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C McCollum

Publications and source records attributed to C McCollum.

At least 19 recordsLinked to original sources
PubMed2006

Relationship of deep white matter hyperintensities and cerebral blood flow in severe carotid artery stenosis.

Leukoaraiosis (LA) has been associated with abnormalities of both large and small blood vessels. This study attempts to clarify the pathogenesis of LA by testing the hypothesis that increased frequency of LA with occlusive extra-cranial arterial disease results directly from global reduction in cerebral blood flow (CBF). Thirty-five normal subjects and 55 patients with carotid stenosis (>70%) were studied using MR. CBF was measured using phase contrast MR angiography and LA was scored using previously validated scoring system. Patients were divided into those with evidence of previous infarction on MRI and those without. LA was more severe in patients than in normal subjects (P<0.01) and correlated with age in normal subjects but not in patients. CBF in patients with (809+/-214 ml/min) and without infarction (mean 792+/-181 ml/min) was significantly lower than in normal subjects (mean 1073+/-194 ml/min). There was no correlation between the severity of LA and measured CBF in any group. The severity of LA is greater in patients with severe carotid stenosis but is not correlated to reductions in CBF. This suggests that microvascular abnormality is the dominant pathogenetic factor in LA even in the presence of severe stenotic/occlusive large vessel disease.

Aged↗
PubMed2006

Paradoxical embolization: a potential cause of cerebral damage in Alzheimer's disease?

BACKGROUND: There are considerable overlaps between vascular dementia and Alzheimer's disease (AD), with a suggestion that cerebrovascular disease (CVD) contributes to the neurodegenerative pathology of AD. Paradoxical embolization of venous emboli into the systemic circulation through a venous to arterial circulation shunt (v-aCS), the most commonly a patent foramen ovale (PFO), is known to cause cryptogenic stroke in younger people. We reviewed the potential role of paradoxical embolization in AD. METHODS: A review of the literature on paradoxical embolization in neurological disorders and techniques to detect v-aCS and PFO, supplemented by data from our own studies. RESULTS: Before our research, the role of paradoxical embolism in dementia had not been studied. The potential role of embolization in cerebral damage was highlighted by studies in patients undergoing coronary artery bypass or carotid surgery. Paradoxical embolization was found to occur in patients with cryptogenic stroke, migraine, decompression sickles and during hip surgery. The methods for detecting v-aCS or PFO had not been standardized. We found 'significant' v-aCS (equivalent to PFO) in 32% of AD patients compared with 22% of controls, but the study was not sufficiently powered to test the statistic significance of this difference. In AD, there was evidence of an association between 'significant' v-aCS and the severity of white matter hyperintensities on magnetic resonance imaging (MRI). CONCLUSION: Paradoxical embolization through a v-aCS may be a potentially preventable or treatable cause of CVD in AD.

Alzheimer Disease↗
PubMed2006

Cost-effectiveness of cell salvage and alternative methods of minimising perioperative allogeneic blood transfusion: a systematic review and economic model.

