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Biomedical subjects

A Laupacis

Publications and source records attributed to A Laupacis.

At least 37 records · Page 2Linked to original sources
PubMed2001

The Canadian CT Head Rule Study for patients with minor head injury: rationale, objectives, and methodology for phase I (derivation).

Head injuries are among the most common types of trauma seen in North American emergency departments, with an estimated 1 million cases seen annually. "Minor" head injury (sometimes known as "mild") is defined by a history of loss of consciousness, amnesia, or disorientation in a patient who is conscious and talking, that is, with a Glasgow Coma Scale score of 13 to 15. Although most patients with minor head injury can be discharged without sequelae after a period of observation, in a small proportion, their neurologic condition deteriorates and requires neurosurgical intervention for intracranial hematoma. The objective of the Canadian CT Head Rule Study is to develop an accurate and reliable decision rule for the use of computed tomography (CT) in patients with minor head injury. Such a decision rule would allow physicians to be more selective in their use of CT without compromising care of patients with minor head injury. This paper describes in detail the rationale, objectives, and methodology for Phase I of the study in which the decision rule was derived. [Stiell IG, Lesiuk H, Wells GA, McKnight RD, Brison R, Clement C, Eisenhauer MA, Greenberg GH, MacPhail I, Reardon M, Worthington J, Verbeek R, Rowe B, Cass D, Dreyer J, Holroyd B, Morrison L, Schull M, Laupacis A, for the Canadian CT Head and C-Spine Study Group. The Canadian CT Head Rule Study for patients with minor head injury: rationale, objectives, and methodology for phase I (derivation). Ann Emerg Med. August 2001;38:160-169.]

Adolescent↗
PubMed2001

The future of evidence-based medicine.

Evidence-based medicine (EBM) stresses the examination of evidence from clinical research as an important basis for the practice of medicine. EBM is an approach that is intuitively reasonable, and is increasingly taught in medical schools and incorporated into practice. Although it is often not feasible for busy clinicians to find and appraise original research themselves, EBM is now frequently used to develop clinical practice guidelines. However, there are often 'grey areas' in the interpretation of the evidence, some of which are discussed in this paper. Clinical medicine can be complex, and EBM will never provide easy answers to difficult problems, which means that there will always be an art to clinical medicine. As well, EBM is practised in complex, semirational, constantly changing health care systems, which sometimes actually establish barriers to the incorporation of evidence into practice.

Canada↗
PubMed2001

The use of technologies to decrease peri-operative allogenic blood transfusion: results of practice variation in Israel.

BACKGROUND: Concern about the side effects of allogeneic blood transfusion has led to increased interest in methods of minimizing peri-operative transfusion. Technologies to minimize allogeneic transfusion include drugs such as aprotinin, desmopressin, tranexamic acid and erythropoietin, and techniques such as acute normovolemic hemodilution, cell salvage and autologous pre-donation. OBJECTIVE: To survey the current use in Israel of these seven technologies to minimize allogeneic blood transfusion. METHODS: Our survey was conducted in 1996-97 in all hospitals in Israel with more than 50 beds and at least one of the following departments: cardiac or vascular surgery, orthopedics, or urology. All departments surveyed were asked: a) whether the technologies were currently being used or not, b) the degree of use, and c) the factors influencing their use and non-use. The survey was targeted at the heads of these departments. RESULTS: Pharmaceuticals to reduce allogeneic blood transfusion were used in a much higher proportion in cardiac surgery departments than in the other three departments. Pre-operative blood donation was used in few of the cardiac, urologic and vascular surgery departments compared to its moderate use in orthopedic departments. The use of acute normovolemic hemodilution was reported in a majority of the cardiac departments only. Moderate use of cell salvage was reported in all departments except urology where it was not used at all. CONCLUSION: There is considerable practice variation in the use of technologies to minimize exposure to peri-operative allogeneic blood transfusion in Israel.

Aprotinin↗
PubMed2001

Differences in treatment preferences between persons who enrol and do not enrol in a clinical trial.

