An economic model for the prevention of MRSA infections after surgery: non-glycopeptide or glycopeptide antibiotic prophylaxis?

AIM: Surgical site infection is commonly caused by Staphylococcus aureus. The multiresistant strains (MRSA) are resistant to most antibiotic prophylaxis regimens. Our aim was to explore whether there is a threshold of MRSA prevalence at which switching to routine glycopeptide-based antibiotic prophylaxis becomes cost-effective. METHODS: An indicative model was designed to explore the cost-effectiveness of vancomycin, cephalosporin or a combination, in patients undergoing primary hip arthroplasty. RESULTS: If the MRSA infection rate is equal to or above 0.25% and the rate of other infections with cephalosporin prophylaxis is equal to or above 0.2%, use of the combination antibiotic prophylaxis is optimal. DISCUSSION: Modelling the cost-effectiveness of interventions for MRSA prevention is complex due to uncertainty around resistance and effectiveness of glycopeptides. CONCLUSIONS: The indicative model provides a framework for evaluation. More work is needed to understand the impact of antibiotic resistance over time in these currently effective antibiotics.

The impact of trial baseline imbalances should be considered in systematic reviews: a methodological case study.

OBJECTIVES: It is possible for baseline imbalances to occur between treatment groups for one or more variables in a randomized controlled trial, although the identification and detection of baseline imbalances remain controversial. If trials with baseline imbalances are combined in a meta-analysis, then this may result in misleading conclusions. STUDY DESIGN AND SETTING: The identification and consequences of baseline imbalances in meta-analyses are discussed. Metaregression using mean baseline scores as a covariate is proposed as a potential method for adjusting baseline imbalances within meta-analysis. We will use a recent systematic review looking at the effect of calcium supplements on weight as an illustrative case study. RESULTS: Meta-analysis conducted using the mean final values of the treatment groups as the outcome resulted in an apparent, statistically significant, treatment effect. However, using a meta-analysis of baseline values, this was shown to be due to the baseline imbalance between treatment groups, rather than as a result of any intervention received by the participants. Applying the method of metaregression demonstrated that there was in fact a smaller, statistically insignificant effect between treatment groups. CONCLUSION: The meta-analyst should always consider the possibility of baseline imbalances and adjustments should be made wherever possible.

Duplex ultrasonography, magnetic resonance angiography, and computed tomography angiography for diagnosis and assessment of symptomatic, lower limb peripheral arterial disease: systematic review.

OBJECTIVES: To determine the diagnostic accuracy of duplex ultrasonography, magnetic resonance angiography, and computed tomography angiography, alone or in combination, for the assessment of lower limb peripheral arterial disease; to evaluate the impact of these assessment methods on management of patients and outcomes; and to evaluate the evidence regarding attitudes of patients to these technologies and summarise available data on adverse events. DESIGN: Systematic review. METHODS: Searches of 11 electronic databases (to April 2005), six journals, and reference lists of included papers for relevant studies. Two reviewers independently selected studies, extracted data, and assessed quality. Diagnostic accuracy studies were assessed for quality with the QUADAS checklist. RESULTS: 107 studies met the inclusion criteria; 58 studies provided data on diagnostic accuracy, one on outcomes in patients, four on attitudes of patients, and 44 on adverse events. Quality assessment highlighted limitations in the methods and quality of reporting. Most of the included studies reported results by arterial segment, rather than by limb or by patient, which does not account for the clustering of segments within patients, so specificities may be overstated. For the detection of stenosis of 50% or more in a lower limb vessel, contrast enhanced magnetic resonance angiography had the highest diagnostic accuracy with a median sensitivity of 95% (range 92-99.5%) and median specificity of 97% (64-99%). The results were 91% (89-99%) and 91% (83-97%) for computed tomography angiography and 88% (80-98%) and 96% (89-99%) for duplex ultrasonography. A controlled trial reported no significant differences in outcomes in patients after treatment plans based on duplex ultrasonography alone or conventional contrast angiography alone, though in 22% of patients supplementary contrast angiography was needed to form a treatment plan. The limited evidence available suggested that patients preferred magnetic resonance angiography (with or without contrast) to contrast angiography, with half expressing no preference between magnetic resonance angiography or duplex ultrasonography (among patients with no contraindications for magnetic resonance angiography, such as claustrophobia). Where data on adverse events were available, magnetic resonance angiography was associated with the highest proportion of adverse events, but these were mild. The most severe adverse events, although rare, were mainly associated with contrast angiography. CONCLUSIONS: Contrast enhanced magnetic resonance angiography seems to be more specific than computed tomography angiography (that is, better at ruling out stenosis over 50%) and more sensitive than duplex ultrasonography (that is, better at ruling in stenosis over 50%) and was generally preferred by patients over contrast angiography. Computed tomography angiography was also preferred by patients over contrast angiography; no data on patients' preference between duplex ultrasonography and contrast angiography were available. Where available, contrast enhanced magnetic resonance angiography might be a viable alternative to contrast angiography.

