Hypothermia for traumatic brain injury: how soon, how cold, and how long?

Neuromonitoring after Pediatric Cardiac Arrest: Cerebral Physiology and Injury Stratification

BACKGROUND

Significant long-term neurologic disability occurs in survivors of pediatric cardiac arrest, primarily due to hypoxic-ischemic brain injury. Postresuscitation care focuses on preventing secondary injury and the pathophysiologic cascade that leads to neuronal cell death. These injury processes include reperfusion injury, perturbations in cerebral blood flow, disturbed oxygen metabolism, impaired autoregulation, cerebral edema, and hyperthermia. Postresuscitation care also focuses on early injury stratification to allow clinicians to identify patients who could benefit from neuroprotective interventions in clinical trials and enable targeted therapeutics.

METHODS

In this review, we provide an overview of postcardiac arrest pathophysiology, explore the role of neuromonitoring in understanding postcardiac arrest cerebral physiology, and summarize the evidence supporting the use of neuromonitoring devices to guide pediatric postcardiac arrest care. We provide an in-depth review of the neuromonitoring modalities that measure cerebral perfusion, oxygenation, and function, as well as neuroimaging, serum biomarkers, and the implications of targeted temperature management.

RESULTS

For each modality, we provide an in-depth review of its impact on treatment, its ability to stratify hypoxic-ischemic brain injury severity, and its role in neuroprognostication.

CONCLUSION

Potential therapeutic targets and future directions are discussed, with the hope that multimodality monitoring can shift postarrest care from a one-size-fits-all model to an individualized model that uses cerebrovascular physiology to reduce secondary brain injury, increase accuracy of neuroprognostication, and improve outcomes.

Temperature Management and Health-Related Quality of Life in Children 3 Years After Cardiac Arrest

OBJECTIVES

Therapeutic hypothermia minimizes neuronal injury in animal models of hypoxic-ischemic encephalopathy with greater effect when used sooner after the insult. Clinical trials generally showed limited benefit but are difficult to perform in a timely manner. In this clinical study, we evaluated the association between the use of hypothermia (or not) and health-related quality of life among survivors of pediatric cardiac arrest as well as overall mortality.

DESIGN

Single-center, retrospectively identified cohort with prospective assessment of health-related quality of life.

SETTING

PICU of a pediatric hospital.

PATIENTS

Children with either out-of-hospital or in-hospital cardiac arrest from January 2012 to December 2017.

INTERVENTIONS

Patients were assigned into two groups: those who received therapeutic hypothermia at less than or equal to 35°C and those who did not receive therapeutic hypothermia but who had normothermia targeted (36-36.5°C). The primary outcome was health-related quality of life assessment and the secondary outcome was PICU mortality.

MEASUREMENTS AND MAIN RESULTS

We studied 239 children, 112 (47%) in the therapeutic hypothermia group. The median (interquartile range) of lowest temperature reached in the 48 hours post cardiac arrest in the therapeutic hypothermia group was 33°C (32.6-33.6°C) compared with 35.4°C (34.7-36.2°C) in the no therapeutic hypothermia group (p < 0.001). At follow-up, 152 (64%) were alive and health-related quality of life assessments were completed in 128. Use of therapeutic hypothermia was associated with higher lactate and lower pH at baseline. After regression adjustment, therapeutic hypothermia (as opposed to no therapeutic hypothermia) was associated with higher physical (mean difference, 15.8; 95% CI, 3.5-27.9) and psychosocial scores (13.6 [5.8-21.5]). These observations remained even when patients with a temperature greater than 37.5°C were excluded. We failed to find an association between therapeutic hypothermia and lower mortality.

CONCLUSIONS

Out-of-hospital or in-hospital cardiac arrest treated with therapeutic hypothermia was associated with higher health-related quality of life scores despite having association with higher lactate and lower pH after resuscitation. We failed to identify an association between use of therapeutic hypothermia and lower mortality.

Mast Cells Promote Seasonal White Adipose Beiging in Humans

Human subcutaneous (SC) white adipose tissue (WAT) increases the expression of beige adipocyte genes in the winter. Studies in rodents suggest that a number of immune mediators are important in the beiging response. We studied the seasonal beiging response in SC WAT from lean humans. We measured the gene expression of various immune cell markers and performed multivariate analysis of the gene expression data to identify genes that predict UCP1. Interleukin (IL)-4 and, unexpectedly, the mast cell marker CPA3 predicted UCP1 gene expression. Therefore, we investigated the effects of mast cells on UCP1 induction by adipocytes. TIB64 mast cells responded to cold by releasing histamine and IL-4, and this medium stimulated UCP1 expression and lipolysis by 3T3-L1 adipocytes. Pharmacological block of mast cell degranulation potently inhibited histamine release by mast cells and inhibited adipocyte UCP1 mRNA induction by conditioned medium (CM). Consistently, the histamine receptor antagonist chlorpheniramine potently inhibited adipocyte UCP1 mRNA induction by mast cell CM. Together, these data show that mast cells sense colder temperatures, release factors that promote UCP1 expression, and are an important immune cell type in the beiging response of WAT.

