Biomedical subjects

M Horrocks

Publications and source records attributed to M Horrocks.

At least 19 recordsLinked to original sources

PubMed2001

Catalytic activity of ADAM28.

ADAMs are membrane-anchored glycoproteins containing a disintegrin and metalloprotease domain that have important roles in fertilization, development, and diseases such as Alzheimer's dementia. Here we present the first evidence for catalytic activity of ADAM28, a protein that is highly expressed in the epididymis and lymphocytes. Recombinant ADAM28 cleaves myelin basic protein at two sites. The catalytic activity of ADAM28 is not sensitive to tissue inhibitors of metalloproteases 1 and 2, but can be abolished by a mutation in the catalytic site. Catalytically active ADAM28 will be valuable for further studies of its role in sperm maturation and lymphocyte function.

ADAM Proteins↗

PubMed2001

Reintervention as a clinical trial endpoint after peripheral arterial bypass surgery.

BACKGROUND: Graft patency is usually the primary endpoint in studies of peripheral arterial bypass surgery, but gives only a limited indication of clinical outcome. The aim of this study was to evaluate reintervention as a study endpoint after femorodistal bypass surgery. METHODS: The database from a multicentre, prospectively planned study of 517 patients undergoing femorodistal bypass for severe ischaemia was used to investigate the predictive value of technical endpoints. Clinical symptoms, graft patency, vascular interventions and clinical outcomes were recorded for 12 months after operation. RESULTS: Complete follow-up data were obtained on 498 patients (96 per cent). Success in terms of patients' need for reintervention agreed with clinical outcome in 90 (95 per cent confidence interval (c.i.) 87-93) per cent of cases. Primary and secondary patency agreed with the clinical outcome in 80 (95 per cent c.i. 77-84) and 81 (95 per cent c.i. 78-85) per cent of patients respectively. However, the best agreement with clinical outcome was obtained from the composite endpoint of 'patient alive without reintervention': 92 (95 per cent c.i. 90-94) per cent. CONCLUSION: Recording the number of patients who did not need reintervention for 12 months after femorodistal bypass gave a more accurate assessment of the number with clinical improvement than was obtained by recording bypass graft patency. Inclusion of patient survival in a composite endpoint increased the clinical relevance of this endpoint in patients with severe ischaemia who had femorodistal bypass surgery.

Amputation, Surgical↗

PubMed2001

The value of transcranial Doppler in predicting cerebral ischaemia during carotid endarterectomy.

OBJECTIVES: transcranial Doppler (TCD) measurement of middle cerebral artery velocity (MCAV) is an indirect method of assessing cerebral blood flow and therefore predicting patients at risk of stroke during carotid endarterectomy (CEA), and may be used to determine the need for shunting. This study evaluates the accuracy of three accepted TCD criteria in predicting the need for a shunt. DESIGN: prospective study. METHODS: one hundred and twenty consecutive CEA were performed under loco/regional anaesthesia. Patients monitored by TCD and Awake neurological examination were included. Shunts were inserted if there was neurological deterioration. Awake patient monitoring was compared with the three TCD criteria. RESULTS: inadequate TCD recordings were obtained in 16 operations (13%). In the remainder (104 cases), 12 developed symptoms of cerebral ischaemia and required a shunt (12%). Comparisons with the three accepted criteria were as follows: (1) m MCAV <30 cm/s had a sensitivity, specificity, PPV and NPV of 92%, 49%, 19%, and 98%, respectively; (2) clamp/pre-clamp ratio <0.6 had a sensitivity, specificity, PPV and NPV of 92%, 75%, 33% and 99%, respectively; (3) greater than 50% reduction in m MCAV had a sensitivity, specificity, PPV and NPV valves of 83%, 77%, 32% and 97%, respectively. CONCLUSIONS: TCD flow velocities are not a reliable method for detecting cerebral ischaemia and therefore determining the need for a shunt in CEA.

Aged↗

PubMed2001

Patient and hospital benefits of local anaesthesia for carotid endarterectomy.

