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

Hypothermia for severe traumatic brain injury in adults: Recent lessons from randomized controlled trials

BACKGROUND

Traumatic brain injury (TBI) is a worldwide health concern associated with significant morbidity and mortality. In the United States, severe TBI is managed according to recommendations set forth in 2007 by the Brain Trauma Foundation (BTF), which were based on relatively low quality clinical trials. These guidelines prescribed the use of hypothermia for the management of TBI. Several randomized controlled trials (RCTs) of hypothermia for TBI have since been conducted. Despite this new literature, there is ongoing controversy surrounding the use of hypothermia for the management of severe TBI.

METHODS

We searched the PubMed database for all RCTs of hypothermia for TBI since 2007 with the intent to review the methodology outcomes of these trials. Furthermore, we aimed to develop evidence-based, expert opinions based on these recent studies.

RESULTS

We identified 8 RCTs of therapeutic hypothermia published since 2007 that focused on changes in neurologic outcomes or mortality in patients with severe TBI. The majority of these trials did not identify improvement with the use of hypothermia, though there were subgroups of patients that may have benefited from hypothermia. Differences in methodology prevented direct comparison between studies.

CONCLUSIONS

A growing body of literature disfavors the use of hypothermia for the management of severe TBI. In general, empiric hypothermia for severe TBI should be avoided. However, based on the results of recent trials, there may be some patients, such as those in Asian centers or with focal neurologic injury, who may benefit from hypothermia.

Study protocol - A systematic review and meta-analysis of hypothermia in experimental traumatic brain injury: Why have promising animal studies not been replicated in pragmatic clinical trials?

Traumatic brain injury (TBI) is a major cause of death and permanent disability. Systemic hypothermia, a treatment used in TBI for many decades, has recently been found to be associated with neutral or unfavourable clinical outcomes despite apparently promising preclinical research. Systematic review and meta‐analysis is a tool to summarize literature and observe trends in experimental design and quality that underpin its general conclusions. Here we aim to use these techniques to describe the use of hypothermia in animal TBI models, collating data relating to outcome and both study design and quality. From here we intend to observe correlations between features and attempt to explain any discrepancies found between animal and clinical data. This protocol describes the relevant methodology in detail.

Anesthesia for Patients with Traumatic Brain Injuries

Traumatic brain injury (TBI) represents a wide spectrum of disease and disease severity. Because the primary brain injury occurs before the patient enters the health care system, medical interventions seek principally to prevent secondary injury. Anesthesia teams that provide care for patients with TBI both in and out of the operating room should be aware of the specific therapies and needs of this unique and complex patient population.

Traumatic brain injury advancements

PURPOSE OF REVIEW

Traumatic brain injury (TBI) remains the leading cause of morbidity and mortality in the United States. Over the last decade, several advancements have been made in the field of TBI all aimed at improving outcomes.

RECENT FINDINGS

Advancements in the management of TBI have been made possible through improved understanding of basic pathophysiology associated with this condition. The aim of this review is to briefly highlight the underlying pathophysiology of TBI and the most recent advancements and novel strategies being used in its treatment. We also briefly discuss coagulopathy of TBI, clinical management of TBI and how it has evolved recently.

SUMMARY

The mortality associated with TBI continues to remain high and several novel strategies have emerged as potential candidates for the treatment of secondary brain injury. The clinical management of TBI and associated coagulopathy has evolved allowing for a more tailored approach toward its management.

A State-of-the-Science Overview of Randomized Controlled Trials Evaluating Acute Management of Moderate-to-Severe Traumatic Brain Injury

