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Biomedical subjects

M R Tyrrell

Publications and source records attributed to M R Tyrrell.

At least 19 recordsLinked to original sources
PubMed1995

Incidence and management of laser-associated oesophageal perforation.

The incidence of oesophageal perforation in 350 patients referred for laser treatment to palliate malignant dysphagia is reported. Perforation occurred in 6 per cent of patients or 2 per cent of treatment episodes. Perforation was usually due to oesophageal dilatation undertaken before laser treatment (23 of 25 perforations). Immediate recognition and the institution of an aggressive non-operative management protocol resulted in survival in 20 of 23 patients.

Deglutition Disorders↗
PubMed1993

Critical leg ischaemia: an appraisal of clinical definitions. Joint Vascular Research Group.

The reliable prediction of imminent limb death remains a clinical problem. The International Vascular Symposium and European working parties each produced similar definitions of 'critical ischaemia', but this is the first attempt to address the issue with prospectively collected data. Complete 3-year follow-up data were available for 213 patients. In addition to the above two definitions, a simplified modification has been evaluated, after review of the data 1 year into this study. All three definitions were able to identify patients likely to require amputation in the absence of successful reconstruction. The sensitivity, specificity and positive predictive values with which they were able to do so was, however, poor. None of the definitions was able to predict which diabetic patients would require amputation. Diabetics were more likely to undergo amputation than non-diabetics. There was, however, no significant difference in the initial ankle artery pressures between the diabetic and non-diabetic patient subgroups. None of the definitions reliably predicted which grafts would occlude, in which event the 3-year mortality rate was approximately 35 per cent. Critical ischaemia by any of these definitions is associated with a high mortality rate. Arterial reconstruction is associated with a reduction in both mortality and amputation rates These data do not support the hypothesis that critical ischaemia is associated with a greater graft occlusion rate than lesser degrees of severe ischaemia.

Amputation, Surgical↗
PubMed1993

Targeting of microdiscs in white cells to tibial abscesses in rabbits.

The ability to deliver drugs to specific foci of infection is a sought-after goal. One solution is to use microparticles as drug carriers. This approach is limited by detection of microparticles by the reticuloendothelial system (RES). In order to reduce RES uptake of such particles, we investigated the possibility of "hiding" microparticles within white cells prior to targeting them to experimental tibial abscesses. We used radioactive silicone microdiscs, supplied by the Royal Signals & Radar Establishment. Twelve rabbits with abscesses in the right tibia were used: six control animals received radioactive opsonised microdiscs intravenously, and six animals received the same dose of microdiscs following incubation of the microdiscs with white cells. Each animal's liver, spleen, lungs, and both tibiae were removed, weighed, and homogenised. Radioactivity counts were obtained from each tissue, and the ratio of counts per gram of tissue for the right/left tibiae was calculated for the two groups of animals. The ratio of counts in the control group was 1.66 (+/- 0.57 SD), and the mean ratio of counts from the rabbits who had microdisc incubated with white cells was 3.32 (+/- 0.52 SD). This difference was statistically significant at p = 0.02 (Mann-Whitney U test).

Abscess↗
PubMed1992

Colour flow imaging in the detection of femoro-distal graft and native artery stenosis: improved criteria.

Vein graft or native artery stenosis after femoro-distal revascularisation is a common cause of graft occlusion. The early detection and treatment of such stenoses offers the potential for better graft patency than salvage procedures undertaken for graft thrombosis. In the past, two criteria using duplex scanning have been used to detect grafts at risk: (a) a localised increase in the peak velocity (V2) by 100% or more in comparison to the peak velocity (V1) 2 cm upstream (i.e. V2/V1 ratio greater than 2.0), and (b) a decrease in average peak velocity to less than 45 cm s-1. Seventy-four consecutive patients with femoro-distal vein grafts have been studied with intravenous digital subtraction angiography to detect stenosis (greater than 50% diameter) and colour flow imaging using both duplex scanning criteria (a) and (b) at 1.5, 3, 6, 9 and 12 months after operation. The results show that the V2:V1 ratio greater than criterion had a sensitivity of 100% and a specificity of 83%. Stenoses in the native distal arteries were not detected. Low average peak velocity less than 45 cm s-1 had a sensitivity of 61% and a specificity of 98%. By combining both criteria the sensitivity for detecting stenoses in both the vein graft and native distal artery, became 100% and the specificity 98%.

