Safety of intravenous thrombolysis for ischemic stroke in patients treated with warfarin

OBJECTIVE

Controversy surrounds the safety of intravenous (IV) tissue plasminogen activator (tPA) in ischemic stroke patients treated with warfarin. The European tPA license precludes its use in anticoagulated patients altogether. American guidelines accept IV tPA use with an international normalized ratio (INR) ≤ 1.7. The influence of warfarin on symptomatic intracerebral hemorrhage (SICH), arterial recanalization, and long-term functional outcome in stroke thrombolysis remains unclear.

METHODS

We analyzed data from 45,074 patients treated with IV tPA enrolled in the Safe Implementation of Thrombolysis in Stroke (SITS) International Stroke Thrombolysis Register. A total of 768 patients had baseline warfarin treatment with INR ≤ 1.7. Outcome measures were SICH, arterial recanalization, mortality, and functional independence at 3 months.

RESULTS

Patients on warfarin with INR ≤ 1.7 were older, had more comorbidities, and had more severe strokes compared to patients without warfarin. There were no significant differences between patients with and without warfarin in SICH rates (adjusted odds ratio [aOR] = 1.23, 95% confidence interval [CI] = 0.72-2.11 per SITS-MOST; aOR = 1.26, 95% CI = 0.82-1.70 per European Cooperative Acute Stroke Study II) after adjustment for age, stroke severity, and comorbidities. Neither did warfarin independently influence mortality (aOR = 1.05, 95% CI = 0.83-1.35) or functional independence at 3 months (aOR = 1.01, 95% CI = 0.81-1.24). Arterial recanalization by computed tomography/magnetic resonance angiography trended higher in warfarin patients (62% [37 of 59] vs 55% [776/1,475], p = 0.066). Recanalization approximated by disappearance at 22 to 36 hours of a baseline hyperdense middle cerebral artery sign was increased (63% [124 of 196] vs 55% [3,901 of 7,099], p = 0.022).

INTERPRETATION

Warfarin treatment with INR ≤ 1.7 did not increase the risk for SICH or death, and had no impact on long-term functional outcome in patients treated with IV tPA for acute ischemic stroke.

Bleeding complications associated with warfarin treatment in ischemic stroke patients with atrial fibrillation: a population-based cohort study

BACKGROUND

Bleeding events are the major obstacle to the widespread use of warfarin for secondary stroke prevention. Previous studies have not examined the use of risk stratification scores to estimate lifetime bleeding risk associated with warfarin treatment in a population-based setting. The purpose of this study is to determine the lifetime risk of bleeding events in ischemic stroke patients with atrial fibrillation (AF) undergoing warfarin treatment in a population-based cohort and to evaluate the use of bleeding risk scores to identify patients at high risk for lifetime bleeding events.

METHODS

The resources of the Rochester Epidemiology Project Medical Linkage System were used to identify acute ischemic stroke patients with AF undergoing warfarin treatment for secondary stroke prevention from 1980 to 1994. Medical information for patients seen at Mayo Clinic and at Olmsted Medical Center was used to retrospectively risk-stratify stroke patients according to bleeding risk scores (including the HAS-BLED and HEMORR2HAGES scores) before warfarin initiation. These scores were reassessed 1 and 5 years later and compared with lifetime bleeding events.

RESULTS

One hundred patients (mean age, 79.3 years; 68% women) were studied. Ninety-nine patients were observed until death. Major bleeding events occurred in 41 patients at a median of 19 months after warfarin initiation. Patients with a history of hemorrhage before warfarin treatment were more likely to develop major hemorrhage (15% versus 3%, P = .04). Patients with baseline HAS-BLED scores of 2 or more had a higher lifetime risk of major bleeding events compared with those with scores of 1 or less (53% versus 7%, P < .01), whereas those with HEMORR2HAGES scores of 2 or more had a higher lifetime risk of major bleeding events compared with those with scores of 1 or less (52% versus 16%, P = .03). Patients with an increase in the HAS-BLED and HEMORR2HAGES scores during follow-up had a higher remaining lifetime risk of major bleeding events compared with those with no change.

