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Biomedical subjects

M Horrocks

Publications and source records attributed to M Horrocks.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1998

Full-dose and half-dose Klean Prep produce clearer images with iliac duplex examination than picolax.

OBJECTIVES: Iso-osmotic bowel preparation (Klean Prep) improves the accuracy of iliac duplex examination and reduces the time of each examination. Full-dose Klean Prep entails 4 l of fluid. We studied the effect of 2 l of Klean Prep (half-dose) and Picolax on image quality. DESIGN: Prospective study comparing clarity of duplex examination after three different bowel preparation regimes with that after 12 h starvation. MATERIALS AND METHODS: Thirty patients underwent iliac duplex examination after 12 h starvation. Scans were scored subjectively for grey scale and colour image quality, and Doppler signal-to-noise ratio. Patients were allocated blindly to: (a) full-dose Klean Prep, (b) half-dose Klean Prep, or (c) Picolax. After out-patient preparation, the scan was repeated and scored by the same observer, blinded to the preparation. RESULTS: Both full- and half-dose Klean Prep produced significant improvements in image quality for all three modalities; Picolax produced minimal change. There was minimal advantage of full-dose over half-dose Klean Prep. Patients preferred half-dose Klean Prep to full-dose. CONCLUSION: Klean Prep significantly improves the image obtained by iliac duplex examination; Picolax does not. Half-dose Klean Prep is an acceptable preparation to patients.

Aged↗
PubMed1998

Photoplethysmography can replace hand-held Doppler in the measurement of ankle/brachial indices.

Ankle/brachial pressure index (ABPI) using hand-held Doppler and sphygmomanometer is a standard assessment for patients with peripheral arterial occlusive disease (PAOD). Good Doppler technique is difficult to master and so we investigated replacing Doppler with photoplethysmography (PPG). Two investigators examined 52 legs in 32 vascular patients. Both used standard sphygmomanometer cuff occlusion. Restoration of flow was detected by either an 8 MHz Doppler ultrasound probe or a PPG transmitter/receiver on index finger or great toe. Doppler-derived ABPIs were compared with PPG-derived ABPIs. Excellent correlation was found between both indices (correlation coefficient 0.875). Four lower limbs had unrecordable PPG traces, one also having an unrecordable Doppler signal. Excluding these four patients, the correlation coefficient rose to 0.975. PPG placed on the pulp of a digit can replace the hand-held Doppler in measuring ABPIs.

Ankle↗
PubMed1997

The effects of platelet inhibitors on platelet uptake and restenosis after femoral angioplasty.

OBJECTIVE: To investigate the effects of two platelet inhibitors, aspirin and iloprost, on platelet uptake and restenosis at the site of angioplasty in patients undergoing femoral or popliteal angioplasty. EXPERIMENTAL DESIGN: Prospective, open, randomised group comparison. SETTING: Two university hospitals. PATIENTS: 43 patients undergoing femoral or popliteal angioplasty were randomised. INTERVENTIONS: Patients received either aspirin (300 mg/day), iloprost (8 hours/day i.v. infusion) or no antiplatelet medication during angioplasty and on the subsequent two days. MEASURES: Platelet uptake was measured using 111Indium-labelled platelets. Restenosis was assessed by repeat angiography at 3 months and clinical symptoms up to 12 months. RESULTS: Median changes in platelet uptake were similar in the three treatment groups, but all platelet radioactivity ratios > 2.0 occurred in the control group. Restenosis at 3 months was observed in 3 control, 5 aspirin and 1 iloprost patient. Further surgical intervention was performed in 3 control and 3 aspirin patients, but in none of the iloprost patients up to 12 months after angioplasty. CONCLUSIONS: Antiplatelet therapy may prevent large increases in platelet deposition at the angioplasty site, but the link between platelet deposition and restenosis was not substantiated in this study.

Aged↗
PubMed1997

An audit of hospital mortality after urgent and emergency surgery in the elderly.

An audit was carried out of 102 patients aged over 75 years undergoing urgent or emergency surgery in a district general hospital. The risk of death in hospital after general surgery (13 deaths in 49 patients) was greater than after orthopaedic surgery (two deaths in 53 patients) (P < 0.05). In particular, laparotomy carried a high in-hospital mortality: 12 of 25 patients undergoing laparotomy died. Risk of death after general surgery increased with increasing preoperative ASA class, increasing medical risk factors and duration of operation. Orthopaedic cases were fitter than the general surgical cases as determined by ASA class and the number of medical risk factors. NCEPOD has recommended increased involvement of senior medical staff in operations, reduced night-time operating and avoidance of futile surgery. A high proportion of cases were operated on and anaesthetised by higher specialist trainees and consultants. Death rate was not affected by the seniority of doctors involved, nor by the time of day the operation took place. General surgical deaths were predictable postoperatively in most cases, but preoperative prediction of outcome was not specific enough to alter management.

Aged↗
PubMed1996

Evaluation of distal run-off before femorodistal bypass.

The quality of distal run-off is one of the most important factors in determining outcome of femorodistal bypass. Accurate evaluation is important. Preoperative intra-arterial digital subtraction angiography and Doppler evaluation with pulse-generated augmentation of 90 patients who underwent femorodistal reconstruction were compared with postoperative angiography. Underestimation of distal run-off of the calf vessels occurred in 33% of cases by preoperative intra-arterial digital subtraction angiography. A below-knee pulse-generated run-off score of 3 or less was associated with a 12-month cumulative patency of 73% compared with 85% with a below-knee pulse-generated run-off score of 4 or more (P=0.079, log rank test; P =0.060, Wilcoxon signed rank test). The 12-month cumulative patency for grafts with a complete, incomplete and occluded arch as defined by pulse-generated run-off was 78, 90 and 38% respectively (P<0.0001 log rank and Wilcoxon signed rank tests). Preoperative evaluation of distal run-off before femorodistal bypass should not be based exclusively on intra-arterial digital subtraction angiography.

