Body temperature correlates with functional outcome and the lesion size of cerebral infarction

Unbalanced thermoregulation in experimental autoimmune encephalitis induced in Lewis rats

Thermoregulation in patients suffering from multiple sclerosis (MS) is impaired and may result in either increases or decreases in body temperature. We have found that rat experimental autoimmune encephalitis (EAE), being a model of MS, is associated with body temperature disturbances as well. The purpose of the current study was to examine whether the altered body temperature in EAE-induced rats is due to either a deficit in thermoregulation or a controlled change in its set point. Subcutaneous injection of encephalitogenic emulsion into both pads of hind feet of the Lewis rats provoked EAE symptoms. Body temperature (Tb) of 6 rats was measured using biotelemetry system, and ambient temperature (Ta) preferred by 6 rats of another group was analyzed using thermal gradient system. Symptoms of EAE started 11 days postinjection and progressed quickly, culminating in a complete paralysis in rats placed in the gradient, which was associated with behavioural fever (accordingly, selected Ta raised to as much as 32.8 ± 0.5 °C vs 27.2 ± 0.6 °C in control rats). On the other hand, EAE rats, placed at a constant Ta of 24 °C, were able to generate fever (Tb of 37.8 ± 0.1 °C) at the start of the illness and then paralysis compromised fever (most likely due to an impairment of thermogenesis), which, surprisingly, resulted in recovery. We conclude that EAE onset in rats is associated with fever and its behavioural supporting leads to aggravation of the autoimmune neurotoxicity.

Management of acute cerebral ischaemia

Stroke is a major public health issue. Many are treatable in the acute stage, provided patients are admitted soon enough. The overall incidence of stroke in Western countries is approximately 2400 per year per million inhabitants, and 80% are due to cerebral ischaemia. The prevalence is approximately 12,000 per million inhabitants. Stroke is associated with increased long-term mortality, handicap, cognitive and behavioural impairments, recurrence, and an increased risk of other types of vascular events. There is strong evidence that stroke patients should be treated in dedicated stroke units; each time 24 patients are treated in a stroke unit, instead of a conventional ward, one death and one dependence are prevented. This effect does not depend on age, severity, and the stroke subtype. For this reason, stroke unit care is the cornerstone of the treatment of stroke, aiming at the detection and management of life-threatening emergencies, stabilization of most physiological parameters, and prevention of early complications. In cerebral ischaemia, besides this general management, specific therapies include intravenous recombinant tissue plasminogen activator, given as soon as possible and before 4.5hours, mechanical thrombectomy on top of rt-PA or alone in case of contra-indication to rt-PA, in patients with proximal large-vessel occlusion, aspirin 300mg, immediately or after 24hours in case of thrombolysis, and, in a few patients, decompressive surgery.

Guidelines for management of ischaemic stroke and transient ischaemic attack 2008

This article represents the update of the European Stroke Initiative Recommendations for Stroke Management. These guidelines cover both ischaemic stroke and transient ischaemic attacks, which are now considered to be a single entity. The article covers referral and emergency management, Stroke Unit service, diagnostics, primary and secondary prevention, general stroke treatment, specific treatment including acute management, management of complications, and rehabilitation.

Prior antiplatelet use and infarct volume in ischemic stroke

BACKGROUND

Conflicting data exist on the role of antiplatelet agents in reducing incident ischemic stroke magnitude, but most prior studies used clinically-assessed neurologic deficit as the index of stroke extent rather than more precise volumetric measurements of infarct size. We assessed the relation of premorbid antiplatelet use to initial diffusion-weighted MRI (DWI) lesion volumes among acute ischemic stroke patients.

METHODS

Consecutive patients presenting within 24 h of ischemic stroke over an 18-month period were studied. DWI lesions were outlined using a semi-automated threshold technique. Subjects were categorized into two groups: antiplatelet (AP) or no antithrombotic (NA). The relationship between prestroke antithrombotic status and DWI infarct volumes was examined using multivariate quantile regression.