CONCLUSIONS

Our findings indicate high lifetime bleeding risk associated with warfarin treatment for patients with ischemic stroke. Risk stratification scores are useful to identify patients at high risk of developing bleeding complications and should be recalculated at regular intervals to evaluate the bleeding risk in anticoagulated patients with ischemic stroke.

Symptomatic intracranial hemorrhage following intravenous thrombolysis for acute ischemic stroke: a critical review of case definitions

BACKGROUND

Symptomatic intracranial hemorrhage (SICH) is a devastating complication of intravenous thrombolysis treatment that is associated with high mortality. Clinical trials, stroke registries and cohort studies employ different case definitions to identify stroke patients with SICH following intravenous thrombolysis. We systematically reviewed the reported rates of SICH following intravenous thrombolysis and compared their consistency with mortality outcomes.

METHODS

Studies were identified from the PubMed and Embase databases from January 1994 to July 2011 by cross-referencing the following MeSH terms: 'thrombolysis', 'recombinant tissue plasminogen activator', 'rtPA', 'hemorrhagic stroke', 'cerebral hemorrhage', 'hematoma' and 'ischemic stroke'. Demographic information, baseline National Institute of Health Stroke Scale (NIHSS) scores, time from stroke onset to intravenous thrombolysis, SICH and mortality rates were derived from published data in 7 randomized controlled trials, 7 stroke registries and 10 cohort studies (4 multicenter and 6 single center) with more than 200 consecutively recruited patients. Mortality rates were considered as the percentage of patients treated with intravenous thrombolysis who died within 90 days after stroke.

RESULTS

The mean age of patients included in this analysis was 68.8 years (standard deviation, SD 2.9, range 63-75), of whom 56.3% (SD 4.5, range 45-63) were men. They presented with a mean baseline NIHSS of 12.5 (SD 1.4, range 9-15) and received intravenous thrombolysis 175 min (SD 62, range 120-328) from stroke onset. The overall mean SICH and mortality rates of patients treated with intravenous thrombolysis were 5.6% (SD 2.3) and 14.7% (SD 4.8), respectively. A moderate correlation was observed between the incidence of SICH and mortality in patients treated with intravenous thrombolysis (r = 0.401, p = 0.050). The variation in SICH rates was highest across studies that reported SICH rates using the Safe Implementation of Thrombolysis in Stroke-Monitoring Study (SITS-MOST) criteria compared with the European Cooperative Acute Stroke Study and National Institute of Neurological Disorders and Stroke (NINDS) criteria. Studies that defined SICH as parenchymal hemorrhage with a neurological decline NIHSS ≥4 occurring within 36 h of intravenous thrombolysis reported a higher consistency between SICH and mortality rates (correlation coefficient 0.631).

CONCLUSIONS

SICH rates vary considerably between studies and these differences may relate to the differences in the criteria used to define SICH. Until a case definition with high interrater agreement and good correlation with stroke outcomes becomes available, detailed information on the type of bleeding, the extent of NIHSS deterioration, neuroimaging features and the time from thrombolysis to diagnosis of hemorrhage should be reported to permit a correct interpretation of SICH rates.

Accurate targeting of botulinum toxin injections: how to and why

Botulinum toxin (BTX), the exotoxin of the obligate anaerobe, Clostridium botulinum, is used to ameliorate pain and treat conditions associated with glandular, smooth and skeletal muscle overactivity. The benefits derived from the injection of BTX may be negated by unintended weakness of uninjected muscles. Performance of BTX injections may be facile, requiring only surface marking or clinical-localisation techniques but may be more technically demanding, necessitating the use of equipment, such as electromyography (EMG) or ultrasonography (U/S). Less often, endoscopic, fluoroscopic or computed tomographic (CT) guidance may be required. Despite evidence to support the efficacy of BTX injections in treating many conditions, there is no evidence to support the superiority of any one injection technique over needle localisation using surface anatomy. This is possibly due to the lack of well-designed controlled studies, that is, current studies are hampered by small patient numbers, lack of consistency of injection technique and the application of different rating scales. Intuitively, certain injection techniques are more suited to injection of specific muscles or conditions, for example, U/S or passive-monitoring EMG should be used to treat cervical dystonia, active-monitoring EMG applied for strabismus injections, whereas either active-monitoring EMG or endoscopy is indicated when giving BTX for spasmodic dysphonia. Finally, electrical-stimulation EMG or U/S (or a combination of both) would be most suitable when injecting the forearm muscles for spasticity or writer's cramps.