Brain death and true patient care

The "brain death" standard as a criterion of death is closely associated with the need for transplantable organs from heart-beating donors. Are all of these potential donors really dead, or does the documented evidence of patients destined for organ harvesting who improve, or even recover to live normal lives, call into question the premise underlying "brain death"? The aim of this paper is to re-examine the notion of "brain death," especially its clinical test-criteria, in light of a broad framework, including medical knowledge in the field of neuro-intensive care and the traditional ethics of the medical profession. I will argue that both the empirical medical evidence and the ethics of the doctor-patient relationship point to an alternative approach toward the severely comatose patient (potential brain-dead donor). Lay Summary: Though legally accepted and widely practiced, the "brain death" standard for the determination of death has remained a controversial issue, especially in view of the occurrence of "chronic brain death" survivors. This paper critically re-evaluates the clinical test-criteria for "brain death," taking into account what is known about the neuro-critical care of severe brain injury. The medical evidence, together with the understanding of the moral role of the physician toward the patient present before him or her, indicate that an alternative approach should be offered to the deeply comatose patient.

Subdural hematoma decompression model: A model of traumatic brain injury with ischemic-reperfusional pathophysiology: A review of the literature

The prognosis for patients with traumatic brain injury (TBI) with subdural hematoma (SDH) remains poor. In accordance with an increasing elderly population, the incidence of geriatric TBI with SDH is rising. An important contributor to the neurological injury associated with SDH is the ischemic damage which is caused by raised intracranial pressure (ICP) producing impaired cerebral perfusion. To control intracranial hypertension, the current management consists of hematoma evacuation with or without decompressive craniotomy. This removal of the SDH results in the immediate reversal of global ischemia accompanied by an abrupt reduction of mass lesion and an ensuing reperfusion injury. Experimental models can play a critical role in improving our understanding of the underlying pathophysiology and in exploring potential treatments for patients with SDH. In this review, we describe the epidemiology, pathophysiology and clinical background of SDH.

Microdialysis as Clinical Evaluation of Therapeutic Hypothermia in Rat Subdural Hematoma Model

Cerebral microdialysis (MD) is a fine laboratory technique which has been established for studying physiological, pharmacological, and pathological changes in the experimental studies of traumatic brain injury (TBI). This technique has also been well translated and widely applied to clinical bedside monitoring to provide pathophysiological analysis in severe TBI patients. The MD technique is thus well suited for straightforward translation from basic science to clinical application.In this chapter, we describe our evaluation of MD method in acute subdural hematoma (ASDH) rat model. With 100 kDa cut-off microdialysis membrane, we could measure several biomarkers such as ubiquitin carboxy hydrolase L1 (UCH-L1), a neuronal marker and glial fibrillary acidic protein (GFAP), and a glial marker in extracellular fluid. In this experiment, we could detect that the peak of extracellular UCH-L1 in the early hypothermia group was significantly lower than in the normothermia group. Also, in the late phase of reperfusion (>2.5 h after decompression), extracellular GFAP in the early hypothermia group was lower than in the normothermia. These data thus suggested that early, preoperatively induced hypothermia could mediate the reduction of neuronal and glial damage in the reperfusion phase of ischemia/reperfusion brain injury.Microdialysis allows for the direct measurement of extracellular molecules in an attempt to characterize metabolic derangements before they become clinically relevant. Advancements in technology have allowed for the bedside assay of multiple markers of ischemia and metabolic dysfunction, and the applications for traumatic brain injury have been well established. As clinicians become more comfortable with these tools their widespread use and potential for clinical impact with continue to rise.

Glial fibrillary acidic protein as a biomarker in severe traumatic brain injury patients: a prospective cohort study

Introduction

Glial fibrillary acidic protein (GFAP) may serve as a serum marker of traumatic brain injury (TBI) that can be used to monitor biochemical changes in patients and gauge the response to treatment. However, the temporal profile of serum GFAP in the acute period of brain injury and the associated utility for outcome prediction has not been elucidated.

Methods

We conducted a prospective longitudinal cohort study of consecutive severe TBI patients in a local tertiary neurotrauma center in Shanghai, China, between March 2011 and September 2014. All patients were monitored and managed with a standardized protocol with inclusion of hypothermia and other intensive care treatments. Serum specimens were collected on admission and then daily for the first 5 days. GFAP levels were measured using enzyme-linked immunosorbent assay techniques. Patient outcome was assessed at 6 months post injury with the Glasgow Outcome Scale and further grouped into death versus survival and unfavorable versus favorable.

Results

A total of 67 patients were enrolled in the study. The mean time from injury to admission was 2.6 hours, and the median admission Glasgow Coma Scale score was 6. Compared with healthy subjects, patients with severe TBI had increased GFAP levels on admission and over the subsequent 5 days post injury. Serum GFAP levels showed a gradual reduction from admission to day 3, and then rebounded on day 4 when hypothermia was discontinued with slow rewarming. GFAP levels were significantly higher in patients who died or had an unfavorable outcome across all time points than in those who were alive or had a favorable outcome. Results of receiver operating characteristic curve analysis indicated that serum GFAP at each time point could predict neurological outcome at 6 months. The areas under the curve for GFAP on admission were 0.761 for death and 0.823 for unfavorable outcome, which were higher than those for clinical variables such as age, Glasgow Coma Scale score, and pupil reactions.

Conclusions

Serum GFAP levels on admission and during the first 5 days of injury were increased in patients with severe TBI and were predictive of neurological outcome at 6 months.

