Moderate hypothermia improves imbalances of thromboxane A2 and prostaglandin I2 production after traumatic brain injury in humans

Severity-Dependent Long-Term Post-Traumatic Changes in the Circulating Oxylipin Profile

Trauma causes the breakdown of membrane phospholipids and the subsequent degradation of the released polyunsaturated fatty acids (PUFAs) to partially bioactive oxylipins. Here, we screened for circulating PUFAs and oxylipins in patients (n = 34) differing from those of uninjured controls (n = 25) and analyzed their diagnostic potential. Patients were followed up for 1 to 240 h after minor/moderate, severe, and very severe injuries. Of the targeted oxylipins, 13 out of 80 (13/80) were detected in almost all patients and controls. Injury caused a long-term decrease in 9- and 13-hydroxyoctadecadienoic acids and in several dihydroxyeicosatetraenoic acids, the stable derivatives of bioactive anti-inflammatory epoxyeicosatrienoic acids, compared to controls. Frequently, these oxylipins correlated inversely to injury severity, days in the intensive care unit and hospital, and/or procalcitonin and pro-inflammatory cytokine levels 48 up to 240 h after trauma. Notably, 20/80 oxylipins were detected in some patients but not or less often in controls. Many of these oxylipins increased transiently immediately after injury. Their level is partly correlated with adverse clinical parameters at this early time point. The circulating oxylipidome was markedly affected by trauma. Several oxylipins showed injury-dependent alterations at different time points in the post-traumatic course.

Therapeutic Hypothermia Compared with Normothermia in Adults with Traumatic Brain Injury; Functional Outcome, Mortality, and Adverse Effects: A Systematic Review and Meta-Analysis

BACKGROUND

The main focus of traumatic brain injury (TBI) management is prevention of secondary injury. Therapeutic hypothermia (TH), the induction of a targeted low core body temperature, has been explored as a potential neuroprotectant in TBI. The aim of this article is to synthesize the available clinical data comparing the use of TH with the use of normothermia in TBI.

METHODS

A systematic search was conducted through MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials for randomized clinical trials including one or more outcome of interest associated with TH use in TBI. Independent reviewers evaluated quality of the studies and extracted data on patients with TBI undergoing TH treatment compared with those undergoing normothermia treatment. Pooled estimates, confidence intervals (CIs), and risk ratios (RRs) or odds ratios were calculated for all outcomes.

RESULTS

A total of 3,909 patients from 32 studies were eligible for analysis. Pooled analysis revealed a significant benefit of TH on mortality and functional outcome (RR 0.81, 95% CI 0.68-0.96, I2 = 41%; and RR 0.77; 95% CI 0.67-0.88, I2 = 68%, respectively). However, subgroup analysis based on risk of bias showed that only studies with a high risk of bias maintained this benefit. When divided by cooling method, reduced poor functional outcome was seen in the systemic surface cooling and cranial cooling groups (RR 0.68, 95% CI 0.59-0.79, I2 = 35%; and RR 0.44, 95% CI 0.29-0.67, I2 = 0%), and no difference was seen for the systemic intravenous or gastric cooling group. Reduced mortality was only seen in the systemic surface cooling group (RR 0.63, 95% CI 0.53-0.75, I2 = 0%,); however, this group had mostly high risk of bias studies. TH had an increased rate of pneumonia (RR 1.24, 95% CI 1.10-1.40, I2 = 32%), coagulation abnormalities (RR 1.63, 95% CI 1.09-2.44, I2 = 55%), and cardiac arrhythmias (RR 1.78, 95% CI 1.05-3.01, I2 = 21%). Once separated by low and high risk of bias, we saw no difference in these complications in the groups with low risk of bias. Overall quality of the evidence was moderate for mortality, functional outcome, and pneumonia and was low for coagulation abnormalities and cardiac arrhythmias.

CONCLUSIONS

With the addition of several recent randomized clinical trials and a thorough quality assessment, we have provided an updated systematic review and meta-analysis that concludes that TH does not show any benefit over normothermia in terms of mortality and functional outcome.

Mild (34 °C) versus moderate hypothermia (24 °C) in a swine model of extracorporeal cardiopulmonary resuscitation

Background

The role of hypothermia in post-arrest neuroprotection is controversial. Animal studies suggest potential benefits with lower temperatures, but high-fidelity ECPR models evaluating temperatures below 30 °C are lacking.

Objectives

To determine whether rapid cooling to 24 °C initiated upon reperfusion reduces brain injury compared to 34 °C in a swine model of ECPR.

Methods

Twenty-four female pigs had electrically induced VF and mechanical CPR for 30 min. Animals were cannulated for VA-ECMO and cooled to either 34 °C for 4 h (n = 8), 24 °C for 1 h with rewarming to 34 °C over 3 h (n = 7), or 24 °C for 4 h without rewarming (n = 9). Cooling was initiated upon VA-ECMO reperfusion by circulating ice water through the oxygenator. Brain temperature and cerebral and systemic hemodynamics were continuously monitored. After four hours on VA-ECMO, brain tissue was obtained for examination.

Results

Target brain temperature was achieved within 30 min of reperfusion (p = 0.74). Carotid blood flow was higher in the 24 °C without rewarming group throughout the VA-ECMO period compared to 34 °C and 24 °C with rewarming (p < 0.001). Vasopressin requirement was higher in animals treated with 24 °C without rewarming (p = 0.07). Compared to 34 °C, animals treated with 24 °C with rewarming were less coagulopathic and had less immunohistochemistry-detected neurologic injury. There were no differences in global brain injury score.

