PubMed Health⌕ Search

Biomedical subjects

T R Magee

Publications and source records attributed to T R Magee.

At least 91 records · Page 5Linked to original sources
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↗
PubMed1994

The acute surgical admission: is mortality predictable in the elderly?

Most scoring systems used to predict mortality are complex. A simple preoperative assessment, the Sickness Assessment (SA), was evaluated as a predictor of mortality in elderly patients admitted as surgical emergencies. The three parameters comprising the SA are: hypotension on admission, the presence of severe chronic disease, whether the patient was independent and self-caring. Prospectively, 487 consecutive patients of over 65 years of age admitted as surgical emergencies were studied. On admission, the SA and the APACHE II score were calculated. Hospital mortality was used as the endpoint. Of 309 patients with zero SA, 21 (7%) died. In 178 with a positive SA, 64 died (36%) (chi 2 = 64.6, P < 0.001). After laparotomy, mortality was 57% (36/67) with a positive SA, but 15% (15/103) with a zero assessment (chi 2 = 33.6, P < 0.001). When the single parameter of hypotension on admission was present, mortality was 77% (23/30). The predictive ability of the APACHE II score was not superior to SA. The SA is a simple preoperative assessment which identifies a high-risk group. It should be used in emergency surgical practice to improve outcome and avoid inappropriate surgery.

Acute Disease↗
PubMed1994

The cost, funding and acceptance of surgical research.

Research is currently a requirement to allow progress in surgical training. For most trainees this is a period of two years and success is judged by the acquisition of a thesis, production of papers for peer review journals and making presentations at meetings. Funding is required for this activity which is obtained from many sources, ranging from soft money to grants from research councils or Government departments. With the development of a more cost-conscious environment there is a need to establish the degree of funding required to support surgical research. With the potential changes inherent in the Calman Report the role of research may be examined critically. A study sponsored by the SRS was conducted to try and obtain information regarding costs and opinions of surgical research.

Attitude of Health Personnel↗
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

Impedance analysis versus colour Duplex in femorodistal vein graft surveillance.

Fifty patients who have undergone femorodistal bypass surgery have been followed up using impedance analysis and colour Duplex, with biplanar intraarterial digital subtraction angiography being used as the arbiter to define "at risk" grafts. An impedance score of 0.49 (0.43-0.55) was found in the "at risk" grafts, all of which underwent an interventional procedure compared to 0.39 (0.36-0.42) (p = 0.003, Mann-Whitney U test) in those with no problem. In total, 166 examinations were performed. The sensitivity and specificity were all greater than 91% when compared to angiography. Impedance analysis is simple, non-invasive, easy to perform and it takes only 10 min to complete the examination. In view of the results obtained using impedance analysis in comparison with Duplex scanning, we suggest that non-invasive impedance is a suitable alternative to colour Duplex for graft surveillance (mean +95% confidence interval).

Adult↗
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↗
PubMed1993

Colour Duplex imaging through wound dressings.

Colour flow Duplex scanning is becoming the method of choice to determine patency and haemodynamic status in infrainguinal grafts and native arteries. Due to surgical wounds and ulcers, there are often dressings covering the leg above the vessel to be scanned. There is no data as to the effect of different wound dressings on colour flow Duplex signals. Ten normal superficial femoral arteries were scanned by a blinded operator. Initially the artery was visualised to assess the normal image produced for each artery on B-mode and colour flow ultrasound and a Doppler reading was taken. Then each of five commonly used dressings were applied to the skin above the artery, in random order and the blinded operator graded the signal produced on a linear analogue scale. Primapore, an absorbent material dressing and Spyroflex, a bilaminate membrane dressing, did not transmit ultra-sound at all. Granuflex extra thin allowed a clear B-mode image of each artery to be visualised and an adequate Doppler waveform to be obtained. However colour flow mapping was less than optimal although it was possible in each of the arteries. Opsite and Tegaderm, two thin membrane dressings allowed excellent B-mode and colour flow images, in addition to clear Doppler signals. In patients who require dressings and who may require colour flow Duplex scanning of vessels in the same area, we would suggest the use of a product that permits ultrasound transmission, thus saving the necessity of removing the dressing for the assessment.