OBJECTIVES: To compare patient outcomes, resource use and costs to the NHS and NHS Blood Transfusion Authority (BTA) associated with cell salvage and alternative methods of minimising perioperative allogeneic blood transfusion. DATA SOURCES: Electronic databases covering the period 1996-2004 for systematic reviews and 1994-2004 for economic evidence. REVIEW METHODS: Existing systematic reviews were updated with data from selected randomised controlled trials (RCTs) that involved adults scheduled for elective non-urgent surgery. Any resource use or cost data were extracted for potential use in populating an economic model. Relative risks or weighted mean difference of each outcome for each intervention were assessed, taking into account the number of RCTs included in each outcome and intervention and the presence of any heterogeneity. This allowed indirect comparison of the relative effectiveness of each intervention when the intervention is compared with allogeneic blood transfusion. A decision analytic model synthesised clinical and economic data from several sources, to estimate the relative cost-effectiveness of cell salvage for people undergoing elective surgery with moderate to major expected blood loss. The perspective of the NHS and patients and a time horizon of 1 month were used. The economic model was developed from reviews of effectiveness and cost-effectiveness and clinical experts. Secondary analysis explored the robustness of the results to changes in the timing and costs of cell salvage equipment, surgical procedure, use of transfusion protocols and time horizon of analysis. RESULTS: Overall, 668 studies were identified electronically for the update of the two systematic reviews. This included five RCTs, of which two were cell salvage and three preoperative autologous donation (PAD). Five published systematic reviews were identified for antifibrinolytics, fibrin sealants and restrictive transfusion triggers, PAD plus erythropoietin, erythropoietin alone and acute normovolaemic haemodilution (ANH). Twelve published studies reported full economic evaluations. All but two of the transfusion strategies significantly reduced exposure to allogeneic blood. The relative risk of exposure to allogeneic blood was 0.59 for the pooled trials of cell salvage (95% confidence interval: 0.48 to 0.73). This varied by the type and timing of cell salvage and type of surgical procedure. For cell salvage, the relative risk of allogeneic blood transfusion was higher in cardiac surgery than in orthopaedic surgery. Cell salvage had lower costs and slightly higher quality-adjusted life years compared with all of the alternative transfusion strategies except ANH. The likelihood that cell salvage is cost-effective compared with strategies other than ANH is over 50%. Most of the secondary analyses indicated similar results to the primary analysis. However, the primary and secondary analyses indicated that ANH may be more cost-effective than cell salvage. CONCLUSIONS: The available evidence indicates that cell salvage may be a cost-effective method to reduce exposure to allogeneic blood transfusion. However, ANH may be more cost-effective than cell salvage. The results of this analysis are subject to the low quality and reliability of the data used and the use of indirect comparisons. This may affect the reliability and robustness of the clinical and economic results. There is a need for further research that includes adequately powered high-quality RCTs to compare directly various blood transfusion strategies. These should include measures of health status, health-related quality of life and patient preferences for alternative transfusion strategies. Observational and tracking studies are needed to estimate reliably the incidence of adverse events and infections transmitted during blood transfusion and to identify the lifetime consequences of the serious hazards of transfusion on mortality, health status and health-related quality of life.

Aminocaproates↗
PubMed2006

The success of routine MRSA screening in vascular surgery: a nine year review.

AIM: Methicillin resistant Staphylococcus aureus (MRSA) infection in vascular patients is associated with increased morbidity and mortality. We investigated whether routine MRSA screening reduced complications related to MRSA infection. METHODS: Data was analysed for all MRSA positive (+ve) vascular patients admitted before (1996-2000) and after (2001-2004) routine MRSA screening was introduced. Outcome measures compared included wound infection, major limb amputation and mortality rates. RESULTS: There were 92 and 188 MRSA +ve patients in the pre- and postscreening periods, respectively. After the introduction of MRSA screening, MRSA wound infection in MRSA +ve elective admissions was significantly reduced from 55.6% (20/36) to 22.4% (15/67), (P=0.002, chi2 test); amputations were reduced from 27.8% (10/36) to 9% (6/67), P value 0.026, and mortality from 16.7% (6/36) to 9% (6/67), P value >0.05. In MRSA +ve emergency admissions wound infection was significantly reduced from 62.5% (35/56) to 43.8% (53/121), P value 0.042, amputations from 50% (28/56) to 38.8% (47/121), P value 0.26, and mortality from 25% (14/56) to 12.4% (15/121), P value 0.067. CONCLUSIONS: While the incidence of MRSA infection continues to rise, we have successfully demonstrated that MRSA screening identifies patients at risk of serious complications and is associated with a reduction in these complications following both elective and emergency surgery. Routine screening of all vascular admissions should be part of the strategy to combat MRSA infection.

Anti-Bacterial Agents↗
PubMed2004

Thrombectomy for acute internal carotid thrombosis: five thrombectomy devices compared.