Conclusions

Despite improvement in carotid blood flow and immunohistochemistry detected neurologic injury, reperfusion at 24 °C with or without rewarming did not reduce early global brain injury compared to 34 °C in a swine model of ECPR.

Clinical Insights and Future Directions in Hypothermia for Severe Traumatic Brain Injury: A Narrative Review

Fever control is essential in patients with severe traumatic brain injury (TBI). The efficacy of therapeutic hypothermia (TH) in severe TBI has been investigated over the last few decades; however, in contrast to experimental studies showing benefits, no evidence of efficacy has been demonstrated in clinical practice. In this review, the mechanisms and history of hypothermia were briefly outlined, while the results of major randomized controlled trials (RCTs) and meta-analyses investigating TH for adult TBI were introduced and discussed. The retrieved meta-analyses showed conflicting results, with a limited number of studies indicating the benefits of TH. Some studies have shown the benefits of long-term TH compared with short-term TH. Although TH is effective at lowering elevated intracranial pressure (ICP), reduced ICP does not lead to favorable outcomes. Low-quality RCTs overestimated the benefits of TH, while high-quality RCTs showed no difference or worse outcomes with TH. RCTs assessing standardized TH quality demonstrated the benefits of TH. As TBI has heterogeneous and complicated pathologies, applying a uniform treatment may not be ideal. A meta-analysis of young patients who underwent early cooling and hematoma removal showed better TH results. TH should not be abandoned, and its optimal usage should be advocated on an individual basis.

Mechanisms of action behind the protective effects of proactive esophageal cooling during radiofrequency catheter ablation in the left atrium

Proactive esophageal cooling for the purpose of reducing the likelihood of ablation-related esophageal injury resulting from radiofrequency (RF) cardiac ablation procedures is increasingly being used and has been Food and Drug Administration cleared as a protective strategy during left atrial RF ablation for the treatment of atrial fibrillation. In this review, we examine the evidence supporting the use of proactive esophageal cooling and the potential mechanisms of action that reduce the likelihood of atrioesophageal fistula (AEF) formation. Although the pathophysiology behind AEF formation after thermal injury from RF ablation is not well studied, a robust literature on fistula formation in other conditions (eg, Crohn disease, cancer, and trauma) exists and the relationship to AEF formation is investigated in this review. Likewise, we examine the abundant data in the surgical literature on burn and thermal injury progression as well as the acute and chronic mitigating effects of cooling. We discuss the relationship of these data and maladaptive healing mechanisms to the well-recognized postablation pathophysiological effects after RF ablation. Finally, we review additional important considerations such as patient selection, clinical workflow, and implementation strategies for proactive esophageal cooling.

The effect of mild hypothermia plus rutin on the treatment of spinal cord injury and inflammatory factors by repressing TGF-β/smad pathway

Purpose

To probe the mechanism of mild hypothermia combined with rutin in the treatment of spinal cord injury (SCI).

Methods

Thirty rats were randomized into the following groups: control, sham, model, mild hypothermia (MH), and mild hypothermia plus rutin (MH+Rutin). We used modified Allen’s method to injure the spinal cord (T10) in rats, and then treated it with MH or/and rutin immediately. BBB scores were performed on all rats. We used HE staining for observing the injured spinal cord tissue; ELISA for assaying TNF-α, IL-1β, IL-8, Myeloperoxidase (MPO), and Malondialdehyde (MDA) contents; Dihydroethidium (DHE) for measuring the reactive oxygen species (ROS) content; flow cytometry for detecting apoptosis; and both RT-qPCR and Western blot for determining the expression levels of TGF-β/Smad pathway related proteins (TGF-β, Smad2, and Smad3).

Results

In comparison with model group, the BBB score of MH increased to a certain extent and MH+Rutin group increased more than MH group (p < 0.05). After treatment with MH and MH+Rutin, the inflammatory infiltration diminished. MH and MH+Rutin tellingly dwindled TNF-β, MDA and ROS contents (p < 0.01), and minified spinal cord cell apoptosis. MH and MH+Rutin could patently diminished TGF-β1, Smad2, and Smad3 expression (p < 0.01).

Conclusions

MH+Rutin can suppress the activation of TGF-β/Smad pathway, hence repressing the cellular inflammatory response after SCI.

Effects of cryotherapy on the regeneration process and muscular mechanical properties after lacerative injury model

Cryotherapy is a therapeutic modality widely used for the treatment of muscle injuries to control pain and inflammatory processes. This study aimed to investigate the effects of cryotherapy on the inflammatory and oxidative stress parameters and mechanical properties of, and pain in, the skeletal muscles of rats with lacerative muscle injury. The rats were anesthetized with 4% isoflurane and subjected to gastrocnemius muscle laceration injury. After injury, all animals in the intervention groups received cryotherapy treatment for 20 minutes using plastic bags containing crushed ice. The protocol comprised three daily applications at 3-hour intervals on the day of injury, with reapplication 24 hours later. Seventy-two male Wistar rats were divided into three groups: sham, muscle injury (MI), and MI + cryotherapy (MI + cryo). Muscle mechanical properties were analyzed by mechanical tensile testing on day 7 after injury. The MI + cryo group showed reduced TNF-α, IFN-γ, and IL1β levels; elevated IL4, IL6, and IL10 levels; reduced oxidant production and carbonyl levels; and elevated sulfhydryl contents. Animals that underwent tissue cooling showed superoxide dismutase activity and glutathione levels close to those of the animals in the sham group. The MI and MI + cryo groups showed reduced values of the evaluated mechanical properties and lower mechanical thresholds compared to those of the animals from the sham group. Our results demonstrated that the proposed cryotherapy protocol reduced the inflammatory process and controlled oxidative stress but did not reverse the changes in the mechanical properties of muscle tissues or provide analgesic effects within the time frame analyzed.