OBJECTIVE: To quantitatively compare preferences for treatment between persons who enrolled in a randomized controlled trial (RCT) and those who were eligible but chose not to enrol. INTERVENTIONS: Participants' thresholds for treatment were determined using a probability trade-off technique. Pertinent health states were described. If not taking Aspirin, the probabilities of stroke, myocardial infarction (MI), and major bleeding were given. Given the risks and benefits of chronic Aspirin therapy, a systematic approach was used to determine patients' thresholds for treatment (the smallest reduction in stroke or MI risk of which patients were willing to take Aspirin). RESULTS: Of 54 participants, 42 enrolled in the RCT, and 12 did not. Compared with persons who enrolled, those who did not enrol required significantly greater increments in treatment benefit to be willing to take Aspirin. CONCLUSIONS: This study shows differences in thresholds for treatment between persons who enrolled in a clinical trial and those who chose not to. Such attitudinal differences may lead to difficulty in the interpretation of clinical trials, especially those using health-related quality-of-life measures. More studies are needed to determine whether the attitudinal differences affect the generalization of results from clinical trials.

Aspirin↗
PubMed2000

When should hypertension be treated? The different perspectives of Canadian family physicians and patients.

BACKGROUND: Hypertension guidelines from different organizations often specify different treatment thresholds, and none explicitly state how these thresholds were chosen. This study was undertaken to determine the treatment thresholds of family physicians and hypertensive patients for mild, uncomplicated essential hypertension. A subject's treatment threshold can be determined by eliciting the minimum reduction in cardiovascular risk that he or she feels outweighs the inconvenience, costs and side effects of antihypertensive therapy (the minimal clinically important difference [MCID]). METHODS: The study subjects consisted of a random sample of family physicians and a consecutive sample of hypertensive patients without overt cardiovascular disease from Ottawa and Edmonton. To determine participants' MCIDs, we used a survey employing hypothetical scenarios (each depicting a different baseline cardiovascular risk) and a probability trade-off tool. RESULTS: Of 94 family physicians and 146 patients approached for the study, 72 and 74 participated respectively. There was marked variability in the MCIDs of both groups. In general, patients were less likely to want antihypertensive therapy than physicians, particularly when baseline cardiovascular risks were low: 49% v. 64% (p = 0.06), 68% v. 92% (p < 0.001) and 86% v. 100% (p = 0.001) for 5-year cardiovascular risks of 2%, 5% and 10% respectively. Moreover, patients expressed larger MCIDs (i.e., wanted greater benefits before accepting therapy) than physicians. However, a subgroup of patients (15% to 26%, depending on the scenario) wanted treatment even if there was no anticipated benefit. Multivariate analysis showed that no sociodemographic factors strongly predicted the MCIDs of either group. INTERPRETATION: Guidelines that set treatment thresholds on the basis of physician or expert opinion may not accurately reflect the preferences of hypertensive patients. There is a need for patient decision aids and attention to patient preferences when initiation of antihypertensive therapy is considered for the prevention of cardiovascular disease. Further research is needed to define treatment thresholds for other chronic conditions and in other groups.

Adult↗
PubMed2000

Antiplatelet therapy for preventing stroke in patients with non-valvular atrial fibrillation and no previous history of stroke or transient ischemic attacks.

