Hyperthermia in human ischemic and hemorrhagic stroke: similar outcome, different mechanisms

Therapeutic modulation of protein RBM3 for ischemic stroke treatment

Several preclinical assays and clinical trials have found hypothermia as an efficient protective treatment for stroke. However, systemic hypothermia impairs several physiological functions being difficult to implement in acute critical patients. A deeper understanding of the mechanisms underlying the therapeutic effects of hypothermia could inspire new treatments based on the protective effects of cold. Furthermore, this could contribute to the reduction of the side effects associated with it. One of the metabolic landmarks of hypothermia is the overexpression of a small subset of shock proteins while global protein synthesis is reduced. Among these cold-shock proteins, RBM3 (RNA-binding motif protein 3) seems to play a central protective role. In physiological conditions, which is involved in the regulation of protein synthesis. In several models of cerebral diseases, in vitro and in vivo, RBM3 exhibited the ability to mitigate apoptosis or increase neural proliferation. In stroke models, RBM3 has shown specially promising effects attenuating neural damage and enhancing cell survival. Future prospects should be directed towards the design of efficient strategies to modulate RBM3 levels. This mini-review aims to summarize the progress made in understanding the role of RBM3 in cerebral tissue protection, while encouraging efforts to address research gaps, particularly in its modulation and clinical application.

Impact of fever on the outcome non-anoxic acute brain injury patients: a systematic review and meta-analysis

BACKGROUND

Fever is a common condition in intensive care unit (ICU) patients, with an incidence between 30 and 50% in non-neurological ICU patients and up to 70-90% in neurological ICU patients. We aim to perform systematic review and meta-analysis of current literature to assess impact of fever on neurological outcomes and mortality of acute brain injury patients.

METHODS

We searched PubMed/Medline, Scopus and Embase databases following the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, and we included both retrospective and prospective observational studies, interventional studies, and randomized clinical trials that had data on body temperature and fever during ICU admission. The primary endpoints were neurological outcome and mortality at any time. Secondary outcomes included: early neurological deterioration, delayed cerebral ischemia (DCI, only for patients with subarachnoid hemorrhage), large infarct or hemorrhage size, hemorrhagic transformation (only for patients with ischemic stroke). This study was registered in PROSPERO (CRD42020155903).

RESULTS

180 studies from 14692 records identified after the initial search were included in the final analysis, for a total of 460,825 patients. Fever was associated with an increased probability of unfavorable neurological outcome (pooled OR 2.37 [95% CI 2.08-2.71], I2:92%), death (pooled OR 1.31 [95% CI 1.28-1.34], I2:93%), neurological deterioration (pooled OR 1.10 [95% CI 1.05-1.15]), risk of DCI (pooled OR 1.96 [95% CI 1.73-2.22]), large infarct size (pooled OR 2.94 [95% CI 2.90-2.98]) and hemorrhagic transformation (pooled OR 1.63 [95% CI 1.34-1.97]) and large hemorrhagic volume (pooled OR 2.38 [95% CI 1.94-2.93]).

CONCLUSION

Fever was associated with poor neurological outcomes and mortality in patients with acute brain injury. Whether normothermia should be targeted in the management of all neuro critically ill patients warrants specific research.

Early fever in patients with primary intracerebral hemorrhage is associated with worse long-term functional outcomes: a prospective study

BACKGROUND

Primary intracerebral hemorrhage (ICH) accounts for 85% of ICH cases and is associated with high morbidity and mortality rates. Fever can cause secondary injury after ICH; however, relevant studies have reported inconsistent results regarding the effects of fever on functional outcomes after ICH. This study examined the effects of early fever on the prognosis of ICH, particularly on long-term functional outcomes.

METHODS

This prospective study recruited patients with primary ICH at a tertiary medical center between 2019 and 2021. Early fever was defined as a tympanic body temperature of ≥ 38 °C upon admission. Barthel Index (BI) and modified Rankin scale (mRS) were examined at 1 year after ICH. A BI of ≤ 60 or mRS of ≥ 4 was considered as indicating severe disability.

