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Biomedical subjects

W H Pearce

Publications and source records attributed to W H Pearce.

At least 127 records · Page 7Linked to original sources
PubMed1988

Detection thresholds of nonocclusive intestinal hypoperfusion by Doppler ultrasound, photoplethysmography, and fluorescein.

Because clinical assessment of bowel viability is unreliable, other methods of determining intestinal perfusion have been recommended. Since none of these quantifies intestinal blood flow, we measured flow at the detection thresholds of Doppler ultrasound, photoplethysmography, and intravenously administered fluorescein, perfused the intestines at these threshold levels, and assessed histologic evidence of ischemic damage. The intestines of five anesthetized dogs were perfused for 4 hours via an in-line pulsatile extra-corporeal circuit assembled between the iliac and superior mesenteric arteries at either relatively physiologic (approximately 20 ml/min/kg body weight) levels or reduced levels representing the flow detection thresholds of Doppler ultrasound or photoplethysmographic probes (approximately 4 ml/min/kg). Intravenously administered fluorescein was detected at even lower perfusion levels (approximately 2.1 ml/min/kg). Clear-cut ischemic changes were documented histologically in all subjects perfused at Doppler/PPG flow detection thresholds but in none of those perfused at normal levels. We conclude that threshold blood flow detection by any one of these methods, especially fluorescein, occurs at levels inadequate to guarantee tissue viability.

Animals↗
PubMed1987

Flexible angioscopy seems faster and more specific than arteriography.

Fiberoptic angioscopy was performed with 2.5- and 3.3-mm angioscopes in 25 arteries and grafts in 19 patients. Radiologically normal and abnormal arteries and anastomotic sites were examined. All vessels and grafts were visualized and images of normal arterial wall, subclinical and obstructing atherosclerotic plaque, and suture lines were defined. Unexpected endovascular findings were noted in five patients (26%) and included large amounts of free-floating clot (one patient), atherosclerotic debris (two patients), and membranelike obstructions (two patients). Angioscopy required three to ten minutes and resulted in no complications. Experience with the flexible angioscope indicates that satisfactory visualization and specific recognition of angiographically unsuspected problems can be obtained. The flexible angioscope is faster and appears more etiologically specific than arteriography.

Angiography↗
PubMed1987

The use of infrared photoplethysmography in identifying early intestinal ischemia.

Acute intestinal ischemia and infarction remain serious clinical problems despite early operative intervention. An accurate and reproducible method of assessing ischemic tissue is critical to determine the precise limits of resection. The purpose of this study was to compare the utility of infrared photoplethysmography, intravenous fluorescein, and Doppler ultrasound in assessing intestinal ischemia in an operative canine model. After five segmental mesenteric arterial ligations in each of six conditioned dogs, the detection threshold for the limits of arterial perfusion of each modality was determined and correlated with the respective histopathologic specimens. Infrared photoplethysmography proved to be 100% sensitive for ischemia when its waveform amplitudes were 50% or greater of matched reference waveforms, whereas both intravenous fluorescein and Doppler ultrasound were 88% sensitive. All were comparably specific. We conclude that infrared photoplethysmography is comparable to intravenous fluorescein and Doppler ultrasound in the assessment of ischemic intestinal segments.

Animals↗
PubMed1987

Sympathectomy for causalgia. Patient selection and long-term results.

Thirty-four sympathectomies were performed for causalgic pain. Overt extremity trauma was the precipitating event in only 26%. In 48%, nerve compression requiring surgical relief preceded the onset of the pain; most common lumbar disk surgery (37%). In the remainder (26%), miscellaneous vascular conditions contributed. Satisfactory immediate relief was obtained in 97% and 61% were completely relieved of pain initially. There were no deaths, 10% wound complication rate, and one instance of Horner's syndrome. Postsympathectomy neuralgia occurred in close to 40%, lasted a little over a month on the average but did not persist beyond ten weeks. In extended follow-up, only one patient failed to sustain satisfactory relief (97% of those relieved, 94% of the total) and 84% continued to enjoy the same degree of relief as they had immediately preoperatively. This frequency, degree, and duration of benefit establishes causalgic pain as one of the best indications for surgical sympathectomy.

