Mild hypothermia therapy for patients with severe brain injury

Piezoelectricity, Pyroelectricity, and Ferroelectricity in Biomaterials and Biomedical Applications

Piezoelectric, pyroelectric, and ferroelectric materials are considered unique biomedical materials due to their dielectric crystals and asymmetric centers that allow them to directly convert various primary forms of energy in the environment, such as sunlight, mechanical energy, and thermal energy, into secondary energy, such as electricity and chemical energy. These materials possess exceptional energy conversion ability and excellent catalytic properties, which have led to their widespread usage within biomedical fields. Numerous biomedical applications have demonstrated great potential with these materials, including disease treatment, biosensors, and tissue engineering. For example, piezoelectric materials are used to stimulate cell growth in bone regeneration, while pyroelectric materials are applied in skin cancer detection and imaging. Ferroelectric materials have even found use in neural implants that record and stimulate electrical activity in the brain. This paper reviews the relationship between ferroelectric, piezoelectric, and pyroelectric effects and the fundamental principles of different catalytic reactions. It also highlights the preparation methods of these three materials and the significant progress made in their biomedical applications. The review concludes by presenting key challenges and future prospects for efficient catalysts based on piezoelectric, pyroelectric, and ferroelectric nanomaterials for biomedical applications.

A meta-analysis of the effects of therapeutic hypothermia in adult patients with traumatic brain injury

Purpose

Therapeutic hypothermia management remains controversial in patients with traumatic brain injury. We conducted a meta-analysis to evaluate the risks and benefits of therapeutic hypothermia management in patients with traumatic brain injury.

Methods

We searched the Web of Science, PubMed, Embase, Cochrane (Central) and Clinical Trials databases from inception to January 17, 2019. Eligible studies were randomised controlled trials that investigated therapeutic hypothermia management versus normothermia management in patients with traumatic brain injury. We collected the individual data of the patients from each included study. Meta-analyses were performed for 6-month mortality, unfavourable functional outcome and pneumonia morbidity. The risk of bias was evaluated using the Cochrane Risk of Bias tool.

Results

Twenty-three trials involving a total of 2796 patients were included. The randomised controlled trials with a high quality show significantly more mortality in the therapeutic hypothermia group [risk ratio (RR) 1.26, 95% confidence interval (CI) 1.04 to 1.53, p = 0.02]. Lower mortality in the therapeutic hypothermia group occurred when therapeutic hypothermia was received within 24 h (RR 0.83, 95% CI 0.71 to 0.96, p = 0.01), when hypothermia was received for treatment (RR 0.66, 95% CI 0.49 to 0.88, p = 0.006) or when hypothermia was combined with post-craniectomy measures (RR 0.69, 95% CI 0.48 to 1.00, p = 0.05). The risk of unfavourable functional outcome following therapeutic hypothermia management appeared to be significantly reduced (RR 0.78, 95% CI 0.67 to 0.91, p = 0.001). The meta-analysis suggested that there was a significant increase in the risk of pneumonia with therapeutic hypothermia management (RR 1.48, 95% CI 1.11 to 1.97, p = 0.007).

Conclusions

Our meta-analysis demonstrated that therapeutic hypothermia did not reduce but might increase the mortality rate of patients with traumatic brain injury in some high-quality studies. However, traumatic brain injury patients with elevated intracranial hypertension could benefit from hypothermia in therapeutic management instead of prophylaxis when initiated within 24 h.

Revisited: A Systematic Review of Therapeutic Hypothermia for Adult Patients Following Traumatic Brain Injury

OBJECTIVES

Therapeutic hypothermia has been of topical interest for many years and with the publication of two international, multicenter randomized controlled trials, the evidence base now needs updating. The aim of this systematic review of randomized controlled trials is to assess the efficacy of therapeutic hypothermia in adult traumatic brain injury focusing on mortality, poor outcomes, and new pneumonia.

DATA SOURCES

The following databases were searched from January 1, 2011, to January 26, 2018: Cochrane Central Register of Controlled Trial, MEDLINE, PubMed, and EMBASE.

STUDY SELECTION

Only foreign articles published in the English language were included. Only articles that were randomized controlled trials investigating adult traumatic brain injury sustained following an acute, closed head injury were included. Two authors independently assessed at each stage.

DATA EXTRACTION

Quality was assessed using the Cochrane Collaboration's tool for assessing the risk of bias. All extracted data were combined using the Mantel-Haenszel estimator for pooled risk ratio with 95% CIs. p value of less than 0.05 was considered statistically significant. All statistical analyses were conducted using RevMan 5 (Cochrane Collaboration, Version 5.3, Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014).

DATA SYNTHESIS

Twenty-two studies with 2,346 patients are included. Randomized controlled trials with a low risk of bias show significantly more mortality in the therapeutic hypothermia group (risk ratio, 1.37; 95% CI, 1.04-1.79; p = 0.02), whereas randomized controlled trials with a high risk of bias show the opposite with a higher mortality in the control group (risk ratio, 0.70; 95% CI, 0.60-0.82; p < 0.00001).

CONCLUSIONS

Overall, this review is in-keeping with the conclusions published by the most recent randomized controlled trials. High-quality studies show no significant difference in mortality, poor outcomes, or new pneumonia. In addition, this review shows a place for fever control in the management of traumatic brain injury.

Therapeutic hypothermia to reduce intracranial pressure after traumatic brain injury: the Eurotherm3235 RCT

BACKGROUND

Traumatic brain injury (TBI) is a major cause of disability and death in young adults worldwide. It results in around 1 million hospital admissions annually in the European Union (EU), causes a majority of the 50,000 deaths from road traffic accidents and leaves a further ≈10,000 people severely disabled.

OBJECTIVE

The Eurotherm3235 Trial was a pragmatic trial examining the effectiveness of hypothermia (32-35 °C) to reduce raised intracranial pressure (ICP) following severe TBI and reduce morbidity and mortality 6 months after TBI.

DESIGN

An international, multicentre, randomised controlled trial.

SETTING

Specialist neurological critical care units.

PARTICIPANTS

We included adult participants following TBI. Eligible patients had ICP monitoring in place with an ICP of > 20 mmHg despite first-line treatments. Participants were randomised to receive standard care with the addition of hypothermia (32-35 °C) or standard care alone. Online randomisation and the use of an electronic case report form (CRF) ensured concealment of random treatment allocation. It was not possible to blind local investigators to allocation as it was obvious which participants were receiving hypothermia. We collected information on how well the participant had recovered 6 months after injury. This information was provided either by the participant themself (if they were able) and/or a person close to them by completing the Glasgow Outcome Scale - Extended (GOSE) questionnaire. Telephone follow-up was carried out by a blinded independent clinician.

INTERVENTIONS

The primary intervention to reduce ICP in the hypothermia group after randomisation was induction of hypothermia. Core temperature was initially reduced to 35 °C and decreased incrementally to a lower limit of 32 °C if necessary to maintain ICP at < 20 mmHg. Rewarming began after 48 hours if ICP remained controlled. Participants in the standard-care group received usual care at that centre, but without hypothermia.

MAIN OUTCOME MEASURES

The primary outcome measure was the GOSE [range 1 (dead) to 8 (upper good recovery)] at 6 months after the injury as assessed by an independent collaborator, blind to the intervention. A priori subgroup analysis tested the relationship between minimisation factors including being aged < 45 years, having a post-resuscitation Glasgow Coma Scale (GCS) motor score of < 2 on admission, having a time from injury of < 12 hours and patient outcome.

RESULTS

We enrolled 387 patients from 47 centres in 18 countries. The trial was closed to recruitment following concerns raised by the Data and Safety Monitoring Committee in October 2014. On an intention-to-treat basis, 195 participants were randomised to hypothermia treatment and 192 to standard care. Regarding participant outcome, there was a higher mortality rate and poorer functional recovery at 6 months in the hypothermia group. The adjusted common odds ratio (OR) for the primary statistical analysis of the GOSE was 1.54 [95% confidence interval (CI) 1.03 to 2.31]; when the GOSE was dichotomised the OR was 1.74 (95% CI 1.09 to 2.77). Both results favoured standard care alone. In this pragmatic study, we did not collect data on adverse events. Data on serious adverse events (SAEs) were collected but were subject to reporting bias, with most SAEs being reported in the hypothermia group.