Acute effects of cigarette smoking on insulin resistance and arterial stiffness in young adults

BACKGROUND

It is unclear whether changes in insulin sensitivity or arterial stiffness in cigarette smokers could explain the link between cigarette smoking and diabetes mellitus. The purpose of the study was to evaluate the acute effects of cigarette smoking on insulin resistance and arterial stiffness in a cohort of young healthy adults.

METHODS

Metabolic risk components, hemodynamic parameters, plasma nitrite/nitrate and high-sensitivity C-reactive protein (hsCRP) levels, were compared between smokers and age- and gender-matched controls (non-smokers). In smokers, these levels were determined 8-h following cigarette abstinence and an hour after smoking.

RESULTS

One hundred nineteen smokers and age-matched non-smokers (mean age, 32 years; 83% men) were included in this study. Compared with non-smokers, smokers had a significantly higher number of abnormal metabolic risk components, HOMA-IR index and total nitrite/nitrate levels. There were no differences in brachial/central blood pressure, augmentation index and hsCRP between smokers and non-smokers. An hour after smoking, smokers had significantly higher levels of HOMA-IR, total nitrite/nitrate, hsCRP and heart rate compared with baseline levels. By contrast, brachial/central blood pressure and augmentation index were unchanged after cigarette smoking. Baseline vascular and insulin resistance status predicted the extent of rise in the HOMA-IR and augmentation indices acutely after cigarette smoking (adjusted R(2) 0.358 and 0.124, p < 0.001 respectively).

CONCLUSIONS

Individuals with more advanced vascular damage and insulin resistance are vulnerable to the acute effects of cigarette smoking.

Usefulness of CT angiography for therapeutic decision making in thrombolyzing intubated patients with suspected basilar artery thrombosis

BACKGROUND AND AIMS

Acute ischemic stroke (AIS) due to basilar artery thrombosis (BAT) causes high mortality and severe disability. Early neurological assessment and timely thrombolysis might improve outcome. BAT is difficult to diagnose due to wide spectrum of presentation and decreased conscious level. Emergency physicians often intubate BAT patients with airway compromise before arrival of stroke neurologist. We evaluated role of computerized tomography (CT) angiography (CTA) of brain and cervical arteries in early diagnosis of acute BAT in intubated patients and facilitating decision for thrombolysis.

METHODS

Consecutive AIS patients presenting between 2007 and 2009 within 6 hours of symptom onset, with sudden deterioration in conscious level and intubation before assessment by neurologist, were included. All patients underwent brain CT and CTA. Outcomes were assessed at 3 months.

RESULTS

Thrombolytic therapy, mainly intravenous tissue plasminogen activator (IV-TPA), was administered to 161 (8.4%) of 1,917 AIS patients during the study period. Acute BAT contributed 10.9% of our cohort. CTA was performed in 152 (94.4%) patients and the rest were excluded due to their impaired renal functions. Five patients (3 males, mean age 72 years) presenting with acute obtundation and airway compromise were intubated, sedated, and paralyzed before assessment by neurologist. CTA showed BAT in all. IV-TPA was initiated at 213 ± 59 minutes in 4 patients while 1 received intraarterial thrombolysis at 13 hours. There was no intracranial hemorrhage. Mean length of hospital stay was 11.8 days. Despite severe stroke at presentation, good functional recovery at 3 months (modified Rankin scale [mRS] 1) occurred in 2 patients; mRS 4 in 1, and 2 died.

CONCLUSION

In patients with BAT, intubated before assessment by neurologist, CTA might help in confirming the diagnosis and facilitating therapeutic decision making for initiating thrombolysis.