Recent antiepileptic and neuroprotective applications of brain cooling

Hypothermia is a widely used clinical practice for neuroprotection and is a well-established method to mitigate the adverse effects of some clinical conditions such as reperfusion injury after cardiac arrest and hypoxic ischemic encephalopathy in newborns. The discovery, that lowering the core temperature has a therapeutic potential dates back to the early 20th century, but the underlying mechanisms are actively researched, even today. Especially, in the area of neural disorders such as epilepsy and traumatic brain injury, cooling has promising prospects. It is well documented in animal models, that the application of focal brain cooling can effectively terminate epileptic discharges. There is, however, limited data regarding human clinical trials. In this review article, we will discuss the main aspects of therapeutic hypothermia focusing on its use in treating epilepsy. The various experimental approaches and device concepts for focal brain cooling are presented and their potential for controlling and suppressing seizure activity are compared.

The effectiveness of early prophylactic hypothermia in adult patients with traumatic brain injury: A systematic review and meta-analysis

OBJECTIVES

Previously published systematic reviews have explored the effects of therapeutic hypothermia on adult patients with traumatic brain injury (TBI). However, none explored the effect of early prophylactic hypothermia (within 6 h from injury to hypothermia induction). Animal studies indicated that early prophylactic hypothermia may reduce secondary injury and improve neurological outcomes. This systematic review aimed to investigate the effects of early prophylactic hypothermia on adult TBI regarding mortality, favourable outcomes, and complications.

DATA SOURCE

We searched electronic databases including Cochrane CENTRAL, PubMed, MEDLINE, CINAHL, EMBASE, Web of Science, OpenGrey, and ClinicalTrials.gov from inception to June 12, 2019. Manual search was conducted for additional information.

REVIEW METHODS

Only randomised controlled trials were included. The Cochrane Collaboration Risk of Bias Tool was used to assess the quality of included studies. We extracted general demographic characteristics, the initiation timing, methods of cooling, duration, target temperature, rewarming rate, mortality, neurological outcomes, and complications.

RESULTS

Six studies with a total of 1207 participants were included. Meta-analyses showed no significant difference in mortality and favourable outcomes (risk ratio = 1.11, 95% confidence interval = 0.90-1.37, P = 0.32; risk ratio = 1.03, 95% confidence interval = 0.91-1.16, P = 0.65, respectively). Similar results were found regarding different durations of hypothermia and different rewarming rates. Various complications were reported in the included studies. No statistical difference was found in three studies, while complications were reported to be significantly higher in the hypothermia group in the other three studies.

CONCLUSIONS

This review does not support the use of early prophylactic hypothermia (within 6 h after injury) as a neurological protection strategy in adult patients with TBI, irrespective of the short term or long term. No significant benefits were found regarding hypothermia with different rewarming rates. Owing to the limited number of studies, more randomised controlled trials with higher quality are required to establish true effects of early hypothermia in adult TBI.

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.

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.

The Implementation of Targeted Temperature Management: An Evidence-Based Guideline from the Neurocritical Care Society

BACKGROUND

Targeted temperature management (TTM) is often used in neurocritical care to minimize secondary neurologic injury and improve outcomes. TTM encompasses therapeutic hypothermia, controlled normothermia, and treatment of fever. TTM is best supported by evidence from neonatal hypoxic-ischemic encephalopathy and out-of-hospital cardiac arrest, although it has also been explored in ischemic stroke, traumatic brain injury, and intracranial hemorrhage patients. Critical care clinicians using TTM must select appropriate cooling techniques, provide a reasonable rate of cooling, manage shivering, and ensure adequate patient monitoring among other challenges.

METHODS

The Neurocritical Care Society recruited experts in neurocritical care, nursing, and pharmacotherapy to form a writing Committee in 2015. The group generated a set of 16 clinical questions relevant to TTM using the PICO format. With the assistance of a research librarian, the Committee undertook a comprehensive literature search with no back date through November 2016 with additional references up to March 2017.

RESULTS

The Committee utilized GRADE methodology to adjudicate the quality of evidence as high, moderate, low, or very low based on their confidence that the estimate of effect approximated the true effect. They generated recommendations regarding the implementation of TTM based on this systematic review only after considering the quality of evidence, relative risks and benefits, patient values and preferences, and resource allocation.

CONCLUSION

This guideline is intended for neurocritical care clinicians who have chosen to use TTM in patient care; it is not meant to provide guidance regarding the clinical indications for TTM itself. While there are areas of TTM practice where clear evidence guides strong recommendations, many of the recommendations are conditional, and must be contextualized to individual patient and system needs.

Hypothermia for traumatic brain injury

BACKGROUND

Hypothermia has been used in the treatment of brain 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 determine the effect of mild hypothermia for traumatic brain injury (TBI) on mortality, long-term functional outcomes and complications.