OBJECTIVES: this study reviews and compares carotid endarterectomy (CEA) performed under local anaesthesia (LA) with CEA performed under general anaesthesia (GA) in a single institution. METHODS: data were collected prospectively from 240 CEA procedures. 140 GA CEA procedures are compared to 100 LA CEA procedures in terms of outcome, operative techniques, complications, and length of stay. RESULTS: the groups were similar for age, gender distribution and preoperative risk factors. There were more asymptomatic patients in the LA group. There were no significant differences in death, stroke or death/stroke rate between the two techniques. LA CEA was associated with lower shunt rate (LA 13%, GA 50%, p < 0.001), lower incidence of intraoperative hypotension (LA 8%, GA 40%, p < 0.001), decreased hospital stay (median (IQ); LA 2 (1-2), GA 3 (1-4), and a cost saving of pound235 per CEA procedure. CONCLUSIONS: carotid endarterectomy can be performed safely under local anaesthesia with the advantage that LA CEA enables the surgeon to monitor and selectively shunt patients more accurately. In addition LA CEA is associated with a shorter hospital stay and important cost savings.

Adult↗

PubMed2001

Changes in the incidence of gastroenteritis and the implementation of public water treatment.

There are few data available on the incidence of endemic waterborne disease in the developed world. This study aims to determine if there was a measurable decline in gastroenteritis related faecal specimens following the introduction of water treatment. The rate of faecal specimens for gastroenteritis was obtained for 17 communities one year before and after the introduction of water treatment in two states of Australia between 1992 and 1996. Of these 17 systems, 10 had filtration added to existing disinfection, while seven had both disinfection and filtration or disinfection alone added to no existing treatment. The rate of faecal sampling varied from a reduction of 55% to an increase of 198%. Large changes in water quality parameters occurred following treatment but there was no significant correlation between these changes and changes in the rate of faecal specimens. In this study there was no consistent change in gastrointestinal related faecal specimens despite marked changes in water quality. This suggests that the reduction in endemic gastrointestinal disease as a result of the introduction of water treatment was small as a percentage of all gastroenteritis. However, water treatment remains essential to protecting public health.

Australia↗

PubMed2001

Emergency surgery: atavistic refuge of the general surgeon?

A prospective audit of emergency soft-tissue surgery for an eight-week period revealed that general surgical emergency operations were more than twice as common as those undertaken in other soft-tissue specialties. The audit reveals that emergency general surgery needs an increase in resources, an increase in available staff and an increase in the role of the consultant general surgeon on call. An alternative solution would be to admit soft-tissue emergencies by specialty and develop specialist emergency services.

Emergencies↗

PubMed2001

Distortion of teatree stems by twine as a means to determine the number of years that the stems have been used to support cannabis plants.

In New Zealand, stems of teatree (Kunzea/Leptospermum) growing around illicit cannabis plots have been used to anchor lengths of twine running through the plots to hold cannabis plants upright. Forensic examinations of distortions of teatree stems caused by the twine have been carried out to determine when the twine had been first tied around the stems, in order to estimate the number of years that plots have been in operation. In this experiment, baling twine was tied around stems of a teatree (Kunzea ericoides) and the effect monitored for a period of three years. Varying degrees of stem distortion occurred during the first year, caused initially by expansion of callus (a wound tissue) rather than constriction of the growth (annual) rings of the xylem. Although this callus has a type of growth ring, these are not annual, therefore cannot be used to determine the number of years that stems have had twine attached. Xylem growth rings of the teatree in this experiment were not restricted until the third year. Distortion of teatree stems allows the determination of a minimum (not absolute) number of years that twine has been attached.

Journal Article↗

PubMed2001

Pollen on grass clippings: putting the suspect at the scene of the crime.

In a case of alleged sexual assault, the pollen content of samples of grass clippings and soil from the suspect's clothing and shoes was compared to that of a sample of grass clippings from the alleged crime scene (a grassy area) to determine whether or not the suspect had been at the scene. The clothing and shoe samples showed a very strong correlation with each other and with the sample from the alleged crime scene in the combination of the different types of pollen present, very strongly supporting the contention that the suspect had been at the scene.

Adult↗

PubMed2000

Association of sex with patency of femorodistal bypass grafts.