BACKGROUND: Atrial fibrillation (AF) carries an increased risk of stroke; antiplatelet agents are proven effective for stroke prevention in other settings. OBJECTIVES: The objective of this review was to determine the efficacy and safety of antiplatelet therapy for prevention of stroke in patients with chronic non-valvular AF. SEARCH STRATEGY: We searched the Cochrane Stroke Group Specialised Register of Trials, MEDLINE database (June 1999), and the database of the Antithrombotic Trialists Collaboration, as well as reference lists of relevant articles. SELECTION CRITERIA: All randomized trials comparing antiplatelet therapies to placebo in patients with non-valvular AF and no history of transient ischemic attack (TIA) or stroke. DATA COLLECTION AND ANALYSIS: Trials for inclusion were independently selected by two reviewers who also extracted each outcome and double-checked the data. The Peto method was used for combining odds ratios. All analysis were, as far as possible, "intention-to-treat". Since the published results of two trials included 3-8% of participants with prior stroke or TIA, unpublished results excluding these participants were obtained from the Atrial Fibrillation Investigators. MAIN RESULTS: Among 1680 participants without prior stroke/TIA, randomized to aspirin (N = 838) or placebo in two trials, aspirin was associated with nonsignificantly lower risks of ischemic stroke (OR = 0.71, CI 95% 0. 46 - 1.10), all stroke (OR = 0.70, CI 95% 0.45 - 1.08) all disabling/fatal stroke (OR =0.88, CI 95% 0.48 - 1.58) and the constellation of stroke, MI or vascular death (OR = 0.76, CI 95% 0. 54 - 1.05 ). Considering all randomized participants including those with prior stroke or TIA, reductions in these events by aspirin were consistently smaller and marginally statistically significant: ischemic stroke (OR = 0.77, CI 95% 0.60-1.00), all stroke (OR = 0.76, CI 95% 0.61 - 0.93), all disabling/fatal stroke (OR = 0.87, CI 95% 0.64 - 1.19) and the combined outcome (OR = 0.79, CI 95% 0.64 - 0. 99). No increase in major hemorrhage was seen, but the number of hemorrhagic events was small. REVIEWER'S CONCLUSIONS: Considering all randomized data, aspirin modestly (by about 20%) reduces stroke and major vascular events in nonvalvular AF. For primary prevention among AF patients with an average stroke rate of 4.5%/year, about 10 strokes would be prevented yearly for every 1000 given aspirin.

Atrial Fibrillation↗
PubMed2000

Oral anticoagulants for preventing stroke in patients with non-valvular atrial fibrillation and no previous history of stroke or transient ischemic attacks.

BACKGROUND: Non-valvular atrial fibrillation (AF) is associated with an increased risk of stroke. OBJECTIVES: The objective of this review was to characterize the efficacy and safety of oral anticoagulation (OAC) with vitamin K antagonists for the primary prevention of stroke in patients with chronic AF. SEARCH STRATEGY: We searched the Cochrane Stroke Group Specialised Register of Trials (June 1999), MEDLINE database, and the database of the Antithrombotic Trialists Collaboration, as well as reference lists of relevant articles. SELECTION CRITERIA: All randomized controlled trials comparing the value of OAC versus control in patients with non-valvular chronic atrial fibrillation and no history of transient ischemic attack (TIA) or stroke. DATA COLLECTION AND ANALYSIS: Trials for inclusion were independently selected by two reviewers who also extracted each outcome and double-checked the data. The Peto method was used for combining odds ratios. All analysis were, as far as possible, "intention-to-treat". Since the published results of four trials included 3-8% of participants with prior stroke or TIA, unpublished results excluding these participants were obtained from the Atrial Fibrillation Investigators. MAIN RESULTS: Of 2313 participants without prior cerebral ischemia from five trials, about half (n = 1154) were randomized to adjusted-dose OAC with an estimated mean INRs ranging between 2.0-2.6 during 1.5 years/participant average follow-up. Participant features and study quality were similar between trials. OAC was associated with large, highly statistically significant reductions in ischemic stroke (OR = 0.34, 95% CI 0.23 - 0.52), all stroke (OR = 0.39, 95% CI 0.26 - 0. 59), all disabling or fatal stroke (OR = 0.47, 95% CI 0.28 - 0.80), and the combined endpoint of all stroke, MI or vascular death (OR = 0.56, 95% CI 0.42 - 0.76). The observed rates of intracranial and extracranial hemorrhage not significantly increased by OAC therapy, but confidence intervals were wide. REVIEWER'S CONCLUSIONS: Adjusted-dose OAC (achieved INRs between 2-3) reduces stroke as well as disabling/fatal stroke for patients with nonvalvular AF, and these benefits were not substantially offset by increased bleeding among participants in randomized clinical trials. Limitations include relatively short follow-up and imprecise estimates of bleeding risks from these selected participants. For primary prevention in AF patients who have an average stroke rate of 4%/year, about 25 strokes and about 12 disabling fatal strokes would be prevented yearly for every 1000 given OAC.