Clinical features and outcomes of posterior reversible encephalopathy syndrome following bevacizumab treatment

BACKGROUND

Posterior reversible encephalopathy syndrome (PRES) is a potentially devastating complication of bevacizumab treatment.

AIM

We examined the clinical features, treatment and outcomes of patients who developed PRES following bevacizumab treatment at our institution and those reported in the literature.

DESIGN

Retrospective audit and systematic review.

METHODS

Patients were identified from the Mayo Clinic database and the published literature using 'PubMed' and 'OVID' databases, from January 2006 to June 2010, who developed PRES features within 3 weeks of bevacizumab treatment, who had brain imaging findings of focal vasogenic edema and radiologic proof of reversibility.

RESULTS

Two patients with definite PRES were identified from our institution and a further 10 cases were identified from the published literature (total, n=12). The mean age of these patients was 52 years (range 4-68 years), four of whom were men and eight women. Headaches (n=7), seizures (n=6), visual disturbances (n=5) and nausea and vomiting (n=3) were the common presenting symptoms. In a majority of patients (n=10), an increase in blood pressure from their baseline values was observed during their acute presentation. PRES resolved following withdrawal of bevacizumab and blood pressure control in all patients.

CONCLUSIONS

PRES is a catastrophic neurological complication of bevacizumab treatment, which responds favorably to prompt bevacizumab withdrawal and blood pressure control.

Oral zinc supplementation does not improve oxidative stress or vascular function in patients with type 2 diabetes with normal zinc levels

OBJECTIVE

There is considerable controversy about what constitutes optimal zinc intakes in patients with type 2 diabetes mellitus. Several studies suggest that higher zinc intakes improve vascular function and decrease oxidative damage. We aimed to assess the effects of zinc supplementation using a range of reliable biomarkers of oxidative damage and vascular function in patients with type 2 diabetes.

METHODS

Forty male type 2 diabetic patients were supplemented either with 240 mg/day of zinc as zinc gluconate (n=20) or with placebo (n=20) for 3 months. Blood and spot urine samples were taken at baseline, days 3 and 7, months 1, 2 and 3 during supplementation and 1 month after cessation. Serum zinc, reliable biomarkers of oxidative damage (F(2)-isoprostanes, neuroprostanes, cholesterol oxidation products, allantoin) as well as hydroxyeicosatetraenoic acid products and vascular-related indices (augmentation index, pulse wave velocity and aortic pressure) were measured.

RESULTS

Despite significantly higher levels of serum zinc in the treatment group, markers of oxidative damage, levels of hydroxyeicosatetraenoic acid products and vascular indices were unchanged by zinc supplementation during the four-month study period.

CONCLUSION

Improving the zinc status in patients with type 2 diabetes with normal zinc levels did not have any impact on oxidative damage and vascular function, and such supplementation may not be generally beneficial in these individuals.

Oxidative damage in ischemic stroke revealed using multiple biomarkers

BACKGROUND AND PURPOSE

We investigated changes in oxidative damage after ischemic stroke using multiple biomarkers.

METHODS

Serial blood and urine samples of ischemic stroke subjects and age-matched control subjects were assayed for F₂-isoprostanes, hydroxyeicosatetraenoic acid products, F₄-neuroprostanes, 24-hydroxycholesterol, allantoin, and urate.

RESULTS

Sixty-six stroke subjects (mean age, 65 years; median National Institutes of Health Stroke Scale 17) and 132 control subjects were recruited. A bimodal pattern of change was observed in plasma and urinary F₂-isoprostanes and plasma 24-hydroxycholesterol. The rise in plasma hydroxyeicosatetraenoic acid products, F₄-neuroprostanes, and allantoin was highest 6 to 12 hours after stroke onset, whereas plasma urate was significantly lower than controls on Days 1 to 3. After adjusting for age and baseline National Institutes of Health Stroke Scale, baseline plasma esterified hydroxyeicosatetraenoic acid products (OR, 1.01; 95% CI, 1.01 to 1.02), plasma urate (1.01; 1.00 to 1.01), and plasma free F₄-neuroprostanes (2.73; 1.76 to 3.93) were associated with 90-day good functional recovery (modified Rankin Scale ≤1).

