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Biomedical subjects

Stephen M Davis

Publications and source records attributed to Stephen M Davis.

At least 55 records · Page 3Linked to original sources
PubMed2003

Risk of ischemic stroke among users of the oral contraceptive pill: The Melbourne Risk Factor Study (MERFS) Group.

BACKGROUND AND PURPOSE: Use of oral contraceptives has increased, and there is uncertainty about the stroke risk associated with their use. Our aim was to investigate this issue. METHODS: Using case-control techniques, we identified consecutive women with ischemic stroke from 4 Melbourne hospitals. All patients were between 15 and 55 years of age and had no prior stroke. Neighborhood-based control subjects were individually age-matched (+/-5 years) and geographically matched to subject cases. A questionnaire administered to participants elicited information about prior exposure to various potential risk factors, including the oral contraceptive pill (OCP). RESULTS: We included 234 cases and 234 controls (mean age, 42 years). Compared with noncurrent use, current use of the OCP, in doses of 20 cigarettes per day (OR, 3.68; 95% CI, 1.22 to 11.09). CONCLUSIONS: There was no evidence for an association between ischemic stroke and use of the OCP in low doses (<or=50 microg estrogen) in young Australian women. Other modifiable risk factors such as hypertension, diabetes mellitus, and smoking are important.

Adolescent↗
PubMed2003

Evidence-based care and outcomes of acute stroke managed in hospital specialty units.

OBJECTIVES: To assess the use of evidence-based investigations and treatments in patients with acute stroke in selected Australian hospitals and to compare management and outcomes between stroke and other types of hospital specialty unit. DESIGN: Retrospective, multicentre audit of hospital case files. SETTING: Eight metropolitan tertiary-care hospitals from five Australian States. SUBJECTS: 300 consecutive patients from each hospital admitted between 17 September 1999 and 23 May 2001 and having a discharge diagnosis of stroke or transient ischaemic attack. MAIN OUTCOME MEASURES: Use of investigations and treatments supported by best available evidence; comparison of management and outcomes between stroke, neurology, general medical and geriatric units. RESULTS: 2383 patients were audited (median age, 72.7 years; 52% men); 72% had ischaemic events, and 28% haemorrhagic events. Use of investigations and treatments varied between hospitals and types of unit. Stroke units or teams cared directly for 23% of patients (range across hospitals, 0-100%). Although 47% of patients with ischaemic events presented within 3 hours of symptom onset (when thrombolysis might provide benefit), only nine (2%) received thrombolysis. Angiotensin-converting enzyme (ACE) inhibitors were given to 28% of survivors at discharge (range, 14%-38%). Stroke units were more likely to use diagnostic tests, while neurology units were more likely to prescribe heparin acutely for patients with ischaemic stroke (not recommended for patients in general), and geriatric units were less likely to discharge patients with atrial fibrillation on anticoagulation therapy. Outcomes also varied significantly between types of unit. In-hospital survival rates were 90% (stroke units), 91% (neurological units), 82% (general medical units) and 79% (geriatric units) (P < 0.001). Stroke units and neurological units sent more patients home than the other units. Stroke units also sent fewer patients to rehabilitation and had longer mean length of stay. CONCLUSIONS: Acute stroke care varies between Australian tertiary-care hospitals and types of specialty unit, with suboptimal use of many evidence-based interventions.

Aged↗
PubMed2003

Acute stroke thrombolysis with intravenous tissue plasminogen activator in an Australian tertiary hospital.