RESULTS

We included 100 patients, and early fever was significantly associated with less functional independence at 1 year post-ICH, as determined using the mRS (p = 0.048; odds ratio [OR] = 0.23), and with severe functional dependency at 1 year post-ICH, as determined using the BI (p = 0.043; OR = 3) and mRS (p = 0.045; OR = 3). In addition, patients with early fever had a longer length of hospital stay (p = 0.002; 95% confidence interval = 21.80-95.91).

CONCLUSIONS

Fever is common among patients with primary ICH. Our data indicate a significant association between early fever and worse functional outcomes in ICH survivors at 1 year after ICH. Additionally, patients with early fever had a significantly longer length of hospital stay after ICH.

Determinants of acute and subacute case-fatality in elderly patients with hypertensive intracerebral hemorrhage

Background

Given that limited reports have described the survival and risk factors for elderly patients with hypertensive intracerebral hemorrhage (HICH), we aimed to develop a valid but simple prediction nomogram for the survival of HICH patients.

Methods

All elderly patients ≥65 years old who were diagnosed with HICH between January 2011 and December 2019 were identified. We performed the least absolute shrinkage and selection operator (Lasso) on the Cox regression model with the R package glmnet. A concordance index was performed to calculate the nomogram discrimination; and calibration curves and decision curves were graphically evaluated by depicting the observed rates against the probabilities predicted by the nomogram.

Results

A total of 204 eligible patients were analyzed, and over 20 % of the population was above the age of 80 (65-79 years old, n = 161; 80+ years old, n = 43). A hematoma volume ≥13.64 cm3 was associated with higher 7-day mortality (OR = 6.773, 95 % CI = 2.622-19.481; p < 0.001) and higher 90-day mortality (OR = 3.955, 95 % CI = 1.611-10.090, p = 0.003). A GCS score between 13 and 15 at admission was associated with a 7-day favorable outcome (OR = 0.025, 95 % CI = 0.005-0.086; p < 0.001) and a 90-day favorable outcome (OR = 0.033, 95 % CI = 0.010-0.099; p < 0.001).

Conclusions

Our nomogram models were visualized and accurate. Neurosurgeons could use them to assess the prognostic factors and provide advice to patients and their relatives.

A New NF-κB Inhibitor, MEDS-23, Reduces the Severity of Adverse Post-Ischemic Stroke Outcomes in Rats

Aim: Nuclear factor kappa B (NF-κB) is known to play an important role in the inflammatory process which takes place after ischemic stroke. The major objective of the present study was to examine the effects of MEDS-23, a potent inhibitor of NF-κB, on clinical outcomes and brain inflammatory markers in post-ischemic stroke rats. Main methods: Initially, a Toxicity Experiment was performed to determine the appropriate dose of MEDS-23 for use in animals, as MEDS-23 was analyzed in vivo for the first time. We used the middle cerebral artery occlusion (MCAO) model for inducing ischemic stroke in rats. The effects of MEDS-23 (at 10 mg/kg, ip) on post-stroke outcomes (brain inflammation, fever, neurological deficits, mortality, and depression- and anxiety-like behaviours) was tested in several efficacy experiments. Key findings: MEDS-23 was found to be safe and significantly reduced the severity of some adverse post-stroke outcomes such as fever and neurological deficits. Moreover, MEDS-23 significantly decreased prostaglandin E2 levels in the hypothalamus and hippocampus of post-stroke rats, but did not prominently alter the levels of interleukin-6 and tumor necrosis factor-α. Significance: These results suggest that NF-κB inhibition is a potential therapeutic strategy for the treatment of ischemic stroke.