SEARCH METHODS

We ran and incorporated studies from database searches to 21 March 2016. We searched the Cochrane Injuries Group's Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE (OvidSP), Embase Classic+Embase (OvidSP), PubMed, ISI Web of science (SCI-EXPANDED, SSCI, CPCI-S & CPSI-SSH), clinical trials registers, and screened reference lists. We also re-ran these searches pre-publication in June 2017; the result from this search is presented in 'Studies awaiting classification'.

SELECTION CRITERIA

We included randomised controlled trials of participants with closed TBI requiring hospitalisation who were treated with hypothermia to a maximum of 35 ºC for at least 12 consecutive hours. Treatment with hypothermia was compared to maintenance with normothermia (36.5 to 38 ºC).

DATA COLLECTION AND ANALYSIS

Two review authors assessed data on mortality, unfavourable outcomes according to the Glasgow Outcome Scale, and pneumonia.

MAIN RESULTS

We included 37 eligible trials with a total of 3110 randomised participants; nine of these were new studies since the last update (2009) and five studies had been previously excluded but were re-assessed and included during the 2017 update. We identified two ongoing studies from searches of clinical trials registers and database searches and two studies await classification.Studies included both adults and children with TBI. Most studies commenced treatment immediately on admission to hospital or after craniotomies and all treatment was maintained for at least 24 hours. Thirty-three studies reported data for mortality, 31 studies reported data for unfavourable outcomes (death, vegetative state or severe disability), and 14 studies reported pneumonia. Visual inspection of the results for these outcomes showed inconsistencies among studies, with differences in the direction of effect, and we did not pool these data for meta-analysis. We considered duration of hypothermia therapy and the length of follow-up in collected data for these subgroups; differences in study data remained such that we did not perform meta-analysis.Studies were generally poorly reported and we were unable to assess risk of bias adequately. Heterogeneity was evident both in the trial designs and participant inclusion. Inconsistencies in results may be explained by heterogeneity among study participants or bias introduced by individual study methodology but we did not explore this in detail in subgroup or sensitivity analyses. We used the GRADE approach to judge the quality of the evidence for each outcome and downgraded the evidence for mortality and unfavourable outcome to very low. We downgraded the evidence for the pneumonia outcome to low.

AUTHORS' CONCLUSIONS

Despite a large number studies, there remains no high-quality evidence that hypothermia is beneficial in the treatment of people with TBI. Further research, which is methodologically robust, is required in this field to establish the effect of hypothermia for people with TBI.

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.

Effect of volume replacement during combined experimental hemorrhagic shock and traumatic brain injury in prostanoids, brain pathology and pupil status

Traumatic brain injury (TBI) is the main cause of trauma-related deaths. Systemic hypotension and intracranial hypertension causes cerebral ischemia by altering metabolism of prostanoids. We describe prostanoid, pupilar and pathological response during resuscitation with hypertonic saline solution (HSS) in TBI. Method Fifteen dogs were randomized in three groups according to resuscitation after TBI (control group; lactated Ringer's (LR) group and HSS group), with measurement of thromboxane, prostaglandin, macroscopic and microscopic pathological evaluation and pupil evaluation.Result Concentration of prostaglandin is greater in the cerebral venous blood than in plasma and the opposite happens with concentration of thromboxane. Pathology revealed edema in groups with the exception of group treated with HSS.Discussion and conclusion There is a balance between the concentrations of prostaglandin and thromboxane. HSS prevented the formation of cerebral edema macroscopically detectable. Pupillary reversal occurred earlier in HSS group than in LR group.

Moderate hypothermia treatment in adult patients with severe traumatic brain injury: a meta-analysis

OBJECTIVES

To evaluate the effect of moderate hypothermia treatment (MHT) in severe traumatic brain injury (sTBI) compared to normothermia management.

METHODS

PubMed, Medline, Springer, Elsevier Science Direct, Cochrane Library and Google scholar were searched up to December 2012. Pooled risk ratios (RRs) and 95% confidence intervals (CIs) for the mortality and clinical neurological outcome of the adult patients with sTBI were collected and calculated in a fixed-effects model or a random-effects model. Summary effect estimates were stratified by study design and ethnicity. Egger's regression asymmetry tests were utilized for detecting the publication bias.

RESULTS

The overall estimates showed that MHT could reduce the mortality (hypothermia vs. normothermia, RR = 0.86, 95% CI = 0.73-1.01, p = 0.06) and unfavourable clinical neurological outcomes (RR = 1.21, 95% CI = 0.95-1.53, p = 0.12) for traumatic brain injured patients without statistical significance. Moreover, the further stratification sub-group analysis indicated that MHT presented a significant reduction (RR = 0.60, 95% CI = 0.44-0.83, p = 0.002) of mortality compared to the normothermia management in an Asian population. Surprisingly, American patients treated with moderate hypothermia showed an increasing mortality (RR = 1.07, 95% CI = 0.83-1.39, p = 0.61).

CONCLUSIONS

MHT may be effective in reducing death and unfavourable clinical neurological outcomes, but this finding is not statistically significant, except for decreasing the mortality in Asian patients.

