Search PubMed⌕ Search

Biomedical subjects

R N Baird

Publications and source records attributed to R N Baird.

At least 73 records · Page 4Linked to original sources
PubMed1994

A multicenter study of popliteal aneurysms. Joint Vascular Research Group.

PURPOSE: The purpose of this study was to determine current practice in the treatment of all categories of popliteal aneurysms (PA) in light of the efficacy of intraarterial thrombolysis in PA presenting as acute ischemia. METHODS: Prospective data collected from 19 vascular surgeons from 200 PA in 137 patients during a 4-year period from 1989. RESULTS: The most common presentation (125 PA) was leg ischemia, with the most severe symptom being claudication in 58, acute limb-threatening ischemia in 56, and digital atheroembolism in 11 limbs. The nonischemic group (75 PA) included 43 symptom-free cases and 32 cases with local symptoms arising from the popliteal fossa. Of 62 patients requiring emergency treatment, bypasses were done in 56, 10 of whom had early occlusion. Thrombolysis was used alone or in combination with bypass on 23 occasions, with 16 successful outcomes. Of 138 PA presenting electively, 80 underwent bypass, with one early occlusion, and 58 were observed. In the observed group, 18 later underwent bypass during a median follow-up of 22 months. The indications for late bypass were expansion of a small (< 2 cm) asymptomatic PA and the development of distal ischemia. There were 18 deaths in the observed group because of medical unfitness; limb ischemia did not develop during follow-up. CONCLUSIONS: Intraarterial thrombolysis is of value in restoring the distal run off before bypass in PA presenting as acute limb-threatening ischemia. However, the results do not justify an expectant policy for asymptomatic aneurysms.

Adult↗
PubMed1994

Early reoperation rates after arterial surgery.

Between 1 January 1985 and 31 December 1991, 2426 patients underwent arterial surgery. Three hundred and seventy one reoperations were performed on 258 patients within 30 days of the initial procedure. One hundred and ninety three (52%) of the operations were attempted revascularisations, 95 (26%) were amputations and 58 (16%) were to control bleeding. One hundred and sixty nine (66%) of first operations were successful, but 76 patients required a further 113 reoperations. The mortality of reoperation was 16%, while the mortality of patients not requiring reoperation was 9% (p < 0.01). The mean hospital stay in days was higher in patients requiring reoperation (p < 0.05). Where appropriate, patients should be informed of the significant incidence of reoperation and reoperative mortality after vascular surgery. The increased hospital stay in reoperated patients has financial implications.

Adolescent↗
PubMed1994

Criteria for identification of the "at-risk" infrainguinal bypass graft.

The criteria for identifying the "at-risk" femorodistal bypass are controversial. Eighty-eight patients were entered into a surveillance programme using ankle-brachial pressure indices (ABPI), colour Duplex and intraarterial digital subtraction angiography (IADSA). Changes in ABPI of more than 0.1 identified 12/22 (51%) grafts thought to be "at-risk". In the 88 grafts, a PMV (peak mean velocity) < 45 cm per second had a sensitivity and specificity of 55 and 85% compared to 91 and 95% if a PMV < 45 cm per second and a V2/V1 ratio of greater than 2 was used to identify the 22 grafts "at-risk". In total 341 examinations were performed, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy for impedance analysis was 70, 90, 48, 97 and 91% respectively, compared to 93, 97, 77, 99 and 97% for colour Duplex in identifying the "at-risk" grafts. Between 6 weeks and 12 months the mean PMV was seen to drop by 29% and the mean impedance score by 19%. The most sensitive mode of non-invasive graft surveillance is colour Duplex providing the assessment involves both a measurement of the velocity ratio and the absolute velocity. However, impedance analysis is a better screening test than ABPI and PMV.

Angiography, Digital Subtraction↗
PubMed1994

Magnetic resonance angiography or IADSA for diagnosis of carotid pseudo occlusion?

Accurate diagnosis of internal carotid artery (ICA) occlusion is essential in the investigation of carotid disease yet may be difficult using Duplex. Traditionally contrast arteriography has been used to confirm the diagnosis despite its cost and potential dangers. Twenty-one patients with 23 ICA occlusions were evaluated by a 3-dimensional time of flight magnetic resonance angiography (MRA) technique. The cervical carotids and circle of Willis were imaged during the MRA examination which lasted 30 minutes. Confirmatory conventional angiography was performed in all patients. Using angiography as the gold standard, all occlusions were correctly diagnosed by MRA and 22 of 23 occlusions correctly diagnosed by Duplex. There was good agreement between MRA and angiography for all 42 ICAs imaged (Kappa statistic 0.83). Diagnosis of internal carotid artery occlusion is critical as it determines the need for operation. In this situation MRA provides a useful non-invasive complement to Duplex. A combination of non-invasive studies may enable arteriography to be rejected with greater confidence in this high risk group.