OBJECTIVE: To report initial experience with the use of intravenous tissue plasminogen activator (tPA) to treat acute ischaemic stroke at an Australian tertiary-care hospital. DESIGN: Retrospective audit of computerised hospital stroke database. PARTICIPANTS AND SETTING: All patients with acute ischaemic stroke treated with intravenous tPA between April 1999 and July 2002 at the Royal Melbourne Hospital, VIC. MAIN OUTCOME MEASURES: Times from stroke onset to arrival at the emergency department (ED) and treatment; rates of symptomatic intracerebral haemorrhage (ICH); clinical outcome at three months; and violations of treatment protocol. RESULTS: Of 932 patients admitted with ischaemic stroke, 30 were treated with intravenous tPA. Median time from stroke onset to tPA treatment was 2 h 48 min, and median door-to-needle time was 1 h 49 min. Door-to-needle time improved in the last 12 months of the audit, with four of 15 patients achieving the recommended 60 min. Eleven patients (37%) had excellent clinical outcomes at three-month follow-up (modified Rankin score, 0-1), and 15 (50%) were functionally independent (score, 0-2). Mortality rate was 10%, similar to that of all ischaemic stroke patients during the audit period. Two patients (7%) had symptomatic ICH. Treatment deviated from protocol in seven patients (23%), five of whom received tPA over three hours after stroke onset. CONCLUSION: Rates of favourable outcomes and symptomatic ICH at our hospital were similar to those achieved in international phase III and IV trials in specialised centres.

Aged↗
PubMed2003

Recommendations for the relationship between sponsors and investigators in the design and conduct of clinical stroke trials.

BACKGROUND: As increasing numbers of clinical trials are being conducted worldwide, there has been concern about the relationship between the sponsors and investigators. Both parties need benchmarks or recommendations to act as a reference point when trials are initiated and conducted. These recommendations are designed to fulfill this role. SUMMARY OF COMMENT: A series of meetings of the International Trial Subcommittee of the International Stroke Liaison Committee, American Stroke Association, were conducted to review a series of draft recommendations that were then modified on the basis of the experience of the committee in the conduct of clinical trials. Consensus was reached on all points of the final document. The recommendations represent the opinions of the authors and do not necessarily reflect the views of the American Stroke Association. The document contains sensible recommendations concerning required sponsor company qualities, trial management structure, protocol development, trial conduct, data management, blinding, data analyses, publication, remuneration, and conflict of interest issues. CONCLUSIONS: The recommendations should provide a simple and practical benchmark for both investigators and sponsors in the conduct of clinical trials. Although designed for trials involving therapies for stroke, the framework allows generalization to other disciplines.

Clinical Trials as Topic↗
PubMed2003

Association between early returns and frequent ED visits at a rural academic medical center.

The objective of this study was to examine the influence of frequent emergency department (ED) use on early returns to the ED at a large rural academic medical center. An analysis was done of all 35,440 visits by 22,442 individuals to a large rural academic medical center ED during calendar year 2000. Of 35,440 ED visits, there were 1,992 (5.62%) return visits within 72 hours (early return). Frequent ED visits (visits made by individuals making 4 or more visits per year) was a predictor of early return visits (odds ratio [OR] 3.21, 95% confidence interval [CI] 2.93-3.52; Wald chi(2), P <.0001). Of 22,442 individuals who came to the ED during the study period, 1,601 (7.13%) returned within 72 hours. Frequency of ED use by a particular individual (4 or more visits per year) was also a predictor of early return for that individual (OR 14.55, 95% CI 12.84-16.48; Wald chi(2), P <.000001). The high rate of early returns to this rural academic ED was significantly associated with frequent visits (4 or more times per year) to the ED by particular individual.

Academic Medical Centers↗
PubMed2003

The role of blood pressure lowering before and after stroke.

PURPOSE OF REVIEW: Elevated blood pressure is one of the most potent risk factors for first ever and recurrent stroke as well as influencing early outcome after acute stroke. There have been a number of significant randomized controlled trials which may influence management in each of these three categories. RECENT FINDINGS: For primary prevention, the recent information from the Heart Outcomes Prevention Evaluation, Losartan Intervention for Endpoint Reduction to Hypertension, Study on Cognition and Prognosis in the Elderly and Australian National Blood Pressure Study support the view that blood pressure lowering protects against stroke regardless of baseline blood pressure level. There is some evidence that blockade of the angiotensin system may give additional protection. For secondary prevention, evidence from the Perindopril Protection against Recurrent Stroke Study shows that blood pressure lowering with perindopril based therapy reduces fatal or non-fatal stroke events, again in hypertensive or normotensive individuals. There is uncertainty about blood pressure lowering in acute stroke, although presentation of the recent Acute Candesartan Cilexetil Evaluation in Stroke Survivors trial in which there was significant protection against vascular events using candesartan suggests that further studies should be undertaken. SUMMARY: Blood pressure lowering for primary prevention of stroke should be undertaken using a variety of therapeutic agents. For secondary stroke prevention perindopril based therapy should be used based on current evidence. Uncertainty still exists as to whether blood pressure lowering in the acute stroke setting is safe or improves outcomes.