Using medical microwave radiometry for brain temperature measurements

Brain temperature (BT) is a crucial physiological parameter used to monitor cerebral status. Physical activities and traumatic brain injuries (TBI) can affect BT; therefore, non-invasive BT monitoring is an important way to gain insight into TBI, stroke, and wellbeing. The effects of BT on physical performance have been studied at length. When humans are under extreme conditions, most of the energy consumed is used to maintain the BT. In addition, measuring the BT is useful for early brain diagnostics. Passive microwave radiometry (MWR) measures the intrinsic radiation of tissues in the 1-4 GHz range. It was shown that non-invasive passive MWR technology can successfully measure BT and identify even small TBIs. Here, we review the potential applications of MWR for assessing BT.

Intracerebral Hemorrhage

PURPOSE OF REVIEW

Nontraumatic intracerebral hemorrhage (ICH) is the second most common type of stroke. This article summarizes the basic pathophysiology, classification, and management of ICH and discusses the available evidence on therapy for hematoma, hematoma expansion, and perihematomal edema.

RECENT FINDINGS

Current available data on potential therapeutic options for ICH are promising, although none of the trials have shown improvement in mortality rate. The literature available on reversal of anticoagulation and antiplatelet agents after an ICH and resumption of these medications is also increasing.

SUMMARY

ICH continues to have high morbidity and mortality. Advances in therapeutic options to target secondary brain injury from the hematoma, hematoma expansion, and perihematomal edema are increasing. Data on reversal therapy for anticoagulant-associated or antiplatelet-associated ICH and resumption of these medications are evolving.

Progress in Borneol Intervention for Ischemic Stroke: A Systematic Review

Background: Borneol is a terpene and bicyclic organic compound that can be extracted from plants or chemically synthesized. As an important component of proprietary Chinese medicine for the treatment of stroke, its neuroprotective effects have been confirmed in many experiments. Unfortunately, there is no systematic review of these studies. This study aimed to systematically examine the neuroprotective effects of borneol in the cascade reaction of experimental ischemic stroke at different periods. Methods: Articles on animal experiments and cell-based research on the actions of borneol against ischemic stroke in the past 20°years were collected from Google Scholar, Web of Science, PubMed, ScienceDirect, China National Knowledge Infrastructure (CNKI), and other biomedical databases. Meta-analysis was performed on key indicators in vivo experiments. After sorting the articles, we focused on the neuroprotective effects and mechanism of action of borneol at different stages of cerebral ischemia. Results: Borneol is effective in the prevention and treatment of nerve injury in ischemic stroke. Its mechanisms of action include improvement of cerebral blood flow, inhibition of neuronal excitotoxicity, blocking of Ca²⁺ overload, and resistance to reactive oxygen species injury in the acute ischemic stage. In the subacute ischemic stage, borneol may antagonize blood-brain barrier injury, intervene in inflammatory reactions, and prevent neuron excessive death. In the late stage, borneol promotes neurogenesis and angiogenesis in the treatment of ischemic stroke. Conclusion: Borneol prevents neuronal injury after cerebral ischemia via multiple action mechanisms, and it can mobilize endogenous nutritional factors to hasten repair and regeneration of brain tissue. Because the neuroprotective effects of borneol are mediated by various therapeutic factors, deficiency caused by a single-target drug is avoided. Besides, borneol promotes other drugs to pass through the blood-brain barrier to exert synergistic therapeutic effects.

Prognostic significance of early pyrexia in acute intracerebral haemorrhage: The INTERACT2 study

INTRODUCTION

Uncertainty exists over the prognostic significance of pyrexia in acute intracerebral haemorrhage (ICH). We aimed to determine the association of elevated body temperature with clinical and imaging outcomes among participants of the main Intensive Blood Pressure Reduction in Acute Cerebral Haemorrhage Trial (INTERACT2).