A Systematic Review of the Effects of Body Temperature on Outcome After Adult Traumatic Brain Injury

OBJECTIVE

This systematic review describes effects of body temperature alterations defined as fever, controlled normothermia, and spontaneous or induced hypothermia on outcome after traumatic brain injury (TBI) in adults.

DATA SOURCES

A search was conducted using PubMed, Cochrane Library database, Cumulative Index to Nursing and Allied Health Literature, EMBASE, and ISI Web of Science in July 2013 with no back date restriction except for induced hypothermia (2009).

STUDY SELECTION

Of 1366 titles identified, 712 were reviewed. Sixteen articles met inclusion criteria: randomized controlled trials in hypothermia since 2009 (last Cochrane review) or cohort studies of temperature in TBI, measure core and/or brain temperature, neurologic outcome reporting, primarily adult patients, and English language publications. Exclusion criteria were as follows: most patients with non-TBI diagnosis, primarily pediatric patients, case reports, or laboratory/animal studies.

DATA SYNTHESIS

Most studies found that fever avoidance resulted in positive outcomes including decreased length of stay in the intensive care unit; mortality; and incidence of hypertension, elevated intracranial pressure, and tachycardia. Hypothermia on admission correlated with poor outcomes. Controlled normothermia improved surrogate outcomes. Prophylactic induced hypothermia is not supported by the available evidence from randomized controlled trial.

CONCLUSION

Setting a goal of normothermia, avoiding fever, and aggressively treating fever may be most important after TBI. Further research is needed to characterize the magnitude and duration of temperature alteration after TBI, determine if temperature alteration influences or predicts neurologic outcome, determine if rate of temperature change influences or predicts neurologic outcome, and compare controlled normothermia versus standard practice or hypothermia.

Rationale, methodology, and implementation of a nationwide multicenter randomized controlled trial of long-term mild hypothermia for severe traumatic brain injury (the LTH-1 trial)

BACKGROUND

Traumatic brain injury (TBI) is a major public health problem recently, however, no intervention showing convincing efficacy. Therapeutic hypothermia with a relatively long duration (more than 48 h), as a promising treatment measure, might improve the patient outcome following severe TBI.

METHODS/DESIGN

The LTH-1 trial is a prospective, nationwide multicenter, randomized, controlled clinical trial to examine the efficacy and safety of long-term mild hypothermia in adult patients after severe traumatic brain injury. A total of 300 consecutive patients will be recruited from 15 large neurosurgical centers in China. The eligible patient will be randomized to receive either long-term mild hypothermia (34-35 °C) for 5 days, or normothermia (36-37 °C). Additionally, a standardized management protocol will be used in all patients. The primary end point is the neurological outcome 6 months post-injury on the Glasgow Outcome Scale. The secondary outcomes include GOS score at one month post-injury, mortality during six months after injury, length of ICU and hospital stay, intracranial pressure control and Glasgow Coma Scale score during the hospital stay and frequency of complications during the six-month follow-up period.

DISCUSSION

Long-term hypothermia is recommended by most recent studies and its efficacy urgently needs to be established in randomized controlled settings. The LTH-1 trial, together with other ongoing studies, will present more evidence for optimal use of hypothermia in severe TBI patients.

Hypothermia enhances induction of protective protein metallothionein under ischemia

BACKGROUND

Hypothermic protection against ischemic stroke has been reported by many studies. Hypothermia is supposed to mitigate the effects of deleterious genes and proteins and promote the activity of protective genes and proteins in the ischemic brain. Metallothionein (MT)-1/2 is thought to be a crucial factor for metal homeostasis, immune function, and apoptosis. This protein was found to exert protective effects in models of brain injury as well. In the present study, we investigated the effect of hypothermia on MT expression and the underlying mechanisms.

METHODS

Cultured bEnd.3 brain endothelial cells were exposed to oxygen glucose deprivation and reperfusion (OGD+R). Reverse transcription PCR and western blot analyses were performed to measure the expression of MT, transcription factors, and methylation regulating factors. Transcription factor binding assays were also performed. Methylation profiles of the promoter area were obtained with pyrosequencing.

RESULTS

Hypothermia protected bEnd.3 cells from OGD+R. When the cells were exposed to OGD+R, MT expression was induced. Hypothermia augmented MT levels. While OGD+R-induced MT expression was mainly associated with metal regulatory transcription factor 1 (MTF-1), MT expression promoted by hypothermia was primarily mediated by the signal transducer and activator of transcription 3 (STAT3). Significantly increased STAT3 phosphorylation at Ser727 was observed with hypothermia, and JSI-124, a STAT-3 inhibitor, suppressed MT expression. The DNA demethylating drug 5-aza-2'-deoxycytidine (5-Aza) enhanced MT expression. Some of the CpG sites in the promoter MT=> it should be "the CpG sites in the MT promoter" showed different methylation profiles and some methylation regulating factors had different expressional profiles in the presence of OGD+R and hypothermia.

CONCLUSIONS

We demonstrated that hypothermia is a potent inducer of MT gene transcription in brain endothelial cells, and enhanced MT expression might contribute to protection against ischemia. MT gene expression is induced by hypothermia mainly through the STAT3 pathway. DNA methylation may contribute to MT gene regulation under ischemic or hypothermic conditions.

