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Biomedical subjects

W V Sharp

Publications and source records attributed to W V Sharp.

At least 19 recordsLinked to original sources
PubMed1992

Initial experience with laparoscopic surgery: establishing a new surgical procedure.

Laparoscopic surgery impacted the surgical world in the United States in 1990. This report reviews the initial experience of 34 surgeons in 8 teaching hospitals of the Northeastern Ohio Universities College of Medicine. There were 538 cases reported from May 1, 1990 to January 31, 1991. There was no mortality and the morbidity rate was 4.8%, including three bile duct injuries. The conversion rate to an open procedure was 6.1%. The criteria for credentialing, training, and resident and faculty education are included. The data reported by the Surgery Department of Northeastern Ohio Universities College of Medicine are very similar to reported series from the current literature.

Adult↗
PubMed1990

A canine model of intimal hyperplasia (IH) in autogenous vein grafting: a preliminary report.

High failure rates (10-40% at 1 year and 2-6% per year thereafter) of autologous vein grafts in peripheral bypass surgery due to progressive intimal hyperplasia (IH) have prompted researchers to search for an animal model that develops IH in a relatively short period of time. This study summarizes our experiences in promoting IH in a canine model. Eight to ten centimeters of both jugular veins were exposed in 40 adult mongrel conditioned dogs. After division into 4-5-cm lengths, the segment of jugular vein most proximal was ballooned at 800-900 mm Hg with a modified 8F Fogarty catheter to induce intimal and medial layer injury. The distal segment was left nonballooned. Segments of these autologous vein grafts, 1.5 cm in length, both ballooned and nonballooned, were then anastomosed, end to end, into the carotid and femoral circulations. Six weeks postoperatively the grafts were perfusion-fixed, harvested, and histologically processed, and the amount of the lumen in midgraft sections occupied by IH was determined by image analysis. In all dogs, the degree of IH was significantly greater in the balloon catheterized vs noncatheterized graft segments. IH was more severe in the femoral than in the carotid arteries. The grafts that developed the most severe intimal hyperplasia were femoral grafts that had been balloon catheterized. We conclude that these protocols are effective in inducing IH in a canine model in short postoperative times.

Animals↗
PubMed1990

Material and structural characterization of human saphenous vein.

Saphenous vein patch rupture after carotid endarterectomy is an infrequent but devastating complication. This study was undertaken to evaluate the material and structural properties of fresh human saphenous veins to understand the causes of this complication. Segments of saphenous veins were obtained from 22 patients from vein harvested during coronary artery bypass surgery. Ninety-three specimens, oriented in both circumferential (n = 45) and longitudinal (n = 48) directions, were prepared from the available vein segments for testing. Specimens were mounted on specially designed grips and then subjected to uniaxial tension testing. For each specimen the following material and structural parameters were determined: vessel diameter, tensile stiffness, failure and ultimate forces, and tensile modulus, failure stress, and strain. The physical properties of specimens evaluated in longitudinal orientations and thus limit the inherent strength of the vein. The physical properties of circumferentially tested vein specimens were negatively correlated to age, female gender, diabetes, and hypertension. The data obtained in this investigation suggest that age, hypertension, as well as diabetes and gender may adversely influence the circumferential tensile strength of human saphenous veins used as patch grafts.

Aged↗
PubMed1989

Derivation of human microvascular endothelial cells for prosthetic vascular graft seeding.

This report summarizes our techniques and experiences deriving microvascular endothelial cells from fat for vascular graft seeding in 17 patients. Microvascular endothelial cells were derived from abdominal wall fat by collagenase incubation. The mean number of cells obtained using the described procedure was 6.83 x 10(5) cells/gram of fat processed. Histologic evaluation of the harvested cells revealed significant numbers of contaminating cell types in addition to Factor VIII-positive microvascular endothelial cells. These cells were seeded onto 6 mm ID PTFE vascular grafts in patients undergoing peripheral vascular arterial revascularization. The mean number of seeded cells was 8.04 x 10(6) cells/graft. Approximately 90 minutes were required to harvest and isolate the microvascular cells from the fat samples. We feel there are significant technical advantages to deriving endothelial cells from microvessels of human fat for vascular graft seeding.