CONCLUSIONS

In participants following TBI and with an ICP of > 20 mmHg, titrated therapeutic hypothermia successfully reduced ICP but led to a higher mortality rate and worse functional outcome.

LIMITATIONS

Inability to blind treatment allocation as it was obvious which participants were randomised to the hypothermia group; there was biased recording of SAEs in the hypothermia group. We now believe that more adequately powered clinical trials of common therapies used to reduce ICP, such as hypertonic therapy, barbiturates and hyperventilation, are required to assess their potential benefits and risks to patients.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN34555414.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 45. See the NIHR Journals Library website for further project information. The European Society of Intensive Care Medicine supported the pilot phase of this trial.

Hypothermia Used in Medical Applications for Brain and Spinal Cord Injury Patients

Despite more than 80 years of animal experiments and clinical practice, efficacy of hypothermia in improving treatment outcomes in patients suffering from cell and tissue damage caused by ischemia is still ongoing. This review will first describe the history of utilizing cooling in medical treatment, followed by chemical and biochemical mechanisms of cooling that can lead to neuroprotection often observed in animal studies and some clinical studies. The next sections will be focused on current cooling approaches/devices, as well as cooling parameters recommended by researchers and clinicians. Animal and clinical studies of implementing hypothermia to spinal cord and brain tissue injury patients are presented next. This section will review the latest outcomes of hypothermia in treating patients suffering from traumatic brain injury (TBI), spinal cord injury (SCI), stroke, cardiopulmonary surgery, and cardiac arrest, followed by a summary of available evidence regarding both demonstrated neuroprotection and potential risks of hypothermia. Contributions from bioengineers to the field of hypothermia in medical treatment will be discussed in the last section of this review. Overall, an accumulating body of clinical evidence along with several decades of animal research and mathematical simulations has documented that the efficacy of hypothermia is dependent on achieving a reduced temperature in the target tissue before or soon after the injury-precipitating event. Mild hypothermia with temperature reduction of several degrees Celsius is as effective as modest or deep hypothermia in providing therapeutic benefit without introducing collateral/systemic complications. It is widely demonstrated that the rewarming rate must be controlled to be lower than 0.5 °C/h to avoid mismatch between local blood perfusion and metabolism. In the past several decades, many different cooling methods and devices have been designed, tested, and used in medical treatments with mixed results. Accurately designing treatment protocols to achieve specific cooling outcomes requires collaboration among engineers, researchers, and clinicians. Although this problem is quite challenging, it presents a major opportunity for bioengineers to create methods and devices that quickly and safely produce hypothermia in targeted tissue regions without interfering with routine medical treatment.

Optimization of brain metabolism using metabolic-targeted therapeutic hypothermia can reduce mortality from traumatic brain injury

BACKGROUND

Therapeutic hypothermia is widely used to treat traumatic brain injuries (TBIs). However, determining the best hypothermia therapy strategy remains a challenge. We hypothesized that reducing the metabolic rate, rather than reaching a fixed body temperature, would be an appropriate target because optimizing metabolic conditions especially the brain metabolic environment may enhance neurologic protection. A pilot single-blind randomized controlled trial was designed to test this hypothesis, and a nested metabolomics study was conducted to explore the mechanics thereof.

METHODS

Severe TBI patients (Glasgow Coma Scale score, 3-8) were randomly divided into the metabolic-targeted hypothermia treatment (MTHT) group, 50% to 60% rest metabolic ratio as the hypothermia therapy target, and the body temperature-targeted hypothermia treatment (BTHT) control group, hypothermia therapy target of 32°C to 35°C body temperature. Brain and circulatory metabolic pool blood samples were collected at baseline and on days 1, 3, and 7 during the hypothermia treatment, which were selected randomly from a subgroup of MTHT and BTHT groups. The primary outcome was mortality. Using H nuclear magnetic resonance technology, we tracked and located the disturbances of metabolic networks.

RESULTS

Eighty-eight severe TBI patients were recruited and analyzed from December 2013 to December 2014, 44 each were assigned in the MTHT and BTHT groups (median age, 42 years; 69.32% men; mean Glasgow Coma Scale score, 6.17 ± 1.02). The mortality was significantly lower in the MTHT than the BTHT group (15.91% vs. 34.09%; p = 0.049). From these, eight cases of MTHT and six cases from BTHT group were enrolled for metabolomics analysis, which showed a significant difference between the brain and circulatory metabolic patterns in MTHT group on day 7 based on the model parameters and scores plots. Finally, metabolites representing potential neuroprotective monitoring parameters for hypothermia treatment were identified through H nuclear magnetic resonance metabolomics.

CONCLUSION

MTHT can significantly reduce the mortality of severe TBI patients. Metabolomics research showed that this strategy could effectively improve brain metabolism, suggesting that reducing the metabolic rate to 50% to 60% should be set as the hypothermia therapy target.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Meta-Analysis of Therapeutic Hypothermia for Traumatic Brain Injury in Adult and Pediatric Patients

OBJECTIVE

Therapeutic hypothermia has been used to attenuate the effects of traumatic brain injuries. However, the required degree of hypothermia, length of its use, and its timing are uncertain. We undertook a comprehensive meta-analysis to quantify benefits of hypothermia therapy for traumatic brain injuries in adults and children by analyzing mortality rates, neurologic outcomes, and adverse effects.

DATA SOURCES

Electronic databases PubMed, Google Scholar, Web of Science, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov and manual searches of studies were conducted for relevant publications up until February 2016.

STUDY SELECTION

Forty-one studies in adults (n = 3,109; age range, 18-81 yr) and eight studies in children (n = 454; age range, 3 mo to 18 yr) met eligibility criteria.

DATA EXTRACTION

Baseline patient characteristics, enrollment time, methodology of cooling, target temperature, duration of hypothermia, and rewarming protocols were extracted.

DATA SYNTHESIS

Risk ratios with 95% CIs were calculated. Compared with adults who were kept normothermic, those who underwent therapeutic hypothermia were associated with 18% reduction in mortality (risk ratio, 0.82; 95% CI, 0.70-0.96; p = 0.01) and a 35% improvement in neurologic outcome (risk ratio, 1.35; 95% CI, 1.18-1.54; p < 0.00001). The optimal management strategy for adult patients included cooling patients to a minimum of 33°C for 72 hours, followed by spontaneous, natural rewarming. In contrast, adverse outcomes were observed in children who underwent hypothermic treatment with a 66% increase in mortality (risk ratio, 1.66; 95% CI, 1.06-2.59; p = 0.03) and a marginal deterioration of neurologic outcome (risk ratio, 0.90; 95% CI, 0.80-1.01; p = 0.06).

CONCLUSIONS

Therapeutic hypothermia is likely a beneficial treatment following traumatic brain injuries in adults but cannot be recommended in children.

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.

Therapeutic hypothermia versus normothermia in adult patients with traumatic brain injury: a meta-analysis

INTRODUCTION

Many single-center studies and meta-analyses demonstrate that therapeutic hypothermia (TH), in which the body temperature is maintained at 32-35°C, exerts significant neuroprotection and attenuates secondary intracranial hypertension after traumatic brain injury (TBI). In 2015, two well-designed multi-center, randomized controlled trials were published that did not show favorable outcomes with the use of TH in adult patients with TBI compared to normothermia treatment (NT). Therefore, we performed an updated meta-analysis to assess the effect of TH in adult patients with TBI.