Prolonged mild therapeutic hypothermia versus fever control with tight hemodynamic monitoring and slow rewarming in patients with severe traumatic brain injury: a randomized controlled trial

Although mild therapeutic hypothermia is an effective neuroprotective strategy for cardiac arrest/resuscitated patients, and asphyxic newborns, recent randomized controlled trials (RCTs) have equally shown good neurological outcome between targeted temperature management at 33 °C versus 36 °C, and have not shown consistent benefits in patients with traumatic brain injury (TBI). We aimed to determine the effect of therapeutic hypothermia, while avoiding some limitations of earlier studies, which included patient selection based on Glasgow coma scale (GCS), delayed initiation of cooling, short duration of cooling, inter-center variation in patient care, and relatively rapid rewarming. We conducted a multicenter RCT in patients with severe TBI (GCS 4-8). Patients were randomly assigned (2:1 allocation ratio) to either therapeutic hypothermia (32-34 °C, n = 98) or fever control (35.5-37 °C, n = 50). Patients with therapeutic hypothermia were cooled as soon as possible for ≥ 72 h and rewarmed at a rate of <1 °C/day. All patients received tight hemodynamic monitoring under intensive neurological care. The Glasgow Outcome Scale was assessed at 6 months by physicians who were blinded to the treatment allocation. The overall rates of poor neurological outcomes were 53% and 48% in the therapeutic hypothermia and fever control groups, respectively. There were no significant differences in the likelihood of poor neurological outcome (relative risk [RR] 1.24, 95% confidence interval [CI] 0.62-2.48, p = 0.597) or mortality (RR 1.82, 95% CI 0.82-4.03, p = 0.180) between the two groups. We concluded that tight hemodynamic management and slow rewarming, together with prolonged therapeutic hypothermia (32-34 °C) for severe TBI, did not improve the neurological outcomes or risk of mortality compared with strict temperature control (35.5-37 °C).

Progress in Clinical Neurosciences: Therapeutic Hypothermia in Severe Traumatic Brain Injury

Severe traumatic brain injury (sTBI) is a relatively common problem with few therapies proven effective. Despite its use for over 50 years, therapeutic hypothermia has not gained widespread acceptance in the treatment of sTBI due to conflicting results from clinical trials. This review will summarize the current evidence from animal, mechanistic and clinical studies supporting the use of therapeutic hypothermia. In addition, issues of rewarming and optimal temperature will be discussed. Finally, the future of hypothermia in sTBI will be addressed.

Mild hypothermia as a treatment for central nervous system injuries: Positive or negative effects

Besides local neuronal damage caused by the primary insult, central nervous system injuries may secondarily cause a progressive cascade of related events including brain edema, ischemia, oxida-tive stress, excitotoxicity, and dysregulation of calcium homeostasis. Hypothermia is a beneficial strategy in a variety of acute central nervous system injuries. Mild hypothermia can treat high intra-cranial pressure following traumatic brain injuries in adults. It is a new treatment that increases sur-vival and quality of life for patients suffering from ischemic insults such as cardiac arrest, stroke, and neurogenic fever following brain trauma. Therapeutic hypothermia decreases free radical produc-tion, inflammation, excitotoxicity and intracranial pressure, and improves cerebral metabolism after traumatic brain injury and cerebral ischemia, thus protecting against central nervous system dam-age. Although a series of pathological and physiological changes as well as potential side effects are observed during hypothermia treatment, it remains a potential therapeutic strategy for central nervous system injuries and deserves further study.

Effect of neuroprotective therapies (hypothermia and cyclosporine a) on dopamine-induced apoptosis in human neuronal SH-SY5Y cells

INTRODUCTION

This study aimed to evaluate the effect of hypothermia and CyA on neuronal survival after induced injury in a neuronal model.

METHODS

Human neuroblastoma SH-SY5Y cells were seeded and allowed to grow. To determine whether lower temperatures protect from dopamine-induced apoptosis, cells were treated with dopamine at 100 µM, at 300 µM or without dopamine and incubated at 32 °C or 37 °C for 24 hours. To assess the effect of CyA, cells were pre-incubated with CyA at 37 °C and after dopamine was added.

RESULTS

After 24 hours of incubation at 37 °C, 100 µM and 300 µM dopamine induced 42% (SD = 21) and 58% (SD = 7.9) apoptotic SH-SY5 cells, respectively. In cultures at 32 °C dopamine-induced apoptosis could be reversed by hypothermia [7% (SD = 1.4) and 3.45% (SD = 1.1) for 100 µM and 300 µM, respectively], similar to levels obtained in non-treated cells [2.4% (SD = 1.5)]. Cyclosporine A treatment did not render the expected result, since CyA-pre-treated cells and SH-SY5Y cells showed higher levels of apoptosis than those observed with dopamine alone

CONCLUSIONS

Hypothermia has a marked protective effect against apoptotic cell death induced by dopamine in a human neuroblastic cell line. The neuroprotective effect of CyA described with other apoptotic cell death stimuli was not demonstrated with our experimental conditions.

Use of hypothermia in the intensive care unit

Used for over 3600 years, hypothermia, or targeted temperature management (TTM), remains an ill defined medical therapy. Currently, the strongest evidence for TTM in adults are for out-of-hospital ventricular tachycardia/ventricular fibrillation cardiac arrest, intracerebral pressure control, and normothermia in the neurocritical care population. Even in these disease processes, a number of questions exist. Data on disease specific therapeutic markers, therapeutic depth and duration, and prognostication are limited. Despite ample experimental data, clinical evidence for stroke, refractory status epilepticus, hepatic encephalopathy, and intensive care unit is only at the safety and proof-of-concept stage. This review explores the deleterious nature of fever, the theoretical role of TTM in the critically ill, and summarizes the clinical evidence for TTM in adults.