Moderate-to-severe traumatic brain injury (TBI) remains a major global challenge, with rising incidence, unchanging mortality and lifelong impairments. State-of-the-science reviews are important for research planning and clinical decision support. This review aimed to identify randomized controlled trials (RCTs) evaluating interventions for acute management of moderate/severe TBI, synthesize key RCT characteristics and findings, and determine their implications on clinical practice and future research. RCTs were identified through comprehensive database and other searches. Key characteristics, outcomes, risk of bias, and analysis approach were extracted. Data were narratively synthesized, with a focus on robust (multi-center, low risk of bias, n > 100) RCTs, and three-dimensional graphical figures also were used to explore relationships between RCT characteristics and findings. A total of 207 RCTs were identified. The 191 completed RCTs enrolled 35,340 participants (median, 66). Most (72%) were single center and enrolled less than 100 participants (69%). There were 26 robust RCTs across 18 different interventions. For 74% of 392 comparisons across all included RCTs, there was no significant difference between groups. Positive findings were broadly distributed with respect to RCT characteristics. Less than one-third of RCTs demonstrated low risk of bias for random sequence generation or allocation concealment, less than one-quarter used covariate adjustment, and only 7% employed an ordinal analysis approach. Considerable investment of resources in producing 191 completed RCTs for acute TBI management has resulted in very little translatable evidence. This may result from broad distribution of research effort, small samples, preponderance of single-center RCTs, and methodological shortcomings. More sophisticated RCT design, large multi-center RCTs in priority areas, increased focus on pre-clinical research, and alternatives to RCTs, such as comparative effectiveness research and precision medicine, are needed to fully realize the potential of acute TBI research to benefit patients.

Hypothermia in Traumatic Brain Injury

For over 50 years, clinicians have used hypothermia to manage traumatic brain injury (TBI). In the last two decades numerous trials have assessed whether hypothermia is of benefit in patients. Mild to moderate hypothermia reduces the intracranial pressure (ICP). Randomized control trials for short-term hypothermia indicate no benefit in outcome after severe TBI, whereas longer-term hypothermia could be of benefit by reducing ICP. This article summarises current evidence and gives recommendations based upon the conclusions.

A multicentre randomized controlled trial of moderate hypothermia to prevent intracranial hypertension in acute liver failure

BACKGROUND & AIMS

Animal models and human case series of acute liver failure (ALF) suggest moderate hypothermia (MH) to have protective effects against cerebral oedema (CO) development and intracranial hypertension (ICH). However, the optimum temperature for patient management is unknown. In a prospective randomized controlled trial we investigated if maintenance of MH prevented development of ICH in ALF patients at high risk of the complication.

METHODS

Patients with ALF, high-grade encephalopathy and intracranial pressure (ICP) monitoring in specialist intensive care units were randomized by sealed envelope to targeted temperature management (TTM) groups of 34°C (MH) or 36°C (control) for a period of 72h. Investigators were not blinded to group assignment. The primary outcome was a sustained elevation in ICP >25mmHg, with secondary outcomes the occurrence of predefined serious adverse effects, magnitude of ICP elevations and cerebral and all-cause hospital mortality (with or without transplantation).

RESULTS

Forty-six patients were randomized, of whom forty-three were studied. There was no significant difference between the TTM groups in the primary outcome during the study period (35% vs. 27%, p=0.56), for the MH (n=17) or control (n=26) groups respectively, relative risk 1.31 (95% CI 0.53-3.2). Groups had similar incidence of adverse events and overall mortality (41% vs. 46%, p=0.75).

CONCLUSIONS

In patients with ALF at high risk of ICH, MH at 33-34°C did not confer a benefit above management at 36°C in prevention of ICH or in overall survival. This study did not confirm advantage of its prophylactic use. (ISRCTN registration number 74268282; no funding.)

LAY SUMMARY

Studies in animals with acute liver failure (ALF) have suggested that cooling (hypothermia) could prevent or limit the development of brain swelling, a dangerous complication of the condition. There is limited data on its effects in humans. In a randomized controlled trial in severely ill patients with ALF we compared the effects of different temperatures and found no benefit on improving survival or preventing brain swelling by controlling temperature at 33-34°C against 36°C.

Traumatic brain injury: physiological targets for clinical practice in the prehospital setting and on the Neuro-ICU

PURPOSE OF REVIEW

Over many years, understanding of the pathophysiology in traumatic brain injury (TBI) has resulted in the development of core physiological targets and therapies to preserve cerebral oxygenation, and in doing so prevent secondary insult. The present review revisits the evidence for these targets and therapies.