CONCLUSIONS

Multiple markers of oxidative damage are increased immediately after stroke and remain elevated for several days. Recognition of these temporal changes may help design better antioxidant treatment trials for acute ischemic stroke.

Biomarkers of oxidative damage in cigarette smokers: which biomarkers might reflect acute versus chronic oxidative stress?

Cigarette smoking predisposes to the development of multiple diseases involving oxidative damage. We measured a range of oxidative damage biomarkers to understand which differ between smokers and nonsmokers and if the levels of these biomarkers change further during the act of smoking itself. Despite overnight abstinence from smoking, smokers had higher levels of plasma total and esterified F(2)-isoprostanes, hydroxyeicosatetraenoic acid products (HETEs), F(4)-neuroprostanes, 7-ketocholesterol, and 24- and 27-hydroxycholesterol. Levels of urinary F(2)-isoprostanes, HETEs, and 8-hydroxy-2'-deoxyguanosine were also increased compared with age-matched nonsmokers. Several biomarkers (plasma free F(2)-isoprostanes, allantoin, and 7β-hydroxycholesterol and urinary F(2)-isoprostane metabolites) were not elevated. The smokers were then asked to smoke a cigarette; this acute smoking elevated plasma and urinary F(2)-isoprostanes, plasma allantoin, and certain cholesterol oxidation products compared to presmoking levels, but not plasma HETEs or urinary 8-hydroxy-2'-deoxyguanosine. Smokers showed differences in plasma fatty acid composition. Our findings confirm that certain oxidative damage biomarkers are elevated in smokers even after a period of abstinence from smoking, whereas these plus some others are elevated after acute smoking. Thus, different biomarkers do not measure identical aspects of oxidative stress.

Subtherapeutic international normalized ratio in warfarin-treated patients increases the risk for symptomatic intracerebral hemorrhage after intravenous thrombolysis

BACKGROUND AND PURPOSE

There is uncertainty whether warfarin-treated patients (despite international normalized ratio < 1.7) have increased risks of symptomatic intracerebral hemorrhage after intravenous thrombolysis.

METHODS

Vascular risk factors, stroke subtype, and outcome measures were compared between warfarin- and nonwarfarin-treated patients undergoing acute thrombolysis within 3 hours of symptom onset.

RESULTS

From 212 patients (mean age, 74 ± 14 years; 50% men) studied, 14 (6.5%) had prior warfarin use. After adjusting for age, baseline National Institutes of Health Stroke Scale, and stroke subtype, warfarin-treated patients had significantly increased risks of developing symptomatic intracerebral hemorrhage (adjusted OR, 14.7; 95% CI, 1.3 to 54.3). A trend for poorer stroke recovery and increased mortality was observed in warfarin-treated patients on univariate, but not on multivariable, analyses.

CONCLUSIONS

Warfarin-treated patients with stroke have increased risks of symptomatic intracerebral hemorrhage after thrombolytic treatment. These data raise safety concerns of thrombolytic treatment in warfarin-treated patients with subtherapeutic international normalized ratio.

Does radiotherapy increase oxidative stress? A study with nasopharyngeal cancer patients revealing anomalies in isoprostanes measurements

This study aimed to examine if exposure to ionizing radiation during clinical radiotherapy (RT) causes increased oxidative damage. Seven patients with nasopharyngeal cancer (NPC) who underwent RT took part in this controlled-trial study. Blood and urine samples were obtained for F(2)-isoprostanes (F(2)-IsoPs) measurement. Urinary F(2)-IsoPs levels were elevated pre-treatment and remained high (but did not increase) during treatment, but decreased to the normal range after treatment. Plasma F(2)-IsoPs decreased significantly after the start of treatment before rising midway through treatment. Levels decreased significantly to below baseline following treatment. However, the patients were observed to have substantially lower levels of plasma esterified arachidonic acid (AA) residues than controls. The data shows that NPC is associated with elevated F(2)-isoprostanes in urine and in plasma after correction for decreased AA levels. RT did not increase these levels and, indeed, was associated with falls in F(2)-IsoPs. The validity and usefulness of correction of plasma F(2)-IsoPs for lowered AA levels is discussed.