Neuroprotective effect of preoperatively induced mild hypothermia as determined by biomarkers and histopathological estimation in a rat subdural hematoma decompression model

OBJECT

In patients who have sustained a traumatic brain injury (TBI), hypothermia therapy has not shown efficacy in multicenter clinical trials. Armed with the post hoc data from the latest clinical trial (National Acute Brain Injury Study: Hypothermia II), the authors hypothesized that hypothermia may be beneficial in an acute subdural hematoma (SDH) rat model by blunting the effects of ischemia/reperfusion injury. The major aim of this study was to test the efficacy of temperature management in reducing brain damage after acute SDH.

METHODS

The rats were induced with acute SDH and placed into 1 of 4 groups: 1) normothermia group (37°C); 2) early hypothermia group, head and body temperature reduced to 33°C 30 minutes prior to craniotomy; 3) late hypothermia group, temperature lowered to 33°C 30 minutes after decompression; and 4) sham group, no acute SDH (only craniotomy with normothermia). To assess for neuronal and glial cell damage, the authors analyzed microdialysate concentrations of GFAP and ubiquitin carboxyl-terminal hydrolase-L1 (UCH-L1) by using a 100-kD probe. Fluoro-Jade B-positive neurons and injury volume with 2,3,5-triphenyltetrazolium chloride staining were also measured.

RESULTS

In the early phase of reperfusion (30 minutes, 2.5 hours after decompression), extracellular UCH-L1 in the early hypothermia group was significantly lower than in the normothermia group (early, 4.9 ± 1.0 ng/dl; late, 35.2 ± 12.1 ng/dl; normothermia, 50.20 ± 28.3 ng/dl; sham, 3.1 ± 1.3 ng/dl; early vs normothermia, p < 0.01; sham vs normothermia, p < 0.01, analyzed using ANOVA followed by a post hoc Bonferroni test). In the late phase of reperfusion (> 2.5 hours after decompression), extracellular GFAP in the early hypothermia group was also lower than in the normothermia and late hypothermia groups (early, 5.5 ± 2.9 ng/dl; late, 7.4 ± 3.4 ng/dl; normothermia, 15.3 ± 8.4 ng/dl; sham, 3.3 ± 1.0 ng/dl; normothermia vs sham; p < 0.01). The number of Fluoro-Jade B-positive cells in the early hypothermia group was significantly smaller than that in the normothermia group (normothermia vs early: 774,588 ± 162,173 vs 180,903 ± 42,212, p < 0.05). Also, the injury area and volume were smaller in the early hypothermia group in which hypothermia was induced before craniotomy and cerebral reperfusion (early, 115.2 ± 15.4 mm(3); late, 344.7 ± 29.1 mm(3); normothermia, 311.2 ± 79.2 mm(3); p < 0.05).

CONCLUSIONS

The data suggest that early, preoperatively induced hypothermia could mediate the reduction of neuronal and glial damage in the reperfusion phase of ischemia/reperfusion brain injury.

The Use of Hypothermia Therapy in Traumatic Ischemic / Reperfusional Brain Injury: Review of the Literatures

Therapeutic mild hypothermia has been used widely in brain injury. It has evaluated in numerous clinical trials, and there is strong evidence for the use of hypothermia in treating patients with several types of ischemic / reperfusional (I/R) injuries, examples being cardiac arrest and neonatal hypoxic-ischemic encephalopathy.In spite of many basic research projects demonstrating effectiveness, therapeutic hypothermia has not been proven effective for the heterogeneous group of traumatic brain injury patients in multicenter clinical trials. In the latest clinical trial, however, researchers were able to demonstrate the significant beneficial effects of hypothermia in one specific group; patients with mass evacuated lesions. This suggested that mild therapeutic hypothermia might be effective for I/R related traumatic brain injury.In this article we have reviewed much of the previous literature concerning the mechanisms of I/R injury to the protective effects of mild therapeutic hypothermia.

Hypothermia in Traumatic Brain Injury – A Literature Review

Traumatic brain injury is the leading cause of death in young people. Induced hypothermia has been used as a therapeutic intervention to improve outcome, based on results of animal studies. This article reviews the mechanisms of brain injury, the results of animal and human studies and the reasons that human studies do not always reflect the success seen in animal studies and why results may be ‘lost in translation’ to treatment of patients. It concludes by suggesting further areas of work to investigate the clinical use of therapeutic hypothermia.

The effect of therapeutic hypothermia on drug metabolism and response: cellular mechanisms to organ function

INTRODUCTION

Therapeutic hypothermia is being employed clinically due to its neuro-protective benefits. Both critical illness and therapeutic hypothermia significantly affect drug disposition, potentially contributing to drug-therapy and drug-disease interactions. Currently, there is limited information on the known alterations in drug concentration and response during mild hypothermia treatment, and there is a limited understanding of the specific mechanisms that underlie alterations in drug concentrations and the potential clinical importance of these changes.

AREAS COVERED

A systemic review of the effect of therapeutic hypothermia on drug metabolism, disposition and response is provided. Specifically, the clinical and preclinical evidence of the effects of therapeutic hypothermia on blood flow, specific hepatic metabolism pathways, transporter function, renal excretion, pharmacodynamics and the effects during rewarming are reviewed.