METHODS

Post-hoc analyses of INTERACT2, an international open, blinded outcome assessed, randomised trial of 2839 patients with spontaneous ICH (<6 h of onset) and elevated systolic blood pressure (SBP, 150-220 mmHg) randomly assigned to intensive (SBP target <140 mmHg) or guideline-recommended (SBP target < 180 mmHg) BP management. Multivariable logistic regression was used to determine associations of elevated baseline body temperature (<37.5 vs. ≥37.5 °C) and 90-day clinical outcome defined on the modified Rankin scale (mRS). Analysis of covariance determined relations of body temperature and haematoma and perihaematomal oedema (PHE) volumes, at baseline and 24 h post-randomisation.

RESULTS

Of 2792 participants with data available at admission, 39 (1.4%) patients had elevated body temperature ≥ 37.5 °C. Elevated body temperature was significantly associated with 90-day mortality (adjusted odds ratio 2.44; 95% confidence interval 1.02-5.82; P = .044) but not with major disability alone (mRS scores 3-5) and combination death or major disability (mRS scores 3-6). Elevated body temperature was also associated with larger PHE volume at baseline (10.89 vs. 3.14 cm³, P < .001;) and 24 h (12.43 vs 5.76 cm³, P = .018) but not with haematoma volumes at these time points.

CONCLUSION

Early pyrexia in mild to moderate ICH is associated with greater mortality and larger PHE volume, suggesting an early inflammatory-mediated reaction.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov (NCT00716079).

Role of the nurse in the hyperacute care and management of patients following stroke

Stroke is a medical emergency that affects millions of people worldwide each year. The first 24-72 hours following a stroke is a critical stage in the patient's management because deterioration can occur during this period. Hyperacute care is a time-sensitive method of managing stroke that has improved the provision of holistic and evidence-based stroke care. This article describes the care and management that patients require in the first 24-72 hours following stroke. It details the evidence-based practice that this involves, and explains the role of the nurse in providing hyperacute care.

Temperature management in acute brain injury: A systematic review of clinical evidence

Temperature alterations in neurocritical care settings are common and have a striking effect on brain metabolism leading to or exacerbating neuronal injury. Hyperthermia worsens acute brain injury (ABI) patients outcome. However conclusive evidence linking control of temperature to improved outcome is still lacking. This review article report an update -results from clinical studies published between March 2006 and March 2020- on the relationship between hyperthermia or Target Temperature Management and functional outcome or mortality in ABI patients.

MATERIALS AND METHODS

A systematic search of articles in PubMed and EMBASE database was accomplished. Only complete studies, published in English in peer-reviewed journals were included.

RESULTS

A total of 63 articles into 5 subchapters are presented: acute ischemic stroke (17), subarachnoid hemorrhage (14), brain trauma (14), intracranial hemorrhage (8), and mixed acute brain injury (10). This evidence confirm and extend the negative impact of hyperthermia in ABI patients on worse functional outcome and higher mortality. In particular "early hyperthermia" in AIS patients seems to have a protective role have as promoting factor of clot lysis but no conclusive evidence is available. Normothermic TTM seems to have a positive effect on TBI patients in a reduced mortality rate compared to hypothermic TTM.

CONCLUSIONS

Hyperthermia in ABI patients is associated with worse functional outcome and higher mortality. The use of normothermic TTM has an established indication only in TBI; further studies are needed to define the role and the indications of normothermic TTM in ABI patients.

Inhibition of cyclooxygenase-1 does not reduce mortality in post-ischemic stroke rats

BACKGROUND

Ischemic stroke is one of the leading causes of mortality and morbidity. The currently available non-invasive therapeutic options are not sufficiently efficacious. Post-ischemic brain is characterized by a prominent inflammatory response. Little is known about the involvement of cyclooxygenase (COX)-1 in the pathophysiology of ischemic stroke.

OBJECTIVE

This study was undertaken to examine the effects of a highly selective COX-1 inhibitor - mofezolac - on clinical outcomes and brain inflammatory markers in post-stroke rats.