Anticoagulants↗
PubMed2000

What should be included in meta-analyses? An exploration of methodological issues using the ISPOT meta-analyses.

OBJECTIVE: To explore the impact of methodologic issues on the results of meta-analyses. The following issues were examined: the type of literature search strategy used; inclusion or exclusion of non-peer-reviewed studies; the inclusion or exclusion of non-English language publications; the effect of trial quality; and the inclusion or exclusion of non-placebo-controlled studies. METHODS: The International Study of Perioperative Transfusion (ISPOT) meta-analyses were used to evaluate each of the methodologic issues. The 10 meta-analyses consisted of technologies to reduce the need for perioperative red blood cell transfusion. The number of trials for each of the meta-analyses varied from 2 to 45. Both EMBASE and MEDLINE searches were conducted, including the use of systematic search strategies. RESULTS: MEDLINE identified the vast majority of trials. Alone, MEDLINE would have missed 8 studies compared to 10 for EMBASE. Use of the systematic search strategies greatly reduced the number of articles to be reviewed compared to open searches. Type of publication, country of study origin, inclusion of non-English publications, and trial quality had very little impact on the estimates of effect. The use of placebo versus open-label control affected the magnitude of the odds ratio for two of the meta-analyses. The results of the two meta-analyses were not statistically significant if only placebo-controlled trials were included. CONCLUSIONS: While methodologic issues had very little impact on the ISPOT meta-analyses, further studies are needed in a variety of other clinical settings. Because MEDLINE, coupled with a review of the references in the identified trials, identified the vast majority of trials, one needs to consider the costs and benefits of searching EMBASE and the pursuance of unpublished and unindexed trials.

Databases, Bibliographic↗
PubMed2000

The use of technologies to minimize exposure to perioperative allogeneic blood transfusion in elective surgery. A survey of Canadian hospitals.

BACKGROUND: Despite the growing medical and public interest in reducing exposure to allogeneic blood, little is known about the use of alternatives to allogeneic transfusion. This study was conducted to determine the availability of these technologies in Canadian hospitals and was undertaken under the auspices of the International Study of Peri-Operative Transfusion (ISPOT), a 10-country study of the effectiveness of, attitudes toward, and practices related to the use of alternatives to allogeneic transfusion. METHODS: A cross-sectional national mail survey of Canadian hospitals with greater than 50 medical/surgical beds. Chiefs of anesthesia, surgery, and the divisions of cardiac, orthopedic, vascular, and urology were initially mailed a brief postcard asking which of seven technologies were used in their center. This was then followed up with a one-page questionnaire asking how frequently the technologies were used, their thoughts on the appropriateness of the use of the technologies, barriers to their greater use, and reasons for nonuse of the technologies. RESULTS: Response rates to the postcard survey ranged from 70%-98%, depending on the technology and type of surgery, and ranged from 27%-53% for the follow-up questionnaire. All technologies were used most frequently in cardiac surgery. Aprotinin, tranexamic acid, aminocaproic acid, desmopressin, and cell salvage were reported used in over 70% of cardiac surgery centers. Of these, tranexamic acid and cell salvage were the only ones used routinely in some centers. Acute normovolemic hemodilution and erythropoietin were used in 45% and 20% of cardiac centers, respectively. The drugs were used in less than 15% of orthopedic, vascular, and urologic divisions, with the exception of desmopressin in urologic and vascular surgery and aminocaproic acid in urologic surgery. The techniques of cell salvage and acute normovolemic hemodilution were used in 30%-45% of these divisions, with the exception of cell salvage, which was used in less than 15% of urology units. In more than 60% of cases, the technologies were considered to be used "about right," although an important minority felt that they were underused. CONCLUSIONS: In general, alternatives to perioperative allogeneic transfusion were rarely used except in cardiac surgery.