RECENT FINDINGS

Achieving oxygen, carbon dioxide, blood pressure, temperature and glucose targets remain a key goal of therapy in TBI, as does the role of effective prehospital care. Physician led air ambulance teams reduce mortality. Normobaric hyperoxia is dangerous to the injured brain; as are both high and low carbon dioxide levels. Hypotension is life threatening and higher targets have now been suggested in TBI. Both therapeutic normothermia and hypothermia have a role in specific groups of patients with TBI. Although consensus has not been reached on the optimal intravenous fluid for resuscitation in TBI, vigilant goal-directed fluid administration may improve outcome. Osmotherapeutic agents such as hypertonic sodium lactate solutions may also have a role alongside conventional agents.

SUMMARY

Maintaining physiological targets in several areas remains part of protocol led care in the acute phase of TBI management. As evidence accumulates however, the target values and therefore therapies may be set to change.

Long-Term Effects of Induced Hypothermia on Local and Systemic Inflammation - Results from a Porcine Long-Term Trauma Model

Background

Hypothermia has been discussed as playing a role in improving the early phase of systemic inflammation. However, information on the impact of hypothermia on the local inflammatory response is sparse. We therefore investigated the kinetics of local and systemic inflammation in the late posttraumatic phase after induction of hypothermia in an established porcine long-term model of combined trauma.

Materials & Methods

Male pigs (35 ± 5kg) were mechanically ventilated and monitored over the study period of 48 h. Combined trauma included tibia fracture, lung contusion, liver laceration and pressure-controlled hemorrhagic shock (MAP < 30 ± 5 mmHg for 90 min). After resuscitation, hypothermia (33°C) was induced for a period of 12 h (HT-T group) with subsequent re-warming over a period of 10 h. The NT-T group was kept normothermic. Systemic and local (fracture hematoma) cytokine levels (IL-6, -8, -10) and alarmins (HMGB1, HSP70) were measured via ELISA.

Results

Severe signs of shock as well as systemic and local increases of pro-inflammatory mediators were observed in both trauma groups. In general the local increase of pro- and anti-inflammatory mediator levels was significantly higher and prolonged compared to systemic concentrations. Induction of hypothermia resulted in a significantly prolonged elevation of both systemic and local HMGB1 levels at 48 h compared to the NT-T group. Correspondingly, local IL-6 levels demonstrated a significantly prolonged increase in the HT-T group at 48 h.

Conclusion

A prolonged inflammatory response might reduce the well-described protective effects on organ and immune function observed in the early phase after hypothermia induction. Furthermore, local immune response also seems to be affected. Future studies should aim to investigate the use of therapeutic hypothermia at different degrees and duration of application.

Neurologic outcome of comatose survivors after hanging: a retrospective multicenter study

PURPOSE

The aim of this study is to identify the neurologic outcome of hanging patients and prognostic factors.

MATERIALS AND METHODS

We retrospectively investigated comatose hanging patients who arrived at the emergency departments (EDs) of twelve academic tertiary care centers during a period of seven years (2006-2012). Patients were analyzed separately according to whether out-of-hospital cardiac arrest (OHCA) occurred or not. The neurologic outcome was evaluated using the Cerebral Performance Category (CPC) at the time of hospital discharge.

RESULTS

A total of 1118 patients were admitted to the ED after hanging attempts. There were 159 comatose patients who did not experience OHCA. Twelve (7.5%) of 159 patients were discharged from the hospital with a poor neurologic outcome (CPC 3-5). These 12 patients received only conservative management without therapeutic hypothermia. On multivariate logistic regression analysis, mental state upon ED arrival and arterial pH were predicting factors for poor prognosis. One hundred twenty-one patients suffered OHCA and experienced restored spontaneous circulation after cardiopulmonary resuscitation. Among them, only five (4.1%) patients recovered consciousness to the level of CPC 1-2. The initial arterial pH and HCO3(-) were prognostic factors in hanging patients with OHCA.

CONCLUSIONS

Even though cardiac arrest did not occur after hanging injuries, 7.5% of patients could not recover consciousness. Therapeutic hypothermia should be considered for such patients. If OHCA occurred after the hanging injury, the proportion of patients with good neurologic outcome was very low at 4.1%.

The European guideline on management of major bleeding and coagulopathy following trauma: fourth edition

BACKGROUND

Severe trauma continues to represent a global public health issue and mortality and morbidity in trauma patients remains substantial. A number of initiatives have aimed to provide guidance on the management of trauma patients. This document focuses on the management of major bleeding and coagulopathy following trauma and encourages adaptation of the guiding principles to each local situation and implementation within each institution.