Adult↗
PubMed1993

Auditory phenomena during transcranial Doppler insonation of the basilar artery.

During transcranial Doppler insonation of the basilar artery, 15 normal subjects heard high-frequency tones similar to tinnitus. The pitch of the tones equated with the PRF, and intensity equated with loudness. Alteration of pulse length did not change the tones heard, and the effect was highly dependent on probe position and direction. This is an example of ultrasonography acting as a sensory stimulus. The exact mechanism and implications of this effect will need to be clarified by further investigation. Although this phenomenon is not proved to be harmful, it would seem prudent to use the minimum transmitted power necessary to obtain a satisfactory signal from the basilar artery.

Acoustics↗
PubMed1993

Preliminary experience of angioscopy in femorodistal bypass.

During femorodistal bypass angioscopy can be used in vein graft preparation allowing valve lysis and the identification of tributaries under direct vision. A total of 30 patients have undergone angioscopic assisted femorodistal bypass using either an Olympus or Stortz system. Nineteen patients have undergone full vein mobilisation and valve lysis under direct vision. Eleven patients had in situ bypass with ligation of tributaries, identified by the angioscope, through small stab incisions. No evidence of fistula or retained valve cusps was found by subsequent duplex scanning and arteriography. One of these grafts failed at 6 days due to an unrecognised outflow stenosis. The mean hospital stay after operation for this latter group of patients was 5.2 days (range 4.4-6.0 days) compared with 9.5 days (8.6-10.3 days) in a historical group of 30 patients (P < 0.001). Angioscopy is a useful aid in the performance of femorodistal bypass. Early experience suggests that hospital stay may be reduced by angioscope assisted in situ femorodistal bypass because of the minimal dissection involved.

Adult↗
PubMed1992

Duplex ultrasonography and pulse-generated run-off in selecting claudicants for femoropopliteal angioplasty.

Non-invasive assessment of lower limb vasculature may avoid unnecessary angiography in claudicants. Colour duplex ultrasonography of the femoral and popliteal arteries was performed to assess patency and the presence of any stenoses, and pulse-generated run-off (PGR) was used to assess the distal vasculature. In 65 legs colour duplex scanning was successful, compared with angiography, in identifying the site and type of disease in the femoropopliteal segment and 23 lesions were correctly identified as suitable for angioplasty. More patent distal vessels were demonstrated by PGR than by angiography; no vessels patent on angiography were missed by PGR. The estimated cost of diagnostic angiography was 330 pounds per test compared with 52 pounds for non-invasive assessment. By using duplex examination as a screening test, a potential saving of 8062 pounds could have been made in this series. Duplex ultrasonography offers a non-invasive and cost-effective alternative to diagnostic angiography for clinically suspected infrainguinal arterial disease presenting as claudication. PGR was not of clinical value in assessing suitability for angioplasty.

Aged↗
PubMed1992

Quality of life following surgery for abdominal aortic aneurysm.

Repair of abdominal aortic aneurysm (AAA) carries a considerable rate of morbidity and mortality, but little information exists on the quality of life following this procedure. During 1988 and 1989, in two hospitals, 211 patients (186 men and 25 women; median age 74 (range 48-87) years) underwent surgery for AAA. There were 77 ruptured aneurysms and 134 electively repaired. Of these, 38 patients died in hospital (27 ruptured, 11 elective); by the time of review a further eight (one ruptured, seven elective) had died from unrelated causes. Of the 165 survivors, 131 (45 ruptured, 86 elective) were reviewed and questioned as to their physical and mental state before and after surgery. Using the Rosser index, a value for quality of life before and after surgery was calculated (1.0, good; 0, dead). The value for the elective group was 0.94 before operation and 0.96 after, but in the ruptured group fell from 0.98 before surgery to 0.87 afterwards. This study shows that patients undergoing elective surgery for repair of AAA retain good quality of life. By contrast, patients surviving emergency surgery following this procedure seem to suffer a deterioration in life quality, which must be endured for the same expected lifetime as that for the elective group. These results support the need for a national AAA ultrasonographic screening programme.