EXPERT OPINION

Available evidence demonstrates that mild hypothermia decreases the clearance of a variety of drugs with apparently little change in drug-protein binding. Recent evidence suggests that the magnitude of the change is elimination route specific. Further research is needed to determine the impact of these alterations on both drug concentration and response in order to optimize the therapeutic hypothermia in this vulnerable patient population.

Controversies of prophylactic hypothermia and the emerging use of brain tissue oxygen tension monitoring and decompressive craniectomy in traumatic brain-injured children

BACKGROUND

Despite being the leading cause of death and disability in the paediatric population, traumatic brain injury (TBI) in this group is largely understudied. Clinical practice within the paediatric intensive care unit (PICU) has been based upon adult guidelines however children are significantly different in terms of mechanism, pathophysiology and consequence of injury.

AIM

To review TBI management in the PICU and gain insight into potential management strategies.

METHOD

To conduct this review, a literature search was conducted using MEDLINE, PUBMED and The Cochrane Library using the following key words; traumatic brain injury; paediatric; hypothermia. There were no date restrictions applied to ensure that past studies, whose principles remain current were not excluded.

RESULTS

Three areas were identified from the literature search and will be discussed against current acknowledged treatment strategies: Prophylactic hypothermia, brain tissue oxygen tension monitoring and decompressive craniectomy.

CONCLUSION

Previous literature has failed to fully address paediatric specific management protocols and we therefore have little evidence-based guidance. This review has shown that there is an emerging and ongoing trend towards paediatric specific TBI research in particular the area of moderate prophylactic hypothermia (MPH).

Discrete cerebral hypothermia in the management of traumatic brain injury: a randomized controlled trial

OBJECT

Hypothermia has been extensively evaluated in the management of traumatic brain injury (TBI), but no consensus as to its effectiveness has yet been reached. Explanatory hypotheses include a possible confounding effect of the neuroprotective benefits by adverse systemic effects. To minimize the systemic effects, the authors evaluated a selective cerebral cooling system, the CoolSystem Discrete Cerebral Hypothermia System (a "cooling cap"), in the management of TBI.

METHODS

A prospective randomized controlled clinical trial was conducted at Grady Memorial Hospital, a Level I trauma center. Adults admitted with severe TBI (Glasgow Coma Scale [GCS] score < or = 8) were eligible. Patients assigned to the treatment group received the cooling cap, while those in the control group did not. Patients in the treatment group were treated with selective cerebral hypothermia for 24 hours, then rewarmed over 24 hours. Their intracranial and bladder temperatures, cranial-bladder temperature gradient, Glasgow Outcome Scale (GOS) and Functional Independence Measure (FIM) scores, and mortality rates were evaluated. The primary outcome was to establish a cranial-bladder temperature gradient in those patients with the cooling cap. The secondary outcomes were mortality and morbidity per GOS and FIM scores.

RESULTS

The cohort comprised 25 patients (12 in the treatment group, 13 controls). There was no significant intergroup difference in demographic data or median GCS score at enrollment (treatment group 3.0, controls 3.0; p = 0.7). After the third hour of the study, the mean intracranial temperature of the treatment group was significantly lower than that of the controls at all time points except Hours 4 (p = 0.08) and 6 (p = 0.08). However, the target intracranial temperature of 33 degrees C was achieved in only 2 patients in the treatment group. The mean intracranial-bladder temperature gradient was not significant for the treatment group (p = 0.07) or the controls (p = 0.67). Six (50.0%) of 12 patients in the treatment group and 4 (30.8%) of 13 in the control group died (p = 0.43). The medians of the maximum change in GOS and FIM scores during the study period (28 days) for both groups were 0. There was no significant difference in complications between the groups (p value range 0.20-1.0).

CONCLUSIONS

The cooling cap was not effective in establishing a statistically significant cranial-bladder temperature gradient or in reaching the target intracranial temperature in the majority of patients. No significant difference was achieved in mortality or morbidity between the 2 groups. As the technology currently stands, the Discrete Cerebral Hypothermia System cooling cap is not beneficial for the management of TBI. Further refinement of the equipment available for the delivery of selective cranial cooling will be needed before any definite conclusions regarding the efficacy of discrete cerebral hypothermia can be reached.

Cold-inducible RNA-binding protein bypasses replicative senescence in primary cells through extracellular signal-regulated kinase 1 and 2 activation

Embryonic stem cells are immortalized cells whose proliferation rate is comparable to that of carcinogenic cells. To study the expression of embryonic stem cell genes in primary cells, genetic screening was performed by infecting mouse embryonic fibroblasts (MEFs) with a cDNA library from embryonic stem cells. Cold-inducible RNA-binding protein (CIRP) was identified due to its ability to bypass replicative senescence in primary cells. CIRP enhanced extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, and treatment with an MEK inhibitor decreased the proliferation caused by CIRP. In contrast to CIRP upregulation, CIRP downregulation decreased cell proliferation and resulted in inhibition of phosphorylated ERK1/2 inhibition. This is the first evidence that ERK1/2 activation, through the same mechanism as that described for a Val12 mutant K-ras to induce premature senescence, is able to bypass senescence in the absence of p16(INK4a), p21(WAF1), and p19(ARF) upregulation. Moreover, these results show that CIRP functions by stimulating general protein synthesis with the involvement of the S6 and 4E-BP1 proteins. The overall effect is an increase in kinase activity of the cyclin D1-CDK4 complex, which is in accordance with the proliferative capacity of CIRP MEFs. Interestingly, CIRP mRNA and protein were upregulated in a subgroup of cancer patients, a finding that may be of relevance for cancer research.

