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Biomedical subjects

P R Bell

Publications and source records attributed to P R Bell.

At least 19 recordsLinked to original sources
PubMed1992

Monitoring and cerebral protection during carotid endarterectomy.

Two recently published multicentre trials have confirmed the overall benefit of carotid endarterectomy in symptomatic patients with severe carotid artery disease. The key to improving further the long-term advantages of carotid endarterectomy, however, remains the continued reduction of the initial operative risk. While the principal responsibility for this continues to be borne by the surgeon, specifically in reducing technical error, the time is perhaps approaching when he or she might also be able to apply some of the recent advances in cerebrovascular research to reduce operative morbidity still further in the future. This article summarizes the aetiology and pathophysiology of operation-related neurological deficits and reviews current approaches towards intraoperative monitoring, cerebral protection and assessment of quality control.

Brain Ischemia↗
PubMed1992

Peripheral tuberculous lymphadenopathy: a review of 67 cases.

Peripheral tuberculous lymphadenopathy is the commonest form of extrapulmonary tuberculosis. Sixty-seven patients with peripheral tuberculous lymphadenopathy who presented to general surgeons and underwent lymph node biopsy between 1979 and 1989 are reviewed. Fifty-four patients (81 per cent) were of Indian subcontinent ethnic origin and 13 (19 per cent) were of white ethnic origin. The sites most commonly affected were the cervical lymph nodes. Biopsy specimens obtained by open operation were sent for microbiological examination in all but 13 cases, of whom seven were patients of white ethnic origin. Tuberculous lymphadenopathy remains an important differential diagnosis of cervical lymphadenopathy and it is essential that peripheral lymph node biopsies are examined both histologically and microbiologically.

Adult↗
PubMed1992

Role of sequential leucocyte counts and C-reactive protein measurements in acute appendicitis.

The accurate clinical diagnosis of acute appendicitis is difficult, and many techniques have been suggested to improve diagnostic accuracy such as laparoscopy, ultrasonography and barium enema examination. In this study serial total leucocyte counts and serial C-reactive protein (CRP) concentrations in acute appendicitis were measured. The sensitivity and specificity of serial leucocyte counts in acute appendicitis were 92 and 100 per cent, and for CRP concentrations 69 and 75 per cent, respectively. The sensitivity and specificity of serial total leucocyte counts fulfilled the criteria for a diagnostic test. It is suggested that in patients with equivocal clinical findings, clinical observation combined with serial leucocyte counts may improve decision making.

Acute Disease↗
PubMed1992

Storage of human pancreatic digest in University of Wisconsin solution significantly improves subsequent islet purification.

Density-gradient purification of human pancreatic islets from the collagenase-digested pancreas relies on the exocrine tissue being denser than the islets. Cold storage of the pancreas before and after digestion causes cell swelling, which can decrease the density of pancreatic exocrine tissue and adversely affect subsequent purification. Using 14 human pancreata (seven perfused in situ with hyperosmolar citrate (HOC) and seven with University of Wisconsin solution (UW)), it is shown that storage of the pancreatic digest in UW significantly increases the density of pancreatic exocrine tissue compared with storage in minimal essential medium (MEM) (P = 0.009). This results in an improvement in islet purity (P = 0.036) for HOC- but not UW-perfused pancreata. Storage in UW for 1 h not only prevented the deterioration that occurred in MEM, but resulted in an improvement in islet purity for five of the seven HOC-perfused pancreata. Most pancreata in the UK are perfused with HOC, but storage of the digest in UW results in significantly better islet purity and, when islets cannot be purified immediately, a period of storage will often improve separation and allow islets to be purified.

Adenosine↗
PubMed1992

Prostacyclin production from seeded prosthetic vascular grafts.

Endothelial cell seeding has been proposed as a method of improving patency rates in small-calibre prosthetic vascular grafts. In vivo, endothelial cells normally produce prostacyclin (PGI2), a potent antiplatelet agent. The aim of this study was to determine whether seeded grafts show significant PGI2 production after in vivo implantation. Grafts were seeded with either autologous canine venous endothelial cells or autologous microvascular endothelial cells. After 12 weeks, PGI2 production was assessed under basal and stimulated conditions. Seeded grafts were compared with non-seeded controls and the corresponding aorta. The overall patency rate in seeded grafts was 80 per cent compared with 10 per cent in non-seeded grafts (P < 0.01). Grafts seeded with cells from either source produced significantly more PGI2 than unseeded grafts in both basal and stimulated states (P < 0.05). The aorta produced significantly more PGI2 than seeded grafts under both conditions (P < 0.01). Endothelial cell seeding produces a functional graft and leads to an improved patency rate.

Animals↗
PubMed1992

Pancreatic function following partial pancreatectomy and anastomosis of the pancreatic duct to the stomach or duodenum in dogs.