Blood Loss, Surgical↗
PubMed2000

Development of a decision aid for atrial fibrillation who are considering antithrombotic therapy.

With patients demanding a greater role in the clinical decision-making process, many researchers are developing and disseminating decision aids for various medical conditions. In this article, we outline the essential elements in the development and evaluation of a decision aid to help patients with atrial fibrillation choose, in consultation with their physicians, appropriate antithrombotic therapy (warfarin, aspirin, or no therapy) to prevent stroke. We also outline possible future directions regarding the implementation and evaluation of this decision aid. This information should enable clinicians to better understand the role that decision aids may have in their interactions with patients.

Anticoagulants↗
PubMed2000

Cost effectiveness of epoetin-alpha to augment preoperative autologous blood donation in elective cardiac surgery.

OBJECTIVE: The objective of this study was to assess the cost effectiveness of using epoetin-alpha (erythropoietin) to augment preoperative autologous donation (PAD) of blood prior to elective cardiac surgery. DESIGN AND SETTING: We designed a decision-analytic model incorporating the risk of receiving allogeneic blood, the costs of blood products, the likelihood of developing transfusion-related diseases, the costs of transfusion-related diseases and their impact on life expectancy, and the effect of epoetin-alpha on the probability of transfusion. INTERVENTIONS: The efficacy of epoetin-alpha was derived from data from a meta-analysis of published randomised trials comparing the use of epoetin-alpha to augment PAD with the use of PAD alone. Estimates for the other parameters were obtained by a systematic review of the literature. MAIN OUTCOME MEASURES AND RESULTS: The use of epoetin-alpha reduced the proportion of patients receiving allogeneic transfusions by 60% (from 31.6 to 12.7%). However, this led to only a modest benefit of 0.000035 life years gained per patient and an incremental cost per life year gained of $Can44.6 million (1998 Canadian dollars). A detailed sensitivity analysis confirmed that the cost-effectiveness ratio was larger than that which is generally considered acceptable. CONCLUSIONS: Our study indicates that the use of epoetin-alpha to reduce perioperative allogeneic transfusions in cardiac surgery is not cost effective.

Blood Transfusion, Autologous↗
PubMed1999

A patient decision aid regarding antithrombotic therapy for stroke prevention in atrial fibrillation: a randomized controlled trial.

CONTEXT: Decision aids are tools designed to help patients participate in the clinical decision-making process. OBJECTIVE: To determine whether use of an audiobooklet (AB) decision aid explaining the results of a clinical trial affected the decision-making process of study participants. DESIGN: Randomized controlled trial conducted from May 1997 to April 1998. SETTING: Fourteen centers that participated in the Stroke Prevention in Atrial Fibrillation (SPAF) III trial. PARTICIPANTS: A total of 287 patients from the SPAF III aspirin cohort study, in which patients with atrial fibrillation and a relatively low risk of stroke received 325 mg/d of aspirin and were followed up for a mean of 2 years. INTERVENTION: At the end of SPAF III, participants were randomized to be informed of the study results with usual care plus use of an AB (AB group) vs usual care alone (control group). The AB included pertinent information to help patients decide whether to continue taking aspirin or switch to warfarin. MAIN OUTCOME MEASURES: Patients' ability to make choices regarding antithrombotic therapy, and 6-month adherence to these decisions. Their knowledge, expectations, decisional conflict (the amount of uncertainty about the course of action to take), and satisfaction with the decision-making process were also measured. RESULTS: More patients in the AB group made a choice about antithrombotic therapy than in the control group (99% vs 94%; P = .02). Patients in the AB group were more knowledgeable and had more realistic expectations about the risk of stroke and hemorrhage (in the AB group, 53%-80% correctly estimated different risks; in the control group, 16%-28% gave correct estimates). Decisional conflict and satisfaction were similar for the 2 groups. After 6 months, a similar percentage of patients were still taking their initial choice of antithrombotic therapy (95% vs 93%; P = .44). CONCLUSIONS: For patients with atrial fibrillation who had participated in a major clinical trial, the use of an AB decision aid improved their understanding of the benefits and risks associated with different treatment options and helped them make definitive choices about which therapy to take. Further studies are necessary to evaluate the acceptability and impact of decision aids in other clinical settings.