Change in pharmacokinetics of model compounds with different elimination processes in rats during hypothermia

We compared the pharmacokinetics of model compounds with different elimination processes between hypothermic and normothermic rats, to obtain basic information concerning drug therapy during hypothermia. Male Wistar rats were anesthetized with sodium pentobarbital and kept at temperatures of 37 degrees C (normothermic group) by heat lamp, and 32 degrees C or 28 degrees C (hypothermic group) by external cooling. We chose phenolsulfonphthalein (PSP), indocyanine green (ICG) and fluorescein isothiocyanate (FITC)-dextran (FD-4, Mw 4400) as model compounds to determine changes in clearance pathways during hypothermia therapy. The plasma concentrations of PSP as biliary, urinary and metabolic elimination type were increased significantly in the hypothermic group (32 degrees C, 28 degrees C) after i.v. administration at a dose of 1 mg, compared to the normothermic group (37 degrees C). Each PSP clearance (bile, urine and metabolites) in the hypothermic group was decreased, suggesting an influence of hypothermia on the active elimination process. The decreasing tendency was marked at a temperature of 28 degrees C. Moreover, the plasma concentrations of ICG as the biliary excretion type after i.v. administration to the hypothermic rats at a dose of 1 mg were higher with more than 50% decrease in the total body clearance compared to normothermic rats. On the other hand, there was almost no difference in the i.v. pharmacokinetics of FD-4 as the urinary excretion type between 37 degrees C and 32 degrees C. However, renal clearance of FD-4 was significantly decreased at a temperature of 28 degrees C. Accordingly, the change in pharmacokinetics of a drug in the hypothermic group could differ with the elimination processes.

Hypothermia treatment potentiates ERK1/2 activation after traumatic brain injury

Traumatic brain injury (TBI) results in significant hippocampal pathology and hippocampal-dependent memory loss, both of which are alleviated by hypothermia treatment. To elucidate the molecular mechanisms regulated by hypothermia after TBI, rats underwent moderate parasagittal fluid-percussion brain injury. Brain temperature was maintained at normothermic or hypothermic temperatures for 30 min prior and up to 4 h after TBI. The ipsilateral hippocampus was assayed with Western blotting. We found that hypothermia potentiated extracellular signal-regulated kinase 1/2 (ERK1/2) activation and its downstream effectors, p90 ribosomal S6 kinase (p90RSK) and the transcription factor cAMP response element-binding protein. Phosphorylation of another p90RSK substrate, Bad, also increased with hypothermia after TBI. ERK1/2 regulates mRNA translation through phosphorylation of mitogen-activated protein kinase-interacting kinase 1 (Mnk1) and the translation factor eukaryotic initiation factor 4E (eIF4E). Hypothermia also potentiated the phosphorylation of both Mnk1 and eIF4E. Augmentation of ERK1/2 activation and its downstream signalling components may be one molecular mechanism that hypothermia treatment elicits to improve functional outcome after TBI.

Efecto de la hipotermia combinada con magnesio y tirilazad en un modelo experimental de isquemia cerebral difusa

OBJECTIVE

To determine the grade of neuroprotection of combined treatment with moderate hypothermia, tirilazad and magnesium sulfate. Cerebral ischemia is one of the problems of great interest at present, with limited therapeutic measures. Hypothermia, one of the more efficient measures, together with neuroprotector pharmaceuticals, could be a valid alternative.

DESIGN

Experimental study with a control group and two levels of application of therapeutic measures.

CONTEXT

Experimental laboratory of the Medicine Faculty.

PARTICIPANTS AND METHOD

Twenty-eight Wistar rats underwent global cerebral ischemia of 10 minutes duration by the combination of bilateral carotid clamping and controlled hypotension (mean arterial pressure: 45 mmHg). Three groups were used: group I, normothermia maintenance; group II, moderate hypothermia (32-33 degrees C) for 2 hours; group III, hypothermia and administration of tirilazad mesylate and magnesium sulfate during the reperfusion and two hours after ischemia. The animals were sacrificed at 7 days and, after processing the tissue, the neurons preserved in layer CA1 of the hippocampus were counted.

RESULTS

There is a significantly greater neuronal preservation in group III with regard to group I (55.4 +/- 5.1 versus 38.7 +/- 8.8, p < 0.0001). If we compare groups II and III, significant differences are only obtained on the right side and in the hippocampus considered globally, favoring the group with hypothermia and drugs. When groups I and II are compared there are no significant differences.

CONCLUSIONS

Association of moderate hypothermia, magnesium sulfate and tirilazad mesylate in the experimental model of transitory global ischemia used is confirmed as an effective neuroprotector measure, surpassing the degree of neuronal preservation of hypothermia alone.

Current status of cerebral protection with mild-to-moderate hypothermia after traumatic brain injury

PURPOSE OF REVIEW

The aim of this article is to review the current status of protective effects of mild-to-moderate hypothermia on traumatic brain injury.