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.

A review of clinical trials of hypothermia treatment for severe traumatic brain injury

Clinical trials of hypothermia treatment of traumatic brain injury can be divided into (1) trials designed to abort the biochemical cascade after injury-neuroprotection, (2) trials primarily designed to test the effect of hypothermia in reducing elevated intracranial pressure (ICP), and (3) trials with features of both neuroprotection and elevated ICP control. Three of the four clinical trials testing hypothermia induction after failure of conventional means of ICP control showed decreased mortality rate, though sample sizes were small and findings were not always statistically significant. Nine randomized trials have tested hypothermia as a neuroprotectant, inducing it from 2.5 to 15 hours after injury and continuing it for a predetermined period of time regardless of ICP. Eight of these nine trials have been negative with three finding an effect in patients with evacuated hematomas, two of these if hypothermia is rendered before or soon after craniotomy. Despite extensive clinical testing over a range of treatment windows after injury, there is no evidence for the use of hypothermia as a neuroprotectant in patients with diffuse brain injury. Four randomized trials have features of neuroprotection and ICP control, randomizing and initiating hypothermia within 15 hours of injury and continuing hypothermia for the duration of ICP elevation. All found improved outcome and reduced ICP. Based on these findings and the negative results of neuroprotection trials that extended hypothermia for a defined period of time, it is likely that the mechanism of protection in these combined mechanism trials was early control of ICP. This literature suggests the need for clinical trials with two distinct objectives-(1) testing hypothermia for ICP control when conventional means (sedation and paralysis, mannitol, hyperventilation, and cerebrospinal fluid drainage) fail and (2) testing early induction of hypothermia before hematoma evacuation individualizing the duration of hypothermia to the patient's ICP responses.

Therapeutic hypothermia: benefits, mechanisms and potential clinical applications in neurological, cardiac and kidney injury

Therapeutic hypothermia involves the controlled reduction of core temperature to attenuate the secondary organ damage which occurs following a primary injury. Clinicians have been increasingly using therapeutic hypothermia to prevent or ameliorate various types of neurological injury and more recently for some forms of cardiac injury. In addition, some recent evidence suggests that therapeutic hypothermia may also provide benefit following acute kidney injury. In this review we will examine the potential mechanisms of action and current clinical evidence surrounding the use of therapeutic hypothermia. We will discuss the ideal methodological attributes of future studies using hypothermia to optimise outcomes following organ injury, in particular neurological injury. We will assess the importance of target hypothermic temperature, time to achieve target temperature, duration of cooling, and re-warming rate on outcomes following neurological injury to gain insights into important factors which may also influence the success of hypothermia in other organ injuries, such as the heart and the kidney. Finally, we will examine the potential of therapeutic hypothermia as a future kidney protective therapy.

Brain temperature: heat production, elimination and clinical relevance

Neurological insults are a leading cause of morbidity and mortality, both in adults and especially in children. Among possible therapeutic strategies to limit clinical cerebral damage and improve outcomes, hypothermia remains a promising and beneficial approach. However, its advantages are still debated after decades of use. Studies in adults have generated conflicting results, whereas in children recent data even suggest that hypothermia may be detrimental. Is it because brain temperature physiology is not well understood and/or not applied properly, that hypothermia fails to convince clinicians of its potential benefits? Or is it because hypothermia is not, as believed, the optimal strategy to improve outcome in patients affected with an acute neurological insult? This review article should help to explain the fundamental physiological principles of brain heat production, distribution and elimination under normal conditions and discuss why hypothermia cannot yet be recommended routinely in the management of children affected with various neurological insults.

Therapeutic hypothermia: critical review of the molecular mechanisms of action

Therapeutic hypothermia (TH) is nowadays one of the most important methods of neuroprotection. The events that occur after an episode of ischemia are multiple and hypothermia can affect the various steps of this cascade. The mechanisms of action of TH are varied and the possible explanation for the benefits of this therapy is probably the multiple mechanisms of action blocking the cascade of ischemia on many levels. TH can affect many metabolic pathways, reactions of inflammation, apoptosis processes, and promote neuronal integrity. To know the mechanisms of action of TH will allow a better understanding about the indications for this therapy and the possibility of searching for other therapies when used in conjunction with hypothermia will provide a therapeutic synergistic effect.

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.

Prophylactic hypothermia for traumatic brain injury: a quantitative systematic review

INTRODUCTION

During the past 7 years, considerable new evidence has accumulated supporting the use of prophylactic hypothermia for traumatic brain injury (TBI). Studies can be divided into 2 broad categories: studies with protocols for cooling for a short, predetermined period (e.g., 24-48 h), and those that cool for longer periods and/or terminate based on the normalization of intracranial pressure (ICP). There have been no systematic reviews of hypothermia for TBI that include this recent new evidence.

METHODS

This analysis followed the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions and the QUOROM (quality of reporting of meta-analyses) statement. We developed a comprehensive search strategy to identify all randomized controlled trials (RCTs) comparing therapeutic hypothermia with standard management in TBI patients. We searched Embase, MEDLINE, Web of Science, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, ProceedingsFirst and PapersFirst. Additional relevant articles were identified by hand-searching conference proceedings and bibliographies. All stages of study identification and selection, quality assessment and analysis were conducted according to prospectively defined criteria. Study quality was determined by assessment of each study for the use of allocation concealment and outcome assessment blinding. Studies were divided into 2 a priori-defined subgroups for analysis based on cooling strategy: short term (< or = 48 h), and long term or goal-directed (> 48 h and/or continued until normalization of ICP). Outcomes included mortality and good neurologic outcome (defined as Glasgow Outcome Scale score of 4 or 5). Pooling of primary outcomes was completed using relative risk (RR) and reported with 95% confidence intervals (CIs).