METHODS

Stroke was induced by subjecting rats to permanent middle cerebral artery occlusion (MCAO). Control rats underwent a sham surgery. Rats were treated with mofezolac (50 mg/kg, intraperitoneally [ip]) once daily for 14 days. Control animals were treated with vehicle. Body temperature (BT), neurological score (NS) and cumulative mortality were monitored at different time points. At the end of the experiment, rats were euthanized and three brain regions (hypothalamus, hippocampus and frontal cortex) were extracted. Levels of interleukin (IL)-6, prostaglandin (PG)E₂ and tumor necrosis factor (TNF)-α in these brain regions were determined by ELISA kits.

RESULTS

BT, NS and cumulative mortality were all significantly higher in post-MCAO rats than in sham-operated rats, irrespective of the treatment given. BT, NS and mortality rate did not differ significantly between mofezolac-treated and vehicle-treated sham-operated animals. BT was significantly lower in mofezolac-treated as compared to vehicle-treated post-MCAO rats. Mofezolac did not significantly alter NS in post-MCAO rats at any time-point. Cumulative 14-day mortality was non-significantly higher in mofezolac-treated as compared to vehicle-treated post-MCAO rats (48 % vs. 21 %, respectively; P =  0.184). Mostly, IL-6 and TNF-α levels did not differ between post-MCAO and sham-operated rats and were not affected by mofezolac treatment. In contrast, mofezolac significantly decreased PGE₂ levels in post-MCAO rats' brains.

CONCLUSION

Overall, these results suggest that chronic treatment with the selective COX-1 inhibitor mofezolac did not reduce morbidity or mortality in post-stroke rats.

Antihyperthermic treatment decreases perihematomal hypodensity

OBJECTIVE

To investigate the effect on perihematomal hypodensity and outcome of a decrease in body temperature in the first 24 hours in patients with intracerebral hemorrhage (ICH).

METHODS

In this retrospective study on a prospectively registered database, among the 1,100 patients, 795 met all the inclusion criteria. Temperature variations in the first 24 hours and perihematomal hypodensity (PHHD) were recorded. Patients ≥37.5°C were treated with antihyperthermic drugs for at least 48 hours. The main objective was to determine the association among temperature variation, PHHD, and outcome at 3 months.

RESULTS

The decrease in temperature in the first 24 hours increased the possibility of good outcome 11-fold. Temperature decrease, lower PHHD volume, and a good outcome were observed in 31.8% of the patients who received antihyperthermic treatment.

CONCLUSION

The administration of early antihyperthermic treatment in patients with spontaneous ICH with a basal axillary temperature ≥37.5°C resulted in good outcome in a third of the treated patients.

Hypothermic neuroprotection during reperfusion following exposure to aglycemia in central white matter is mediated by acidification

Hypoglycemia is a common iatrogenic consequence of type 1 diabetes therapy that can lead to central nervous system injury and even death if untreated. In the absence of clinically effective neuroprotective drugs we sought to quantify the putative neuroprotective effects of imposing hypothermia during the reperfusion phase following aglycemic exposure to central white matter. Mouse optic nerves (MONs), central white matter tracts, were superfused with oxygenated artificial cerebrospinal fluid (aCSF) containing 10 mmol/L glucose at 37°C. The supramaximal compound action potential (CAP) was evoked and axon conduction was assessed as the CAP area. Extracellular lactate was measured using an enzyme biosensor. Exposure to aglycemia, simulated by omitting glucose from the aCSF, resulted in axon injury, quantified by electrophysiological recordings, electron microscopic analysis confirming axon damage, the extent of which was determined by the duration of aglycemia exposure. Hypothermia attenuated injury. Exposing MONs to hypothermia during reperfusion resulted in improved CAP recovery compared with control recovery measured at 37°C, an effect attenuated in alkaline aCSF. Hypothermia decreases pH implying that the hypothermic neuroprotection derives from interstitial acidification. These results have important clinical implications demonstrating that hypothermic intervention during reperfusion can improve recovery in central white matter following aglycemia.

