Luc Lanthier

Emergence of Fluoroquinolones as the Predominant Risk Factor for Clostridium difficile–Associated Diarrhea: A Cohort Study during an Epidemic in Quebec

BACKGROUND Since 2002, an epidemic of Clostridium difficile-associated-diarrhea (CDAD) associated with a high case-fatality rate has involved >30 hospitals in the province of Quebec, Canada. In 2003, a total of 55% of patients with CDAD at our hospital had received fluoroquinolones in the preceding 2 months. It has been suggested that massive use of proton pump inhibitors might have facilitated this epidemic. METHODS To delineate the risk of CDAD associated with specific classes of antibiotics and whether this is modulated by concomitant use of proton pump inhibitors and other drugs altering gastric acidity or gastrointestinal motility, we conducted a retrospective cohort study of patients hospitalized in a teaching hospital in Sherbrooke, Canada, during the period of January 2003 through June 2004. We obtained data on 7421 episodes of care corresponding to 5619 individuals. Patients were observed until they either developed CDAD or died or for 60 days after discharge from the hospital. Adjusted hazard ratios (AHRs) were calculated using Cox regression. RESULTS CDAD occurred in 293 patients. Fluoroquinolones were the antibiotics most strongly associated with CDAD (AHR, 3.44; 95% confidence interval [CI], 2.65-4.47). Almost one-fourth of all inpatients received quinolones, for which the population-attributable fraction of CDAD was 35.9%. All 3 generations of cephalosporins, macrolides, clindamycin, and intravenous beta-lactam/beta-lactamase inhibitors were intermediate-risk antibiotics, with similar AHRs (1.56-1.89). Proton pump inhibitors (AHR, 1.00, 95% CI, 0.79-1.28) were not associated with CDAD. CONCLUSIONS Administration of fluoroquinolones emerged as the most important risk factor for CDAD in Quebec during an epidemic caused by a hypervirulent strain of C. difficile.

Characteristics and Short-Term Prognosis of Perioperative Myocardial Infarction in Patients Undergoing Noncardiac Surgery: A Cohort Study

BACKGROUND Each year, millions of patients worldwide have a perioperative myocardial infarction (MI) after noncardiac surgery. OBJECTIVE To examine the characteristics and short-term outcome of perioperative MI. DESIGN Cohort study. (ClinicalTrials.gov registration number: NCT00182039) SETTING 190 centers in 23 countries. PATIENTS 8351 patients included in the POISE (PeriOperative ISchemic Evaluation) trial. MEASUREMENTS Four cardiac biomarker or enzyme assays were measured within 3 days of surgery. The definition of perioperative MI included either autopsy findings of acute MI or an elevated level of a cardiac biomarker or enzyme and at least 1 of the following defining features: ischemic symptoms, development of pathologic Q waves, ischemic changes on electrocardiography, coronary artery intervention, or cardiac imaging evidence of MI. RESULTS Within 30 days of random assignment, 415 patients (5.0%) had a perioperative MI. Most MIs (74.1%) occurred within 48 hours of surgery; 65.3% of patients did not experience ischemic symptoms. The 30-day mortality rate was 11.6% (48 of 415 patients) among patients who had a perioperative MI and 2.2% (178 of 7936 patients) among those who did not (P < 0.001). Among patients with a perioperative MI, mortality rates were elevated and similar between those with (9.7%; adjusted odds ratio, 4.76 [95% CI, 2.68 to 8.43]) and without (12.5%; adjusted odds ratio, 4.00 [CI, 2.65 to 6.06]) ischemic symptoms. LIMITATION Cardiac markers were measured only until day 3 after surgery, and additional asymptomatic MIs may have been missed. CONCLUSION Most patients with a perioperative MI will not experience ischemic symptoms. Data suggest that routine monitoring of troponin levels in at-risk patients is needed after surgery to detect most MIs, which have an equally poor prognosis regardless of whether they are symptomatic or asymptomatic.

Pneumococcal vaccination and risk of myocardial infarction

Background: Based on promising results from laboratory studies, we hypothesized that pneumococcal vaccination would protect patients from myocardial infarction. Methods: We conducted a hospital-based case–control study that included patients considered to be at risk of myocardial infarction. We used health databases to obtain hospital diagnoses and vaccination status. We compared patients who had been admitted for treatment of myocardial infarction with patients admitted to a surgical department in the same hospital for a reason other than myocardial infarction between 1997 and 2003. Results: We found a total of 43 209 patients who were at risk; of these, we matched 999 cases and 3996 controls according to age, sex and year of hospital admission. Cases were less likely than controls to have been vaccinated (adjusted odds ratio [OR] 0.53, 95% confidence interval [CI] 0.40–0.70). This putative protective role of the vaccine was not observed for patients who had received the vaccine up to 1 year before myocardial infarction (adjusted OR 0.85, 95% CI 0.54–1.33). In contrast, if vaccination had occurred 2 years or more before the hospital admission, the association was stronger (adjusted OR 0.33, 95% CI 0.20–0.46). Interpretation: Pneumococcal vaccination was associated with a decrease of more than 50% in the rate myocardial infarction 2 years after exposure. If confirmed, this association should generate interest in exploring the putative mechanisms and may offer another reason to promote pneumococcal vaccination.