RECENT FINDINGS

More than 30 clinical studies have reported effects of therapeutic hypothermia on outcome of traumatic brain injury and cerebral ischemia. Only one clinical trial of short-term mild hypothermia did not show any effect in patients with severe traumatic brain injury. Long-term mild hypothermia may be useful for severe traumatic brain-injured patients.

SUMMARY

Mild-to-moderate hypothermia plays a significant role in cerebral protection after traumatic brain injury.

Successful Use of Prolonged Mild Hypothermia in a Patient With Severe Head Injury and Diffuse Brain Swelling-Case Report-

A 19-year-old female was admitted to our hospital after severe head injury in a traffic accident. On admission, she had no spontaneous respiration, but did have heart beat with a blood pressure of 100/60 mmHg. Neurological examination demonstrated that the Glasgow Coma Scale score was 3 and her pupils were fixed and dilated. Computed tomography (CT) showed diffuse brain swelling with disappearance of the perimesencephalic cistern. Chest CT showed bilateral lung contusions. Mild hypothermia with a target temperature of 33 degrees C was immediately induced, and was continued for 28 days to control the persistent increase in intracranial pressure (ICP). Subsequently, she recovered, and 20 months after admission, could speak and walk with slight hemiparesis on the left. Prolonged mild hypothermia may be effective to control persistent increase in ICP due to diffuse brain swelling.

Effect of long-term mild hypothermia or short-term mild hypothermia on outcome of patients with severe traumatic brain injury

To compare the effect of long-term mild hypothermia versus short-term mild hypothermia on the outcome of 215 severe traumatic brain injured patients with cerebral contusion and intracranial hypertension. At three medical centers, 215 patients aged 18 to 45 years old with an admission Glasgow Coma Scale < or =8 within 4 h after injury were randomly divided into two groups: long-term mild hypothermia group (n = 108) for 5+/-1.3 days mild hypothermia therapy and short-term mild hypothermia group (n = 107) for 2+/-0.6 days mild hypothermia therapy. All patients had intracranial hypertension and frontotemporoparietal contusion with midline shift >1 cm confirmed on computed tomographic scan. Glasgow Outcome Scale at 6-month follow-up, 47 cases had favorable outcome (43.5%), and other 61 cases had unfavorable outcome (56.5%) in the long-term mild hypothermia group. However, only 31 cases had favorable outcome (29.0%), and other 76 cases had unfavorable outcome (71.0%) in the short-term mild hypothermia group (P < 0.05). The intracranial pressure significantly rebounded after rewarming in the short-term mild hypothermia group, but not in the long-term mild hypothermia (P < 0.05). Furthermore, the incidence of stress ulcer, epilepsy, pulmonary infection, intracranial infection did not significantly differ between the two groups (P > 0.05). Compared with short-term mild hypothermia, long-term mild hypothermia significantly improves the outcome of severe traumatic brain injured patients with cerebral contusion and intracranial hypertension without significant complications. Our data suggest that 5 days of long-term cooling is more efficacious than 2 days of short-term cooling when mild hypothermia is used to control refractory intracranial hypertension in patients with severe traumatic brain injury.

Cirp protects against tumor necrosis factor-alpha-induced apoptosis via activation of extracellular signal-regulated kinase

Mild hypothermia shows protective effects on patients with brain damage and cardiac arrest. To elucidate the molecular mechanisms underlying these effects, we analyzed the effects of low culture temperature (32 degrees C) and cold-inducible RNA-binding protein (Cirp) expression on apoptosis in vitro. In BALB/3T3 cells treated with tumor necrosis factor (TNF)-alpha and cycloheximide, the down-shift in temperature from 37 degrees C to 32 degrees C increased the expression of Cirp and suppressed the apoptosis. Activation of caspase-8 was suppressed, and the level of phosphorylated extracellular signal-regulated kinase (ERK) was increased. Transduction of Cirp into the Cirp-deficient mouse fibroblasts increased the level of phosphorylated ERK and suppressed the TNF-alpha-induced apoptosis both at 37 degrees C and 32 degrees C. The ERK-specific inhibitor PD98059 decreased the cytoprotective effect of Cirp as well as that of low culture temperature. These data suggest that mild hypothermia protects cells from TNF-alpha-induced apoptosis, at least partly, via induction of Cirp, and that Cirp protects cells by activating the ERK pathway.

CURRENT CONTROVERSIES IN THE MANAGEMENT OF PATIENTS WITH SEVERE TRAUMATIC BRAIN INJURY

BACKGROUND

Traumatic brain injury is a major cause of mortality and morbidity, particularly among young men. The efficacy and safety of most of the interventions used in the management of patients with traumatic brain injury remain unproven. Examples include the 'cerebral perfusion pressure-targeted' and 'volume-targeted' management strategies for optimizing cerebrovascular haemodynamics and specific interventions, such as hyperventilation, osmotherapy, cerebrospinal fluid drainage, barbiturates, decompressive craniectomy, therapeutic hypothermia, normobaric hyperoxia and hyperbaric oxygen therapy.

METHODS

A review of the literature was performed to examine the evidence base behind each intervention.

RESULTS

There is no class I evidence to support the routine use of any of the therapies examined.

CONCLUSION

Well-designed, large, randomized controlled trials are needed to determine therapies that are safe and effective from those that are ineffective or harmful.