METHODS

We reviewed the PubMed, EMbase, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure, and Wanfang Databases. We included randomized controlled trials that compared TH and NT in adult patients with TBI. Two reviewers assessed the quality of each study and independently collected the data. We performed the meta-analysis using the Cochrane Collaboration's RevMan 5.3 software.

RESULTS

We included 18 trials involving 2177 patients with TBI. There was no significant heterogeneity among the studies. TH could not decrease mortality at 3 months post-TBI (RR 0.95; 95 % CI 0.59, 1.55; z = 0.19, P = 0.85) or 6 months post-TBI (RR 0.96; 95 % CI 0.76, 1.23; z = 0.29, P = 0.77). There were no significant differences in unfavorable clinical outcomes when TH was compared to NT at 3 months post-TBI (RR 0.79; 95 % CI 0.56, 1.12; z = 1.31, P = 0.19) or 6 months post-TBI (RR 0.80; 95 % CI 0.63, 1.00; z = 1.92, P = 0.05). TH was associated with a significant increase in pneumonia (RR 1.51; 95 % CI 1.12, 2.03; z = 2.72, P = 0.006) and cardiovascular complications (RR 1.75; 95% CI 1.14, 2.70; z = 2.54, P = 0.01).

CONCLUSIONS

Therapeutic hypothermia failed to demonstrate a decrease in mortality and unfavorable clinical outcomes at 3 or 6 months post-TBI. Additionally, TH might increase the risk of developing pneumonia and cardiovascular complications.

Mild hypothermia for treatment of diffuse axonal injury: a quantitative analysis of diffusion tensor imaging

Fractional anisotropy values in diffusion tensor imaging can quantitatively reflect the consistency of nerve fibers after brain damage, where higher values generally indicate less damage to nerve fibers. Therefore, we hypothesized that diffusion tensor imaging could be used to evaluate the effect of mild hypothermia on diffuse axonal injury. A total of 102 patients with diffuse axonal injury were randomly divided into two groups: normothermic and mild hypothermic treatment groups. Patient's modified Rankin scale scores 2 months after mild hypothermia were significantly lower than those for the normothermia group. The difference in average fractional anisotropy value for each region of interest before and after mild hypothermia was 1.32-1.36 times higher than the value in the normothermia group. Quantitative assessment of diffusion tensor imaging indicates that mild hypothermia therapy may be beneficial for patients with diffuse axonal injury.

Therapeutic temperature modulation in severe or moderate traumatic brain injury: a propensity score analysis of data from the Nationwide Japan Neurotrauma Data Bank

OBJECTIVE

In patients with severe traumatic brain injury (TBI), a randomized controlled trial revealed that outcomes did not significantly improve after therapeutic hypothermia (TH) or normothermia (TN). However, avoiding pyrexia, which is often associated with intracranial disorders, might improve clinical outcomes. The objective of this study was to compare neurological outcomes among patients with moderate and severe TBI after therapeutic temperature modulation (TTM) in the absence of other interventions.

METHODS

Data from 1091 patients were obtained from the Japan Neurotrauma Data Bank Project 2009, a cohort observational study. Patients with cardiac arrest, those with a Glasgow Coma Scale score of 3 and dilated fixed pupils, and those whose cause of death was injury to another area of the body were excluded, leaving 687 patients aged 16 years or older in this study. The patients were divided into 2 groups: the TTM group underwent TN (213 patients) or TH (82 patients), and the control group (392 patients) did not receive TTM. The primary end point for this study was the rate of poor outcome at hospital discharge, and the secondary end point was in-hospital death. Out of the 208 total items in the database, 29 variables that could potentially affect outcome were matched using the propensity score (PS) method in order to reduce selection bias and balance the baseline characteristics.

RESULTS

From each group, 141 patients were extracted using the PS-matching process. Among the patients in the TTM group, 29 had undergone TH and 112 had undergone TN. In a log-rank test using Kaplan-Meier survival curves, no significant differences in patient outcome or death were observed between the 2 groups (poor outcome, p = 0.83; death, p = 0.18). A Cox proportional-hazards regression analysis established the HR for poor outcome and mortality at 1.03 (95% CI 0.78-1.36, p = 0.83) and 1.34 (95% CI 0.87-2.07, p = 0.18), respectively.

CONCLUSIONS

There was no clear improvement in neurological outcomes after TTM in patients with moderate or severe TBI. To elucidate the role of TTM in patients with these injuries, a prospective study is needed with long-term follow-up using specific target temperatures.

Therapeutic Hypothermia Reduces Intracranial Pressure and Partial Brain Oxygen Tension in Patients with Severe Traumatic Brain Injury: Preliminary Data from the Eurotherm3235 Trial

Traumatic brain injury (TBI) is a significant cause of disability and death and a huge economic burden throughout the world. Much of the morbidity associated with TBI is attributed to secondary brain injuries resulting in hypoxia and ischemia after the initial trauma. Intracranial hypertension and decreased partial brain oxygen tension (PbtO2) are targeted as potentially avoidable causes of morbidity. Therapeutic hypothermia (TH) may be an effective intervention to reduce intracranial pressure (ICP), but could also affect cerebral blood flow (CBF). This is a retrospective analysis of prospectively collected data from 17 patients admitted to the Western General Hospital, Edinburgh. Patients with an ICP >20 mmHg refractory to initial therapy were randomized to standard care or standard care and TH (intervention group) titrated between 32°C and 35°C to reduce ICP. ICP and PbtO2 were measured using the Licox system and core temperature was recorded through rectal thermometer. Data were analyzed at the hour before cooling, the first hour at target temperature, 2 consecutive hours at target temperature, and after 6 hours of hypothermia. There was a mean decrease in ICP of 4.3±1.6 mmHg (p<0.04) from 15.7 to 11.4 mmHg, from precooling to the first epoch of hypothermia in the intervention group (n=9) that was not seen in the control group (n=8). A decrease in ICP was maintained throughout all time periods. There was a mean decrease in PbtO2 of 7.8±3.1 mmHg (p<0.05) from 30.2 to 22.4 mmHg, from precooling to stable hypothermia, which was not seen in the control group. This research supports others in demonstrating a decrease in ICP with temperature, which could facilitate a reduction in the use of hyperosmolar agents or other stage II interventions. The decrease in PbtO2 is not below the suggested treatment threshold of 20 mmHg, but might indicate a decrease in CBF.

Cooling for cerebral protection during brain surgery

BACKGROUND

Patients undergoing neurosurgery are at risk of cerebral ischaemia with resultant cerebral hypoxia and neuronal cell death. This can increase both the risk of mortality and long term neurological disability. Induced hypothermia has been shown to reduce the risk of cerebral ischaemic damage in both animal studies and in humans who have been resuscitated following cardiac arrest. This had lead to an increasing interest in its neuroprotective potential in neurosurgical patients. This review was originally published in 2011 and did not find any evidence of either effectiveness or harm in these patients. This updated review was designed to capture current evidence to readdress these issues.

OBJECTIVES

To evaluate the effectiveness and safety profile of induced hypothermia versus normothermia for neuroprotection in patients undergoing brain surgery. Effectiveness was to be measured in terms of short and long term mortality and functional neurological outcomes. Safety was to be assessed in terms of the rate of the adverse events infection, myocardial infarction, ischaemic stroke, congestive cardiac failure and any other adverse events reported by the authors of the included studies.

SEARCH METHODS

For the original review, the authors searched the databases Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OvidSP), EMBASE (OvidSP) and LILACS to November 2010. For the updated review all these databases were re-searched from November 2010 to May 2014.For both the original and updated versions, grey literature was sought by searching reference lists of identified studies and relevant review articles, and conference proceedings. No language restrictions were applied.

SELECTION CRITERIA

As in the original review, we included randomized controlled trials (RCTs) of induced hypothermia versus normothermia for neuroprotection in patients of any age and gender undergoing brain surgery, which addressed mortality, neurological morbidity or adverse event outcomes.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted data and two independently assessed the risk of bias of the included studies. Any discrepancies were resolved by discussion between authors.