Angiography, Digital Subtraction↗
PubMed1990

Evaluation of fine catheter aspiration cytology of the peritoneum as an adjunct to decision making in the acute abdomen.

Fine catheter aspiration cytology of the peritoneal cavity was performed successfully in 61 patients admitted with acute abdominal pain. Aspirates were examined microscopically and the percentage of neutrophils in the specimen counted. In patients in whom the clinical need for operation was certain (n = 25) all patients required surgery and the peritoneal neutrophil count was greater than 50 per cent. In patients in whom the clinical need for operation was uncertain (n = 36) 19 patients required operation: the peritoneal neutrophil count was greater than 50 per cent in 18 and in one patient with ectopic pregnancy fresh blood was aspirated. Of the 17 patients not requiring operation the peritoneal neutrophil count was less than 10 per cent in 15 and greater than 50 per cent in two patients (both had acute pelvic inflammatory disease). This study confirms peritoneal cytology as a useful adjunct to decision making in those patients with acute abdominal pain in whom the decision to operate is in doubt.

Abdomen, Acute↗
PubMed1990

Graft stenosis: justification for 1-year surveillance.

In all, 412 femorodistal grafts (femoropopliteal and femorocrural), performed between 1984 and 1988, have been prospectively studied at 6 weeks and 3, 6, 9 and 12 months after operation and at intervals of 6 months thereafter by duplex scanning and intravenous digital subtraction angiography. The overall incidence of stenoses was 16 per cent (femorocrural 20 per cent, femoropopliteal 15 per cent). All stenoses were detected in the first year after operation and none occurred after this. Twenty-four non-haemodynamically significant stenoses were not treated but were followed at intervals of 3 months. Forty-two haemodynamically significant stenoses were detected and secondary procedures were performed in 30 grafts at a mean of 8 months after surgery. Thirteen had percutaneous balloon dilatation and six (46 per cent) remain patent at a mean follow-up of 22 months. Two grafts which occluded within 30 days and three which restenosed at a mean of 8 months had tertiary procedures. Seventeen grafts were surgically revised, nine with patch grafts and eight with bypass grafts. Eleven of these remain patent at a mean follow-up of 30 months. One occluded immediately and three occluded late. Two grafts which restenosed at a mean of 19 months had successful tertiary procedures. In total, seven grafts had tertiary procedures (two had balloon dilatation and five had surgery) and six of these remain patent at a mean follow-up of 13.5 months. In conclusion, 37 procedures have been performed on 30 grafts, of which 23 (77 per cent) remain patent at a mean follow-up of 12 months. Approximately one-quarter of femorodistal grafts will develop graft-related stenoses and graft surveillance is worthwhile, but only for the first year after operation.

Angiography, Digital Subtraction↗
PubMed1990

Experimental evidence to support the use of interposition vein collars/patches in distal PTFE anastomoses.

We have conducted three in vitro experiments (using cadaver internal mammary artery as a model for crural artery), which establish the advantage of the Miller collar and Taylor patch over direct PTFE-artery anastomoses: (1) A new method of simultaneously measuring longitudinal and circumferential elasticity in human saphenous vein (n = 16) has demonstrated the latter to be anisotropic (i.e.: greater longitudinal than transverse compliance, P less than 0.002). This suggests that benefit may be gained by aligning the saphenous vein's longitudinal axis with that of the arteriotomy--a feature of both vein interposition anastomoses. (2) We have compared maximal pulsatile and constant flow across each type of anastomosis (n = 10 of each) using a flow model incorporating standard pressure, viscosity, graft and outflow vessel length, and anastomotic angle. This experiment has demonstrated loss of anastomotic reliability only in direct PTFE-artery anastomoses (i.e. no correlation between flow and vessel diameter, r = 0.04). (3) Casts of the internal anatomy of the anastomoses (n = 10 of each) have demonstrated a greater degree of oval distortion of the toe of the outflow vessel of direct PTFE-artery anastomoses than either of the other techniques (P less than 0.01). This experimental evidence suggests that both of these vein interposition techniques optimise the mechanical properties of saphenous vein and protect small arteries from anastomotic distortion. These benefits do not occur with direct PTFE-artery anastomoses.