OBJECTIVE: To test the safety and efficiency of commercially available thrombectomy catheters in clearing simulated internal carotid artery (ICA) thrombosis. DESIGN: Comparative in vitro study. MATERIALS AND METHODS: A model of the ICA was filled with human thrombus, the 'circle of Willis' back pressure was set at either 10 or 30 cm of water. Five thrombectomy devices (Hydrolyser, Clot Buster, Acolysis System, AngioJet and Fogarty embolectomy catheter) were compared for (i) efficiency at removing thrombus, (ii) pressure changes at the tip of each device, and (iii) distal embolisation by flow cytometry. RESULTS: Thrombus clearance was greatest with the AngioJet (median 95%, range 92-97%) and least with the Acolysis System (median 34%, range 12-50%). The Clot Buster and Hydrolyser were safest as they produced only negative tip pressures, the AngioJet and Balloon catheter produced positive and negative pressures risking distal embolisation. The Acolysis system produced no pressure change during use. Distal embolisation (of particles between 5 and 40 microm diameter) was greatest with the Fogarty balloon catheter at 10 cm water (P<0.05) and least with the Hydrolyser and Clot Buster. CONCLUSION: Balloon embolectomy for ICA thrombosis risks further embolic cerebral damage. The Hydrolyser and the Clot Buster show the greatest promise for ICA thrombectomy.

Acute Disease↗
PubMed2004

Paradoxical cerebral embolisation. An explanation for fat embolism syndrome.

Fat embolism occurs following fractures of a long bone or arthroplasty. We investigated whether paradoxical embolisation through a venous-to-arterial circulation shunt (v-a) could lead to cerebral embolisation during elective hip or knee arthroplasty. Transcranial Doppler ultrasound (TCD), following the intravenous injection of microbubble contrast, identified the presence of a shunt in 41 patients undergoing hip (n = 20) or knee (n = 21) arthroplasty. Intra-operative cerebral embolism was detected during continuous TCD monitoring. Of the 41 patients, 34 had a v-a shunt of whom 18 had an embolism and embolism only occurred in patients with a shunt (p = 0.012). Spontaneous and larger shunts were associated with a greater number of emboli (rs = 0.67 and rs = 0.71 respectively, p < 0.01). Observations in two patients with large spontaneous shunts revealed 368 and 203 emboli and unexplained post-operative confusion and pancreatitis. Paradoxical cerebral embolisation only occurred in patients with a shunt and may explain both postoperative confusion and fat embolism syndrome following surgery.

Adult↗
PubMed2001

Prosodic structure and wh-questions.

This study examines the influence of wh-gaps on the prosodic contour of spoken utterances. A previous study (Nagel, Shapiro, & Nawy, 1994) claimed that the phonological representation of a sentence containing a filler-gap dependency explicitly encodes the location of the syntactic gap. In support of this hypothesis, Nagel et al. presented evidence that the word immediately preceding a gap is lengthened and that there is a reliable increase in pitch excursion across the gap location. Our study challenges Nagel et al.'s claim. We argue that their materials confounded the presence/ absence of a gap with other factors that are known to affect intonational phrasing independently. We show that, when these factors are separated, the evidence that syntactic gaps are explicitly encoded in the phonological representation of a sentence disappears.

Adult↗
PubMed2001

Heparin-bonded Dacron or polytetrafluoroethylene for femoropopliteal bypass grafting: a multicenter trial.

BACKGROUND: Dacron (polyester fiber) was largely abandoned for femoropopliteal bypass grafts 30 years ago because saphenous vein achieved better patencies. However, in patients taking aspirin, patency in above-knee femoropopliteal bypass grafts has recently been shown to be equivalent to that with saphenous vein. We compared heparin-bonded Dacron (HBD) and polytetrafluoroethylene (PTFE) in a randomized multicenter trial including below-knee popliteal or tibioperoneal trunk bypass graft where the long saphenous vein was absent or inadequate. METHODS: Over 28 months, 209 patients undergoing femoropopliteal bypass grafts (180 above-knee, 29 below-knee) were randomized to HBD (n = 106) or PTFE (n = 103). Each patient was given aspirin (300 mg/d) before surgery, and this continued unless the patient had intolerance to the aspirin. RESULTS: The mean follow-up was 42 months (range, 28-55). Fifteen (7.1%) patients died with patent grafts, and three (1.4%) infected grafts were removed. Patency (measured with Kaplan-Meier survival analysis) at 1, 2, and 3 years for HBD was 70%, 63%, and 55% compared with 56%, 46%, and 42%, respectively, for PTFE (P =.044). A total of 67 secondary interventions were performed on 48 thrombosed grafts; long-term patency was achieved in only three. Risk factors for arterial disease did not significantly influence patency. Amputations have been performed in 23 patients, six after HBD and 17 after PTFE bypass grafts (P =.015). CONCLUSIONS: HBD achieved better patency than PTFE, which carried a high risk of subsequent amputation.