Angiography, Digital Subtraction↗
PubMed1994

The aetiology of vein graft stenoses.

The aetiology of vein graft stenosis is poorly understood. In a cohort of 88 patients, the mean internal diameter of the vein grafts that developed a stenosis was 3.7 (3.1-4.2) mm compared to 4.7 (4.4-5.0) mm in those that did not (p = 0.006). The mean lowest compliance value in the 11 patients who developed a stenosis was 0.1 (0.07-0.13) % per mmHg compared to 0.21 (0.19-0.23) % per mmHg in the rest (p < 0.001). The presence of vein incompetence, site of tributaries or valves and the degree of endothelial cell loss were not related to the development of vein graft stenoses. The presence of a macrophage infiltrate (p < 0.001), lymphocyte infiltrate (p < 0.025) and subendothelial smooth muscle cells (p < 0.05) were all significantly more common in those grafts that developed a stenosis. Vein quality is an important factor in the development of graft stenoses.

Aged↗
PubMed1994

Prediction of long saphenous vein graft adaptation.

The ability of vein to dilate may allow smaller veins to be used for bypass if this change could be predicted. Sixty patients undergoing femorodistal popliteal or infrapopliteal bypass have had their long saphenous vein studied. Diameter measurements of the long saphenous vein have been performed using an ATL Duplex scanner at the groin, mid-thigh and knee. Measurements were performed preoperatively both at rest and with a venous occlusion cuff to dilate the vein and subsequently at 7 days and 3, 6, 9, 12 months after implantation. The mean diameter of the vein at the mid thigh was 4.2 mm non dilated, 5.1 mm with occlusion, 5.4 mm 7 days postoperatively and 5.5 mm at 12 months (p < 0.01 ANOVA). The mean diameter of the vein at the knee was 3.8 mm non-dilated, 4.8 mm with occlusion, 4.8 mm at 7 days and 5.0 mm at 12 months after operation (p < 0.01 ANOVA). If the minimum resting internal diameter of vein regarded as being suitable for bypass was 3 mm, this technique would have increased the vein utilisation rate by 22%. These results show that by using a technique of venous occlusion at the time of preoperative vein mapping the adaptive response of the vein can be predicted and this can result in an increased rate of vein utilisation.

Aged↗
PubMed1994

Angioplasty gives good results in critical lower limb ischaemia. A 5-year follow-up in patients with known ankle pressure and diabetic status having femoropopliteal dilations.

137 consecutive patients with known ankle pressures and diabetic status had attempted femoro-popliteal dilatation for lower limb ischaemia in an English provincial teaching hospital. All except one were followed until failure or death to assess survival and amputation rates. Non-diabetic patients with critical limb ischaemia had a 5 year survival rate of 62.2% (SE 17.1) compared to 50.5% (SE 7.0) for claudicants, with no significant difference on logrank testing. Diabetics had a relative risk of amputation of 11.2 compared to nondiabetics. Patients with pre-treatment ankle pressures of 50 mm or less had a relative risk of amputation of 2.6 compared to those with higher resting pressures. It is concluded that angioplasty should be the treatment of first choice in critical lower limb ischaemia whenever it is technically possible. Including patients with rest pain in the critical ischaemia group does not significantly affect cumulative patency rates.

Adult↗
PubMed1994

Blood flow in the internal carotid artery and velocity in the middle cerebral artery during carotid endarterectomy.

A stenosing atherosclerotic plaque of the internal carotid artery acts as a source of emboli and may impede flow. The contribution made by a stenosed carotid artery to cerebral perfusion is unclear. This study examined blood flow in the internal carotid artery and a comparison was made with the effect of clamping on flow velocity in the middle cerebral artery. Some 50 patients were assessed before carotid endarterectomy by preoperative duplex scanning, triplanar arteriography and transcranial Doppler ultrasonography. At operation, maximal flow in the internal carotid artery was measured using a Doppler flowmeter and flow velocity was monitored by transcranial Doppler. No correlation was found between the degree of stenosis and resting flow velocity. Mean flow in the internal carotid artery in patients with > 90% stenosis was significantly lower than those with lesser stenoses (P < 0.01). However, a mean minimal blood flow of 141 ml/min passed through the > 90% stenoses. The effect of internal carotid artery clamping on flow velocity was similar irrespective of the degree of stenosis. In patients with > 90% stenosis, the internal carotid artery continues to make an important contribution to cerebral perfusion.