Adolescent↗
PubMed1987

Traumatic popliteal and trifurcation vascular injuries: determinants of functional limb salvage.

Forty-seven patients with 64 popliteal or trifurcation arterial injuries were analyzed to elucidate the influence of associated limb trauma on ultimate functional recovery. Nerve, bone, and soft tissue injuries appeared to be critical risk factors. Two or more risk factors were present in 60 percent of 30 blunt injuries, compared with 17 percent of 18 penetrating injuries. All limbs with less than two of these risk factors recovered to a functional state, whereas none of the limbs with all three risk factors had a good outcome, and 7 of 13 limbs (54 percent) were amputated. Vascular reconstruction was successful in 90 percent of the 48 limbs, and patency was 100 percent among the 27 limbs with less than two risk factors. Patients with all three risk factors should be considered for early amputation. We believe reports of peripheral vascular trauma must delineate associated limb injuries to facilitate analysis of patients stratified by relative risk.

Adolescent↗
PubMed1987

Cerebral ischemia-reperfusion injury in the gerbil.

Gerbils subjected to cerebral ischemia (unilateral carotid occlusion for 6 hr) were either asymptomatic or developed increasingly severe neurologic deficits which correlated with degrees of brain swelling (weights of ischemic hemisphere versus the contralateral control hemispheres) following 3 hr of reperfusion. Asymptomatic gerbils or gerbils suffering only mild deficits survived for 1 week following reperfusion while gerbils suffering moderate to severe deficits had a poor survival rate with only 22% remaining alive after 1 week.

Animals↗
PubMed1987

Infrarenal venous anomalies and aortic surgery: avoiding vascular injury.

Anomalies of the left renal vein (retroaortic left renal vein and left renal vein collar) and the inferior vena cava (left-sided inferior vena cava and caval duplication) occur relatively infrequently but pose potential hazards to the surgeon during aortic repair. We report the cases of three patients in which one or a combination of these anomalies of the renal vein and inferior vena cava was present. The embryologic origins of each of the anomalies are discussed, and suggestions, both surgical and nonsurgical, are proposed that might aid the surgeon in avoiding injury and subsequent bleeding from these anomalous structures during surgical operations on the abdominal aorta.

Aged↗
PubMed1987

Extra-anatomic bypass: a closer view.

The results of 60 femorofemoral, 27 axillobifemoral, and 15 axillounifemoral bypasses were analyzed. Considered in this order, the operative mortality rate was zero, 11%, and 13%, respectively; initial hemodynamic failure was 7%, 13%, and 9%, respectively; 5-year overall primary patency rate was 67%, 62%, and 19%, respectively; and the secondary patency rate was 74%, 82%, and 37%, respectively. However, axillobifemoral patency was made to seem better by including six cases (12 graft limbs) performed because of nonocclusive disease (aneurysm or failure of graft performed for aneurysm). Excluding these, axillobifemoral primary and secondary patency decreased to 47% and 69%, respectively. Femorofemoral bypass results were made worse by cases performed because of unilateral failure of an aortic bifurcation graft. Exclusion of these bypasses increased primary and secondary patency rates to 74% and 82%, respectively. Occlusion of the major outflow artery (superficial femoral) markedly affected long-term patency of all three bypasses. Thus, "good" and "poor" runoff primary patencies were, respectively, for femorofemoral bypass 79% and 53%, for axillobifemoral bypass 92% and 41%, respectively (occlusive disease only), and for axillounifemoral bypass 54% and zero, respectively. This detailed breakdown of results explains the wide variances in the reported results for these extra-anatomic bypasses and provides a better perspective for their application in different clinical settings.