Adult↗
PubMed2001

Stroke in young adults: the role of paradoxical embolism.

Stroke in young adults may be devastating and frequently no cause can be found. However, there is ample literature to suggest an association between cryptogenic stroke in young people and paradoxical embolisation via a venous to arterial circulation shunt (v-aCS), commonly due to patent foramen ovale (PFO). Although paradoxical embolisation is assumed to be a rare event, this review suggests that it is an important or even dominant cause of stroke in young people and that a transcranial Doppler (TCD) technique may be the investigation of choice to identify v-aCS.

Adult↗
PubMed2000

In vitro cloning of complex mixtures of DNA on microbeads: physical separation of differentially expressed cDNAs.

We describe a method for cloning nucleic acid molecules onto the surfaces of 5-micrometer microbeads rather than in biological hosts. A unique tag sequence is attached to each molecule, and the tagged library is amplified. Unique tagging of the molecules is achieved by sampling a small fraction (1%) of a very large repertoire of tag sequences. The resulting library is hybridized to microbeads that each carry approximately 10(6) strands complementary to one of the tags. About 10(5) copies of each molecule are collected on each microbead. Because such clones are segregated on microbeads, they can be operated on simultaneously and then assayed separately. To demonstrate the utility of this approach, we show how to label and extract microbeads bearing clones differentially expressed between two libraries by using a fluorescence-activated cell sorter (FACS). Because no prior information about the cloned molecules is required, this process is obviously useful where sequence databases are incomplete or nonexistent. More importantly, the process also permits the isolation of clones that are expressed only in given tissues or that are differentially expressed between normal and diseased states. Such clones then may be spotted on much more cost-effective, tissue- or disease-directed, low-density planar microarrays.

Cloning, Molecular↗
PubMed2000

Regional variation in incidence and case fatality of myocardial infarction among young women in England, Scotland and Wales.

OBJECTIVES: To examine the regional variation in incidence and case fatality of myocardial infarction among young women. DESIGN: Cross sectional survey, using population based incidence data. SETTING: England, Scotland and Wales. SUBJECTS: Subjects were women aged 16-44 with a diagnosis of myocardial infarction between 1 October 1993 and 15 October 1995. OUTCOME MEASURES: Incidence of myocardial infarction per 100,000 women years, with case fatality as a percentage of total cases. RESULTS: Incidence of myocardial infarction rose steeply from age 33 upwards, (maximum = 20.2 cases per 100,000 women years at age 44). The adjusted incidence rate for myocardial infarction was 3.7 (95% CI 3.2, 4.2) times greater in Scotland than in southern England. In contrast, case fatality was significantly lower in Scotland: 18.5% (95% CI 13.1%, 25.0%), compared with 31.0% (95% CI 25.9%, 36.0%) in southern England. CONCLUSIONS: The incidence of myocardial infarction varied widely within the United Kingdom. Case fatality variation may reflect differences in ambulance response, or in diagnostic acumen, within the regions.

Adolescent↗
PubMed1999

Oral contraceptives and myocardial infarction: results of the MICA case-control study.

OBJECTIVES: To determine the association between myocardial infarction and use of different types of oral contraception in young women. DESIGN: Community based case-control study. Data from interviews and general practice records. SETTING: England, Scotland, and Wales. PARTICIPANTS: Cases (n=448) were recruited from women aged between 16 and 44 who had suffered an incident myocardial infarction between 1 October 1993 and 16 October 1995. Controls (n=1728) were women without a diagnosis of myocardial infarction matched for age and general practice. MAIN OUTCOME MEASURES: Odds ratios for myocardial infarction in current users of all combined oral contraceptives stratified by their progestagen content compared with non-users; current users of third generation versus second generation oral contraceptives. RESULTS: The adjusted odds ratio for myocardial infarction was 1.40 (95% confidence interval 0.78 to 2. 52) for all combined oral contraceptive users, 1.10 (0.52 to 2.30) for second generation users, and 1.96 (0.87 to 4.39) for third generation users. Subgroup analysis by progestagen content did not show any significant difference from 1, and there was no effect of duration of use. The adjusted odds ratio for third generation users versus second generation users was 1.78 (0.66 to 4.83). 87% of cases were not exposed to an oral contraceptive, and 88% had clinical cardiovascular risk factors or were smokers, or both. Smoking was strongly associated with myocardial infarction: adjusted odds ratio 12.5 (7.29 to 21.5) for smoking 20 or more cigarettes a day. CONCLUSIONS: There was no significant association between the use of oral contraceptives and myocardial infarction. The modest and non-significant point estimates for this association have wide confidence intervals. There was no significant difference between second and third generation products.