Aged↗
PubMed1993

Choice of agent for peripheral thrombolysis.

Evidence has been accumulating that tissue plasminogen activator (tPA) is a more rapid and effective agent than streptokinase for peripheral thrombolysis. Twenty-three patients with acute limb-threatening ischaemia treated with tPA (0.5 mg h-1) over 15 months were compared with 20 consecutive patients previously receiving streptokinase (5000-10,000 units h-1). There were no major differences between the rates of complete and partial lysis (61 per cent for tPA versus 65 per cent for streptokinase) or limb salvage (65 versus 55 per cent respectively). Complication rates were also similar. It was not possible to show that tPA, an agent ten times more expensive than streptokinase, was superior for peripheral thrombolysis.

Adult↗
PubMed1993

Intraoperative measurement of vascular graft resistance as a predictor of early outcome.

The quality of distal run-off is one of the most important factors influencing the early outcome of femorodistal vein grafting. During femoropopliteal and infrapopliteal bypass, assessment of graft resistance and flow were made using a combination of Doppler flowmeter recordings and measurements of arterial pressure. In a series of 100 reconstructions there were 12 early failures. The mean (95 per cent confidence interval (c.i.)) maximal flow measurement in the group of grafts that failed when anastomosed to the popliteal artery or tibioperoneal trunk was 125 (74-176) ml/min compared with 256 (223-289) ml/min in successful grafts (P = 0.006). The corresponding figures for grafts inserted into a single crural vessel were 99 (72-126) and 165 (137-193) ml/min (P < 0.02). In the group that failed the mean (95 per cent c.i.) resistance after papaverine injection was 1.02 (0.82-1.22) peripheral resistance units (p.r.u.) compared with 0.47 (0.44-0.51) p.r.u. in the successful group (P < 0.001). Using a combination of resistance > 0.9 p.r.u. and capacity loss ratio after papaverine injection < 10 per cent to identify grafts that subsequently failed, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 92, 97, 85, 99 and 97 per cent respectively. These results confirm that haemodynamic measurements can be used at operation to identify a group of patients in whom bypass is likely to fail.

Adult↗
PubMed1993

Acute limb deterioration during intra-arterial thrombolysis.

Approximately 12 per cent of limbs undergoing intra-arterial thrombolysis (IAT) develop distal embolism or extension of thrombus during the procedure. These are usually of little clinical consequence and can be treated by increasing the rate of administration of the lytic agent. However, in some patients the clinical condition of the limb deteriorates rapidly. In an attempt to define the incidence of acute limb deterioration during IAT, information was collected from five centres in the UK with experience of the technique. A total of 866 treatments were recorded, with 20 limbs (2.3 per cent) undergoing acute deterioration. This complication was more common during the treatment of thrombosed popliteal aneurysm than during that of emboli or thrombosed atheromatous arteries or grafts (P < 0.001). The amputation rate associated with the complication was high, and operative intervention provided better results than continuation of lysis.

Aneurysm↗
PubMed1993

Pre-bypass morphological changes in vein grafts.

Random vein samples taken prior to bypass surgery have shown certain pathological features. Long saphenous vein was taken from the groin (proximal) and knee to mid-calf (distal) of 85 patients undergoing femoro-distal bypass over a 2-year period. During this period only four patients had cephalic arm vein used; this was also studied. Histological examination was performed using haematoxylin and eosin and van Geison stains. Intimal hyperplasia was seen in 62 (73%) proximal and 74 (87%) distal samples. There were significantly more distal veins with moderate to severe focal hyperplasia and circular muscle hypertrophy (p < 0.05 and p < 0.001). Changes of diffuse intimal hyperplasia were seen in three of the cephalic veins. Muscle hypertrophy occurred in 58 (68%) of proximal segments compared to 75 (88%) of distal segments (p < 0.005). This study shows that significant pathological changes are seen in long saphenous and cephalic veins thought to be "normal". These changes are more evident in the distal long saphenous vein. These changes may have a significant effect on the outcome of vein bypass.

Aged↗