Adipose Tissue↗
PubMed1989

Angioscope-assisted occlusion of venous tributaries with prolamine in in situ femoropopliteal bypass: preliminary results of canine experiments.

Ten mongrel dogs underwent left lower extremity in situ femoropopliteal bypass with femoral vein. A 20 to 25 cm myocutaneous bridge was left between femoral and popliteal anastomoses. A 2.8 mm angioscope was introduced intraluminally to visualize venous tributaries (VT). A balloon occlusion catheter was placed alongside the angioscope and directed in each VT. Prolamine was injected into each VT to effect occlusion. Seven dogs were followed up for 1 week and three dogs for 1 month. A total of 34 VT (range one to five per dog) were available for attempted occlusion. Twenty-nine of 84 (85%) VT were able to be occluded based on comparison of pre-VT and post-VT occlusion angiograms. Poor visualization of VT or VT too small to admit the 5F catheter were reasons for failure. We conclude that (1) in the canine model studied angioscope-assisted occlusion of femoropopliteal during bypass is technically feasible, (2) this technical detail makes unnecessary medial thigh dissection for exposure of the vein graft, and (3) during short-term observation prolamine appeared to be a suitable occluding substance.

Anastomosis, Surgical↗
PubMed1989

Analysis of benefit of anticoagulation after placement of Kimray-Greenfield filter.

The Kimray-Greenfield venal caval filter is widely accepted as a means of preventing pulmonary embolism when medical anticoagulation has failed or complications have developed. When indicated, anticoagulants are usually resumed after placement of the filter. A retrospective study was performed comparing the thromboembolic and postphlebitic complications in patients who continued to receive anticoagulants after placement of the filter versus those who did not. Sixty-eight Kimray-Greenfield filters were placed in 68 patients (43 men and 25 women) during a four year period. After placement of the filter, 26 patients received anticoagulants and 42 did not. Three of those receiving anticoagulants and six of those who did not had significant swelling of the leg; two of those receiving anticoagulants and two of those who did not had a recurrent deep venous thrombosis. There were no instances of recurrent pulmonary embolism. There were no significant differences in the results of these two groups of patients. These results are consistent with those reported in the literature in that no correlation has been found between the use of anticoagulants after placement of the filter and recurrent thromboembolism or stasis sequelae. In view of the complications associated with medical anticoagulation, we recommend its discontinuation in all patients after placement of the Kimray-Greenfield filter.

Anticoagulants↗
PubMed1988

The effects of pore size and endothelial cell seeding upon the performance of small-diameter e-PTFE vascular grafts under controlled flow conditions.

The purpose of this study was to determine the effects of endothelial cell seeding and graft internodal distance upon the performance of 4-mm-ID e-PTFE grafts during acute reduced blood flow conditions. PTFE grafts especially manufactured with three different mean internodal distances (28, 40, and 52 microns) were evaluated. Fifteen dogs (n = 5 for each design of PTFE graft) underwent bilateral carotid artery replacements with 6 cm lengths of 4-mm-ID PTFE grafts. In each dog one graft was seeded with enzymatically derived endothelial cells; the contralateral graft was nonseeded. All grafts were evaluated 5 weeks postoperatively. Dogs with bilaterally patent grafts were subsequently subjected to flow conditions through the graft that were maintained at 30% of the initial flow rates for 4 hr. Following controlled low flows the grafts were excised and assessed for patency, thrombus-free surface area, inner capsule thickness and prostacyclin production. Endothelial cell seeding of these small-diameter e-PTFE vascular grafts improved patency and thrombus-free surface areas in grafts of all pore sizes, with these parameters being greatest in the 40-microns grafts. Inner-capsule healing in these grafts was controlled and related to the pore size. PGI2 production was improved in endothelial cell seeded grafts of all pore sizes. However, neither endothelial cell seeding nor graft pore size affected the performance of these e-PTFE grafts under conditions of reduced blood flows.