MAIN RESULTS

In this updated review, one new ongoing study was found but no new eligible completed studies were identified. This update was therefore conducted using the same four studies included in the original review. These studies included a total of 1219 participants, mean age 40 to 54 years. All included studies were reported as RCTs. Two were multicentred, together including a total of 1114 patients who underwent cerebral aneurysm clipping, and were judged to have an overall low risk of bias. The other two studies were single centred. One included 80 patients who had a craniotomy following severe traumatic brain injury and was judged to have an unclear or low risk of bias. The other study included 25 patients who underwent hemicranicectomy to relieve oedema following cerebral infarction and was judged to have an unclear or high risk of bias. All studies assessed hypothermia versus normothermia. Overall 608 participants received hypothermia with target temperatures ranging from 32.5 °C to 35 °C, and 611 were assigned to normothermia with the actual temperatures recorded in this group ranging form 36.5 °C to 38 °C. For those who were cooled, 556 had cooling commenced immediately after induction of anaesthesia that was continued until the surgical objective of aneurysm clipping was achieved, and 52 had cooling commenced immediately after surgery and continued for 48 to 96 hours.Pooled estimates of effect were calculated for the outcomes mortality during treatment or follow-up (ranging from in-hospital to one year); neurological outcome measured in terms of the Glasgow Outcome Score (GOS) of 3 or less; and adverse events of infections, myocardial infarction, ischaemic stroke and congestive cardiac failure. With regards to mortality, the risk of dying if allocated to hypothermia compared to normothermia was not statistically significantly different (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.59 to 1.27, P = 0.47). There was no indication that the time at which cooling was started affected the risk of dying (RR with intraoperative cooling 0.95, 95% CI 0.60 to 1.51, P = 0.83; RR for cooling postoperatively 0.67, 95% CI 0.34 to 1.35, P = 0.26). For the neurological outcome, the risk of having a poor outcome with a GOS of 3 or less was not statistically different in those who received hypothermia versus normothermia (RR 0.80, 95% CI 0.61 to 1.04, P = 0.09). Again there was no indication that the time at which cooling was started affected this result. Regarding adverse events, there was no statistically significant difference in the incidence in those allocated to hypothermia versus normothermia for risk of surgical infection (RR 1.20, 95% CI 0.73 to 1.97, P = 0.48), myocardial infarction (RR 1.86, 95% CI 0.69 to 4.98, P = 0.22), ischaemic stroke (RR 0.93, 95% CI 0.82 to 1.05, P = 0.24) or congestive heart failure (RR 0.85, 95% CI 0.60 to 1.21, P = 0.38). In contrast to other outcomes, where time of application of cooling did not change the statistical significance of the effect estimates, there was a weak statistically significant increased risk of infection in those who were cooled postoperatively versus those who were not cooled (RR 1.77, 95% CI 1.05 to 2.98, P = 0.03). Overall, as in the original review, no evidence was found that the use of induced hypothermia was either beneficial or harmful in patients undergoing neurosurgery.

AUTHORS' CONCLUSIONS

We found no evidence that the use of induced hypothermia was associated with a significant reduction in mortality or severe neurological disability, or an increase in harm in patients undergoing neurosurgery.

The use of targeted temperature management for elevated intracranial pressure

The use of hypothermia for treatment of intracranial hypertension is controversial, despite no other medical therapy demonstrating consistent improvements in morbidity or mortality. Much of this may be the result of negative results from randomized controlled trials. However, the patients selected for these trials may have obscured the results in the populations most likely to benefit. Further, brain injury does not behave uniformly, not even within a diagnosis. Therefore, therapies may have more benefit in some diseases, less in others. This review focuses on the effect on outcome of intracranial hypertension in common disease processes in the neurocritical care unit, and identifies who is most likely to benefit from the use of hypothermia.

Better Glasgow outcome score, cerebral perfusion pressure and focal brain oxygenation in severely traumatized brain following direct regional brain hypothermia therapy: A prospective randomized study

BACKGROUND

Induced hypothermia for treatment of traumatic brain injury is controversial. Since many pathways involved in the pathophysiology of secondary brain injury are temperature dependent, regional brain hypothermia is thought capable to mitigate those processes. The objectives of this study are to assess the therapeutic effects and complications of regional brain cooling in severe head injury with Glasgow coma scale (GCS) 6-7.

MATERIALS AND METHODS

A prospective randomized controlled pilot study involving patients with severe traumatic brain injury with GCS 6 and 7 who required decompressive craniectomy. Patients were randomized into two groups: Cooling and no cooling. For the cooling group, analysis was made by dividing the group into mild and deep cooling. Brain was cooled by irrigating the brain continuously with cold Hartmann solution for 24-48 h. Main outcome assessments were a dichotomized Glasgow outcome score (GOS) at 6 months posttrauma.

RESULTS

A total of 32 patients were recruited. The cooling-treated patients did better than no cooling. There were 63.2% of patients in cooling group attained good GOS at 6 months compared to only 15.4% in noncooling group (P = 0.007). Interestingly, the analysis at 6 months post-trauma disclosed mild-cooling-treated patients did better than no cooling (70% vs. 15.4% attained good GOS, P = 0.013) and apparently, the deep-cooling-treated patients failed to be better than either no cooling (P = 0.074) or mild cooling group (P = 0.650).

CONCLUSION

Data from this pilot study imply direct regional brain hypothermia appears safe, feasible and maybe beneficial in treating severely head-injured patients.

A systematic review of therapeutic hypothermia for adult patients following traumatic brain injury

Introduction

Research into therapeutic hypothermia following traumatic brain injury has been characterised by small trials of poor methodological quality, producing variable results. The Cochrane review, published in 2009, now requires updating. The aim of this systematic review is to assess the effectiveness of the application of therapeutic hypothermia to reduce death and disability when administered to adult patients who have been admitted to hospital following traumatic brain injury.

Methods

Two authors extracted data from each trial. Unless stated in the trial report, relative risks and 95% confidence intervals (CIs) were calculated for each trial. We considered P < 0 · 05 to be statistically significant. We combined data from all trials to estimate the pooled risk ratio (RR) with 95% confidence intervals for death, unfavourable outcome, and pneumonia. All statistical analyses were performed using RevMan 5.1 (Cochrane IMS, Oxford, UK) and Stata (Intercooled Version 12.0, StataCorp LP). Pooled RRs were calculated using the Mantel-Haenszel estimator. The random effects model of DerSimonian and Laird was used to estimate variances for the Mantel-Haenszel and inverse variance estimators.

Results

Twenty studies are included in the review, while 18 provided mortality data. When the results of 18 trials that evaluated mortality as one of the outcomes were statistically aggregated, therapeutic hypothermia was associated with a significant reduction in mortality and a significant reduction in poor outcome. There was a lack of statistical evidence for an association between use of therapeutic hypothermia and increased onset of new pneumonia.

Conclusions

In contrast to previous reviews, this systematic review found some evidence to suggest that therapeutic hypothermia may be of benefit in the treatment of traumatic brain injury. The majority of trials were of low quality, with unclear allocation concealment. Low quality trials may overestimate the effectiveness of hypothermia treatment versus standard care. There remains a need for more, high quality, randomised control trials of therapeutic hypothermia after traumatic brain injury.

PROSPERO Systematic Review Registration Number 2012: CRD42012002449.

