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Biomedical subjects

R M Greenhalgh

Publications and source records attributed to R M Greenhalgh.

At least 127 records · Page 7Linked to original sources
PubMed1987

Elastin degradation in abdominal aortic aneurysms.

Histological sections through the walls of abdominal aortic aneurysms showed scarce and disrupted elastic tissue. The elastin content of the aneurysmal aortic media was only 8.1 +/- 3.2% dry defatted weight (n = 11). The elastin content of grossly normal age and anatomically matched aortic media was 35.0 +/- 3.2% dry weight (n = 4) and the elastin content of severely atherosclerotic, stenosed infrarenal aortic media was 22.0 +/- 7.2% dry weight (n = 6). There was an inverse correlation of elastin content with the elastinolytic activity of aortic media homogenates, r = -0.78. Elastase activity, measured by the hydrolysis of [3H]elastin, was highest in aneurysmal aortic homogenates, 92.1 +/- 43.7 U/mg protein (n = 18), falling to 46.9 +/- 13.3 U/mg protein (n = 13) in severely stenosed atherosclerotic aortic homogenates and 35.5 +/- 11.9 U/mg (n = 6) in grossly normal aortic homogenates. The elastinolytic activity of stenotic aorta contained leukocyte elastase as an important component. In aneurysmal homogenates leukocyte elastase was also found but the increased elastase activity resulted from a protease(s) (Mr 95,000) extracted in 2 M urea, having minimal specificity for alanyl bonds and no immunological cross-reactivity with leukocyte elastase.

Aged↗
PubMed1987

Femoral artery pulse rise time: an objective test for aorto-iliac disease.

A method is described for assessing stenosis in the aorto-iliac arterial segment using a hand-held variable capacitance pressure transducer to take objective measurements from the common femoral pulse. The aorto-iliac segments were studied in 51 arteriopaths and the common femoral pulse rise time derived. The patients also underwent an independent clinical examination. The rise time results from 88 common femoral pulses were compared with subsequent arteriographic assessment of the aorto-iliac segments, and in 67 cases with direct intra-arterial pressure measurements from the common femoral artery. A highly significant correlation coefficient was found between the common femoral pulse rise time and the degree of aorto-iliac stenosis on the arteriogram (r = 0.80). Similarly, there was good correlation between pulse rise time and the direct common femoral/radial pressure ratios (r = -0.82). The results were analysed in terms of sensitivity, specificity and diagnostic accuracy for determining greater or less than 50% stenosis on the arteriogram. Using a pulse rise time of 200 ms a sensitivity of 97%, specificity of 93% and diagnostic accuracy of 94% were obtained. This was significantly better than clinical examination which gave a diagnostic accuracy of 83% (X2 = 5.57, P less than 0.02). The results suggest that this non-invasive method of objective pulse assessment gives superior accuracy for diagnosing aorto-iliac stenotic disease. The ease of use and relative simplicity of the apparatus are advantages over more complex non-invasive techniques employing microprocessors in the analysis of blood velocity.

Adult↗
PubMed1987

Multifactorial inheritance of abdominal aortic aneurysm.

The possible genetic predisposition to abdominal aortic aneurysm was investigated by recording the family history from 60 consecutive patients presenting for aneurysm repair. Twenty patients, age 63.2 +/- 9.3 years, had at least one first degree relative with abdominal aortic aneurysm. Thirty six patients, age 69.6 +/- 6.3 years, knew of no aortic aneurysm amongst first degree relatives and four patients could not give a full family history. A total of 25 among 320 first degree relatives (8%) or 14 amongst 192 siblings (7%) had an abdominal aortic aneurysm. Both the younger age of presentation (P less than 0.01) and the concentration of women amongst those with a positive family history argue for multifactorial inheritance of abdominal aortic aneurysm, with the genetic component calculated as approximately 70%. These same factors suggest that it might be worthwhile screening for aneurysmal disease the sibling smokers of female and younger male probands.

Aged↗
PubMed1987

Transaxillary angiography: an acceptable approach when perfemoral angiography is not acceptable.

Transaxillary angiography has been performed in a consecutive series wherever patients were unsuitable for perfemoral angiography. Between 1984 and 1986, transaxillary angiography was performed for 103 patients (81 males and 22 females with a mean age of 64 years). Major complications occurred in 2 patients (1.9%) who required surgical embolectomy with no long term sequelae. Three (2.9%) had a transient neurological deficit which lasted less than 1 week. In our hands transaxillary angiography is the best alternative when perfemoral angiography is not possible.

Adult↗
PubMed1987

Management of asymptomatic carotid bruit.