The impact of hyperthermia after acute carbon monoxide poisoning on neurological sequelae

This study investigated whether hyperthermia within the first 24 h after presentation was associated with long-term neurological outcomes after acute carbon monoxide (CO) poisoning. This retrospective study included 200 patients with acute severe CO poisoning. Hyperthermia (≥ 37.5°C) developed during the first 24 h after presentation in 55 (27.5%) patients, and poor long-term neurological sequelae assessed at 23 months after acute CO poisoning developed in 19.5% of the patients. The incidence of poor long-term neurological outcomes was significantly higher in the hyperthermia group than in the normothermia group. Patients with poor long-term neurological outcomes had higher maximum temperatures than patients with good outcomes. No significant difference was found in the time of hyperthermia onset within the first day according to the neurological outcomes. Hyperthermia (adjusted odds ratio (aOR) 5.009 (95% confidence interval (CI) 1.556-16.126)) and maximum temperature (aOR 2.581 (95% CI 1.098-6.063)) within the first 24 h after presentation to the emergency department were independently associated with poor long-term neurological outcomes. Body temperature measurements, which are easily and noninvasively recorded at the bedside in any facility, help to predict the risk for poor long-term neurological outcomes. This study carefully emphasizes fastidious control of pyrexia, particularly during the early period after acute CO poisoning.

Inflammation, edema and poor outcome are associated with hyperthermia in hypertensive intracerebral hemorrhages

Background and purpose

The deleterious effect of hyperthermia on intracerebral hemorrhage (ICH) has been studied. However, the results are not conclusive and new studies are needed to elucidate clinical factors that influence the poor outcome. The aim of this study was to identify the clinical factors (including ICH etiology) that influence the poor outcome associated with hyperthermia and ICH. We also tried to identify potential mechanisms involved in hyperthermia during ICH.

Methods

We conducted a retrospective study enrolling patients with non‐traumatic ICH from a prospective registry. We used logistic regression models to analyze the influence of hyperthermia in relation to different inflammatory and endothelial dysfunction markers, hematoma growth and edema volume in hypertensive and non‐hypertensive patients with ICH.

Results

We included 887 patients with ICH (433 hypertensive, 50 amyloid, 117 by anticoagulants and 287 with other causes). Patients with hypertensive ICH showed the highest body temperature (37.5 ± 0.8°C) as well as the maximum increase in temperature (0.9 ± 0.1°C) within the first 24 h. Patients with ICH of hypertensive etiologic origin, who presented hyperthermia, showed a 5.3‐fold higher risk of a poor outcome at 3 months. We found a positive relationship (r = 0.717, P < 0.0001) between edema volume and hyperthermia during the first 24 h but only in patients with ICH of hypertensive etiologic origin. This relationship seems to be mediated by inflammatory markers.

Conclusion

Our data suggest that hyperthermia, together with inflammation and edema, is associated with poor outcome only in ICH of hypertensive etiology.

Impact of acute-phase complications and interventions on 6-month survival after stroke. A prospective observational study

The outcome of stroke patients is complex and multidimensional. We evaluated the impact of acute-phase variables, including clinical state, complications, resource use and interventions, on 6-month survival after first-ever stroke, taking into account baseline conditions exerting a possible effect on outcome.

As part of a National Research Program, we performed a prospective observational study of acute stroke patients in four Italian Regions. Consecutive patients admitted for a period of 3 months to the emergency rooms of participating hospitals were included.

A total of 1030 patients were enrolled (median age 76.0 years, 52.1% males). At 6 months, 816 (79.2%) were alive, and 164 (15.9%) deceased. Survival status at the 6-month follow-up was missing for 50 (4.9%). Neurological state in the acute phase was significantly worse in patients deceased at 6 months, who showed also higher frequency of acute-phase complications. Cox regression analysis adjusted for demographics, pre-stroke function, baseline diseases and risk factors, indicated as significant predictors of 6-month death altered consciousness (HR, 1.70; 95% CI, 1.14–2.53), total anterior circulation infarct (HR, 2.13; 95% CI, 1.44–3.15), hyperthermia (HR, 1.70; 95% CI, 1.18–2.45), pneumonia (HR, 1.76; 95% CI, 1.18–2.61), heart failure (HR, 2.87; 95% CI, 1.34–6.13) and nasogastric feeding (HR, 2.35; 95% CI, 1.53–3.60), while antiplatelet therapy during acute phase (HR, 0.56; 95% CI, 0.39–0.79), and early mobilisation (HR, 0.55; 95% CI, 0.36–0.84) significantly increased 6-month survival.