Aged↗
PubMed1996

Comparison of magnetic resonance imaging measurements of abdominal aortic aneurysms with measurements obtained by other imaging techniques and intraoperative measurements: possible implications for endovascular grafting.

PURPOSE: Abdominal aortic aneurysm morphologic evaluation with conventional imaging techniques is inadequate when endovascular repair is being contemplated. This study has addressed the problem with magnetic resonance imaging (MRI). METHODS: Twenty patients (14 men, 6 women) with a median age of 73 years were recruited and assessed according to current endovascular graft selection criteria. Thirteen patients subsequently underwent open aneurysmorrhaphy, and the intraoperative parameters have been compared with those of duplex ultrasonography and MRI. RESULTS: No significant difference was demonstrated in the diameter of the infrarenal neck among ultrasonography, MRI, and intraoperative findings (p > 0.05, Mann Whitney U Test) and also during assessment of infrarenal neck length; however, duplex sonography accurately defined the renal ostia in only five cases. MRI visualized 38 of 40 renal arteries. Distal aortic involvement (cuff diameter and length) and the length and diameter of the common iliac arteries were accurately determined by MRI in all cases, and no significant difference was demonstrated with the intraoperative findings. Comparison of the intraoperative and MRI aneurysm lengths suggested a slight trend of overestimation by MRI resulting from angulation of the aneurysm, but this figure did not reach statistical significance. Only two patients met the current criteria for endoluminal straight grafting. CONCLUSIONS: Both MRI and duplex sonography accurately predicted aortic morphologic characteristics; however, MRI provided the most comprehensive anatomic picture for patient selection and should be considered the nonionizing imaging modality of choice when an endovascular repair is being contemplated.

Aged↗
PubMed1996

Intraoperative duplex scanning as a means of quality control during carotid endarterectomy.

OBJECTIVES: To identify correctable technical errors following carotid endarterectomy using intraoperative colour duplex sonography (ATL, UM9, HDI). Results were compared with intraoperative flow measurements using an operative flow meter and with middle cerebral artery velocity measured by trans-cranial Doppler (TCD). DESIGN: Prospective study. MATERIALS AND METHODS: 50 consecutive patients undergoing carotid endarterectomy were investigated. Follow-up was performed at 6 weeks using duplex scanning and clinical evaluation. RESULTS: Significant intraoperative technical errors were detected in three patients and were re-explored. Two scans demonstrated kinking or pinching at the distal endarterectomy site requiring patch-plasty and the third revealed a large mass of intramural thrombus. A further 18 endarterectomies yielded 21 additional minor abnormalities. CONCLUSIONS: Duplex sonography provides a sensitive intraoperative technique for detecting thrombus and technical errors. It yields both anatomic and hemodynamic details and is superior to intraoperative flow measurements and transcranial doppler.

Aged↗
PubMed1995

Aortoiliac segment examination with colour flow Duplex--a pilot study using Klean Prep. to improve the image quality.

OBJECTIVES: Currently colour flow Duplex examination of the iliac arteries is at best 84-92% sensitive. In an attempt to find a technique to improve on this sensitivity we have studied the effect of Klean Prep, an iso-osmotic bowel preparation, on the Duplex image and Doppler signal obtained when scanning iliac arteries. METHODS: Twenty iliac segments in 10 arteriopaths were scanned by a blinded observer, after either starving for 12 h or having Klean Prep bowel preparation. Grey scale image, colour mapping and Doppler signal to noise ratios were scored on a linear analogue system. Each patient was subsequently rescanned after the other method of preparation and was once again scored by a blinded observer. The two sets of scores were then compared. RESULTS: We found significant improvements in the linear analogue scoring of grey scale images, colour mapping and Doppler signal to noise ratios, when using Klean Prep as opposed to starving the patient prescan. CONCLUSIONS: Preparing patients with Klean Prep before iliac Duplex examination improves the visualisation of these arteries.

Aorta, Abdominal↗
PubMed1995

Iso-osmotic bowel preparation improves the accuracy of iliac artery colour flow duplex examination.

Colour flow duplex ultrasonography is currently the non-invasive method of choice for investigating the iliac arteries. However it is only 84-92% sensitive in the best hands when compared with biplanar angiography. Bowel gas and faeces overlying the iliac arteries obscure the vessels and prevent a good ultrasound image. We have previously shown that preparation of the bowel with an iso-osmotic bowel preparation (Klean Prep) improves the clarity of duplex image of the iliac arteries. This is caused by a volume effect which flushes out gas and faeces, leaving a fluid-filled bowel transparent to ultrasound. The aim of this study was to investigate whether this enhanced image increased the diagnostic accuracy of duplex examination. We performed iliac duplex examinations on 56 patients with clinically suspected iliac artery disease, initially with the normal preparation of starving the patients for 12 h and subsequently after preparation by Klean Prep. The results from each investigation were compared with the gold standard of biplanar intra-arterial digital substraction angiography. The use of iso-osmotic bowel preparation (Klean Prep) significantly improved the accuracy of iliac duplex ultrasonography over preparation by 12 h starvation, when compared with biplanar angiography.

Angiography, Digital Subtraction↗