OBJECTIVE: There is evidence for superior patency in infra-inguinal bypass procedures in men compared to women. A large, prospectively planned series was investigated in order to confirm this finding and to determine the origin of this difference in outcome. METHODS: Patients underwent femorodistal bypass surgery and a prospectively planned 12-month follow-up. Outcomes in male and female patients were compared and investigated for associations with characteristics of the patients and the surgical procedures. RESULTS: A total of 517 patients received femorodistal bypass grafts, including 424 vein grafts and 93 prosthetic and vein-prosthetic composite grafts. Patency was confirmed to be higher in male than in female patients (56% vs. 42%, p=0.005). Fewer male patients received prosthetic or composite grafts (21% vs. 33%, p=0.005), but the difference in patency was evident only in patients receiving vein grafts. Female patients were smaller, included fewer smokers (p<0.001) and had worse symptoms (p=0.03), but none of these characteristics explained the difference in outcome. Patency in vein grafts was associated with graft diameter (p=0.004), but graft diameter was not significantly associated with sex (p=0.09) or with body size. CONCLUSIONS: It was confirmed that patency of femorodistal bypasses is significantly higher in males than females. None of the factors investigated here explain this difference, but the greater use of prosthetic and composite grafts in female patients suggests that poorer vein quality should be investigated as a possible source of the inferior outcome in female patients.

Aged↗

PubMed2000

Incidence of stenoses in femorodistal bypass vein grafts in a multicentre study.

OBJECTIVES: To establish the incidence of graft stenosis in a large population of patients undergoing femorodistal bypass procedures and to investigate the differences in incidence between individual surgical centres and other subpopulations. PATIENTS AND METHODS: A total of 277 patients with femorodistal bypasses underwent duplex scanning of vein grafts for 12 months for the detection of graft stenoses. A standard definition of a significant stenosis was used in all twenty participating centres. RESULTS: Overall stenosis rate was 27%. Stenoses were more common in composite vein grafts (43%) than in single segment vein grafts (25%) p=0.05. Stenoses were more common in female patients (38%) than males (22%) p=0.02. Stenosis rates in individual centres entering more than 20 patients varied from 9% to 56%. In a multiple regression analysis only aspirin use, sex and centre were significant factors predicting the likelihood of graft stenosis. CONCLUSION: Female patients, those taking aspirin and patients with composite vein grafts appear to be more at risk of graft stenosis, but this does not fully explain wide variations in the incidence of stenoses reported by individual centres.

Adult↗

PubMed1999

Experience with heparin-bonded collagen-coated grafts for infrainguinal bypass.

The perfect conduit for infrainguinal reconstructive surgery does not exist. When autologous vein is not available, then a prosthetic graft must be used. The use of a heparin-bonded graft has the theoretical advantage of reducing smooth muscle cell proliferation and thrombus formation, thereby reducing occlusion rates. The application of a collagen layer to the external surface of the graft serves to reduce transfabric haemorrhage. Forty-six patients underwent 47 infrainguinal reconstructions using heparin-bonded collagen-coated Dacron grafts over a 4-year period. Twenty grafts were for disabling claudication and 27 for critical ischaemia. Twenty-two grafts were to the above knee popliteal artery (47%), 10 to the below knee popliteal (21%) and 15 to one of the crural vessels (32%). There was a cumulative patency at 4 years of 69% for the above knee grafts, and 30-month patency of 58% and 45% for the below knee and crural grafts, respectively. There were three deaths over the study period and eight patients required major amputations.

Aged↗

PubMed1999

The incorporation of a stent-graft into the porcine aorta and the inflammatory response to the endoprosthesis.