In a prospective observational study, stroke severity and some acute-phase complications, potentially modifiable, significantly increased the risk of 6-month death, independently of baseline variables. Early mobilisation positively affected survival, highlighting the role of early rehabilitation after stroke.

Is temperature an important variable in recovery after mild traumatic brain injury?

With nearly 42 million mild traumatic brain injuries (mTBIs) occurring worldwide every year, understanding the factors that may adversely influence recovery after mTBI is important for developing guidelines in mTBI management. Extensive clinical evidence exists documenting the detrimental effects of elevated temperature levels on recovery after moderate to severe TBI. However, whether elevated temperature alters recovery after mTBI or concussion is an active area of investigation. Individuals engaged in exercise and competitive sports regularly experience body and brain temperature increases to hyperthermic levels and these temperature increases are prolonged in hot and humid ambient environments. Thus, there is a strong potential for hyperthermia to alter recovery after mTBI in a subset of individuals at risk for mTBI. Preclinical mTBI studies have found that elevating brain temperature to 39°C before mTBI significantly increases neuronal death within the cortex and hippocampus and also worsens cognitive deficits. This review summarizes the pathology and behavioral problems of mTBI that are exacerbated by hyperthermia and discusses whether hyperthermia is a variable that should be considered after concussion and mTBI. Finally, underlying pathophysiological mechanisms responsible for hyperthermia-induced altered responses to mTBI and potential gender considerations are discussed.

Cerebral Vascular Control and Metabolism in Heat Stress

This review provides an in-depth update on the impact of heat stress on cerebrovascular functioning. The regulation of cerebral temperature, blood flow, and metabolism are discussed. We further provide an overview of vascular permeability, the neurocognitive changes, and the key clinical implications and pathologies known to confound cerebral functioning during hyperthermia. A reduction in cerebral blood flow (CBF), derived primarily from a respiratory-induced alkalosis, underscores the cerebrovascular changes to hyperthermia. Arterial pressures may also become compromised because of reduced peripheral resistance secondary to skin vasodilatation. Therefore, when hyperthermia is combined with conditions that increase cardiovascular strain, for example, orthostasis or dehydration, the inability to preserve cerebral perfusion pressure further reduces CBF. A reduced cerebral perfusion pressure is in turn the primary mechanism for impaired tolerance to orthostatic challenges. Any reduction in CBF attenuates the brain's convective heat loss, while the hyperthermic-induced increase in metabolic rate increases the cerebral heat gain. This paradoxical uncoupling of CBF to metabolism increases brain temperature, and potentiates a condition whereby cerebral oxygenation may be compromised. With levels of experimentally viable passive hyperthermia (up to 39.5-40.0 °C core temperature), the associated reduction in CBF (∼ 30%) and increase in cerebral metabolic demand (∼ 10%) is likely compensated by increases in cerebral oxygen extraction. However, severe increases in whole-body and brain temperature may increase blood-brain barrier permeability, potentially leading to cerebral vasogenic edema. The cerebrovascular challenges associated with hyperthermia are of paramount importance for populations with compromised thermoregulatory control--for example, spinal cord injury, elderly, and those with preexisting cardiovascular diseases.