One hundred forty-nine consecutive patients who had peripheral arterial disease (PAD) with clinically audible asymptomatic bruits were studied. Sixty-two of these patients were age- and sex-matched with 62 PAD patients in whom no bruits were detected. The PAD was demonstrated by angiography or by the 1-minute exercise test. Clinical assessment was performed every 6 months and oculoplethysmography and carotid phonoangiography (OPG/CPA) were performed every year. Angiography and reconstructive surgery were performed only if symptoms of transient ischemic attack (TIA) or stroke occurred. Life-table analysis revealed that over a 5.5-year follow-up, 32% of 211 PAD patients were expected to die. In the control study 45% of bruit patients and 32% of control patients were expected to die (no significant difference). Myocardial infarction accounted for 59% of deaths in the bruit group compared with 28% in the control group (no significant difference). TIA occurred more commonly in the bruit group (26.5%) than in the controls (6%) (p less than 0.02). However, stroke without warning occurred in 9% of bruit patients compared with 8% of controls (no significant difference). It is concluded that for asymptomatic carotid bruit it is safe to wait for the onset of symptoms before angiography and corrective reconstructive surgery.

Actuarial Analysis↗
PubMed1987

Collagen in abdominal aortic aneurysm: typing, content, and degradation.

The collagen content of the media of infrarenal aorta has been compared in age- and sex-matched normal aorta and dilated and nondilated atherosclerotic aorta. The proportion of collagen was increased in aneurysmal aorta from 62% to 84% and appears to be the result of preferential elastin degradation. The ratio of type I to type III collagen, estimated from sodium dodecyl sulfate-polyacrylamide gel electrophoresis of specific cyanogenbromide peptides, did not vary significantly from 2:1 in any of the three groups of aortas. There was no evidence of increased collagenase activity in unruptured aneurysmal aorta. Collagenase activity was increased in ruptured aneurysmal aorta but could only be satisfactorily measured after resolution from the endogenous tissue inhibitor of metalloproteinases. We suggest that only limited collagen turnover occurs in the media of abdominal aortic aneurysms before rupture. A subgroup of three patients with a significant family history of aneurysm had lower amounts of type III collagen in the aortic media, suggesting that abnormalities in type III collagen may be one of the genetic factors contributing to familial clustering of aneurysms.

Aorta, Abdominal↗
PubMed1987

Whole blood clotting tests: an evaluation of five methods.

Five different methods of measuring the clotting time of fresh whole blood have been compared. The Biobridge was the best instrument, and was able to measure both anticoagulation and hypercoagulation accurately and reproducibly.

Blood Coagulation Tests↗
PubMed1987

Neurological morbidity of arch and carotid arteriography in cerebrovascular disease. The influence of contrast medium and radiologist.

A prospective study of 230 arch and carotid arteriograms in 229 patients with symptomatic cerebrovascular disease revealed that neurological morbidity was not significantly affected by patient age, nature of neurological symptoms, duration of procedure, volume of contrast medium or degree of arterial stenosis. The total neurological morbidity of 132 examinations carried out with non-ionic contrast medium (iohexol) was slightly lower than that of 98 examinations carried out with ionic contrast medium (meglumine and sodium iothalamate) but the difference was not statistically significant. However, the morbidity of 185 examinations performed by an experienced vascular radiologist was significantly lower (p less than 0.025) than the morbidity of 45 examinations performed by a series of radiologists in training and the mean time required for the procedure was 18 min longer in the latter group (p less than 0.001). These findings suggest that the neurological morbidity of arch and carotid arteriography in patients with cerebrovascular disease depends largely upon catheter technique and will not be significantly reduced by the use of non-ionic contrast medium.

Cerebral Angiography↗
PubMed1987

Aneurysm jig for anastomosis technique.

A new jig is described which enables the technique for abdominal aortic aneurysm to be taught and practiced as it is performed by arterial surgeons at the present time. The aneurysm jig enables a plastic simulated aortic aneurysm to be opened as at operation to allow the inlaying of a Dacron tube sutured into place with continuous sutures.

Anastomosis, Surgical↗
PubMed1986

Effect of early blood transfusion on gastrointestinal haemorrhage.

The effect of citrated stored blood on coagulation was studied initially in a pilot study where 25 patients with acute severe gastrointestinal haemorrhage had their whole blood coagulation measured using the Biobridge Impedance Clotting Time (ICT). This demonstrated that there is a hypercoagulable response to haemorrhage which was partially reversed by blood transfusion. Similar changes were noted in Kaolin Cephalin Clotting Times (KCCT). A further 50 patients were then randomized to receive, during the 24 h after admission, either at least 2 units of blood or no blood transfusion unless the haemoglobin fell below 8 g/dl or they were shocked. In the transfused group nine patients re-bled compared with only one in the non-transfused group (P less than 0.01, chi 2 with Yates' correction). Early blood transfusion appears to reverse the hypercoagulable response to haemorrhage thereby encouraging re-bleeding and hence the need for an operation.

Blood Coagulation Disorders↗
PubMed1986

An implanted ultrasound Doppler probe for microvascular monitoring: an experimental study.