Analysis of Variance↗
PubMed1986

Fibrin glue as a biologic vascular patch--a comparative study.

Fibrin glue is a biologic two component hemostatic adhesive. Fibrin glue acts as an effective vascular plus after arterial injury without suture at pressures twice systolic. It is also effective on vein at physiologic pressures, however, venous distensibility precludes its efficacy beyond these limits. Recent studies have documented its utility as a preclot material on vascular grafts and as a seal for sutured vascular anastomoses. This study was designed to characterize the glue's sealant ability when applied to open arterial and venous injuries, and to compare its efficacy with currently available hemostatic agents. Segments of canine peripheral artery and vein were isolated and perforated with a 16-gauge needle. This injury was treated by random application of either fibrin sealant (FS), oxidized cellulose (OC), microcrystalline collagen (MC), or MC plus thrombin (MCT). Five minutes after patch application, intralumenal pressure was increased progressively with saline infusion to ascertain bursting threshold. The arterial bursting threshold was significantly higher for FA (250 +/- 59.7 mm Hg) than for OC (12.5 +/- 6.1 mm Hg), MC (17.2 +/- 21.9 mm Hg) or MCT (10.8 +/- 13.8 mm Hg) (P less than 10(6)). The bursting threshold of FS applied to vein (17.5 +/- 11.7) was not significantly different from other agents (P less than 0.05).

Animals↗
PubMed1986

Radiation exposure risk to the surgeon during operative angiography.

Intraoperative angiography has become an essential adjunct to reconstructive vascular surgery. Therefore, radiation exposure and its potential risks to the performing surgeon need to be known. To study this, we designed experimental and clinical tests quantifying the radiation exposure to the surgeon during different intraoperative angiograms. Radiation exposure to various parts of the surgeon's body was quantified by thermoluminescence dosimetry. During each exposure a surgeon standing one foot from the x-ray tube received an absorbed dose equivalent to 0.24 to 1.4 millirems, which is about half that of an intraoperative cholangiogram. With 5 000 millirems considered the maximum permissible dose, this would imply that an upper limit of about 3 500 intraoperative angiograms each year (68 each week) could be performed safely. Comparatively, abdominal angiography carried the most significant risk (p = 0.01) and peripheral angiography was the least hazardous. Fluoroscopy increased radiation exposure more than four times that of nonfluoroscopic procedures (p = 0.05). The surgeon's extremities received the greatest dose, followed by the eyes and neck, suggesting the need for individual monitoring devices for those parts to be worn by surgeons who perform operative angiograms more frequently than average. Our study indicates that the radiation dose received by the surgeon during operative angiography, especially that of peripheral vessels, is minimal. Operative arteriography is not only a simple and readily available diagnostic tool, but it is quite a safe procedure if applied correctly.

Angiography↗
PubMed1985

Bacterial adherence to vascular grafts after in vitro bacteremia.

All currently used arterial prosthetics have a greater susceptibility to infection following bacteremia than does autogenous tissue. This experiment compares quantitative bacterial adherence to various prosthetic materials after bacteremia carried out in a tightly controlled and quantitative fashion. Ten centimeters long, 4 mm i.d. Dacron, umbilical vein (HUV), and polytetrafluoroethylene (PTFE) grafts, as well as PTFE grafts with a running suture line at the midportion were tested. Each graft was interposed into a pulsatile perfusion system modified from a Waters MOX 100 TM renal transplant pump. Indium-111-labeled Staphylococcus aureus were added to heparinized canine blood to give a mean concentration of 4.7 X 10(6) bacteria/cc. This infected blood was recirculated through each graft for 30 min at a rate of 125 cc/m, 100 Torr (sys), 60 beats/min. The gamma counts/graft were used to calculate the number of bacteria/cm2 of graft surface. After nine experiments, a mean of 9.63 X 10(5) bacteria/cm2 were adherent to the Dacron, 1.04 X 10(5) bacteria/cm2 to the HUV, and 2.15 X 10(4) bacteria/cm2 to the PTFE. These differences were all significant at the 0.05 level. The addition of a suture line increased bacterial adherence to the PTFE graft by 50%. These results suggest that PTFE is the vascular graft material of choice when a prosthetic graft must be implanted despite a high risk of subsequent clinical bacteremia. Our in vitro, pulsatile perfusion model gave accurate and reproducible results, and appears well suited for further studies of bacterial, or platelet adherence to grafts, as well as the biomechanics of vascular conduits.