The Effect of Hypothermia and Hyperthermia on Acute Brain Injury

The brain is extraordinarily susceptible to changes in temperature. Hyperthermia has been shown to exacerbate the biochemical cascade of secondary brain injury. Inversely, hypothermia limits the damaging effects of secondary brain injury. There has been a great deal of investigation regarding the detrimental effects of hyperthermia and the neuroprotection of hypothermia in animal studies. Within the last decade, clinical trials have begun to establish how the brain reacts to both temperature extremes. In the future, studies of hypothermia will continue in the quest of the optimal timing and degree of hypothermia. Hyperthermia will be examined in depth for its detrimental effects on an injured brain. Interventions for the prevention and treatment of hyperthermia will be explored. Nurses will implement cooling strategies to induce hypothermia, applying interventions to prevent complications, and they will also diagnose hyperthermia, deciding when and if to intervene pharmacologically and therapeutically. These advanced nursing actions will be guided by knowledge and understanding of available evidence. This article presents the pathophysiology of secondary brain injury and how it is affected by both hypothermia and hyperthermia. A review of the research leading up to clinical trials is explored, as well as a discussion of the future of temperature modulation for the brain injury patient. This information will help healthcare providers understand the effect that both hypothermia and hyperthermia have on the acutely injured brain.

Low temperature protects mammalian cells from apoptosis initiated by various stimuli in vitro

Mild hypothermia shows protective effects on patients with brain damage and cardiac arrest. To elucidate the molecular mechanisms underlying these effects, we examined the effects of low temperature (32 degrees C) on cells exposed to a variety of stress in vitro. We found that 32 degrees C suppressed induction of apoptosis by cytotoxic stimuli such as adriamycin, etoposide, thapsigargin, NaCl, H(2)O(2), and anti-Fas antibody. In adriamycin-treated BALB/3T3 cells, the down-shift in temperature from 37 degrees C to 32 degrees C increased the Bcl-xL protein level and decreased the mRNA level of Puma and mitochondrial translocation of Bax, suppressing caspase-9-mediated apoptosis. Furthermore, the protein level and stability of p53 were decreased, and its nuclear export was increased concomitant with Mdm2 mRNA upregulation. The low temperature effect was not observed in p53(-/-)/Mdm2(-/-) mouse embryonic fibroblasts, suggesting that the effect is mediated by suppression of the p53 pathway. In contrast, while thapsigargin-induced apoptosis was suppressed by the low temperature, no effect on the p53 protein level was observed. Furthermore, the survival rate of p53(-/-)/Mdm2(-/-) cells exposed to thapsigargin was increased when cultured at 32 degrees C compared with 37 degrees C. In conclusion, mild hypothermia protects cells from a variety of stress by p53-dependent and p53-independent mechanisms.

Commentary on the prevention of paralysis after traumatic spinal cord injury in humans: the neglected factor—urgent restoration of spinal cord circulation

Although advances in the management of spinal injuries during the past 60 years have led to greatly increased life expectancy for paralysed patients, most remain disabled. Around the world, spinal injury centres have become specialized rehabilitation units, where staff accepts the inevitability of persisting paralysis. In part, this pessimism has been based on incorrect information about the anatomy and function of the circulation of the spinal cord. Since the publication of accurate descriptions of the segmental nature of spinal vasculature, research and clinical data suggest that reversal or prevention of paralysis after spinal injury may be possible in many patients. These improved outcomes will depend on the recognition that urgent correction of cord blood supply in patients with traumatic spinal injury is critical to the long-term results of treatment. The creation of specialist spinal units within trauma centres for the urgent treatment of patients following spinal injury will require considerable logistical change, but has the potential to lead to a revolution in spinal care, driven by the knowledge that spinal cord function can often be saved.

Traumatic brain injury: physiology, mechanisms, and outcome

PURPOSE OF REVIEW

This review on traumatic brain injury consolidates the substantial current literature available on the pathophysiology, mechanisms, developments, and their subsequent effects on outcome. In particular, it tries to conceptualize why our greatly improved understanding of pathophysiology and neurobiology in traumatic brain injury has not translated into clear outcome improvements.

RECENT FINDINGS

Early cerebral ischaemia has been characterized further, with ischaemic brain volume correlating with 6-month outcome. The Brain Trauma Foundation has revised perfusion pressure targets, and there are additional data on the outcome impact of brain tissue oxygen response and asymmetric patterns of cerebral autoregulation. Mechanistic studies have highlighted the role of inflammation and introduced concepts such as therapeutic vaccination and immune modulation. Experimental neurogenesis and repair strategies show promise. Despite continuing gains in knowledge, the experimental successes have not yet translated to the clinic. Indeed, several major articles have attempted to understand the clinical failure of highly promising strategies such as hypothermia, and set out the framework for further studies (e.g. addressing decompressive craniectomy). High-dose mannitol has shown promise in poor grade patients, while hypertonic saline has shown better intracranial pressure control. Negative results may be the consequence of ineffective therapies. However, there is a gathering body of work that highlights the outcome impact of subtle neurocognitive changes, which may not be quantified adequately by outcome measures used in previous trials. Such knowledge has also informed improved definition of mild traumatic brain injury, and allowed validation of management guidelines.

SUMMARY

The evidence base for current therapies in this heterogeneous patient group is being refined, with greater emphasis on long-term functional outcomes. Improved monitoring techniques emphasize the need for individualization of therapeutic interventions.