RESULTS

Of 1709 articles, 12 studies with 1327 participants were selected for quantitative analysis. Eight of these studies cooled according to a long-term or goal-directed strategy, and 4 used a short-term strategy. Summary results demonstrated lower mortality (RR 0.73, 95% CI 0.62-0.85) and more common good neurologic outcome (RR 1.52, 95% CI 1.28-1.80). When only short-term cooling studies were analyzed, neither mortality (RR 0.98, 95% CI 0.75-1.30) nor neurologic outcome (RR 1.31, 95% CI 0.94-1.83) were improved. In 8 studies of long-term or goal-directed cooling, mortality was reduced (RR 0.62, 95% CI 0.51-0.76) and good neurologic outcome was more common (RR 1.68, 95% CI 1.44-1.96).

CONCLUSION

The best available evidence to date supports the use of early prophylactic mild-to-moderate hypothermia in patients with severe TBI (Glasgow Coma Scale score < or = 8) to decrease mortality and improve rates of good neurologic recovery. This treatment should be commenced as soon as possible after injury (e.g., in the emergency department after computed tomography) regardless of initial ICP, or before ICP is measured. Most studies report using a temperature of 32 degrees -34 degrees C. The maximal benefit occurred with a long-term or goal-directed cooling protocol, in which cooling was continued for at least 72 hours and/or until stable normalization of intracranial pressure for at least 24 hours was achieved. There is large potential for further research on this therapy in prehospital and emergency department settings.

Hypothermia and rapid rewarming is associated with worse outcome following traumatic brain injury

PURPOSE

The purpose of the present study was to determine (1) the prevalence and degree of hypothermia in patients on emergency department admission and (2) the effect of hypothermia and rate of rewarming on patient outcomes.

METHODS

Secondary data analysis was conducted on patients admitted to a level I trauma center following severe traumatic brain injury (n = 147). Patients were grouped according to temperature on admission according to hypothermia status and rate of rewarming (rapid or slow). Regression analyses were performed.

FINDINGS

Hypothermic patients were more likely to have lower postresuscitation Glasgow Coma Scale scores and a higher initial injury severity score. Hypothermia on admission was correlated with longer intensive care unit stays, a lower Glasgow Coma Scale score at discharge, higher mortality rate, and lower Glasgow outcome score-extended scores up to 6 months postinjury (P < .05). When controlling for other factors, rewarming rates more than 0.25°C/h were associated with lower Glasgow Coma Scale scores at discharge, longer intensive care unit length of stay, and higher mortality rate than patients rewarmed more slowly although these did not reach statistical significance.

CONCLUSION

Hypothermia on admission is correlated with worse outcomes in brain-injured patients. Patients with traumatic brain injury who are rapidly rewarmed may be more likely to have worse outcomes. Trauma protocols may need to be reexamined to include controlled rewarming at rates 0.25°C/h or less.

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.

Mechanisms of action, physiological effects, and complications of hypothermia

BACKGROUND

Mild to moderate hypothermia (32-35 degrees C) is the first treatment with proven efficacy for postischemic neurological injury. In recent years important insights have been gained into the mechanisms underlying hypothermia's protective effects; in addition, physiological and pathophysiological changes associated with cooling have become better understood.

OBJECTIVE

To discuss hypothermia's mechanisms of action, to review (patho)physiological changes associated with cooling, and to discuss potential side effects.

DESIGN

Review article.

INTERVENTIONS

None.

MAIN RESULTS

A myriad of destructive processes unfold in injured tissue following ischemia-reperfusion. These include excitotoxicty, neuroinflammation, apoptosis, free radical production, seizure activity, blood-brain barrier disruption, blood vessel leakage, cerebral thermopooling, and numerous others. The severity of this destructive cascade determines whether injured cells will survive or die. Hypothermia can inhibit or mitigate all of these mechanisms, while stimulating protective systems such as early gene activation. Hypothermia is also effective in mitigating intracranial hypertension and reducing brain edema. Side effects include immunosuppression with increased infection risk, cold diuresis and hypovolemia, electrolyte disorders, insulin resistance, impaired drug clearance, and mild coagulopathy. Targeted interventions are required to effectively manage these side effects. Hypothermia does not decrease myocardial contractility or induce hypotension if hypovolemia is corrected, and preliminary evidence suggests that it can be safely used in patients with cardiac shock. Cardiac output will decrease due to hypothermia-induced bradycardia, but given that metabolic rate also decreases the balance between supply and demand, is usually maintained or improved. In contrast to deep hypothermia (<or=30 degrees C), moderate hypothermia does not induce arrhythmias; indeed, the evidence suggests that arrhythmias can be prevented and/or more easily treated under hypothermic conditions.

CONCLUSIONS

Therapeutic hypothermia is a highly promising treatment, but the potential side effects need to be properly managed particularly if prolonged treatment periods are required. Understanding the underlying mechanisms, awareness of physiological changes associated with cooling, and prevention of potential side effects are all key factors for its effective clinical usage.

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.