Adhesiveness↗
PubMed1985

Endothelial cell seeding of a new PTFE vascular prosthesis.

Previous attempts to line polytetrafluoroethylene (PTFE) prostheses with enzymatically derived endothelial cells have not been as successful as similar work with Dacron grafts because of the failure of such prostheses to develop a satisfactory subendothelium. This article reports our experience with a new, highly porous, unreinforced PTFE prosthesis that appears to circumvent this problem. Segments (4 mm I.D., 10 cm in length) of this new graft were implanted in 41 mongrel dogs as carotid interposition grafts. One graft in each dog was seeded with the dog's own endothelial cells, whereas the contralateral graft was treated in an identical fashion except for the inclusion of endothelium. After a mean period of 7 weeks of implantation, the grafts were harvested, their patencies were noted, the thrombus-free area of their luminal surface was calculated with computerized quantitative planimetry, and graft segments were submitted for scanning and transmission electron microscopy. In seven dogs the luminal surface was scraped from each graft and measured quantitatively. Although seeded grafts failed to show a statistically significant increase in patency during the short course of this experiment, a trend in that direction was quite striking. Furthermore, seeded grafts had a significant increase in thrombus-free area on their luminal surface as well as a significant reduction in the volume of luminal thrombus. Histologically, seeded grafts developed a substantial 75 to 100 microns cellular subendothelium beneath a confluent endothelial lining. No endothelial lining was noted in control grafts. We believe that the superior handling characteristics of this new prosthesis and its ability to develop a substantial subendothelium with a confluent endothelial lining suggest potential future applications and warrant further investigation.

Animals↗
PubMed1985

Bacterial adherence to endothelial-seeded polytetrafluoroethylene grafts.

Since infections of an arterial prosthesis pose a serious threat to life and limb, efforts to produce a graft that is resistant to hematogenous bacteremia continue. We studied the effect of endothelial seeding on bacterial adherence to polytetrafluoroethylene grafts in a canine model. Enzymatically derived venous endothelial cells were seeded in 10 cm long, 4 mm inner diameter polytetrafluoroethylene grafts, which were then implanted as carotid interpositions opposite contralateral unseeded controls. After 4 to 8 weeks, each dog received an intravenous infusion of 3 X 10(8) radiolabeled Staphylococcus aureus. Seeded grafts had significantly fewer adherent viable bacteria than had control grafts (mean, 432 versus 989; p less than 0.05) and significantly fewer radiolabeled bacteria (mean, 2 X 10(5) versus 8 X 10(5); p less than 0.05). Seeded grafts also had significantly more thrombus-free, luminal surface area than had control grafts (mean, 72% versus 40.6%; p less than 0.05). Scanning electron microscopy and autoradiography of seeded grafts confirmed that the sites of bacterial adherence largely corresponded to accumulations of surface thrombus. In this experiment, endothelial seeding appeared to protect against bacterial adherence after a hematogenous challenge 4 to 8 weeks after implantation by reducing luminal thrombi.

Adhesiveness↗
PubMed1985

Kinetics of endothelial cell seeding.