Aged↗
PubMed1992

Vein compliance: a preoperative indicator of vein morphology and of veins at risk of vascular graft stenosis.

Compliance measurements of 53 long saphenous veins before femorodistal bypass have been performed using a duplex scanner with venous occlusion for distension. These have been compared with the histological features of the veins. There was significantly more moderate or severe focal hyperplasia and circular muscle hypertrophy in distal long saphenous vein than in its proximal counterpart (P < 0.01 and P < 0.05 respectively). The mean (95 per cent confidence interval) compliance of distal vein with moderate or severe hyperplasia was 0.16 (0.13-0.19) compared with 0.29 (0.22-0.36) for that with no, minimal or mild hyperplasia (P = 0.001). The mean compliance of distal vein with moderate or severe muscle hypertrophy was 0.19 (0.17-0.21) and of vein with no, minimal or mild hypertrophy 0.25 (0.21-0.29) (P = 0.14). The mean lowest compliance in seven patients who developed stenosis was 0.10 (0.07-0.13) compared with 0.21 (0.16-0.26) in the rest (P < 0.001). Preoperative measurement of vein compliance can be used to identify vein with marked pre-existing intimal hyperplasia and as a predictor of future graft stenosis.

Compliance↗
PubMed1992

DNA damage-inducible origins of DNA replication in Escherichia coli.

Upon induction of the SOS response in Escherichia coli, the mode of initiation of DNA replication is altered such that it can occur in the absence of normally required protein synthesis. This type of DNA replication has been termed induced stable DNA replication (iSDR). We examined the origin usage during iSDR and found that the initiation of iSDR occurs primarily in the oriC and terC regions of the chromosome in a manner completely independent of transcription, translation and DnaA protein. Minichromosomes (oriC plasmids) pOC23 and pOC81 were induced to replicate in the absence of DnaA protein and transcription after SOS induction. The results localized one of the iSDR origin activities in a 596 bp region which includes the minimal oriC.

Bacterial Proteins↗
PubMed1992

Reinforced vascular grafts: a comparative study.

Reinforced vascular grafts are designed to resist compression and flexion forces, for example in axillo-femoral or below-knee femoropopliteal reconstruction. This study compared eight types of 6-mm reinforced grafts (five polytetrafluoroethylene (PTFE) and 3 Dacron). On a specially designed rig, graft diameter and flow were measured during compression by a standard series of weights up to 3.6 kg, and on another rig grafts were flexed through 135 degrees. Meadox Microvel graft resisted compression best (p less than 0.05) but there were no important differences between the other grafts (Vascutek; Bard; Goretex Standard, Thin Walled and Removable Ring; Impra Standard and Thin Wall). Flexion produced no significant changes in flow through the grafts. In addition, five general surgeons were asked to score the ease of removal of reinforcement, passage of sutures, and the tendency of sutures to cut out of each graft. Removal of reinforcement and passage of sutures were easier with the PTFE grafts, but the Dacron was more resistant to sutures cutting out. This study shows that these grafts resist flexion and compression well. Their different handling characteristics and data on patency at different sites should remain the main determinants in choice of graft.

Blood Flow Velocity↗
PubMed1992

Praxilene (naftidrofuryl oxalate) as an alternative for the augmentation of femoro-distal bypass blood flow.

In 30 patients undergoing femoro-distal bypass the effect of papaverine and praxilene on blood flow in the graft was measured. The mean resting flow was 129 ml min-1 (range: 91-167) and after papaverine was 202 ml min-1 (142-262) and after praxilene was 205 ml min-1 (143-267). Praxilene has a similar effect to papaverine in the augmentation of blood flow, and further investigation is needed to see if long-term praxilene administration might improve graft survival.

Adult↗