The influence of medical students’ self‐explanations on diagnostic performance

Medical Education 2011: 45: 688–695

Students' self-explanations while solving unfamiliar cases: the role of biomedical knowledge

General guidelines for teaching clinical reasoning have received much attention, despite a paucity of instructional approaches with demonstrated effectiveness. As suggested in a recent experimental study, self‐explanation while solving clinical cases may be an effective strategy to foster reasoning in clinical clerks dealing with less familiar cases. However, the mechanisms that mediate this benefit have not been specifically investigated. The aim of this study was to explore the types of knowledge used by students when solving familiar and less familiar clinical cases with self‐explanation.

Chronic antiplatelet therapy and mortality among patients with infective endocarditis

Whether antiplatelet therapy is associated with better outcomes among patients with infective endocarditis (IE) remains controversial. A retrospective study was conducted concerning all patients with IE, treated in a tertiary-care centre of Canada between 1991 and 2006, who satisfied the modified Duke criteria for a definite or possible IE. The primary outcome was all-cause mortality within 90 days of diagnosis. A secondary outcome was the development of major systemic embolism. In total, 241 patients satisfied the inclusion criteria, 75 of whom had been on chronic antiplatelet therapy prior to developing endocarditis. Seventy-one (29.5%) patients died. According to multivariate analysis, age, a high Charlson score, aortic valve involvement, myocardial infarction and presence of a perivalvular abscess were strongly associated with mortality. Undergoing valvular replacement (adjusted OR (AOR) 0.28, 95% CI 0.09-0.84) and chronic antiplatelet therapy before IE (AOR 0.27, 95% CI 0.11-0.64) correlated with lower mortality. There was a trend for lower mortality among patients started on antiplatelet drugs after admission (AOR 0.29, 95% CI 0.08-1.13). The effect of aspirin on mortality was much the same in patients who received 325 or 80 mg daily. Chronic antiplatelet therapy was not associated with a significantly lower risk of major embolism. In conclusion, chronic antiplatelet therapy was associated with lower mortality among patients with IE, independently of any effect on major embolism. Whether or not a beneficial effect could be replicated by initiating antiplatelet therapy at the time of diagnosis remains unproven.

A single-nucleotide polymorphism of alanine to threonine at position 163 of the human angiotensin II type 1 receptor impairs Losartan affinity.

Background and objective AT1 is the principal receptor for angiotensin II (AngII), which regulates blood pressure and osmotic homeostasis. Earlier studies have shown that position 163 interacts with the antihypertensive nonpeptide antagonist, Losartan. A recently discovered polymorphism found in humans (rs12721226) coding for residue 163 led us to determine whether this polymorphism would affect Losartan antihypertensive therapies. The pharmacological properties of the A163T hAT1 variant are described. Method and results The A163T hAT1 mutation was evaluated by testing its affinity by dose displacement of AngII analogs in COS-7 cells expressing either wild-type hAT1 or the A163T hAT1. The expressions of the receptors were evaluated by saturation binding and the efficacies were assessed by measuring the 3H-inositol phosphate production. The results showed that the A163T hAT1 receptor is comparable with the affinity, expression, and efficacy of native hAT1 towards peptide ligands. The affinities were also tested with nonpeptide antagonists Losartan, L-158 809, valsartan, telmisartan, irbesartan, candesartan, and EXP3174. Losartan and EXP3174 displayed a 7-fold loss in affinity towards A163T hAT1. The ability of Losartan to inhibit AngII-induced inositol triphosphate production also confirmed a loss in efficacy. Molecular modeling showed a higher steric and hydrophilic hindrance of the A163T hAT1-Losartan complex. Conclusion The polymorphism that codes for the A163T hAT1 variant results in a receptor with normal physiological properties toward the endogenous hormone. However, the significant reduction in affinity to Losartan and its active metabolite, EXP3174, could significantly impair the clinical effectiveness of an antihypertensive therapy using Losartan with patients bearing the A163T polymorphism.

Knowledge Translation Strategy to Reduce the Use of Potentially Inappropriate Medications in Hospitalized Elderly Adults.

To evaluate the effect of a knowledge translation (KT) strategy to reduce potentially inappropriate medication (PIM) use in hospitalized elderly adults.

An Interprofessional Qualitative Study of Barriers and Potential Solutions for the Safe Use of Insulin in the Hospital Setting

OBJECTIVE Insulin is regularly used in hospitalized patients for glycemic control but is associated with significant risks. The goals of this study were to describe the strengths and weaknesses of a university health centre in the safe use of insulin, to collect improvement proposals from health professionals involved in the management of insulin therapy and to assess inpatient glycemic control. METHODS This is a qualitative study. Physicians, nurses and pharmacists practising at the Centre Hospitalier Universitaire de Sherbrooke (CHUS) for at least 2 years were invited to join focus groups on safe insulin treatment. Themes up for discussion were roles of professionals in insulin therapy, problems encountered, solutions put forward and strengths of the hospital. The Quality Hyperglycemia Score (QHS) was assessed using an existing cohort of inpatients who were prescribed insulin. RESULTS A total of 5 focus groups were held in February and March of 2012, involving 31 healthcare professional participants. Several groups pointed out the same problems, namely, lack of access to useful information for optimal management of insulin therapy and lack of communication among personnel on different work shifts. Results of the QHS suggest room for improvement in blood glucose control at our institution. CONCLUSION These focus groups allowed better identification of the management problems related to the use of insulin in our health institution and possible interventions to solve them. The QHS will be reassessed to measure quality of inpatient glycemic control over time.

Low-dose ionising radiation from medical imaging in patients hospitalised in Internal Medicine.

Background:  Medical imaging is responsible for increasing exposure to low‐dose ionising radiation in the general population. The extent of exposure in specific patient populations remains to be determined.