Skin alterations of intact skin and risk factors associated with pressure ulcer development in surgical patients: a cohort study.

BACKGROUND: The pathology literature suggests three types of pressure ulcer with six possible mechanisms leading to tissue breakdown. A limitation of current evidence is the difficulty in replicating the clinical situation and in determining the point at which a tissue assault becomes irreversible and results in tissue breakdown. In particular clinical observations of alteration in darkly pigmented skin, blanching erythema, non-blanching erythema and non-blanching erythema with other skin changes including induration, oedema, pain, warmth or discolouration have not been assessed in relation to subsequent skin/tissue loss and their pathophysiological and aetiological importance is not fully understood. OBJECTIVES: To assess the validity of clinical signs of erythema as predictors of pressure ulcer development and identify variables which independently are predictive of Grade 2 pressure ulcer development. DESIGN: Prospective cohort study. PARTICIPANTS: 109 general, vascular and orthopaedic hospital patients, aged over 55 years with an expected length of stay of 5 days were recruited. Of these 97 were pressure ulcer free at baseline and/or had complete follow-up including 59 women and 38 men with a median age of 75 years (range 55-95). SETTING: Single centre large acute UK NHS hospital. METHODS: To identify clinical signs of erythema predictive of skin loss, the odds of pressure ulcer development were examined using logistic regression. To identify variables independently predictive of Grade 2 pressure ulcer development logistic regression modeling was undertaken. RESULTS: There was significantly increased odds of pressure ulcer development associated with non-blanching erythema (7.98, p=0.002) and non-blanching erythema with other skin changes (9.17, p=0.035). Logistic regression modeling identified non-blanching erythema, pre-operative albumin, weight loss, and intra-operative minimum diastolic blood pressure, as independent predictors of Grade > or =2 pressure ulcer development. CONCLUSIONS: Non-blanching erythema with or without other skin changes is distinct from normal skin/blanching erythema and is associated with subsequent pressure ulcer development.

Pressure relieving support surfaces (PRESSURE) trial: cost effectiveness analysis.

OBJECTIVE: To assess the cost effectiveness of alternating pressure mattresses compared with alternating pressure overlays for the prevention of pressure ulcers in patients admitted to hospital. DESIGN: Cost effectiveness analysis carried out alongside the pressure relieving support surfaces (PRESSURE) trial; a multicentre UK based pragmatic randomised controlled trial. SETTING: 11 hospitals in six UK NHS trusts. PARTICIPANTS: Intention to treat population comprising 1971 participants. MAIN OUTCOME MEASURES: Kaplan Meier estimates of restricted mean time to development of pressure ulcers and total costs for treatment in hospital. RESULTS: Alternating pressure mattresses were associated with lower overall costs (283.6 pounds sterling per patient on average, 95% confidence interval--377.59 pounds sterling to 976.79 pounds sterling) mainly due to reduced length of stay in hospital, and greater benefits (a delay in time to ulceration of 10.64 days on average,--24.40 to 3.09). The differences in health benefits and total costs for hospital stay between alternating pressure mattresses and alternating pressure overlays were not statistically significant; however, a cost effectiveness acceptability curve indicated that on average alternating pressure mattresses compared with alternating pressure overlays were associated with an 80% probability of being cost saving. CONCLUSION: Alternating pressure mattresses for the prevention of pressure ulcers are more likely to be cost effective and are more acceptable to patients than alternating pressure overlays.