Therapeutic Hypothermia in Children and Adults with Severe Traumatic Brain Injury

Great expectations have been raised about neuroprotection of therapeutic hypothermia in patients with traumatic brain injury (TBI) by analogy with its effects after heart arrest, neonatal asphyxia, and drowning in cold water. The aim of this study is to review our present knowledge of the effect of therapeutic hypothermia on outcome in children and adults with severe TBI. A literature search for relevant articles in English published from year 2000 up to December 2013 found 19 studies. No signs of improvement in outcome from hypothermia were seen in the five pediatric studies. Varied results were reported in 14 studies on adult patients, 2 of which reported a tendency of higher mortality and worse neurological outcome, 4 reported lower mortality, and 9 reported favorable neurological outcome with hypothermia. The quality of several trials was low. The best-performed randomized studies showed no improvement in outcome by hypothermia-some even indicated worse outcome. TBI patients may suffer from hypothermia-induced pulmonary and coagulation side effects, from side effects of vasopressors when re-establishing the hypothermia-induced lowered blood pressure, and from a rebound increase in intracranial pressure (ICP) during and after rewarming. The difference between body temperature and temperature set by the biological thermostat may cause stress-induced worsening of the circulation and oxygenation in injured areas of the brain. These mechanisms may counteract neuroprotective effects of therapeutic hypothermia. We conclude that we still lack scientific support as a first-tier therapy for the use of therapeutic hypothermia in TBI patients for both adults and children, but it may still be an option as a second-tier therapy for refractory intracranial hypertension.

The effect of admission spontaneous hypothermia on patients with severe traumatic brain injury

INTRODUCTION

Recent information has emerged regarding the harmful effects of spontaneous hypothermia at time of admission in trauma patients. However the volume of evidence regarding the role of spontaneous hypothermia in TBI patients is inadequate.

METHODS

We performed secondary data analysis of 10 years of the Pennsylvania trauma outcome study (PTOS) database. Unadjusted comparisons of the association of admission spontaneous hypothermia with mortality were performed. In addition, full assessment of the association of hypothermia with mortality was conducted using multivariable logistic regressions reporting the odds ratios (OR) with the 95% confidence intervals (CI) and P-values.

RESULTS

There were 11,033 patients identified from the PTOS with severe TBI. There were 4839 deaths (43.9%). The proportion of deaths in hypothermic patients was higher than the proportion of deaths in normothermic patients (53.9% vs. 37.4% respectively; P value<0.001). In a multivariable logistic regression model adjusted for demographics, injury characteristics, and information at admission to the trauma centre, the odds of death among patients with hypothermia were 1.70 times the odds of death among patients with normothermia (OR 1.70, 95% CI 1.50-1.93), indicating that the probability of death was significantly higher when patients arrived hypothermic at the trauma centre.

CONCLUSION

The presence of spontaneous hypothermia at hospital admission is associated with a significant increase in the risk of mortality in patients with severe TBI. The benefit of maintaining normothermia in severe TBI patients, the impact of prolonged re-warming in patients with established hypothermia and the introduction of prophylactic measures to complications of hypothermia are key points that require further investigation.

The study of systemic general circulation disturbance during the initiation of therapeutic hypothermia: Pit fall of hypothermia

Aims:

Neurointensive care has reduced the mortality and improved the outcome of patients for severe brain damage, over recent decades, and made it possible to perform this therapy in safety. However, we have to understand the complications of this therapy well. The purpose of our study was to determine the systemic circulation disturbance during the initiation of therapeutic hypothermia by using this continuous neurointensive monitoring system.

Materials and Methods:

Ten severe brain damage patients treated with hypothermia were enrolled. All patients had Glasgow Coma Scale (GCS) less than or equal to 8, on admission.

Results:

We verified that heart rate, cardiac output, and oxygen delivery index (DO2I) decreased with decreasing core temperature. We recognized that depressed cardiac index (CI) was attributed to bradycardia, dehydration, and increased systemic vascular resistance index (SVRI) upon initiation of hypothermia.

Conclusion:

Although the hypothermia has a therapeutic role in severe brain damage patients, we have to carry out this therapy while maintaining their cardiac output using multimodality monitoring devices during hypothermia period.

Therapeutic hypothermia for the management of intracranial hypertension in severe traumatic brain injury: a systematic review

BACKGROUND

Traumatic brain injury (TBI) is a major source of death and severe disability worldwide. Raised Intracranial pressure (ICP) is an important predictor of mortality in patients with severe TBI and aggressive treatment of elevated ICP has been shown to reduce mortality and improve outcome. The acute post-injury period in TBI is characterized by several pathophysiologic processes that start in the minutes to hours following injury. All of these processes are temperature-dependent; they are all aggravated by fever and inhibited by hypothermia.

METHODS

This study reviewed the current clinical evidence in support of the use of therapeutic hypothermia (TH) for the treatment of intracranial hypertension (ICH) in patients with severe TBI.

RESULTS

This study identified a total of 18 studies involving hypothermia for control of ICP; 13 were randomized controlled trials (RCT) and five were observational studies. TH (32-34°C) was effective in controlling ICH in all studies. In the 13 RCT, ICP in the TH group was always significantly lower than ICP in the normothermia group. In the five observational studies, ICP during TH was always significantly lower than prior to inducing TH.

CONCLUSIONS

Pending results from large multi-centre studies evaluating the effect of TH on ICH and outcome, TH should be included as a therapeutic option to control ICP in patients with severe TBI.

Cooling for cerebral protection during brain surgery

BACKGROUND

The brain is at risk of ischaemia during a variety of neurosurgical procedures, and this can lead to devastating results. Induced hypothermia is the controlled lowering of core body temperature for therapeutic purposes. This remains the current practice during neurosurgery for the prevention or minimization of ischaemic brain injury. Brain surgery may lead to severe complications due to factors such as requirement for brain retraction, vessel occlusion, and intraoperative haemorrhage. Many anaesthesiologists believe that induced hypothermia is indicated to protect the central nervous system during surgery. Although hypothermia is often used during brain surgery, clinical efficacy has not yet been established.

OBJECTIVES

To evaluate the effectiveness and safety of induced hypothermia versus normothermia for neuroprotection in patients undergoing brain surgery.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 10), MEDLINE, LILACS, EMBASE and Current Controlled Trials (from inception to November 2010), reference lists of identified trials, and bibliographies of published reviews. We also contacted researchers in the field. There were no language restrictions.

SELECTION CRITERIA

We included randomized controlled trials and quasi-randomized controlled trials of induced hypothermia versus normothermia for neuroprotection in patients undergoing brain surgery.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We contacted study authors for additional information.

MAIN RESULTS

We included four trials of cooling for cerebral protection during brain surgery, involving a total of 1219 patients. We did not find any evidence that hypothermia for neuroprotection in patients undergoing brain surgery is either effective or unsafe when compared to normothermia.

AUTHORS' CONCLUSIONS

Although there is some evidence that mild hypothermia is safe, its effectiveness is not clear when compared with normothermia. We need to perform more clinical trials in order to establish the benefit, if any, of hypothermia for cerebral protection during brain surgery before making firm recommendations for the routine use of this intervention.

Contemporary management of traumatic intracranial hypertension: is there a role for therapeutic hypothermia?

OBJECTIVE

Intracranial hypertension (ICH) remains the single most difficult therapeutic challenge for the acute management of severe traumatic brain injury (TBI). We reviewed the published trials of therapeutic moderate hypothermia to determine its effect on ICH and compared its efficacy to other commonly used therapies for ICH.

METHODS

A PubMed database search was done using various combinations of the search terms "brain injury," "therapeutic hypothermia," "intracranial hypertension," "barbiturates," "mannitol," "hypertonic saline," "hyperventilation," "decompressive craniectomy," and "CSF drainage."

RESULTS

We identified 11 prospective randomized clinical TBI trials comparing hypothermia vs. normothermia treatment for which intracranial pressure (ICP) data was provided, and 6 prospective cohort studies that provided ICP data before and during hypothermia treatment. In addition, we identified 37 clinical TBI studies of lumbar CSF drainage, mannitol, hyperventilation, barbiturates, hypertonic saline, and decompressive craniectomy that provided pre- and posttreatment ICP data. Hypothermia was at least as effective as the traditional therapies for ICH (hyperventilation, mannitol, and barbiturates), but was less effective than hypertonic saline, lumbar CSF drainage, and decompressive craniectomy. Ultimately, however, therapeutic hypothermia does appear to have a favorable risk/benefit profile.