Animals↗
PubMed1988

Microvascular endothelial cell seeding of small-diameter Dacron vascular grafts.

One obstacle to the clinical implementation of endothelial cell seeding of vascular prostheses is the difficulty in derivation of large numbers of autologous endothelial cells from blood vessels of patients requiring vascular grafting. Capillary endothelial cells obtained from fat have been suggested as an abundant alternative to large-vessel endothelium for graft seeding. The object of this study was to evaluate the performance of 4-mm internal diameter (ID) Dacron Microvel grafts seeded with omentally derived microvascular endothelial cells. Six-cm lengths of the test grafts were implanted bilaterally into canine carotid arteries. One of each pair of grafts was seeded with endothelial cells (means = 8.4 x 10(6)) derived from collagenase digestion of autologous omental fat samples. The contralateral graft of each pair was nonseeded. At 5 weeks postoperatively, the grafts were harvested and evaluated. The mean patencies of both the seeded and nonseeded grafts were 89 percent. The mean thrombus-free surface area for seeded grafts was 95 +/- 11 percent. This value was significantly different statistically from the mean thrombus-free surface area of nonseeded grafts, which was 43 +/- 19 percent (P less than .05). Histologically, midgraft regions of seeded grafts were cellular, stained positive for collagen, and were characterized by inner capsules ranging in thickness between 35-94 microns. Luminal cells were identified as endothelial by peroxidase antiperoxidase staining techniques. Midgraft regions of nonseeded grafts demonstrated thrombus accumulation, limited cellularity, and inner capsules between 59-194 microns thick. Scanning electron microscopy of seeded grafts revealed smooth luminal surfaces with tight junctions between adjacent cells; surface cells were not present on midgraft regions of nonseeded grafts. In conclusion, endothelial cells derived from omental fat successfully surfaced on Dacron grafts and imparted characteristics to the graft that would predict long-term graft success.

Animals↗
PubMed1988

Experimental pharmacologic cerebroprotection.

In the first part of this experiment, the effects of pharmacotherapy on the neurologic consequences of transient global ischemia were examined in Wistar rats. The control and four experimental groups each contained six rats. In comparison to the control group receiving normal saline (NS) solution, in which no rats survived, all rats given naloxone (Nx) (23 mg/kg), superoxide dismutase (SOD) (10,000 U/kg), or allopurinol (APL) (35 mg/kg), 15 minutes before interruption of cerebral blood flow, survived the 20-minute period of global ischemia (p less than 0.01, p less than 0.01, p less than 0.01, respectively). No rat receiving deferoxamine (DEF) (20 mg/kg) survived the same ischemic period. In the second part of the experiment, the arachidonic acid (AA) content of brain samples was determined by gas chromatography and was used as an indicator of cerebral ischemia. Two control and four experimental groups consisted of six rats each. An ischemia control group received NS, whereas experimental groups were given Nx, SOD, APL, or DEF with the same previous dosage schedule. The animals were decapitated 15 minutes after drug infusion and cerebral ischemia was simulated by incubation of the heads in a 37 degrees C water bath for 60 minutes. AA content of ischemic brain treated with NS was markedly elevated (60.0 +/- 24.1 micrograms/gm of brain tissue), whereas in comparison the AA content of brain treated with Nx (5.1 +/- 3.0 micrograms/gm of brain tissue, p less than 0.05), SOD (3.5 +/- 2.7 micrograms/gm of brain tissue, p less than 0.05), or APL (2.9 +/- 1.5 micrograms/gm of brain tissue, p less than 0.05) all demonstrated much lower levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Allopurinol↗
PubMed1987

A metropolitan experience with infrainguinal revascularization. Operative risk and late results in northeastern Ohio.