Randomised, controlled trial of alternating pressure mattresses compared with alternating pressure overlays for the prevention of pressure ulcers: PRESSURE (pressure relieving support surfaces) trial.

OBJECTIVE: To compare whether differences exist between alternating pressure overlays and alternating pressure mattresses in the development of new pressure ulcers, healing of existing pressure ulcers, and patient acceptability. DESIGN: Pragmatic, open, multicentre, randomised controlled trial. SETTING: 11 hospitals in six NHS trusts. PARTICIPANTS: 1972 people admitted to hospital as acute or elective patients. INTERVENTIONS: Participants were randomised to an alternating pressure mattress (n = 982) or an alternating pressure overlay (n = 990). MAIN OUTCOME MEASURES: The proportion of participants developing a new pressure ulcer of grade 2 or worse; time to development of new pressure ulcers; proportions of participants developing a new ulcer within 30 days; healing of existing pressure ulcers; and patient acceptability. RESULTS: Intention to treat analysis found no difference in the proportions of participants developing a new pressure ulcer of grade 2 or worse (10.7% overlay patients, 10.3% mattress patients; difference 0.4%, 95% confidence interval--2.3% to 3.1%, P = 0.75). More overlay patients requested change owing to dissatisfaction (23.3%) than mattress patients (18.9%, P = 0.02). CONCLUSION: No difference was found between alternating pressure mattresses and alternating pressure overlays in the proportion of people who develop a pressure ulcer. TRIAL REGISTRATION: ISRCTN 78646179.

Pathology, diagnosis, and classification of pressure ulcers: comparing clinical and imaging techniques.

Pressure ulcer classification systems are based on the clinical manifestations of the skin and tissue layer affected rather than underlying pathology. The objective of this study was to compare the validity of the clinical grading of erythema (blanching and nonblanching) with a measurement of skin perfusion. Therefore, an exploratory study comparing erythema with laser Doppler imaging of the sacrum and buttock skin areas was undertaken. Acute and major elective general, vascular, and orthopedic surgical in-patients, aged 55 years or over with an expected length of hospital stay of 5 or more days were recruited. Fifty laser Doppler images from 37 patients were obtained and included in a discriminant analysis. Discriminant analysis suggested that blanching and nonblanching erythema were physiologically distinct from "normal" skin; clinically, these could be assessed with reasonable accuracy. Imaging also determined that high blood flow of differing intensity characterized blanching and nonblanching erythema. There was no evidence of the "no flow" phenomenon.

Assessment of non-ST-segment elevation acute coronary syndromes with cardiac magnetic resonance imaging.

OBJECTIVES: The goal of this study was to determine: 1) if the presence of significant coronary stenosis in patients presenting with non-ST-segment elevation acute coronary syndromes (NSTE-ACS) can be predicted by cardiac magnetic resonance (CMR) imaging; and 2) if the analysis of several CMR methods improves its diagnostic yield compared with analysis of individual methods. BACKGROUND: With modern acquisition techniques, several CMR methods for the assessment of coronary artery disease (CAD) can be combined in a single noninvasive scanning session. Such a multicomponent CMR examination has not previously been applied to a large patient population, in particular those with a high prevalence of CAD in an acute situation. METHODS: Sixty-eight patients presenting with NSTE-ACS underwent CMR imaging of myocardial function, perfusion (rest and adenosine-stress), viability (by late contrast enhancement), and coronary artery anatomy. Visual analysis of CMR was carried out. First, all CMR data were reviewed in combination ("comprehensive analysis"). In further separate analyses, each CMR method was analyzed individually. The ability of CMR to detect coronary stenosis >/=70% on X-ray angiography was determined. RESULTS: Comprehensive CMR analysis yielded a sensitivity of 96% and a specificity of 83% to predict the presence of significant coronary stenosis and was more accurate than analysis of any individual CMR method; CMR was significantly more sensitive and accurate than the Thrombolysis In Myocardial Infarction risk score (p < 0.001). CONCLUSIONS: Cardiac magnetic resonance imaging accurately predicts the presence of significant CAD in patients with NSTE-ACS. In this study, a comprehensive analysis of several CMR methods improved the accuracy of the test.