An experimental investigation is presented into the use of pulsed ultrasound Doppler flowmetry with a percutaneously implanted probe as a monitor of microvascular anastomotic patency. The method accurately indicated and distinguished between experimental arterial and venous occlusion in epigastric island flaps. In free flaps it had advantages over manipulative, intraoperative tests of anastomotic patency and was a reliable post-operative monitor of flap circulation in the experimental model. The technique appears to have great potential as a post-operative monitor for free flaps, including those without a visible surface.

Animals↗
PubMed1986

Maximizing the use of autogenous vein using the in situ (valve incision) technique.

Bypass grafting to vessels beyond the popliteal bifurcation is an established method for treating severe limb ischaemia. Failure rate is high, however, especially when prosthetic vascular substitutes have to be used. When left in situ, saphenous vein can be used down to much smaller diameters than would be possible with reversed vein. With this method, vein utilization of around 90% can be achieved with respective increases in patency and limb salvage. Our early results with 26 in situ grafts are presented. In two cases the presence of a suitable tributary of the saphenous vein allowed a 'bifurcated' or 'femorotibial' graft to be performed. All patients (17 males, nine females) were admitted with limb threatening ischaemia. Mean ankle pressure index was 0.29 (s.d. = 0.09), range 0.18-0.53. Average graft intra-operative flow rate measured 96 ml/min. Twenty grafts remain patent while six grafts have failed. In three of these failures, performed early in the series, the graft could not be made to function at the time of surgery. The mean postoperative ankle pressure index was 0.87 (s.d. = 0.19). Cumulative patency rate at 24 months is 74%. This rises to 83% if the three 'on table' failures are excluded. Five amputations were required; four as a result of graft failure and one despite a functioning graft. Four grafts clotted within 24 h but have remained patent following immediate thrombectomy. One patient required ligation of an arteriovenous fistula on the third postoperative day.

Aged↗
PubMed1985

An experimental investigation into the use of implanted thermocouples and differential thermometry as monitors for microvascular anastomoses.

It has been suggested that direct monitoring of arterial temperature using implanted thermocouples, may have value as a clinical postoperative monitor for vascularized free tissue transfers, including those with no visible surfaces. This study evaluated the technique in experimental animals, using simple, inexpensive equipment. Mean arterial differential temperature changes, with ipsilateral (n = 20) and contralateral (n = 21) references, of 0.6 degrees C and 0.5 degrees C respectively, reliably indicated occlusion of the superficial femoral artery in situ. In epigastric island flaps, arterial occlusion (n = 24) produced mean arterial temperature changes of 0.5 degrees C, but changes after venous occlusion were not significantly greater than unoccluded base line fluctuation. Venous differential temperature did not change significantly after either arterial or venous occlusion. In six epigastric free flaps, success or failure could not be distinguished, as the wide variation in measurements in the four successful flaps overlapped the recordings in the two which failed. It was shown that the nearer to the body core, the less the temperature difference between arterial wall and periarterial tissue. Occlusion of deeply sited arteries produced little or no change in arterial temperature. In view of these findings and because of the invasive nature of the technique, the authors did not pursue it clinically.

Anastomosis, Surgical↗
PubMed1985

Carotid endarterectomy in patients with actively changing neurological deficits--correlations with CT brain scans.

The place of carotid endarterectomy in patients with actively changing neurological deficits (ACND) is yet to be defined. This is a study of 15 patients with ACND who underwent carotid endarterectomy. All patients had demonstrable neurological deficits at the time of surgery. However no patient had severe devastating symptomatology or decreased levels of consciousness. Eight patients (Group I) were classified as stroke-in-evolution (SIE) according to Millikan. Seven other patients (Group II) were also unstable with deficits of recent onset but did not demonstrate a classical progressive or stepwise deterioration. Average internal carotid stenosis was 80% (range 50-90%). In each of the Group I patients CT scans of the brain demonstrated cerebral infarction in the area appropriate to the deficit. CT scans were performed in four of the Group II patients, two of whom showed cerebral infarction while two were normal. Seven of the eight Group I patients improved after surgery while one progressed to a completed stroke. Six of the seven Group II patients improved following surgery while one died on the third postoperative day. These results suggest an improved outlook with surgery when compared either with the natural history of SIE or with the results when anticoagulants alone are used.

Brain↗
PubMed1985

Brachio-cephalic revascularization from the intrathoracic aorta: use of a T-piece graft.

Ready made T-piece dacron grafts have been available for some time for use in axillo-bifemoral procedures. This report illustrates the use of such a graft in two cases of brachiocephalic revascularization from the intrathoracic aorta. In each case the aortic arch branches were severely diseased. The technique allows placement of the 8 mm diameter limb on the ascending aorta deep to the sternum, where, because of its lack of bulk, it can sit without compression. The 8 mm side piece can be manoeuvred to follow any direction required and avoids placement of an anastomosis in an otherwise awkward area. If required, a third limb can be sutured onto the proximal limb beyond the region where compression would occur.

Aorta, Thoracic↗