Aged↗
PubMed1999

Choosing antithrombotic therapy for elderly patients with atrial fibrillation who are at risk for falls.

OBJECTIVE: To determine whether the risk of falling (with a possible increased chance of subdural hematoma) should influence the choice of antithrombotic therapy in elderly patients with atrial fibrillation. DESIGN: A Markov decision analytic model was used to determine the preferred treatment strategy (no antithrombotic therapy, long-term aspirin use, or long-term warfarin use) for patients with atrial fibrillation who are 65 years of age and older, are at risk for falling, and have no other contraindications to antithrombotic therapy. Input data were obtained by systematic review of MEDLINE. Outcomes were expressed as quality-adjusted life-years. RESULTS: For patients with average risks of stroke and falling, warfarin therapy was associated with 12.90 quality-adjusted life-years per patient; aspirin therapy, 11.17 quality-adjusted life-years; and no antithrombotic therapy, 10.15 quality-adjusted life-years. Sensitivity analysis demonstrated that, regardless of the patients' age or baseline risk of stroke, the risk of falling was not an important factor in determining their optimal antithrombotic therapy. CONCLUSIONS: For elderly patients with atrial fibrillation, the choice of optimal therapy to prevent stroke depends on many clinical factors, especially their baseline risk of stroke. However, patients' propensity to fall is not an important factor in this decision.

Accidental Falls↗
PubMed1999

Autologous versus allogeneic transfusion: patients' perceptions and experiences.

BACKGROUND: Preoperative autologous donation is one way to decrease a patient's exposure to allogeneic blood transfusion. This study was designed to determine patients' perceptions about the autologous blood donation process and their experiences with transfusion. METHODS: To assess patient perception, a questionnaire was administered a few days before surgery to patients undergoing elective cardiac and orthopedic surgery in a Canadian teaching hospital. All patients attending the preoperative autologous donation clinic during a 10-month period were eligible. A convenience sample of patients undergoing the same types of surgery who had not predonated blood were selected from preadmission clinics. Patient charts were reviewed retrospectively to assess actual transfusion practice in all cases. RESULTS: A total of 80 patients underwent cardiac surgery (40 autologous donors, 40 nondonors) and 73 underwent orthopedic surgery (38 autologous donors, 35 nondonors). Of the autologous donors, 75 (96%) attended all scheduled donation appointments, 73 (93%) said that they were "very likely" or "likely" to predonate again, and 75 (96%) said that they would recommend autologous donation to others. There was little difference in preoperative symptoms between the autologous donors and the nondonors, although the former were more likely than the latter to report that their overall health had remained the same during the month before surgery (30 [75%] v. 21 [52%] for the cardiac surgery patients and 30 [79%] v. 18 [51%] for the orthopedic surgery patients). When the autologous donors were asked what they felt their chances would have been of receiving at least one allogeneic blood transfusion had they not predonated, the median response was 80%. When they were asked what their chances were after predonating their own blood, the median response was 0%. The autologous donors were significantly less likely to receive allogeneic blood transfusions (6 [15%] for cardiac surgery and 3 [8%] for orthopedic surgery) than were the nondonors (14 [35%] for cardiac surgery and 16 [46%] for orthopaedic surgery). They were, however, more likely to receive any transfusion (autologous or allogeneic) than were the nondonors (25 [63%] v. 14 [35%] for cardiac surgery and 31 [81%] v. 16 [46%] for orthopedic surgery). INTERPRETATION: Patients who underwent preoperative autologous blood donation were positive about the experience and did not report more symptoms than patients who did not donate blood preoperatively. Autologous donors overestimated their chances of receiving allogeneic blood transfusions had they not predonated and underestimated their chances after they had predonated. They were less likely to receive allogeneic transfusions, but more likely to receive any type of transfusion, than were patients who did not predonate.

Aged↗