CONCLUSION

Therapeutic moderate hypothermia is as effective, or more effective, than most other treatments for ICH. If used for 2-3 days or less there is no evidence that it causes clinically significant adverse events. The lack of consistent evidence that hypothermia improves long-term neurologic outcome should not preclude consideration of its use for the primary treatment of ICH since no other ICP therapy is held to this standard.

European society of intensive care medicine study of therapeutic hypothermia (32-35 °C) for intracranial pressure reduction after traumatic brain injury (the Eurotherm3235Trial)

BACKGROUND

Traumatic brain injury is a major cause of death and severe disability worldwide with 1,000,000 hospital admissions per annum throughout the European Union.Therapeutic hypothermia to reduce intracranial hypertension may improve patient outcome but key issues are length of hypothermia treatment and speed of re-warming. A recent meta-analysis showed improved outcome when hypothermia was continued for between 48 hours and 5 days and patients were re-warmed slowly (1 °C/4 hours). Previous experience with cooling also appears to be important if complications, which may outweigh the benefits of hypothermia, are to be avoided.

METHODS/DESIGN

This is a pragmatic, multi-centre randomised controlled trial examining the effects of hypothermia 32-35 °C, titrated to reduce intracranial pressure <20 mmHg, on morbidity and mortality 6 months after traumatic brain injury. The study aims to recruit 1800 patients over 41 months. Enrolment started in April 2010.Participants are randomised to either standard care or standard care with titrated therapeutic hypothermia. Hypothermia is initiated with 20-30 ml/kg of intravenous, refrigerated 0.9% saline and maintained using each centre's usual cooling technique. There is a guideline for detection and treatment of shivering in the intervention group. Hypothermia is maintained for at least 48 hours in the treatment group and continued for as long as is necessary to maintain intracranial pressure <20 mmHg. Intracranial hypertension is defined as an intracranial pressure >20 mmHg in accordance with the Brain Trauma Foundation Guidelines, 2007.

DISCUSSION

The Eurotherm3235Trial is the most important clinical trial in critical care ever conceived by European intensive care medicine, because it was launched and funded by the European Society of Intensive Care Medicine and will be the largest non-commercial randomised controlled trial due to the substantial number of centres required to deliver the target number of patients. It represents a new and fundamental step for intensive care medicine in Europe. Recruitment will continue until January 2013 and interested clinicians from intensive care units worldwide can still join this important collaboration by contacting the Trial Coordinating Team via the trial website http://www.eurotherm3235trial.eu.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN34555414.

Mild hypothermia therapy reduces blood glucose and lactate and improves neurologic outcomes in patients with severe traumatic brain injury

PURPOSE

The study aimed to investigate the association between blood glucose or lactate and the outcomes of severe traumatic brain injury (TBI), and to evaluate the effect of mild hypothermia therapy on glucose and lactate levels.

METHODS

Eighty-one patients with TBI were randomly divided into normothermia (n = 41) and mild hypothermia (n = 40) group. Body temperature of hypothermia group was maintained at 32.7°C for 72 hours. Arterial blood glucose and lactic acid were determined before and after hypothermia therapy. Glasgow Outcome Scale (GOS) score was assessed 3 months after the treatment.

RESULTS

The mean glucose (7.04 ± 0.51 vs 9.71 ± 1.63 mmol/L, P < .05) in the hypothermia group was lower than in the normothermia group after hypothermia therapy. There were more patients with good neurologic function (GOS 4-5) in the hypothermia group than in the normothermia group (75.0% vs 51.2%, P = .038). Multivariate regression analysis showed that blood glucose greater than 10 mmol/L (adjusted risk ratio, 5.7; 95% confidence interval, 1.4-13.2; P < .05) was an independent predictor for poor neurologic outcomes in these patients, and hypothermia therapy was an independent predictor for favorable outcomes (risk ratio, 4.9; 95% confidence interval, 1.0-15.6; P < .05). No significant association between lactate and GOS scores was identified in the multivariate analysis.

CONCLUSION

Hyperglycemia after TBI was associated with poor clinical outcomes, but the predictive value of blood lactate level requires further investigation. Hypothermia therapy improves neurologic outcomes in patients with severe TBI, and reduction in blood glucose may be partially responsible for the improved outcomes.

Acute management of acquired brain injury part I: an evidence-based review of non-pharmacological interventions

PRIMARY OBJECTIVE

To review the literature on non-pharmacological interventions used in acute settings to manage elevated intracranial pressure (ICP) and minimize cerebral damage in patients with acquired brain injury (ABI).

MAIN OUTCOMES

A literature search of multiple databases (CINAHL, EMBASE, MEDLINE and PSYCHINFO) and hand-searched articles covering the years 1980-2008 was performed. Peer reviewed articles were assessed for methodological quality using the PEDro scoring system for randomized controlled trials (RCTs) and the Downs and Black tool for RCTs and non-randomized trials. Levels of evidence were assigned and recommendations made.

RESULTS

Five non-invasive interventions for acute ABI management were assessed: adjusting head posture, body rotation (continuous rotational therapy and prone positioning), hyperventilation, hypothermia and hyperbaric oxygen. Two invasive interventions were also reviewed: cerebrospinal fluid (CSF) drainage and decompressive craniectomy (DC).

CONCLUSIONS

There is a paucity of information regarding non-pharmacological acute management of patients with ABI. Strong levels of evidence were found for only four of the seven interventions (decompressive craniectomy, cerebrospinal fluid drainage, hypothermia and hyperbaric oxygen) and only for specific components of their use. Further research into all interventions is warranted.

Contemporary practices in postcardiac arrest syndrome: the role of mild therapeutic hypothermia

Out-of-hospital cardiac arrest remains a major cause of mortality and morbidity despite progress in resuscitative practices. The number of survivors with severe neurological impairment at hospital discharge is similarly dismal. Recently, much attention has been directed toward the use of mild therapeutic hypothermia in the care of comatose survivors with postcardiac arrest syndrome. Recent research suggests mild hypothermia lowers mortality and improves neurological outcome after successful treatment of cardiac arrest. The current 2005 updated guidelines of International Liaison Committee on Resuscitation and European Resuscitation Council recommend the utilization of mild induced hypothermia in postresuscitation treatment. Hypothermia induction in order to avoid the pathophysiological mechanisms of euthermia and hyperthermia and subsequent complications are briefly discussed. Cooling methods, potential side effects and questions regarding implementation of therapeutic hypothermia recommendations in every day clinical practice and future investigation are also addressed.

Bench-to-bedside review: Hypothermia in traumatic brain injury

Traumatic brain injury remains a major cause of death and severe disability throughout the world. Traumatic brain injury leads to 1,000,000 hospital admissions per annum throughout the European Union. It causes the majority of the 50,000 deaths from road traffic accidents and leaves 10,000 patients severely handicapped: three quarters of these victims are young people. Therapeutic hypothermia has been shown to improve outcome after cardiac arrest, and consequently the European Resuscitation Council and American Heart Association guidelines recommend the use of hypothermia in these patients. Hypothermia is also thought to improve neurological outcome after neonatal birth asphyxia. Cardiac arrest and neonatal asphyxia patient populations present to health care services rapidly and without posing a diagnostic dilemma; therefore, therapeutic systemic hypothermia may be implemented relatively quickly. As a result, hypothermia in these two populations is similar to the laboratory models wherein systemic therapeutic hypothermia is commenced very soon after the injury and has shown so much promise. The need for resuscitation and computerised tomography imaging to confirm the diagnosis in patients with traumatic brain injury is a factor that delays intervention with temperature reduction strategies. Treatments in traumatic brain injury have traditionally focussed on restoring and maintaining adequate brain perfusion, surgically evacuating large haematomas where necessary, and preventing or promptly treating oedema. Brain swelling can be monitored by measuring intracranial pressure (ICP), and in most centres ICP is used to guide treatments and to monitor their success. There is an absence of evidence for the five commonly used treatments for raised ICP and all are potential 'double-edged swords' with significant disadvantages. The use of hypothermia in patients with traumatic brain injury may have beneficial effects in both ICP reduction and possible neuro-protection. This review will focus on the bench-to-bedside evidence that has supported the development of the Eurotherm3235Trial protocol.