Aged↗
PubMed2003

Can the time window for administration of thrombolytics in stroke be increased?

Level 1 evidence now shows that thrombolysis in cases of acute ischaemic stroke is effective if administered within 3 hours of stroke onset. This benefit has been shown to be time dependent and potentially extends beyond 3 hours, with evidence that potentially viable penumbral tissue may be present in a significant proportion of cases well beyond 3-6 hours and, in isolated cases, perhaps up to 48 hours. This exposes a "stroke recovery gap", the difference observed between the clinical response to thrombolytic therapy in a given population of patients presenting with ischaemic stroke and the potential clinical recovery if all of the penumbra were salvaged under ideal circumstances. The means of bridging this "stroke recovery gap" using thrombolysis must involve extending the therapeutic time window (i.e. the time between stroke onset and administration of thrombolytics). Approaches to do this include the use of: (i) improved patient selection with modern neuroimaging techniques, particularly magnetic resonance imaging using perfusion-weighted image/diffusion-weighted image mismatch; (ii) newer thrombolytic agents; (iii) lower doses of these agents; (iv) varied methods of administration of thrombolytic therapy including combined intravenous and intra-arterial approaches; and (v) adjunctive therapies such as neuroprotectants. Should these means of extending the time window for thrombolysis prove successful, a more widespread use of this form of acute stroke therapy will be possible.

Dose-Response Relationship, Drug↗
PubMed2002

The Avoid Stroke as Soon as Possible (ASAP) general practice stroke audit.

OBJECTIVES: To determine the prevalence of stroke risk factors in a general practice population and to identify pharmacotherapies currently used in management of stroke risk factors. DESIGN: Multicentre, observational study by 321 randomly selected general practitioners who each collected data on 50 consecutive patients attending their surgery. PATIENTS AND SETTING: 16 148 patients aged 30 years or older attending general practices across Australia during 2000. OUTCOME MEASURES: Prevalence of hypertension, current smoking, diabetes, hypercholesterolaemia, atrial fibrillation, recent history of stroke or TIA; extent of pharmacotherapy use in risk-factor management. RESULTS: 70% of patients had one or more risk factors and 34% had two or more. Hypertension was the risk factor with greatest prevalence (44%), followed by hypercholesterolaemia (43%) and current smoking (17%). The prevalence of risk factors generally increased with age, except for current smoking, where a decrease with age was seen. The most common pharmacotherapies were cardiovascular agents, followed by antiplatelet agents. Two-thirds of patients with hypertension were taking cardiovascular drugs, most commonly angiotensin-converting enzyme inhibitors. CONCLUSIONS: Stroke risk factors are highly prevalent in general practice patients and GPs are ideally placed for opportunistic case-finding. There is considerable scope for improving management of stroke risk factors. The Avoid Stroke as Soon as Possible (ASAP) general practice stroke audit provides a baseline against which progress in risk-factor management can be measured.

Adult↗
PubMed2002

Diffusion- and perfusion-weighted MRI response to thrombolysis in stroke.