Acceptability of medical students by patients from private and public family practices and specialist outpatient clinics

INTRODUCTION

Previous studies on patient acceptance of medical student teaching were from Western populations and in one setting only. However, there has been no prospective study comparing patient acceptability before and after an actual experience. We studied patient acceptability of medical student teaching in private and public family practices and public hospital specialist outpatient clinics in Singapore, and before and after an actual medical student teaching consultation.

MATERIALS AND METHODS

We conducted an anonymous cross-sectional survey from March through October 2007 of Singaporean or permanent resident patients attending 76 teaching private family practices, 9 teaching public family practices and 8 specialty clinics in a teaching public hospital. We used pre-consultation cross-sectional patient surveys in all three settings. For private family practice setting only, post-consultation patient survey was conducted after an actual experience with medical student presence.

RESULTS

Out of 5123 patients, 4142 participated in the cross-sectional survey (80.9%) and 1235 of 1519 patients in the prospective cohort study (81.3%). Eighty percent were comfortable with medical students present, 79% being interviewed and 60% being examined. Regarding being examined by medical students, parents of children were least comfortable while patients between 41 to 60 years were most comfortable (adjusted OR = 1.99 [1.55-2.57]). Females were less comfortable with medical student teaching than males. Chinese patients were the least comfortable about being interviewed or examined by medical students among the ethnic groups. Indians were most comfortable with being interviewed by medical students (adjusted OR = 1.38 [1.02-1.86]) but Malays were the most comfortable being examined by them (adjusted OR = 1.32 [1.07-1.62]). Family practice patients were more receptive to medical student teaching than the hospital's specialist outpatients. Common barriers to patient acceptance were lack of assurance of patient privacy, dignity and confidentiality. Actual exposure to medical student teaching did not change levels of patient acceptance.

CONCLUSIONS

Compared to similar studies from Western countries, Asian patients appear to be less receptive to medical student teaching than Western patients. Family practice settings offer medical students a more receptive learning environment.

Oxidative damage in Parkinson disease: Measurement using accurate biomarkers

Oxidative damage has been implicated in the pathogenesis of Parkinson disease (PD) but the literature data are confusing. Using products of lipid and DNA oxidation measured by accurate methods, we assessed the extent of oxidative damage in PD patients. The levels of plasma F(2)-isoprostanes (F(2)-IsoPs), hydroxyeicosatetraenoic acid products (HETEs), cholesterol oxidation products, neuroprostanes (F(4)-NPs), phospholipase A(2) (PLA(2)) and platelet activating factor-acetylhydrolase (PAF-AH) activities, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), and serum high-sensitivity C-reactive protein were compared in 61 PD patients and 61 age-matched controls. The levels of plasma F(2)-IsoPs, HETEs, 7beta-and 27-hydroxycholesterol, 7-ketocholesterol, F(4)-NPs, and urinary 8-OHdG were elevated, whereas the levels of plasma PLA(2) and PAF-AH activities were lower, in PD patients compared to controls (p< 0.05). The levels of plasma F(2)-IsoPs, HETEs, and urinary 8-OHdG were higher in the early stages of PD (p trend< 0.05). There was a significant negative correlation between the cumulative intake of levodopa and urinary 8-OHdG (r= -0.305, p= 0.023) and plasma total HETEs (r= -0.285, p= 0.043). Oxidative damage markers are systemically elevated in PD, which may give clues about the relation of oxidative damage to the onset and progression of PD.