METHODS

The pan-European, multidisciplinary Task Force for Advanced Bleeding Care in Trauma was founded in 2004 and included representatives of six relevant European professional societies. The group used a structured, evidence-based consensus approach to address scientific queries that served as the basis for each recommendation and supporting rationale. Expert opinion and current clinical practice were also considered, particularly in areas in which randomised clinical trials have not or cannot be performed. Existing recommendations were reconsidered and revised based on new scientific evidence and observed shifts in clinical practice; new recommendations were formulated to reflect current clinical concerns and areas in which new research data have been generated. This guideline represents the fourth edition of a document first published in 2007 and updated in 2010 and 2013.

RESULTS

The guideline now recommends that patients be transferred directly to an appropriate trauma treatment centre and encourages use of a restricted volume replacement strategy during initial resuscitation. Best-practice use of blood products during further resuscitation continues to evolve and should be guided by a goal-directed strategy. The identification and management of patients pre-treated with anticoagulant agents continues to pose a real challenge, despite accumulating experience and awareness. The present guideline should be viewed as an educational aid to improve and standardise the care of the bleeding trauma patients across Europe and beyond. This document may also serve as a basis for local implementation. Furthermore, local quality and safety management systems need to be established to specifically assess key measures of bleeding control and outcome.

CONCLUSIONS

A multidisciplinary approach and adherence to evidence-based guidance are key to improving patient outcomes. The implementation of locally adapted treatment algorithms should strive to achieve measureable improvements in patient outcome.

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.

Prolonged Localized Mild Hypothermia Does Not Affect Seizure Activity After Intracerebral Hemorrhage in Rats

Intracerebral hemorrhage (ICH) is a devastating stroke with high morbidity and mortality. Post-ICH seizures are a common complication, potentially increasing brain injury and the risk of delayed epilepsy. Mild therapeutic hypothermia (HYPO, ∼33°C) is neuroprotective against several brain insults, such as ischemia, while also mitigating seizure incidence and severity in some instances. Therefore, we tested whether brain-selective HYPO reduced electrographic seizure activity after a collagenase-induced striatal ICH in rats. Animals were injected unilaterally with 0.14 U of bacterial collagenase, implanted with a unilateral brain cooling device, and a probe to bilaterally record electroencephalographic (EEG) activity. Cooling began 6 hours after collagenase infusion and was maintained for 48 hours, followed by rewarming over 6 hours. Our protocol did not affect EEG activity in naïve rats, nor did it increase bleeding after ICH (∼50 μL). Epileptiform activity commonly occurred in untreated ICH rats (∼60% of animals), but HYPO did not affect the incidence, timing, total duration of seizures, or the peaks occurring during epileptiform activity. However, longer average duration was detected on the ipsilateral side to stroke in the HYPO group (p < 0.05). Cooling did not affect neurological deficits (e.g., circling), measured 7 and 14 days after ICH, or lesion volume (∼35 mm(3)). In addition, there was no relationship among endpoints (e.g., seizures and lesion size). In summary, HYPO failed to reduce seizure activity after ICH, which fits with our separate findings that cooling does not mitigate thrombin and iron-mediated secondary injury mechanisms thought to cause seizures after ICH. Additional research is needed to identify better HYPO protocols and the use of cotreatments to maximize the benefit of HYPO to ICH patients.

Therapeutic hypothermia and targeted temperature management in traumatic brain injury: Clinical challenges for successful translation

The use of therapeutic hypothermia (TH) and targeted temperature management (TTM) for severe traumatic brain injury (TBI) has been tested in a variety of preclinical and clinical situations. Early preclinical studies showed that mild reductions in brain temperature after moderate to severe TBI improved histopathological outcomes and reduced neurological deficits. Investigative studies have also reported that reductions in post-traumatic temperature attenuated multiple secondary injury mechanisms including excitotoxicity, free radical generation, apoptotic cell death, and inflammation. In addition, while elevations in post-traumatic temperature heightened secondary injury mechanisms, the successful implementation of TTM strategies in injured patients to reduce fever burden appear to be beneficial. While TH has been successfully tested in a number of single institutional clinical TBI studies, larger randomized multicenter trials have failed to demonstrate the benefits of therapeutic hypothermia. The use of TH and TTM for treating TBI continues to evolve and a number of factors including patient selection and the timing of the TH appear to be critical in successful trial design. Based on available data, it is apparent that TH and TTM strategies for treating severely injured patients is an important therapeutic consideration that requires more basic and clinical research. Current research involves the evaluation of alternative cooling strategies including pharmacologically-induced hypothermia and the combination of TH or TTM approaches with more selective neuroprotective or reparative treatments. This manuscript summarizes the preclinical and clinical literature emphasizing the importance of brain temperature in modifying secondary injury mechanisms and in improving traumatic outcomes in severely injured patients. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Hypothermia for Intracranial Hypertension after Traumatic Brain Injury