Adolescent↗
PubMed1999

Soluble intercelluar adhesion molecule-1, E-selectin, vascular cell adhesion molecule-1 and von Willebrand factor in stroke.

We investigated the role of endothelial cell and leukocyte adhesion in the pathophysiology of acute stroke. The immunocytochemical expression of adhesion molecules in brain tissue from six patients who died following acute ischaemic stroke showed weak endothelial expression of intercellular adhesion molecule-1 (ICAM-1), but intense expression of vascular cell adhesion molecule-1 (VCAM-1) by astrocytes and endothelial cells from the infarcted, but not the non-infarcted areas. We also measured soluble adhesion molecules E-selectin, ICAM-1, VCAM-1 and von Willebrand factor (all by enzyme-linked immunosorbent assay) in 21 patients after an acute ischaemic stroke (ictus < 12 h), and again 3 months later. Blood levels in the stroke patients were compared with 82 healthy controls and 22 subjects with carotid atherosclerosis. Compared with healthy controls, both patient groups had raised levels of von Willebrand factor (P < 0.02) but the level of soluble VCAM-1 was raised only in patients with acute stroke (P < 0.02). Levels of von Willebrand factor and soluble VCAM-1 in the stroke patients were still high at 3 months follow-up. We suggest that there might be changes in adhesion molecule expression and release in the acute and chronic stages of ischaemic stroke, where blood levels are related to immunocytochemical findings on infarcted brain. These changes may perhaps be part of the complex pathophysiological responses to infarction and repair of brain tissue following stroke.

Aged↗
PubMed1999

Risk of myocardial infarction in young female smokers.

OBJECTIVES: To determine the extent of risk of myocardial infarction from cigarette smoking in young women, and to examine the relation of smoking with other putative risk factors. DESIGN: Community based case control study. SETTING: England, Scotland, and Wales. PATIENTS: Women (n = 448) between 16 and 44 years old with a diagnosis of incident myocardial infarction between 1 October 1993 and 16 October 1995. Controls (n = 1728) were age and general practice matched women without a diagnosis of myocardial infarction. OUTCOMES MEASURES: Odds ratios for risk of myocardial infarction associated with smoking and other risk factors. RESULTS: Odds ratios for myocardial infarction in smokers versus non-smokers showed a strong dose response, from 2.47 (95% confidence interval (CI) 1.12 to 5.45) in smokers of 1-5 cigarettes per day to 74.6 (95% CI 33.0 to 169) in smokers of >/= 40 cigarettes per day. There was no interaction of smoking with use of oral contraceptives, but there were additive risks with other clinical risk factors such as hypertension and diabetes. It is estimated that if all women aged 16-44 years were able to stop smoking, 400 cases of myocardial infarction per annum (of whom 112 would die) would be prevented. CONCLUSIONS: In young women the risk of myocardial infarction from smoking was considerable, and heavy smokers with other risk factors were especially at risk.

Adolescent↗
PubMed1999

Tension-free mesh hernia repair: recovery and recurrence after one year.

The outcome of 200 consecutive patients with inguinal hernias repaired by the tension-free mesh technique at a specialist clinic was assessed one year after operation. There were no recurrences and no major complications. The wound infection rate was 1%. Less than 10% of patients had only minor complaints and 99% of patients were satisfied or very satisfied with the operation and its outcome. Low recurrence rates after one year imply low long-term recurrence and testify to the benefits of a specialist approach.

Adolescent↗