Oxidative damage in dengue fever

Oxidative stress may be important in the pathogenesis of dengue infection. Using accurate markers of oxidative damage, we assessed the extent of oxidative damage in dengue patients. The levels of hydroxyeicosatetraenoic acid products (HETEs), F(2)-isoprostanes (F(2)-IsoPs), and cholesterol oxidation products (COPs) were measured in 28 adult dengue patients and 28 age-matched study controls during the febrile, defervescent, and convalescent stages of infection. We compared the absolute and the percentage change in these markers in relation to key clinical parameters and inflammatory markers. The levels of total HETEs and total HETEs/arachidonate, total F(2)-IsoPs/arachidonate, and COPs/cholesterol were higher during the febrile compared to the convalescent level. Total HETEs correlated positively with admission systolic blood pressure (r=0.52, p<0.05), whereas an inverse relationship was found between 7beta-hydroxycholesterol and systolic and diastolic blood pressure (r=-0.61 and -0.59, respectively, p<0.01). The urinary F(2)-IsoP level was higher in urine during the febrile stage compared to the convalescent level. Despite lower total cholesterol levels during the febrile stage compared to convalescent levels, a higher percentage of cholesterol was found as COPs (7beta-, 24-, and 27-hydroxycholesterol). The levels of platelet-activating factor-acetylhydrolase activity, vascular cellular adhesion molecule-1, tumor necrosis factor-alpha, and high-sensitivity C-reactive protein were higher during the febrile stage compared to their convalescent levels (p<0.01). Markers of oxidative damage are altered during the various stages of dengue infection.

Is uric acid protective or deleterious in acute ischemic stroke? A prospective cohort study

Contrasting observations have been made between serum urate and ischemic stroke outcomes in studies involving Caucasian populations. To assess the hypothesis that urate is associated with stroke outcomes, a prospective follow-up study was performed in a cohort of Asian patients with ischemic stroke. Patients diagnosed with transient ischemic attack, first or recurrent ischemic stroke were included in this study. Serum urate, measured using high-performance liquid chromatography, was correlated with 12-month functional and vascular stroke outcomes. Poor functional outcome was defined as a modified Rankin scale exceeding 2 and vascular outcome was defined as a composite of recurrent stroke, myocardial infarction or vascular death during the study period. A total of 503 patients of mean age 63 (SD 12) years were included. A U-shaped relationship between urate quartiles and poor functional outcomes was demonstrated. More patients with low (<280microM) and high (>410microM) urate levels had poor functional outcomes (36% and 27% respectively), compared to those with urate levels between 340 and 410microM (14%). No significant relationship was observed between urate and vascular outcomes. Depending on its level, serum urate may exhibit protective and deleterious effects on stroke outcomes.

The challenges of "continuing medical education" in a pandemic era

Closure of medical schools or the barring of "live patient" contact during an epidemic or pandemic is potentially disruptive to medical education. During the SARS epidemic, the use of web-based learning, role play, video vignettes and both live and mannequin-based simulated patients minimised disruptions to medical education. This article examines the pedagogical innovations that allow clinical teaching to continue without medical students examining actual patients, and proposes a contingency plan in the event of future outbreaks that may necessitate similar containment measures.

Allantoin in human plasma, serum, and nasal-lining fluids as a biomarker of oxidative stress: avoiding artifacts and establishing real in vivo concentrations

Urate is the terminal product of purine metabolism in primates, including humans. Urate is also an efficient scavenger of oxidizing species and is thought to be an important antioxidant in human body fluids. Allantoin, the major oxidation product of urate, has been suggested as a candidate biomarker of oxidative stress because it is not produced metabolically. Although urate is converted to allantoin under strongly alkaline pH, such conditions have been used in the past to facilitate extraction of allantoin. We evolved a method for the determination of allantoin concentrations in human plasma and serum by gas chromatography-mass spectrometry without such artifact. With this method, we show that alkaline conditions do indeed cause breakdown of urate, leading to significant overestimation of allantoin concentration in human samples. By using our alternative method, serum samples from 98 volunteers were analyzed, and allantoin levels were found to be significantly lower than was previously reported. The in vivo utility and sensitivity of our method was further evaluated in human nasal-lining fluids. We were able to demonstrate an ozone-induced increase in allantoin, in the absence of increases in either ascorbate or glutathione oxidation products.