fistula (AVF) and arteriovenous end-to-side anastomosis (AVA) were evaluated as potential methods of revascularization. AVA reversed or minimized both hemodynamic and metabolic indices of ischemia; AVF did not. After AVA segmental blood pressures at the thigh returned to normal, and those at the calf returned to 0.8 from an ischemic level of 0. Both postocclusion toe pulse reappearance times and the toe pulse volumes partially returned toward normal. IN addition, gastrocnemium intramuscular Po2 returned from an ischemic level of 5.3 to 45.5 mm Hg, compared to a control normal of 47.6 mm Hg. Muscle surface pH returned to 7.40 from the ischemic level of 7.06. AVA appears to offer an approach to the treatment of severe, diffuse arterial disease that would utilize the distal venous tree to transport blood to the capillaries for the support of adequate tissue nutrition.

Animals↗
PubMed1980

Hemodynamic response to exercise in the unanesthetized calf with pulseless arterial flow.

In a chronic unanesthetized calf model with a centrifugal pump inserted from left ventricle to aorta, calves were trained to perform treadmill exercise and undergo hemodynamic measurements. Resting hemodynamic changes with pulseless pumping included increases in cardiac output, aortic pressure, and heart rate, with some decrease in systemic vascular assistance. Treadmill exercise was associated with further increases in cardiac output and heart rate, which progressively increased during the 10 days of observation, with little change in mean aortic pressure. Pump autoregulation responded to the decreased systemic vascular resistance associated with exercise by increasing pump output about 15%, at constant pump rotatory speed. These experiments add further evidence regarding the ability of a centrifugal left ventricular assistance system to support the failing heart and to permit moderate degrees of exercise in the intact unanesthetized calf.

Animals↗
PubMed1979

Effect of pulseless perfusion on gastrointestinal blood flow and its distribution.

The effect of nonpulsatile (NP) arterial perfusion on gastrointestinal organ blood flow and intraorgan flow distribution was studied in 10 anesthetized (pentobarbital) dogs utilizing the radionuclide-labeled microsphere (15 micrometer) technique. Measurements of flow to the stomach, small intestine, and colon were made during a pulsatile perfusion control period and after 1- and 2-h periods of NP perfusion with a centrifugal left ventricular bypass pump (Medtronic). Total gastric blood flow (0.178 +/- 0.021 ml/min per g) as well as the partitioning of that flow between gastric subsegments such as antrum (17% of total gastric flow), body (83%), and mucosa (73%) was not significantly altered during the 2-h period of NP perfusion (P greater than 0.20). Similarly, flow to the intestine showed significant change during NP perfusion. Under conditions of equivalent hemodynamic states (mean perfusion pressure), nonpulsatile arterial perfusion results in no significant alteration in gastrointestinal blood flow or its intraorgan distribution.

Animals↗
PubMed1979

Renin secretion in the chronically perfused pulseless calf. Evidence for failure of stimulation by decreased pulse pressure.

To study the influence of arterial pulse pressure on renin release, a chronic pulseless calf preparation was developed using a centrifugal left ventricular bypass blood pump. After pump implantation and recovery, control measurements of renal vein and arterial plasma renin activity, arterial pressure, and renal artery flow were obtained. The centrifugal bypass pump rate then was increased to capture cardiac output completely, and nine conscious calves were perfused in a nonpulsatile manner (pulse pressure less than 5-10 mm Hg) for 48 hours. Nonpulsatile perfusion was well tolerated and serum sodium, potassium, creatinine, and blood urea nitrogen were unchanged during bypass. Mean arterial pressure remained relatively constant [114 +/- 3 (SE) mm Hg] during bypass, and was not significantly changed from control. Although renal blood flow decreased slightly from control (667 +/- 84 ml/min) during the nonpulsatile perfusion period (555 +/- 73 ml/min), renin secretion did not increase significantly from control (482 +/- 81 ng angiotensin I/ml per hr per min) during the bypass period (531 +/- 99). A diurnal cycle of renin secretin was observed during the pulseless perfusions. These data document the lack of any significant stimulatory influence of decreased pulse pressure on renin secretion in a chronic awake calf model.

Animals↗