BACKGROUND

In patients with traumatic brain injury, hypothermia can reduce intracranial hypertension. The benefit of hypothermia on functional outcome is unclear.

METHODS

We randomly assigned adults with an intracranial pressure of more than 20 mm Hg despite stage 1 treatments (including mechanical ventilation and sedation management) to standard care (control group) or hypothermia (32 to 35°C) plus standard care. In the control group, stage 2 treatments (e.g., osmotherapy) were added as needed to control intracranial pressure. In the hypothermia group, stage 2 treatments were added only if hypothermia failed to control intracranial pressure. In both groups, stage 3 treatments (barbiturates and decompressive craniectomy) were used if all stage 2 treatments failed to control intracranial pressure. The primary outcome was the score on the Extended Glasgow Outcome Scale (GOS-E; range, 1 to 8, with lower scores indicating a worse functional outcome) at 6 months. The treatment effect was estimated with ordinal logistic regression adjusted for prespecified prognostic factors and expressed as a common odds ratio (with an odds ratio <1.0 favoring hypothermia).

RESULTS

We enrolled 387 patients at 47 centers in 18 countries from November 2009 through October 2014, at which time recruitment was suspended owing to safety concerns. Stage 3 treatments were required to control intracranial pressure in 54% of the patients in the control group and in 44% of the patients in the hypothermia group. The adjusted common odds ratio for the GOS-E score was 1.53 (95% confidence interval, 1.02 to 2.30; P=0.04), indicating a worse outcome in the hypothermia group than in the control group. A favorable outcome (GOS-E score of 5 to 8, indicating moderate disability or good recovery) occurred in 26% of the patients in the hypothermia group and in 37% of the patients in the control group (P=0.03).

CONCLUSIONS

In patients with an intracranial pressure of more than 20 mm Hg after traumatic brain injury, therapeutic hypothermia plus standard care to reduce intracranial pressure did not result in outcomes better than those with standard care alone. (Funded by the National Institute for Health Research Health Technology Assessment program; Current Controlled Trials number, ISRCTN34555414.).

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

Introduction

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

Methods

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

Results

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

Conclusions

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

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.

Induced hypothermia during resuscitation from hemorrhagic shock attenuates microvascular inflammation in the rat mesenteric microcirculation

Microvascular inflammation occurs during resuscitation following hemorrhagic shock, causing multiple organ dysfunction and mortality. Preclinical evidence suggests that hypothermia may have some benefit in selected patients by decreasing this inflammation, but this effect has not been extensively studied. Intravital microscopy was used to visualize mesenteric venules of anesthetized rats in real time to evaluate leukocyte adherence and mast cell degranulation. Animals were randomly allocated to normotensive or hypotensive groups and further subdivided into hypothermic and normothermic resuscitation (n = 6 per group). Animals in the shock groups underwent mean arterial blood pressure reduction to 40 to 45 mmHg for 1 h via blood withdrawal. During the first 2 h following resuscitation by infusion of shed blood plus double that volume of normal saline, rectal temperature of the hypothermic groups was maintained at 32°C to 34°C, whereas the normothermic groups were maintained between 36°C to 38°C. The hypothermic group was then rewarmed for the final 2 h of resuscitation. Leukocyte adherence was significantly lower after 2 h of hypothermic resuscitation compared with normothermic resuscitation: (2.8 ± 0.8 vs. 8.3 ± 1.3 adherent leukocytes, P = 0.004). Following rewarming, leukocyte adherence remained significantly different between hypothermic and normothermic shock groups: (4.7 ± 1.2 vs. 9.5 ± 1.6 adherent leukocytes, P = 0.038). Mast cell degranulation index (MDI) was significantly decreased in the hypothermic (1.02 ± 0.04 MDI) versus normothermic (1.22 ± 0.07 MDI) shock groups (P = 0.038) after the experiment. Induced hypothermia during resuscitation following hemorrhagic shock attenuates microvascular inflammation in rat mesentery. Furthermore, this decrease in inflammation is carried over after rewarming takes place.