The evidence for hypothermia as a neuroprotectant in traumatic brain injury

This article reviews published experimental and clinical evidence for the benefits of modest hypothermia in the treatment of traumatic brain injury (TBI). Therapeutic hypothermia has been reported to improve outcome in several animal models of CNS injury and has been successfully translated to specific patient populations. A PubMed search for hypothermia and TBI was conducted, and important papers were selected for review. The research summarized was conducted at major academic institutions throughout the world. Experimental studies have emphasized that hypothermia can affect multiple pathophysiological mechanisms thought to participate in the detrimental consequences of TBI. Published data from several relevant clinical trials on the use of hypothermia in severely injured TBI patients are also reviewed. The consequences of mild to moderate levels of hypothermia introduced by different strategies to the head-injured patient for variable periods of time are discussed. Both experimental and clinical data support the beneficial effects of modest hypothermia following TBI in specific patient populations. Following on such single-institution studies, positive findings from multicenter TBI trials will be required before this experimental treatment can be considered standard of care.

Current and future role of therapeutic hypothermia

Therapeutic moderate hypothermia has been advocated for use in traumatic brain injury, stroke, cardiac arrest-induced encephalopathy, neonatal hypoxic-ischemic encephalopathy, hepatic encephalopathy, and spinal cord injury, and as an adjunct to aneurysm surgery. In this review, we address the trials that have been performed for each of these indications, and review the strength of the evidence to support treatment with mild/moderate hypothermia. We review the data to support an optimal target temperature for each indication, as well as the duration of the cooling, and the rate at which cooling is induced and rewarming instituted. Evidence is strongest for prehospital cardiac arrest and neonatal hypoxic-ischemic encephalopathy. For traumatic brain injury, a recent meta-analysis suggests that cooling may increase the likelihood of a good outcome, but does not change mortality rates. For many of the other indications, such as stroke and spinal cord injury, trials are ongoing, but the data are insufficient to recommend routine use of hypothermia at this time.

A survey on application of quantitative methods on analysis of brain parameters changing with temperature

Brain temperature fluctuations occur in consequence of physiological and pathophysiological conditions and indicate changes in brain metabolism, cerebral blood flow (CBF), brain functions and neural damage. Lowering the brain temperature of patients with traumatic brain injuries achieves considerable improvements. When the human brain is cooled down to 30°C, it switches to a sub functional regime where it can live longer with less oxygen, glucose and other supplies. Fluctuations in brain temperature cause changes in brain parameters which can be measured by electroencephalogram (EEG) and transcranial Doppler (TCD). It is very important to understand the temperature dependencies of brain's electrical activity and blood flow and their interrelations considering the good clinical results achieved by lowering the brain temperature of neurologically injured patients. Since protecting the patient's brain is of primary importance in many fields including cardiology, neurology, traumatology and anesthesia it can be clearly seen that this subject is very important. In this study, we survey the "state-of-the-art" in analysis of EEG and TCD brain parameters changing with temperature and present further research opportunities.

The influence of focal brain cooling on neurophysiopathology: validation for clinical application

Object

Focal brain cooling has been recognized to have a suppressive effect on epileptiform discharges or a protective effect on brain tissue. However, the precise influence of brain cooling on normal brain function and histology has not yet been thoroughly investigated. The aim of this study was to investigate the neurophysiopathological consequences of focal cooling and to detect the threshold temperature that causes irreversible histological change and motor dysfunction.

Methods

The experiments were performed in adult male Sprague-Dawley rats (weighing 250–350 g) after induction of halothane anesthesia. A thermoelectric chip (6 × 6 × 2 mm) was used as a cooling device and was placed on the surface of the sensorimotor cortex after a 10 × 8–mm craniotomy. A thermocouple was placed between the chip and the brain surface. Focal cooling of the cortex was performed at the temperatures of 20, 15, 10, 5, 0, and −5°C for 1 hour (5 rats in each group). Thereafter, the cranial window was repaired. Motor function was evaluated using the beam-walking scale (BWS) every day for 7 days. The rats were killed 7 days after the operation for histological examination with H & E, Klüver-Barrera, glial fibrillary acidic protein, and terminal deoxynucleotidyl transferasemediated deoxyuridine triphosphate nick-end labeling stainings. The authors also euthanized some rats 24 hours after cooling and obtained brain sections by the same methods.

Results

The BWS score was decreased on the day after cooling only in the −5°C group (p < 0.05), whereas the score did not change in the other temperature groups. Histologically, the appearance of cryoinjury such as necrosis, apoptosis, loss of neurons, and marked proliferation of astrocytes at the periphery of the lesion was observed only in the −5°C group, while no apparent changes were observed in the other temperature groups.

Conclusions

The present study confirmed that the focal cooling of the cortex for 1 hour above the temperature of 0°C did not induce any irreversible histological change or motor dysfunction. These results suggest that focal brain cooling above 0°C has the potential to be a minimally invasive and valuable modality for the treatment of severe brain injury or to assist in the examination of brain function.

Hypothermia for traumatic head injury

BACKGROUND

Hypothermia has been used in the treatment of head injury for many years. Encouraging results from small trials and laboratory studies led to renewed interest in the area and some larger trials.

OBJECTIVES

To estimate the effect of mild hypothermia for traumatic head injury on mortality and long-term functional outcome complications.

SEARCH STRATEGY

We searched the Injuries Group Specialised Register, Current Controlled Trials MetaRegister of trials, Zetoc, ISI Web of Science: Science Citation Index Expanded (SCI-EXPANDED) and Conference Proceedings Citation Index-Science (CPCI-S), CENTRAL (The Cochrane Library), MEDLINE and EMBASE. We handsearched conference proceedings and checked reference lists of all relevant articles. The search was last updated in January 2009.

SELECTION CRITERIA

Randomised controlled trials of hypothermia to a maximum of 35 degrees C for at least 12 consecutive hours versus control in patients with any closed traumatic head injury requiring hospitalisation. Two authors independently assessed all trials.

DATA COLLECTION AND ANALYSIS

Data on death, Glasgow Outcome Scale and pneumonia were sought and extracted, either from published material or by contacting the investigators. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each trial on an intention-to-treat basis.

MAIN RESULTS

We found 23 trials with a total of 1614 randomised patients. Twenty-one trials involving 1587 patients reported deaths. There were fewer deaths in patients treated with hypothermia than in the control group (OR 0.84, 95% CI 0.67 to 1.05). Nine trials with good allocation concealment showed no decrease in the likelihood of death compared with the control group, and this result was not statistically significant (OR 1.08, 95% CI 0.79 to 1.47). Twenty-one trials involving 1587 patients reported data on unfavourable outcomes (death, vegetative state or severe disability). Patients treated with hypothermia were less likely to have an unfavourable outcome than those in the control group (OR 0.76, 95% CI 0.61 to 0.93). Nine trials with good allocation concealment showed patients treated with hypothermia were less likely to have an unfavourable outcome than those in the control group, but the reduction was small and non-significant (OR 0.91, 95% CI 0.69 to 1.20). Hypothermia treatment was associated with a slight increase in the odds of pneumonia (OR 1.31, 95% CI 0.93 to 1.86) but there was a reduction in pneumonia for trials with good allocation concealment (4 trials analysed separately, 294 patients, OR 0.79, 95% CI 0.49 to 1.27) although in both cases the results are not statistically significant.