Despite being of fundamental importance, the late results of major arterial reconstruction rarely have been documented throughout a large metropolitan area. In this study of 932 patients entered into the computer registry of the Cleveland Vascular Society, 19 surgeons representing 13 community hospitals and referral centers in Cleveland and Akron report the intermediate-term outcome during a mean interval of 35 months after infrainguinal lower extremity revascularization performed in northeastern Ohio from 1978 through 1982. Operative risk (5%), the early amputation rate (7%), and actuarial 5-year survival (48% to 55%) for patients with rest pain or tissue necrosis were significantly worse (p less than 0.05) than comparable figures (0.6%, 0%, and 77%, respectively) for others who underwent procedures for disabling claudication. Although both materials had similar success above the knee, the cumulative 3-year patency rate of autogenous vein bypass to the distal popliteal (69% to 88%; p less than 0.05) and tibioperoneal arteries (43%; 0.05 less than p less than 0.1) was superior to the results of polytetrafluoroethylene grafts (32% to 50% and 19%, respectively). Moreover, polytetrafluoroethylene grafts required reoperations at three times the rate of vein grafts to maintain limb salvage.

Aged↗
PubMed1987

Endothelial cell seeding improves 4 mm PTFE vascular graft performance in antiplatelet medicated dogs.

The ideal prosthetic vascular graft for the replacement or bypass of small vessels has not yet been developed. Many studies have documented the success of endothelial cell seeding in small-diameter Dacron grafts, but few have reported the application of this protocol to small-diameter PTFE grafts, and none have reported seeding small-diameter PTFE grafts in antiplatelet medicated dogs. The present study was undertaken to assess the efficacy of endothelial cell seeding of small-diameter (4 mm ID) PTFE (Gore-Tex) carotid artery interposition grafts in the antiplatelet medicated dog. Twenty-five male mongrel dogs were included in this study. In each dog one carotid artery was replaced with an endothelial cell seeded PTFE graft; the contralateral artery was replaced with a nonseeded graft. The in vivo progress of graft performance was evaluated from 1 to 4 weeks postoperatively. The endothelial cell seeded grafts achieved significantly higher patencies and mean thrombus-free surfaces than nonseeded grafts. Midgraft endothelium was identified only on the seeded grafts at 3 and 4 weeks, with a maximal luminal coverage of 10-12%. The measurements of prostacyclin (PGI2) production indicated that the antiplatelet agent therapy did inhibit endothelial cell cyclooxygenase. The presence of outer capsule vasa vasora, anastomotic pannus ingrowth, transinterstitial cellular ingrowth, and thin inner capsules characterized the endothelial cell seeded grafts in contrast to the nonseeded grafts. We conclude that enhancement of graft performance is achieved by combining both an antiplatelet regimen and endothelial cell seeding in small-diameter PTFE vascular grafts.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Prostaglandin biochemistry of seeded endothelial cells on Dacron prostheses.

The beneficial effect of seeding endothelial cells on synthetic vascular conduits has been well established. The biochemical production and interaction of the prostaglandins, prostacyclin (PGI2) and thromboxane (TxA2), were studied on Dacron vascular grafts that were seeded with autogenous venous endothelial cells. Seventy-three seeded and nonseeded grafts were implanted into the carotid arteries of dogs. Animals were medicated with either cyclooxygenase inhibitors (aspirin and dipyridamole, or ibuprofen, or U-53,059), or dipyridamole alone, or a thromboxane synthase inhibitor, U-63557A. All animals were killed at 5 weeks and analyzed for patency, thrombus-free surface (TFS), and PGI2 and TxA2 production from mid-graft punch biopsies. PGI2 and TxA2 identifications were made by radioimmunoassay determination of 6-keto PGF1 alpha and TxB2, respectively. Results of the study demonstrated in nonmedicated animals a slightly increased patency rate in seeded vs. nonseeded grafts (50% vs. 40%) and a more significant difference in TFS (49% vs. 24%). The addition of cyclooxygenase inhibitors or TxA2 synthase inhibitors significantly improved both patency (90% vs. 47%) and TFS (87% vs. 9%) in seeded vs. nonseeded grafts. PGI2 production was decreased in seeded grafts with the use of cyclooxygenase inhibitors in all cases. It is concluded that seeded endothelial cells on Dacron velour grafts can synthesize PGI2; these PGI2 levels are far less than PGI2 levels produced by endothelial cells from the adjacent carotid artery; and TxA2 synthase inhibitors best improve thromboresistance of seeded grafts without significant reduction in PGI2 production.