RESULTS

One hundred sixty-six individuals met study criteria: 75 AP and 91 NA patients. Median DWI volume was lower in the AP group than in the NA group (1.5 cc vs. 5.4 cc, p=0.031). A multivariable model (adjusting for age, history of transient ischemic attack, admission temperature, admission blood pressure, admission serum glucose, stroke onset to imaging interval, stroke mechanism, premorbid statin and antihypertensive use) demonstrated smaller infarcts in the AP vs. NA group (adjusted volume difference: -1.3 cc, 95% CI=-0.09, -2.5, p=0.037). Prior statin use, no history of TIA, large vessel atherosclerosis and microvascular ischemic disease stroke mechanism were also independently associated with reduced infarct volume.

CONCLUSIONS

Prior antiplatelet treatment is independently associated with reduced cerebral infarct volume among acute ischemic stroke patients. Premorbid statin use, TIA history and stroke mechanism also predict infarct volume in ischemic stroke.

The time course and determinants of temperature within the first 48 h after ischaemic stroke

BACKGROUND AND PURPOSE

Previous research has attempted to analyze the relationship between post-stroke hyperthermia and prognosis. These analyses have been hindered by a lack of information about the time course and determinants of temperature change after stroke.

METHODS

Serial temperatures were measured until 48 h after ischaemic stroke in a prospectively recruited cohort. Potential determinants of temperature, including stroke severity [measured using the National Institutes of Health Stroke Scale (NIHSS)], infection and paracetamol use were recorded. Mixed-effects models were used to model serial temperature measurements over time, adjusted for significant determinants.

RESULTS

In 155 patients the mean temperature rose from 36.5 degrees C at the time of stroke to 36.7 degrees C approximately 36 h later. The factors with significant multivariable associations with serial temperatures were: first- and second-order time components, infection, paracetamol administration and the interaction between stroke severity (NIHSS > or =6) and time (all p < 0.1). Patients with admission NIHSS > or =6 had a mean temperature rise of 0.35 degrees C during the first 36 h after stroke, compared with a rise of 0.17 degrees C in those with NIHSS < or =5.

CONCLUSIONS

Temperature spontaneously rises during the first 36 h after stroke, particularly after severer stroke and in the presence of infection.

Hyperthermia in the delivery: potential impact on neonatal mortality and morbidity

In recent years, it has become apparent that temperature can modify the extent of hypoxic-ischemic brain injury. There is an increasing body of experimental and clinical data showing a reduction in the extent of brain injury after intrapartum hypoxia-ischemia with induced hypothermia. Conversely, there is experimental evidence indicating a worsening of cerebral injury during or after ischemia under conditions of elevations in temperature in a variety of animal species. Neonatal experimental studies are limited, and the data are conflicting. This article addresses the available evidence concerning the potential impact of hyperthermia in the delivery on neonatal mortality and morbidity.

PAIS: paracetamol (acetaminophen) in stroke; protocol for a randomized, double blind clinical trial [ISCRTN 74418480]

Background

In patients with acute stroke, increased body temperature is associated with large lesion volumes, high case fatality, and poor functional outcome. A 1°C increase in body temperature may double the odds of poor outcome. Two randomized double-blind clinical trials in patients with acute ischemic stroke have shown that treatment with a daily dose of 6 g acetaminophen (paracetamol) results in a small but rapid and potentially worthwhile reduction of 0.3°C (95% CI: 0.1–0.5) in body temperature. We set out to test the hypothesis that early antipyretic therapy reduces the risk of death or dependency in patients with acute stroke, even if they are normothermic.

Methods/design

Paracetamol (Acetaminophen) In Stroke (PAIS) is a randomized, double-blind clinical trial, comparing high-dose acetaminophen with placebo in 2500 patients. Inclusion criteria are a clinical diagnosis of hemorrhagic or ischemic stroke and the possibility to start treatment within 12 hours from onset of symptoms. The study will have a power of 86% to detect an absolute difference of 6% in the risk of death or dependency at three months, and a power of 72% to detect an absolute difference of 5%, at a 5% significance level.