Anastomosis, Surgical↗
PubMed1990

Questionnaire identification of surgical patients at risk of HIV infection.

The prevalence of human immunodeficiency virus (HIV) infection is increasing. Risks of hospital transmission, though small, will consequently also increase. Precautions taken during invasive procedures, particularly surgery, and in the handling of specimens from patients diminish this risk. As HIV antibody screening is not permissible, we have assessed the possible efficacy of a routine questionnaire to identify high-risk groups. Of 525 questionnaires given to routine surgical patients, 506 (96%) were completed. Twenty-eight (5.5%) indicated that they were in a high-risk group. High-risk patients were more likely to present with anorectal disease, to be male and to be young compared with patients from the remainder of the sample. The questionnaire was acceptable to 97% of patients although to a significantly smaller number (82%) of high-risk patients. Routine HIV antibody testing would be acceptable to 88% of low-risk patients but to only 60% of high-risk patients. Questionnaire assessment is an acceptable and perhaps more reliable method of assessing HIV risk status than the other currently available options. It has to be accepted that it will never result in complete identification but we recommend this method as one approach to the problem faced by the surgical team.

Adolescent↗
PubMed1990

The practical consequences of research in arteriosclerosis.

Despite the impressive volume of work that has been undertaken, the successful medical therapy of arteriosclerosis continues to elude us--preventive measures and surgical treatment of its complications persist as the primary modalities of treatment. While research into the fundamental pathophysiology surrounding arteriosclerosis is not complete and our understanding is plagued by the current plethora of confusing and contradictory reports, the cellular mechanisms underlying this process are gradually being clarified. As yet, this basic research has had limited impact for vascular surgical patients, who have benefited more as a result of epidemiological studies. For instance, we are more diligent in looking for occult disease, less ready to operate on obvious lesions, and more persuasive in our attempts to alter the patient's lifestyle--particularly smoking habits.

Arteriosclerosis↗
PubMed1989

Is arterial reconstruction to the ankle worthwhile in the absence of autologous vein?

Autologous vein from either the arm or the leg is the preferred conduit for femoro-crural grafting. Limb salvage rates using prosthetic grafts have been sufficiently disappointing for many surgeons to consider primary amputation in the absence of suitable vein. We have attempted to improve prosthetic graft patency by the creation of a compliant, wide diameter vein collar at the distal anastomosis. Thirty patients with critical ischaemia (i.e.: rest pain with distal tissue loss or doppler ankle pressure less than 40 mmHg2.3) have undergone grafting to a crural vessel in the lower third of the calf using 6 mm externally supported PTFE (IMPRA) with a vein collar (17% of all lower calf grafts, 9% of all femoro-distal procedures). Five of the grafts occluded in the peri-operative period, resulting in major amputations. Another 4 grafts occluded within 12 months of operation resulting in amputation. A further 7 grafts have occluded but not required amputation. Fourteen (47%) grafts remain patent at a mean follow-up of 13.9 months (range 1-49) with a mean graft patency of 10 months. The aim of salvage surgery is to maintain independence until death supervenes. In this series 6 (20%) patients have died during follow-up and the best possible result in the 30 patients would have been a total of 417 "amputation avoided" months. In fact 300 "amputation avoided" months were achieved. Moreover, 21 legs (70%) have avoided amputation during the patient's lifetime, or at the most recent follow-up. These results suggest that femorocrural grafting using PTFE with a vein collar is worthwhile and preferable to primary amputation in the elderly patient.

Aged↗