Diffusion- and perfusion-weighted magnetic resonance imaging provides important pathophysiological information in acute brain ischemia. We performed a prospective study in 19 sub-6-hour stroke patients using serial diffusion- and perfusion-weighted imaging before intravenous thrombolysis, with repeat studies, both subacutely and at outcome. For comparison of ischemic lesion evolution and clinical outcome, we used a historical control group of 21 sub-6-hour ischemic stroke patients studied serially with diffusion- and perfusion-weighted imaging. The two groups were well matched for the baseline National Institutes of Health Stroke Scale and magnetic resonance parameters. Perfusion-weighted imaging-diffusion-weighted imaging mismatch was present in 16 of 19 patients treated with tissue plasminogen activator, and 16 of 21 controls. Perfusion-weighted imaging-diffusion-weighted imaging mismatch patients treated with tissue plaminogen activator had higher recanalization rates and enhanced reperfusion at day 3 (81% vs 47% in controls), and a greater proportion of severely hypoperfused acute mismatch tissue not progressing to infarction (82% vs -25% in controls). Despite similar baseline diffusion-weighted imaging lesions, infarct expansion was less in the recombinant tissue plaminogen activator group (14cm(3) vs 56cm(3) in controls). The positive effect of thrombolysis on lesion growth in mismatch patients translated into a greater improvement in baseline to outcome National Institutes of Health Stroke Scale in the group treated with recombinant tissue plaminogen activator, and a significantly larger proportion of patients treated with recombinant tissue plaminogen activator having a clinically meaningful improvement in National Institutes of Health Stroke Scale of > or = 7 points. The natural evolution of acute perfusion-weighted imaging-diffusion-weighted imaging mismatch tissue may be altered by thrombolysis, with improved stroke outcome. This has implications for the use of diffusion- and perfusion-weighted imaging in selecting and monitoring patients for thrombolytic therapy.

Acute Disease↗
PubMed2002

Acute hyperglycemia adversely affects stroke outcome: a magnetic resonance imaging and spectroscopy study.

Controversy exists whether acute hyperglycemia is causally associated with worse stroke outcome or simply reflects a more severe stroke. In reversible ischemia models, hyperglycemia is associated with lactic acidosis and conversion of penumbral tissue to infarction. However, the relationship between hyperglycemia, lactic acidosis, and stroke outcome has not been explored in humans. Sixty-three acute stroke patients were prospectively evaluated with serial diffusion-weighted and perfusion-weighted magnetic resonance imaging and acute blood glucose measurements. Patients with hypoperfused at-risk tissue were identified by acute perfusion-diffusion lesion mismatch. As a substudy, acute and subacute magnetic resonance spectroscopy was performed in the 33 most recent patients to assess the relationship between acute blood glucose and lactate production in the ischemic region. In 40 of 63 patients with acute perfusion-diffusion mismatch, acute hyperglycemia was correlated with reduced salvage of mismatch tissue from infarction, greater final infarct size, and worse functional outcome. These correlations were independent of baseline stroke severity, lesion size, and diabetic status. Furthermore, higher acute blood glucose in patients with perfusion-diffusion mismatch was associated with greater acute-subacute lactate production, which, in turn, was independently associated with reduced salvage of mismatch tissue. In contrast, acute blood glucose levels in nonmismatch patients did not independently correlate with outcome measures, nor was there any acute-subacute increase in lactate in this group. Acute hyperglycemia increases brain lactate production and facilitates conversion of hypoperfused at-risk tissue into infarction, which may adversely affect stroke outcome. These findings support the need for randomized controlled trials of aggressive glycemic control in acute stroke.

Acute Disease↗
PubMed2002

Neuroimaging, the ischaemic penumbra, and selection of patients for acute stroke therapy.

Advances in neuroimaging have been central to the expansion of knowledge in the neurosciences over the past 20 years. One of the most important roles of brain imaging is in the selection of patients for acute stroke therapy. Currently, computed tomography (CT) is commonly used to select patients who have had strokes for thrombolytic therapy on the basis of the absence of haemorrhage and, more controversially, the presence of early CT changes of ischaemia. Since patients with ischaemic penumbra are more likely than those without to respond to therapy, identification of patients with this feature will become increasingly important. Although several imaging modalities can identify the penumbra, the most practical is magnetic resonance imaging (MRI) showing perfusion-weighted and diffusion-weighted imaging mismatch. Although uncertainties in image interpretation remain, surrogate MRI outcome measures are becoming an important component of translational research. Future developments in imaging technologies may provide other opportunities for surrogate outcome studies.

Acute Disease↗