Animals↗
PubMed1986

Abdominal aortic aneurysm and the pseudorupture syndrome.

A consistently high mortality for ruptured abdominal aortic aneurysm has given rise to an aggressive approach in the management of these patients. However, there is a group of patients who present with signs and symptoms suggesting a ruptured abdominal aortic aneurysm but instead have other life threatening conditions. These patients and their management are presented herein.

Adenocarcinoma↗
PubMed1985

Effects of antiplatelet agents in combination with endothelial cell seeding on small-diameter Dacron vascular graft performance in the canine carotid artery model.

The purpose of this study was to assess the success of endothelial cell-seeded and non-seeded small-diameter vascular grafts in dogs medicated with antiplatelet agents. Eighty dogs underwent bilateral carotid artery replacements with 6 cm lengths of 4 mm I.D. double-velour Dacron grafts. In each dog one graft was seeded with enzymatically derived autologous endothelial cells; the contralateral graft was nonseeded. The following anti-platelet medications were administered beginning 4 days preoperatively: aspirin (5 grains every day); dipyridamole (50 mg twice a day); aspirin plus dipyridamole (5 grains each day plus 50 mg twice a day); aspirin (1.25 grains every other day); ibuprofen (10 mg/kg/day); U-53,059, a cyclooxygenase inhibitor (3 mg/kg/day); and U-63557A, a thromboxane synthase inhibitor (10 mg/kg/day). Grafts were harvested 5 weeks postoperatively. Graft success was evaluated by patency, thrombus-free surface area, area endothelialized, and graft production of prostacyclin. None of the medications prevented neoendothelialization of seeded grafts. Mean patencies of endothelial cell-seeded grafts from medicated dogs were significantly greater than mean patencies of endothelial cell-seeded grafts from nonmedicated dogs. The cyclooxygenase inhibitors best maintained patency in nonseeded grafts. Thrombus-free surface areas of endothelial cell-seeded grafts from medicated dogs were significantly greater than from nonseeded control grafts from the medicated dogs. All medications impaired prostacyclin synthesis. We conclude that the combination of endothelial cell seeding plus antiplatelet medication is most efficacious in small-vessel grafting success and that high levels of prostacyclin production by vascular grafts are not necessary to maintain patency in dogs medicated with antiplatelet agents.

Animals↗
PubMed1985

Small-diameter vascular prostheses: two designs of PTFE and endothelial cell-seeded and nonseeded Dacron.

Despite numerous advances in biomaterials design and utilization, the perfect artificial small-vessel substitute has yet to be developed. Dacron and expanded polytetrafluoroethylene (PTFE) are two materials potentially appropriate for use as small-vessel prostheses. We report the patencies of endothelial cell-seeded and nonseeded 4 mm I.D. Dacron grafts and two designs of nonseeded 4 mm I.D. PTFE (Gore-Tex and Impra) in the carotid position in dogs. All graft lengths exceeded the calculated maximum critical length for the material being tested. Dacron grafts, both endothelial cell-seeded and nonseeded, achieved higher patencies than both designs of PTFE. Endothelial cell-seeded Dacron grafts achieved the highest patencies. Endothelium was present to a significant extent only on endothelial cell-seeded Dacron grafts. There was little pannus ingrowth or midgraft pseudointima on nonseeded Dacron or on patent PTFE grafts although thrombus-free surface areas of patent PTFE grafts were high. These comparative data support the utility of endothelial cell seeding in achieving high patencies of small-diameter vascular grafts.

Animals↗
PubMed1984

Blunt trauma to the axillary artery.

Blunt trauma to the axillary artery is an unusual injury. Patients with these injuries may not present with "classic" signs of arterial insufficiency; therefore a high index of suspicion is necessary to avoid delay in treatment. This article presents three patients with unusual injuries to the axillary artery and discusses their management.

Adult↗