AUTHORS' CONCLUSIONS

There is no evidence that hypothermia is beneficial in the treatment of head injury. Hypothermia may be effective in reducing death and unfavourable outcomes for traumatic head injured patients, but significant benefit was only found in low quality trials. Low quality trials have a tendency to overestimate the treatment effect. The high quality trials found no decrease in the likelihood of death with hypothermia, but this finding was not statistically significant and could be due to the play of chance. Hypothermia should not be used except in the context of a high quality randomised controlled trial with good allocation concealment.

Induced normothermia attenuates intracranial hypertension and reduces fever burden after severe traumatic brain injury

INTRODUCTION

Hyperthermia following a severe traumatic brain injury (TBI) is common, potentiates secondary injury, and worsens neurological outcome. Conventional fever treatment is often ineffective. An induced normothermia protocol, utilizing intravascular cooling, was used to assess the impact on fever incidence and intracranial pressure (ICP) in patients with severe TBI.

METHODS

A comparative cohort study of 21 adult patients with severe TBI (GCS <or= 8) treated with induced normothermia [36-36.5 degrees C rectal probe setting; intravascular cooling catheter (CoolLine, Alsius Corporation, Irvine, CA)] were matched by age, gender, and severity of injury to 21 historical control severe TBI patients treated with conventional fever control methods. ICP was measured via an external ventricular catheter and time duration for ICP > 25 mmHg was calculated for the initial 72-h monitoring period. Non-parametric rank tests were performed.

RESULTS

Mean (+/-SD) or median [range] demographics did not differ between groups [total N = 42 (6 female, 36 male, age 36.4 +/- 14.8 years and initial GCS 7 [3-8], median and range]. Fever burden in the first 3 days (time >38 degrees C) in the induced normothermia versus control group was significantly less at 1.6% versus 10.6%, respectively (P = 0.03). Mean ICP for patients with induced normothermia versus control was 12.74 +/- 4.0 and 16.37 +/- 6.9 mmHg, respectively. Furthermore, percentage of time with ICP > 25 mmHg was significantly less in the induced normothermia group (P = 0.03).

CONCLUSION

Induced normothermia (fever prophylaxis via intravascular cooling catheter) is effective in reducing fever burden and may offer a means to attenuate secondary injury, as evidenced by a reduction in the intracranial hypertension burden.

A review of selective hypothermia in the management of traumatic brain injury

Object

Traumatic brain injury (TBI) remains a significant cause of morbidity and death in the US and worldwide. Resuscitative systemic hypothermia following TBI has been established as an effective neuroprotective treatment in multiple studies in animals and humans, although this intervention carries with it a significant risk profile as well. Selective, or preferential, methods of inducing cerebral hypothermia have taken precedence over the past few years in order to minimize systemic adverse effects. In this report, the authors explore the current methods available for inducing selective cerebral hypothermia following TBI and review the literature regarding the results of animal and human trials in which these methods have been implemented.

Methods

A search of the PubMed archive (National Library of Medicine) and the reference lists of all relevant articles was conducted to identify all animal and human studies pertaining to the use of selective brain cooling, selective hypothermia, preferential hypothermia, or regional hypothermia following TBI.

Results

Multiple methods of inducing selective cerebral hypothermia are currently in the experimental phases, including surface cooling, intranasal selective hypothermia, transarterial or transvenous endovascular cooling, extraluminal vascular cooling, and epidural cerebral cooling.

Conclusions

Several methods of conferring preferential neuroprotection via selective hypothermia currently are being tested. Class I prospective clinical trials are required to assess the safety and efficacy of these methods.

Induced hypothermia and fever control for prevention and treatment of neurological injuries

Increasing evidence suggests that induction of mild hypothermia (32-35 degrees C) in the first hours after an ischaemic event can prevent or mitigate permanent injuries. This effect has been shown most clearly for postanoxic brain injury, but could also apply to other organs such as the heart and kidneys. Hypothermia has also been used as a treatment for traumatic brain injury, stroke, hepatic encephalopathy, myocardial infarction, and other indications. Hypothermia is a highly promising treatment in neurocritical care; thus, physicians caring for patients with neurological injuries, both in and outside the intensive care unit, are likely to be confronted with questions about temperature management more frequently. This Review discusses the available evidence for use of controlled hypothermia, and also deals with fever control. Besides discussing the evidence, the aim is to provide information to help guide treatments more effectively with regard to timing, depth, duration, and effective management of side-effects. In particular, the rate of rewarming seems to be an important factor in establishing successful use of hypothermia in the treatment of neurological injuries.

Use of induced hypothermia for neuroprotection: indications and application

Therapeutic temperature regulation has become an exciting field of interest. Mild-to-moderate hypothermia is a safe and feasible management strategy for neuroprotection and control of intracranial pressure in neurological catastrophies such as traumatic brain injury, subarachnoid and intracerebral hemorrhage, and large hemispheric stroke. Fever is associated with worse neurological outcome in patients with brain injury, normothermia may be of benefit in this patient population. The efficacy of mild-to-moderate hypothermia has been proven for neuroprotection after cardiac arrest with ventricular fibrillation as initial rhythm, and after neonatal asphyxia. Application of hypothermia and fever control in neurocritical care, available cooling technologies and systemic effects and complications of hypothermia will be discussed.

Temperature distribution and blood perfusion response in rat brain during selective brain cooling

A rat model was used in this study to examine the transient temperature distribution and blood flow response in the brain during selective brain cooling (SBC) and rewarming. SBC was induced by a head cooling helmet with circulating water of 18 degrees C or 0 degrees C. It has been shown that the brain temperature reductions were 1.7+/-0.2 degrees C (5 mm beneath the brain surface) and 3.2+/-1.1 degrees C (2 mm beneath the brain surface) when the temperature of the water was 18 degrees C (moderate cooling). The cooling of the brain tissue was more evident when the circulating water was colder (0 degrees C, deep cooling). The characteristic time that it took for the tissue temperatures to reach a new steady state after the initiation of cooling varied from 5 to more than 35 min and it depended strongly on the blood flow response to the cooling. We used an ultrasound flow meter to measure continuously the blood flow rate in the common carotid artery during the cooling and rewarming. The blood flow rate dropped by up to 22% and 44% during the cooling from its baseline in the moderate cooling group and in the deep cooling group, respectively. Although all brain temperatures recovered to their baseline values 50 min after the helmet was removed, the blood flow rate only recovered to 92% and 77% of its baseline values after the moderate and deep cooling, respectively, implying a possible mismatch between the blood perfusion and metabolism in the brain. The current experimental results can be used to study the feasibility of inducing brain hypothermia by SBC if the blood flow responses in the rat are applicable to humans. The simultaneous recordings of temperature and blood flow rate in the rat brain can be used in the future to validate the theoretical model developed previously.

Mild hypothermia for acute liver failure: a review of mechanisms of action

Brain edema with intracranial hypertension is a major complication in patients with acute liver failure. Current therapies for this complication include a variety of pharmacologic and interventional measures, some of which are frequently associated with adverse effects or contraindications. Even though these measures usually allow the control of intracranial hypertension for a certain period of time, recurrence is common. New therapies are therefore needed. Increasing clinical and experimental evidence suggests that induction of mild hypothermia (32 degrees C-35 degrees C) may be a therapeutic alternative. Similar to traumatic brain injury or brain stroke, induction of mild hypothermia seems highly effective to reduce intracranial pressure in patients with acute liver failure. Several mechanisms by which mild hypothermia may prevent brain edema and intracranial hypertension in this condition have been disclosed and may include beneficial effects on ammonia metabolism, as well as on the disturbances of brain osmolarity, cerebrovascular hemodynamics, brain glucose metabolism, inflammation, and others. Improvement of systemic hemodynamics and amelioration of liver injury may be other benefits of the systemic induction of mild hypothermia, but the impact of potential adverse events, such as infection, should also be taken into account. At a time when mild hypothermia is increasingly used in several specialized centers, performance of a randomized controlled trial seems critical to confirm the benefits of mild hypothermia in acute liver failure and to provide adequate guidelines for its use.