[Therapeutic hypothermia in neurocritical patients]

Induced hypothermia in neurocritical patients is one of the most promising neuroprotective therapies in the last decade. Unfortunately, the promising results obtained in experimental studies have had an unequal reflection in the different diseases that affect the neurocritical patient. The use of therapeutic hypothermia is clearly established in patients with neurological deterioration after cardiac arrest. On the contrary, its use in patients with traumatic brain injury is highly controversial. There is not enough evidence in stroke and hemorrhagic patients to support its use except in clinical trials. Nowadays, the greater understanding of the pathophysiology of secondary brain damage, the go od clinical results obtained in randomized clinical trials in patients with cerebral anoxia after ventricular fibrillation and the new cooling methods that have appeared have improved the interest of hypothermia in neurocritical patients. Induced hypothermia has a role in the intensive care unit. Critical care physicians should be familiar with the physiologic effects, current indications, techniques, and complications of induced hypothermia. This review elaborates on the clinical implications of hypothermia research in traumatic brain injury, anoxic, brain injury, stroke and intracerebral hemorrhage.

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, Web of Knowledge; Science Citation Index [expanded], CENTRAL, MEDLINE and EMBASE. We handsearched conference proceedings and checked reference lists of relevant articles. The search was updated on 23 May 2008.

SELECTION CRITERIA

Randomised controlled trials of hypothermia to a maximum of 35 degrees C for at least 12 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 22 trials with a total of 1409 randomised patients. Twenty trials involving 1382 patients reported deaths. There were fewer deaths in patients treated with hypothermia than in the control group (OR 0.76, 95% CI 0.60 to 0.97). Eight trials with good allocation concealment showed a non-significant reduction in the likelihood of death for patients treated with hypothermia (OR 0.96, 95% CI 0.68 to 1.35). Twenty trials involving 1382 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 0.69, 95% CI 0.55 to 0.86). Eight trials with good allocation concealment showed a non-significant reduction in the likelihood of unfavourable outcome for patients treated with hypothermia (OR 0.79, 95% CI 0.57 to 1.08). Hypothermia treatment was associated with an increase in odds of pneumonia but this increase was not statistically significant for trials with good allocation concealment (3 trials, 69 patients, OR 1.06, 95% CI 0.38 to 2.97).

AUTHORS' CONCLUSIONS

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 some statistically non-significant benefit of hypothermia which could be due to the play of chance. Hypothermia may increase the risk of pneumonia. Due to uncertainties in its effects, hypothermia should only be given to patients taking part in a randomised controlled trial with good allocation concealment.

[Indications and uses of neuromuscular blocking agents in the ICU]

Although many questions are still debated, some recommendations can be formulated regarding the use of neuromuscular blocking agents in the ICU. A transient curarization can be used during brief diagnostic or therapeutic procedures in order to avoid haemodynamic consequences of deep sedation. A volume controlled ventilation has to be used during the procedure. In ARDS patients, a prolonged curarization of 48 h or more is beneficial regarding systemic oxygenation, even in patients well adapted to their ventilator. The use of cisatracurium should be recommended in this context. The depth of curarization has to be checked by using a train of four stimulation at the corugator supercilii with an endpoint of 2/4 responses. A recovery from curarization should be daily envisaged if possible, in order to check the depth of the underlying sedation. In brain injured patients, a curarization can be envisaged if adaptation to the ventilator remains difficult or if normothermia or moderate hypothermia, if indicated, cannot be obtained. However, these attitudes are not based on specific data at the present time.

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.

Hypothermia treatment for traumatic brain injury: a systematic review and meta-analysis

In this study, we conducted an updated meta-analysis of the effects of hypothermia therapy on mortality, favorable neurologic outcome, and associated adverse effects in adults with traumatic brain injury (TBI) for use by Brain Trauma Foundation (BTF)/American Association of Neurological Surgeons (AANS) task force to develop evidence-based treatment guidelines. Our data sources relied on handsearches of four previous good-quality systematic reviews, which all conducted electronic searches of primarily MEDLINE (OVID), EMBASE, and Cochrane Library. An independent, supplemental electronic search of MEDLINE was undertaken as well (last searched June 2007). Only English-language publications of randomized controlled trials of therapeutic hypothermia in adults with TBI were selected for analysis. Two reviewers independently abstracted data on trial design, patient population, hypothermia and cointervention protocols, patient outcomes, and aspects of methodological quality. Pooled relative risks (RR) and associated 95% confidence intervals (CIs) were calculated for each outcome using random-effects models. In the current study, only 13 trials met eligibility criteria, with a total of 1339 randomized patients. Sensitivity analyses revealed that outcomes were influenced by variations in methodological quality. Consequently, main analyses were conducted based on eight trials that demonstrated the lowest potential for bias (n = 781). Reductions in risk of mortality were greatest (RR 0.51; 95% CI 0.33, 0.79) and favorable neurologic outcomes much more common (RR 1.91; 95% CI 1.28, 2.85) when hypothermia was maintained for more than 48 h. However, this evidence comes with the suggestion that the potential benefits of hypothermia may likely be offset by a significant increase in risk of pneumonia (RR 2.37; 95% CI 1.37, 4.10). In sum, the present study's updated meta-analysis supports previous findings that hypothermic therapy constitutes a beneficial treatment of TBI in specific circumstances. Accordingly, the BTF/AANS guidelines task force has issued a Level III recommendation for optional and cautious use of hypothermia for adults with TBI.

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.

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.