The fate of a non-sutured anastomosis and the inflammatory response to an endoprosthesis in a porcine aorta was determined. Self-expanding aorto-aortic endovascular prostheses were deployed into the infrarenal aorta of Large White pigs by the transfemoral route, in accordance with Home Office regulations. Animals were followed up at intervals to 1 year. The aortas were explanted and specimens were subjected to light microscopy. Thirteen animals, mean weight 103 kg, underwent placement of a prosthesis. There was early evidence of a neointima at 4 weeks and a well-developed neointima by 12 weeks, with complete incorporation of the endoprosthesis. The early acute inflammatory reaction seen at 4 weeks had become chronic by 12 and was largely absent by 26 weeks. There was no evidence of atypia. Complete incorporation of the non-sutured anastomosis is seen in this model. The acute inflammatory reaction to the prosthesis seen at 4 weeks had largely subsided by 26 weeks.

Acute Disease↗

PubMed1999

Adjuvant medical therapy in peripheral bypass surgery.

BACKGROUND: A review was conducted of published clinical trials of adjuvant medical therapy in infrainguinal bypass procedures to evaluate the strength of the evidence for the use of various agents. METHODS: Trials were identified by literature search. The methods used were reviewed and the results with each agent tested were assessed taking into account the soundness of the study design. RESULTS: Thirty-three studies were identified; fewer than half had a randomized and double-blind design. Most were single-centre studies including a mixture of different surgical procedures and patients with varying degrees of lower limb ischaemia. Clinical outcomes were seldom reported. The median sample size was 61. The median follow-up duration was 12 months, but was often not standardized for all patients in a trial. Only aspirin in prosthetic grafts and ticlopidine in vein grafts have been shown in well designed, double-blind, randomized, controlled trials to reduce the likelihood of occlusion in infrainguinal bypass grafts. CONCLUSION: The majority of the trials reviewed had significant deficiencies in their design, reducing the reliance that can be placed on their results. Further studies are required to investigate adequately the effectiveness of existing medical therapies for the maintenance of infrainguinal bypass grafts.

Alprostadil↗

PubMed1999

Vascular surgical society of great britain and ireland: Re-evaluation of criteria for reoperation in carotid endarterectomy using intraoperative duplex imaging

BACKGROUND: The aim of this study was to compare data obtained during surgery with data collected at 6 weeks after operation to evaluate appropriate criteria for reoperation. METHODS: One hundred and twenty consecutive patients undergoing carotid endarterectomy had duplex scans at operation and 6 weeks later. Neurological evaluation was also documented. RESULTS: Of 96 patients who had a normal intraoperative duplex scan by standard criteria, 91 had normal scans at 6 weeks. One occluded an internal carotid artery (ICA) at 6 weeks with no symptoms. Four had kinks or high-grade contralateral lesions leading to velocity enhancement but no filling defect. All were asymptomatic. Twenty-four patients had abnormal intraoperative scans. Thirteen patients had visible kinking of the ICA or reperfusion hyperaemia; 12 of these patients had normal 6-week scans and one had a mild residual kink but no symptoms. Eleven patients had visible colour-filling defects and significant velocity enhancement. Nine of these were reopened and refashioned. Subsequent duplex imaging was satisfactory in all cases and 6-week scans were normal. One patient had an occluded ICA at operation and developed a dense stroke after operation. Another had residual raised velocities distally which remained at 6 weeks. This patient had no symptoms. CONCLUSION: Intraoperative velocity measurements alone cannot be relied upon as an indication for reoperation. Significant velocity enhancement combined with a visible filling defect appears to represent a satisfactory criterion for reoperation. There were no complications as a result of reoperation. There was no early restenosis in the whole group and there were no neurological sequelae in any patient with a satisfactory scan using the above criteria.

Journal Article↗

PubMed1999

Vascular surgical society of great britain and ireland: near-infrared spectroscopic monitoring of patients undergoing carotid endarterectomy under locoregional anaesthesia

BACKGROUND: The level of cerebral desaturation, which is associated with a change in level of consciousness during carotid endarterectomy, was measured by near-infrared spectroscopy. METHODS: Patients were recruited in two centres over 24 months. Surgery was performed under deep and superficial cervical block using 0.5 per cent bupivacaine, with temazepam as a premedication. Cerebral oxygenation was measured by Critikon 2020 near-infrared spectrophotometers (Johnson and Johnson Medical, Newport, UK). RESULTS: Forty-nine procedures were performed on 45 patients (39 men; age range 52-84 (mean 68) years). Recordings were made from the ipsilateral frontal site in 38 patients, from the ipsilateral temporal site in 23 and bifrontally in eight patients. Monitoring failed in three subjects. Percentage changes in regional cerebral oxygen saturation are detailed below. CONCLUSION: Significantly different levels of cerebral desaturation occur in patients with neurological compromise during carotid endarterectomy compared with those who are unaffected.