Endothelial cell seeding improves patency of small-diameter Dacron grafts and facilitates the development of a complete endothelial flow surface. However, the ideal number of cells relative to the length of graft to be seeded has not been determined. With a canine model previously shown to result in a well-endothelialized graft within 4 to 6 weeks, this study measured the quantity of autogenous endothelial cells labeled with indium 111-oxine that initially adhered to 10 cm long, experimental, porous 4 mm I.D. polytetrafluoroethylene grafts and then calculated their subsequent disappearance following implantation as carotid interposition grafts. Graft radioactivity was monitored with a gamma camera and compared with that of control vials of indium 111 implanted in the same animals. Counts were measured immediately at implantation and for up to 72 hours following restoration of flow. Data were analyzed by linear regression. The mean number of harvested endothelial cells was 6.2 X 10(5). A mean of 19.8% of the harvested cells were adherent to the grafts initially after seeding. In the first 30 minutes following restoration of flow, there was a rapid loss of these cells to a mean value, which was 70.2% of those initially present. From 30 minutes to 24 hours, cell losses continued at a constant rate of 3.7%/hr (r = -0.922, p less than 0.001). Beyond 24 hours, further loss was insignificant. Consequently, approximately 2.72 X 10(4) cells, or only 4.4% of all cells originally harvested, appear adequate to seed 12.5 cm2 of graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Extended autogenous profundaplasty and aortofemoral grafting: an alternative to synchronous distal bypass.

The success of aortofemoral reconstruction in patients with superficial femoral artery occlusion depends on the restoration of satisfactory inflow to the profunda femoris artery (PFA). When significant occlusive disease exists within this vessel, two options exist: femoral-distal bypass or reconstruction of the PFA. In 165 aortofemoral reconstructions for occlusive disease, 29 limbs (9%) underwent an extended autogenous profundaplasty. The cumulative 5-year patency rate of autogenous reconstructions was 86%, with a 72% limb salvage rate without distal bypass. Two limbs were amputated early for sepsis with patent grafts. One early and one late femoral-popliteal bypass was performed. Groin wound complications, primarily lymphoceles and wound edge necrosis, were numerous (38%). There were no graft infections. Relief of ischemic symptoms was achieved regardless of patency of the popliteal artery. Furthermore, noninvasive testing, clinical history, and angiography failed to accurately predict the results. In patients with advanced PFA disease undergoing aortofemoral grafting, the extended autogenous profundaplasty is a durable procedure with excellent relief of ischemic symptoms.

Aged↗
PubMed1984

Sequential changes in coagulation and platelet function following femorotibial bypass.

Twenty-four patients who received no antiplatelet medications and underwent femorotibial bypass grafting (nine vein, 12 polytetrafluoroethylene [PTFE], and three composite PTFE-vein) had serial measurements taken of their platelet function and coagulation. The concentration of collagen required to produce half-maximal platelet aggregation (Kd), the platelet aggregation ratio, antithrombin III, factor VIII-related antigen, and fibrinolytic activity (platelet-rich plasma) was measured preoperatively and 3 and 7 days after surgery. Before surgery eight patients exhibited an increase of platelet reactivity to collagen. Following femorotibial bypass grafting, the mean preoperative Kd of 0.52 +/- 0.37 microgram/ml fell to 0.34 +/- 0.35 microgram/ml on the third postoperative day (P less than 0.001) and returned to 0.41 +/- 0.72 microgram/ml on day 7. Factor VIII-related antigen increased from a mean preoperative value of 248 +/- 29% of normal activity to a mean of 360 +/- 96% on postoperative day 3 (p less than 0.01) and further increased to 428 +/- 78% on day 7 (p less than 0.01). Fourteen patients had antithrombin III measurements taken, and their levels also fell on the third postoperative day (110 +/- 5.7% to 71 +/- 6.5%; p less than 0.001). No significant changes in fibrinolytic activity were noted. Persistent platelet reactivity was found in seven patients beyond the seventh postoperative day. After administration of 325 mg of aspirin, the abnormal platelet reactivity ceased. Increased platelet reactivity to collagen, factor VIII-related antigen, and a decrease in the antithrombin III level are indicative of a hypercoagulable state in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens↗