Matrix Metalloproteinase Expression in Contusional Traumatic Brain Injury: A Paired Microdialysis Study

Matrix metalloproteinases (MMPs) are extracellular enzymes that have been implicated in the pathophysiology of blood–brain barrier (BBB) breakdown, contusion expansion, and vasogenic edema after traumatic brain injury (TBI). Specifically, in focal injury models, increased MMP-9 expression has been observed in pericontusional brain, and MMP-9 inhibitors reduce brain swelling and final lesion volume. The aim of this study was to examine whether there is a similarly localized increase of MMP concentrations in patients with contusional TBI. Paired microdialysis catheters were inserted into 12 patients with contusional TBI (with or without associated mass lesion) targeting pericontusional and radiologically normal brain defined on admission computed tomography scan. Microdialysate was pooled every 8 h and analyzed for MMP-1, -2, -7, -9, and -10 using a multiplex immunoassay. Concentrations of MMP-1, -2, and -10 were similar at both monitoring sites and did not show discernible temporal trends. Overall, there was a gradual increase in MMP-7 concentrations in both normal and injured brain over the monitoring period, although this was not consistent in every patient. MMP-9 concentrations were elevated in pericontusional, compared to normal, brain, with the maximal difference at the earliest monitoring times (i.e., <24 h postinjury). Repeated-measures analysis of variance showed that MMP-9 concentrations were significantly higher in pericontusional brain (p=0.03) and within the first 72 h of injury, compared with later in the monitoring period (p=0.04). No significant differences were found for the other MMPs assayed. MMP-9 concentrations are increased in pericontusional brain early post-TBI and may represent a potential therapeutic target to reduce hemorrhagic progression and vasogenic edema.

[News and perspectives in neurocritical care]

Neurocritical care is an ever-evolving discipline and its implementation in intensive care leads to reduction in mortality and to improvement of functional outcome in patients with devastating injuries to the nervous system. However, the decisive elements of the complete field of neurocritical care remain relatively unclear, as well as the exact ways to optimize them. During recent years new insights have been gained and new exciting studies have been initiated from which results are soon to be expected. This review focuses on the following management aspects: neuromonitoring, airway and ventilation, endovascular therapy, cerebrospinal fluid drainage, decompressive craniectomy, hematoma evacuation, blood pressure, and targeted temperature management. The application of these measures to brain diseases and injuries frequently treated in neurointensive care units will be addressed in the context of current studies.

Can Therapeutic Hypothermia Be Guided by Advanced Neuromonitoring in Neurocritical Care Patients? A Review

The impact of therapeutic hypothermia (TH) on long-term neurological outcome is still controversial. Data on the effects of TH on brain homeostasis are mostly derived from experimental research. Invasive multimodal neuromonitoring techniques may provide additional insight into pathophysiological changes associated with primary or secondary brain injury in humans. In this study we describe the principles of multimodal neuromonitoring and its potential in the clinical setting of TH. We call for more research using multimodal neuromonitoring techniques in patients undergoing TH to optimize cooling and rewarming strategies.

Considerations for neuroprotection in the traumatic brain injury population

Traumatic brain injury can occur very quickly, but the sequelae of the injury can be life ending or life altering. Aside from prevention, the primary injury cannot be controlled; however, health care workers can influence the amount of secondary injury to the brain. This article describes potential neuroprotective methods, such as cooling, craniectomy, and medications, to help to save the brain.

Prophylactic antibiotics are associated with a lower incidence of pneumonia in cardiac arrest survivors treated with targeted temperature management

INTRODUCTION

Prophylactic antibiotics (PRO) reduce the incidence of early-onset pneumonia in comatose patients with structural brain injury, but have not been examined in cardiac arrest survivors undergoing targeted temperature management (TTM). We investigated the effect of PRO on the development of pneumonia in that population.