Discussion

This is a simple trial, with a drug that only has a small effect on body temperature in normothermic patients. However, when lowering body temperature with acetaminophen does have the expected effectiveness, 20 patients will have to be treated to prevent dependency or death in one.

Hypothermia in acute stroke

Moderate hypothermia (MH) is neuroprotective in animal models of focal ischemia when it is induced during, or within few hours after, onset of ischemia. In patients with acute stroke, several observational studies suggested normothermia or mild hypothermia as independent prognostic factors for favorable outcome. Currently, mild hypothermia was only examined in one clinical study that showed its feasibility and safety, but was not powered to examine efficacy. Limited clinical data on MH in humans suggest that this treatment probably reduces mortality in patients with malignant middle cerebral artery infarction. Still, MH in humans is associated with several side effects, intensive medical treatment, and a prolonged stay in the neurologic intensive care unit. Use of MH should be limited to specialized units, applying this treatment within research protocols or observational studies.

Hypothermic protection in rat focal ischemia models: strain differences and relevance to "reperfusion injury"

Hypothermic protection was compared in Long-Evans and spontaneously hypertensive rat (SHR) strains using transient focal ischemia, and in Wistar and SHR strains using permanent focal ischemia. Focal ischemia was produced by distal surgical occlusion of the middle cerebral artery and tandem occlusion of the ipsilateral common carotid artery (MCA/CCAO). Moderate hypothermia of 2 hours' duration was produced by systemic cooling to 32 degrees C, with further cooling of the brain achieved by reducing to 30 degrees C the temperature of the saline drip superfusing the exposed occlusion site. Infarct volume was determined from serial hematoxylin and eosin-stained frozen sections obtained routinely at 24 hours, or in some cases after 3 days' survival. In the SHR, moderate hypothermia was only effective when initiated before recirculation after a 90-minute occlusion period. In contrast, the same intervention was strikingly effective in the Long-Evans rat even when initiated after as long as 30-minute reperfusion after a 3-hour occlusion. This magnitude and duration of cooling was not protective in permanent MCA/CCAO in the SHR, but such transient hypothermia did effectively reduce infarct volume after permanent occlusions in Wistar rats. These results show striking differences in the temporal window for hypothermic protection among rat focal ischemia models. As expected, "reperfusion injury" in the Long-Evans strain is particularly responsive to delayed cooling. The finding that the SHR can be protected by hypothermia initiated immediately before recirculation suggests a rapidly evolving component of injury occurs subsequent to reperfusion in this model as well. Hypothermic protection after permanent occlusion in Wistar rats identifies a transient, temperature-sensitive phase of infarct evolution that is not evident in the unreperfused SHR. These observations confirm that distinct mechanisms can underlie the temporal progression of injury in rat stroke models, and emphasize the critical importance of considering model and strain differences in extrapolating results of hypothermic protection studies in animals to the design of interventions in clinical stroke.

Microalbuminuria and hyperthermia independently predict long-term mortality in acute ischemic stroke patients

OBJECTIVES

To investigate the association between microalbuminuria (MA) and hyperthermia in acute ischemic stroke and to evaluate their significance as the predictors of long-term mortality after stroke.

MATERIAL AND METHODS

We assessed neurologic deficit, urinary albumin excretion and body temperature in 60 patients admitted within 24 h after the onset of their first ischemic stroke. Outcome was assessed by 90-day and 1-year mortality.

RESULTS

MA was found in 46.7% of patients. Hyperthermia was found in 18.3% patients on Day 1 and in 25% patients on Day 2. The correlation between albuminuria on Day 2 and the body temperature on Days 1 and 2 was found (r = 0.45, and r = 0.30, respectively; both P < 0.05). The mortality was significantly higher in the group of patients with both MA and hyperthermia on Day 2 (73% vs 10% after 90 days; P < 0.0001 and 73% vs 18% after 1 year, P < 0.005). In the logistic regression analysis, albuminuria (P = 0.017), hyperthermia on Day 1 (P = 0.028) and neurologic deficit on admission (P = 0.044) independently predicted 1-year mortality after ischemic stroke.