The effects of pancreatic duct anastomosis to stomach (stomach group) or duodenum (duodenal group) on pancreatic function were examined in dogs following two thirds pancreatectomy. Normal fasting blood glucose concentrations were maintained in both groups despite significant reductions in glucose tolerance in the stomach group, and reductions in fasting insulin and insulin peak response in both groups. Pancreatic exocrine function was significantly decreased in both groups, though plasma p-aminobenzoic acid (PABA) concentrations were generally higher in the duodenal group. A correlation was found between plasma trypsin-like immunoreactivity (TLI) and pancreatic weight. These results indicate that anastomosis of the pancreas to bowel can be undertaken with minimal postoperative complications and that the site of the anastomosis influences pancreatic function. They suggest that preservation of more than one third of the pancreas is required for optimal function. The complementary information provided by the PABA and TLI tests suggests their dual application will be clinically useful for the detection and characterisation of naturally occurring pancreatic diseases.

4-Aminobenzoic Acid↗
PubMed1992

Intensive blood flow monitoring following femoro-distal bypass: can early outcome be reliably predicted?

Forty-two femoro-distal vein grafts were studied in the early post-operative period for up to 1 week using a newly developed Doppler monitoring system designed to make frequent, automatic assessments which were stored on tape. Thirty-three grafts remained patent at 1 month with clinical improvement but in nine cases, all performed for critical ischaemia, reconstruction was unsuccessful with six grafts thrombosing and three remaining patent without clinical improvement (haemodynamic failure). The system was shown to provide good quality data, subsequent analysis of which with respect to the time-averaged mean velocity (TAMV) and pulsatility index (PI) revealed good separation between successful and failed grafts. In 30/33 cases a good result was predicted by the early establishment of hyperaemic flow (TAMV greater than 10 cm s-1, PI less than 2), whereas in three a "low flow" state was observed (TAMV less than 10 cm s-1, PI 2-3) which also resulted in a successful outcome. Graft thrombosis was heralded by the rapid development of high pulsatility (PI greater than 6) or a progressive departure from initial hyperaemia towards more pulsatile flow within a few days. Haemodynamic failure was associated with poor flow (TAMV less than 10 cm s-1) accompanied by a PI greater than 3.5. Intensive post-operative monitoring with this new system offers a means whereby early graft outcome can be reliably predicted and also has the potential to study the effects of any intervention used to salvage high risk grafts.

Blood Flow Velocity↗
PubMed1992

Endothelial cell injury secondary to surgical preparation of reversed and in situ saphenous vein bypass grafts.

Failure of infra-inguinal vein grafts appears to be due to the development of intrinsic lesions (intimal hyperplasia, fibrous stenoses) within the graft which lead to narrowing of the lumen, poor blood flow and thrombosis. The cause of these lesions remains unknown but recently it has been suggested that endothelial injury might be an aetiological factor. The damage that can occur after preparation of reversed vein grafts includes loss of endothelial cells and functional impairment of those cells that remain, in that the ability to produce prostacyclin and endothelium-derived relaxing factor (EDRF) is reduced. The preparation of in situ grafts is different to that for reversed grafts in that a valvulotome is passed along the lumen of the vein to destroy the valves. However, little is known about the degree of endothelial injury that this technique causes. Vein samples were obtained from patients undergoing infra-inguinal and coronary artery bypass grafting. The veins were mounted in an organ bath system to measure isometric tension and exposed to the endothelium-dependent agents acetylcholine, bradykinin, adenosine, histamine and the endothelium-independent agent sodium nitroprusside. The results indicate that preparation of reversed vein grafts leads to some loss of endothelial cells with functional impairment of the cells that remain. However, preparation of in situ grafts leads to severe or total loss of endothelial cells which resulted in an absence of detectable EDRF release. These findings were confirmed by histological examination of the vein samples.

Aged↗
PubMed1992

Popliteal embolectomy: does it still have a role?

The failure of a femoral embolectomy presents a difficult problem. The role of popliteal embolectomy in the subsequent management is still not clear. A study of 12 patients who underwent a secondary popliteal embolectomy is reported. Nine of the 12 patients had successful results in terms of limb salvage. The question that has to be addressed is the role of popliteal embolectomy as opposed to thrombolysis. Recent studies tend to favour the latter approach. It is concluded that if an embolectomy catheter will not pass or will not clear the distal segment, the surgeon should consider intraoperative thrombolysis or popliteal embolectomy prior to embarking on a bypass procedure.

Amputation, Surgical↗
PubMed1992

Endothelial cell seeding of damaged native vascular surfaces: prostacyclin production.

Endothelial cell seeding has been successful in reducing the thrombogenicity of prosthetic vascular grafts in animal and clinical studies. The reduction in thrombogenicity may be attributed to the intrinsic properties of endothelial cells themselves, and their ability to produce anti-thrombogenic mediators such as prostacyclin, and endothelium-derived relaxing factor. Endothelial seeding of damaged vascular surfaces produced during percutaneous transluminal angioplasty and endarterectomy is an attractive possibility due to the excellent attachment characteristics of the sub-endothelial tissue exposed during these procedures. The ability of endothelial seeded damaged vascular surfaces to produce prostacyclin was measured in an in vitro model of vascular injury. Endothelial-seeded damaged surfaces produced significantly higher prostacyclin release than did vessels damaged by balloon dilatation (265.5 pg cm-2 min-1 and 87.5 pg cm-2 min-1 respectively). This study provides evidence that endothelial seeding of damaged native vascular surfaces is technically feasible and that seeding may reduce the thrombogenicity of vascular surfaces following balloon dilatation.

Angioplasty, Balloon↗