Journal Article↗

PubMed1999

Experimental assessment of proximal stent-graft (InterVascular) fixation in human cadaveric infrarenal aortas.

OBJECTIVES: This paper investigates the radial deformation load of an aortic endoluminal prosthesis and determines the longitudinal load required to cause migration in a human cadaveric aorta of the endoprosthesis. DESIGN AND METHODS: The endovascular prosthesis under investigation was a 24 mm diameter, nitinol, self-expanding aortoaortic device (InterVascular, Clearwater, Florida, U.S.A.). Initially, a motorised digital force gauge developed an incremental load which was applied to the ends of five stent-grafts, to a maximum of 10 mm (42%) compression. Secondly, using a simple bench model, each ends of four stent-grafts were deployed into 10 cadaveric experimental aneurysm necks and a longitudinal load applied to effect distraction. RESULTS: Increasing load produced increasing percentage deformation of the stent-grafts. The mean longitudinal distraction load for an aneurysm neck of 20 mm was 409 g (200-480 g), for 15 mm was 277 g (130-410 g) and for 10 mm was 218 g (130-340 g). The aneurysm diameter and aortic calcification had p values of 0.002 and 0.047, respectively, while the p value for aneurysm neck length was less than 0.00001. CONCLUSIONS: These results suggest that there is a theoretical advantage of oversizing an aortic prosthesis and that sufficient anchorage is achieved in an aortic neck of 10 mm to prevent migration when fully deployed.

Aorta, Abdominal↗

PubMed1999

Relationship of femorodistal bypass patency to clinical outcome. Iloprost Bypass International Study Group.

OBJECTIVE: To investigate the relationship between bypass patency, limb survival and clinical symptoms after femorodistal bypass procedures. DESIGN: Multicentre, prospectively planned 12-month postoperative follow-up. PATIENTS AND METHODS: Five hundred and seventeen patients undergoing femorodistal bypass surgery for severe ischaemia. Clinical symptoms, bypass patency were recorded at regular intervals up to 12 months postoperatively. RESULTS: Complete follow-up data was obtained on 498 patients (96%). Fifty-six (17%) of the 341 patients with patent bypasses had either rest pain or ulcers or had undergone major amputation at 12 months. Of the 167 patients with an occluded bypass, 22 patients (13%) had improved clinical symptoms and a total of 59 patients (35%) had avoided major amputation at 12 months. The clinical outcome for patients classified preoperatively as Fontaine stage IV was significantly worse than for those in stage III preoperatively despite similar bypass patency rates. CONCLUSIONS: There is a fair correlation between technical and clinical outcome after femorodistal bypass surgery at 12 months, but there are significant numbers of patients with occluded bypasses who have a good clinical outcome and of patients with patent bypasses who have a poor clinical outcome. The reporting of symptoms in addition to bypass patency would aid the interpretation of surgical results.

Adult↗

PubMed1999

Age-related outcome for peripheral thrombolysis.

OBJECTIVES: To investigate the age-related outcome of peripheral thrombolysis and determine for which patient group this treatment is worthwhile. DESIGN AND METHODS: A combined retrospective and prospective analysis of consecutive patients undergoing thrombolysis for acute lower-limb ischaemia was made with respect to age-related outcome and other risk factors. RESULTS: One hundred and two patients underwent thrombolysis for acute limb ischaemia. In the under 60 age group there was a 40% amputation rate. Seventy-three per cent of this group smoked. In the over 80 age group, the amputation rate was 15% and only 8% were smokers. CONCLUSION: Advancing age is not an adverse risk factor for thrombolysis which appears to be safe and effective in this patient group. There is a high incidence of smoking in the younger age group (< 60 years), in whom failed thrombolysis frequently leads to amputation.

Acute Disease↗