Treatment of acute stroke: an update

Stroke is the second leading cause of global mortality after coronary heart disease, and a major cause of neurological disability. About 17 million strokes occur worldwide each year. Patients with stroke often require long-term rehabilitation following the acute phase, with ongoing support from the community and nursing home care. Thus, stroke is a devastating disease and a major economic burden on society. In this overview, we discuss current strategies for specific treatment of stroke in the acute phase, focusing on intravenous thrombolysis and mechanical thrombectomy. We will consider two important issues related to intravenous thrombolysis treatments: (i) how to shorten the delay between stroke onset and treatment and (ii) how to reduce the risk of symptomatic intracerebral haemorrhage. Intravenous thrombolysis has been approved treatment for acute ischaemic stroke in most countries for more than 10 years, with rapid development towards new treatment strategies during that time. Mechanical thrombectomy using a new generation of endovascular tools, stent retrievers, is found to improve functional outcome in combination with pharmacological thrombolysis when indicated. There is an urgent need to increase public awareness of how to recognize a stroke and seek immediate attention from the healthcare system, as well as shorten delays in prehospital and within-hospital settings.

Blood glutamate grabbing does not reduce the hematoma in an intracerebral hemorrhage model but it is a safe excitotoxic treatment modality

Recent studies have shown that blood glutamate grabbing is an effective strategy to reduce the excitotoxic effect of extracellular glutamate released during ischemic brain injury. The purpose of the study was to investigate the effect of two of the most efficient blood glutamate grabbers (oxaloacetate and recombinant glutamate oxaloacetate transaminase 1: rGOT1) in a rat model of intracerebral hemorrhage (ICH). Intracerebral hemorrhage was produced by injecting collagenase into the basal ganglia. Three treatment groups were developed: a control group treated with saline, a group treated with oxaloacetate, and a final group treated with human rGOT1. Treatments were given 1 hour after hemorrhage. Hematoma volume (analyzed by magnetic resonance imaging (MRI)), neurologic deficit, and blood glutamate and GOT levels were quantified over a period of 14 days after surgery. The results observed showed that the treatments used induced a significant reduction of blood glutamate levels; however, they did not reduce the hematoma, nor did they improve the neurologic deficit. In the present experimental study, we have shown that this novel therapeutic strategy is not effective in case of ICH pathology. More importantly, these findings suggest that blood glutamate grabbers are a safe treatment modality that can be given in cases of suspected ischemic stroke without previous neuroimaging.

Emergence of cognitive deficits after mild traumatic brain injury due to hyperthermia

Mild elevations in core temperature can occur in individuals involved in strenuous activities that are risky for potentially sustaining a mild traumatic brain injury (mTBI) or concussion. Recently, we have discovered that mild elevations in brain temperature can significantly aggravate the histopathological consequences of mTBI. However, whether this exacerbation of brain pathology translates into behavioral deficits is unknown. Therefore, we investigated the behavioral consequences of elevating brain temperature to mildly hyperthermic levels prior to mTBI. Adult male Sprague Dawley rats underwent mild fluid-percussion brain injury or sham surgery while normothermic (37 °C) or hyperthermic (39 °C) and were allowed to recover for 7 days. Animals were then assessed for cognition using the water maze and cue and contextual fear conditioning. We found that mTBI alone at normothermia had no effect on long-term cognitive measures whereas mTBI animals that were hyperthermic for 15 min prior to and for 4h after brain injury were significantly impaired on long-term retention for both the water maze and fear conditioning. In contrast, hyperthermic mTBI animals cooled within 15 min to normothermia demonstrated no significant long-term cognitive deficits. Mild TBI irrespective of temperature manipulations resulted in significant short-term working memory deficits. Cortical atrophy and contusions were detected in all mTBI treatment groups and contusion volume was significantly less in hyperthermic mTBI animals that were cooled as compared to hyperthermic mTBI animals that remained hyperthermic. These results indicate that brain temperature is an important variable for mTBI outcome and that mildly elevated temperatures at the time of injury result in persistent cognitive deficits. Importantly, cooling to normothermia after mTBI prevents the development of long-term cognitive deficits caused by hyperthermia. Reducing temperature to normothermic levels soon after mTBI represents a rational approach to potentially mitigate the long-term consequences of mTBI.