CONCLUSION

Daily urinary albumin excretion correlates with the body temperature in acute stroke patients, but the predictive power of both these variables is independent of that association.

The emerging role of induced hypothermia in the management of acute stroke

Current treatment of acute stroke remains unsatisfactory. This review presents experimental and clinical data which suggest that mild induced hypothermia could be a potent and practicable neuroprotective treatment of acute ischaemic stroke and intracerebral haemorrhage. Hypothermia, if proven to be safe, effective and widely practicable in patients with acute stroke, could have an enormous positive impact on reducing the burden of stroke worldwide. Critical issues that will need to be considered in a well designed randomised controlled trial of induced hypothermia in acute stroke patients are discussed.

Programmable microchip monitoring of post-stroke pyrexia: effects of aspirin and paracetamol on temperature and infarct size in the rat

BACKGROUND

Recent studies have demonstrated spontaneous and prolonged hyperthermia following stroke in both humans and rodents. However, a full characterization of these pyretic changes and the effects of anti-pyretic drugs on outcome is not available.

METHODS

The aims of this study were to monitor conscious body temperature (n=10 per group) using programmable microchips for up to 24 h in rats following either permanent (p) or 90 min transient (t) middle cerebral artery occlusion (MCAO) or sham surgery, and to evaluate the relationship to hypothalamic damage. Also, the effects of anti-pyretic drug therapy on body temperature and infarct volume were evaluated in animals treated with vehicle, optimal doses of either aspirin or paracetamol (250 mg/kg i.p.) following pMCAO (n=10 per group).

RESULTS

At 1 h, body temperature significantly (P<0.01) increased to 38.6+/-0.2 degrees C following tMCAO and 38.9+/-0.1 degrees C following pMCAO compared with sham-operated animals (37.1+/-0.1 degrees C). Sustained hyperthermia (> or =38.1 degrees C) was observed for up to 24 h following pMCAO but approached baseline within 30 min (37.6+/-0.2 degrees C) following tMCAO with reperfusion. The post-stroke pyrexia was related to the degree of ischemia where hypothalamic damage was observed in (80%) of the animals undergoing pMCAO and (0%) in the tMCAO group (P<0.05). Treatment with paracetamol (250 mg/kg i.p.) significantly attenuated (P<0.05) but did not normalize core body temperature up to 2 h (38.2+/-0.4 degrees C) compared with vehicle treated animals (39.3+/-0.1 degrees C). Aspirin had no effect on temperature under these conditions. Hypothalamic damage and lesion volume were not different between animals treated with paracetamol (253.3+/-8.5 mm(3)), aspirin (264.0+/-11.6 mm(3)) or vehicle (274.4+/-8.2 mm(3)).

CONCLUSIONS

This study is the first to demonstrate the utility of programmable microchips to monitor serial changes in post-stroke hyperthermia. The sustained post-stroke pyrexia and negative effects of antipyretic treatment may be attributed to the extensive hypothalamic injury suggesting that better pharmacologic approaches to reduce body temperature should be identified and evaluated for brain protection in severe experimental stroke.

Is temperature important in delivery room resuscitation?

The possibility that temperature may affect the outcome of resuscitation from severe perinatal asphyxia has been a long-standing focus of research. Experimentally it is now well established that even small changes in temperature during severe hypoxia-ischemia critically modulate outcome. Clinical and experimental studies have now shown that hypoxic-ischemic injury continues to evolve after resuscitation. Experimentally, prolonged mild to moderate hypothermia can dramatically reduce this delayed injury, while mild hyperthermia over the same period worsens injury. Indeed there are data indicating that moderate post-ischemic hyperthermia can be deleterious as late as 24 h after reperfusion. Hypothermia has significant potential adverse effects, and at present its clinical use is restricted to large randomized controlled trials. The present paper reviews evidence suggesting that both primary prevention of maternal pyrexia during labour, and secondary prevention of hyperthermia after neonatal resuscitation, have the potential to significantly reduce the consequences of perinatal hypoxia-ischemia.