METHODS

We conducted a retrospective cohort study comparing patients treated with PRO to those not receiving PRO (no-PRO) using Northern Hypothermia Network registry data. Cardiac arrest survivors ≥ 18 years of age with a GCS<8 at hospital admission and treated with TTM at 32-34 °C were enrolled in the registry. Differences were analyzed in univariate analyses and with logistic regression models to evaluate independent associations of clinical factors with incidence of pneumonia and good functional outcome.

RESULTS

416 of 1240 patients (33.5%) received PRO. Groups were similar in age, gender, arrest location, initial rhythm, and time from collapse to return of spontaneous circulation. PRO patients had less pneumonia (12.6% vs. 54.9%, p < 0.001) and less sepsis (1.2 vs. 5.7%, p < 0.001) compared to no-PRO patients. ICU length of stay (98 vs. 100 h, p = 0.2) and incidence of a good functional outcome (41.1 vs. 36.6%, p = 0.19) were similar between groups. Backwards stepwise logistic regression demonstrated PRO were independently associated with a lower incidence of pneumonia (OR 0.09, 95% 0.06-0.14, p < 0.001) and a similar incidence of good functional outcome.

CONCLUSIONS

Prophylactic antibiotics were associated with a reduced incidence of pneumonia but a similar rate of good functional outcome.

Temperature modulation with an esophageal heat transfer device - a pediatric swine model study

Background

An increasing number of conditions appear to benefit from control and modulation of temperature, but available techniques to control temperature often have limitations, particularly in smaller patients with high surface to mass ratios. We aimed to evaluate a new method of temperature modulation with an esophageal heat transfer device in a pediatric swine model, hypothesizing that clinically significant modulation in temperature (both increases and decreases of more than 1°C) would be possible.

Methods

Three female Yorkshire swine averaging 23 kg were anesthetized with inhalational isoflurane prior to placement of the esophageal device, which was powered by a commercially available heat exchanger. Swine temperature was measured rectally and cooling and warming were performed by selecting the appropriate external heat exchanger mode. Temperature was recorded over time in order to calculate rates of temperature change. Histopathology of esophageal tissue was performed after study completion.

Results

Average swine baseline temperature was 38.3°C. Swine #1 exhibited a cooling rate of 3.5°C/hr; however, passive cooling may have contributed to this rate. External warming blankets maintained thermal equilibrium in swine #2 and #3, demonstrating maximum temperature decrease of 1.7°C/hr. Warming rates averaged 0.29°C/hr. Histopathologic analysis of esophageal tissue showed no adverse effects.

Conclusions

An esophageal heat transfer device successfully modulated the temperature in a pediatric swine model. This approach to temperature modulation may offer a useful new modality to control temperature in conditions warranting temperature management (such as maintenance of normothermia, induction of hypothermia, fever control, or malignant hyperthermia).

Early Implementation of THAM for ICP Control: Therapeutic Hypothermia Avoidance and Reduction in Hypertonics/Hyperosmotics

Background. Tromethamine (THAM) has been demonstrated to reduce intracranial pressure (ICP). Early consideration for THAM may reduce the need for other measures for ICP control. Objective. To describe 4 cases of early THAM therapy for ICP control and highlight the potential to avoid TH and paralytics and achieve reduction in sedation and hypertonic/hyperosmotic agent requirements. Methods. We reviewed the charts of 4 patients treated with early THAM for ICP control. Results. We identified 2 patients with aneurysmal subarachnoid hemorrhage (SAH) and 2 with traumatic brain injury (TBI) receiving early THAM for ICP control. The mean time to initiation of THAM therapy was 1.8 days, with a mean duration of 5.3 days. In all patients, after 6 to 12 hours of THAM administration, ICP stability was achieved, with reduction in requirements for hypertonic saline and hyperosmotic agents. There was a relative reduction in mean hourly hypertonic saline requirements of 89.1%, 96.1%, 82.4%, and 97.0% for cases 1, 2, 3, and 4, respectively, comparing pre- to post-THAM administration. Mannitol, therapeutic hypothermia, and paralytics were avoided in all patients. Conclusions. Early administration of THAM for ICP control could potentially lead to the avoidance of other ICP directed therapies. Prospective studies of early THAM administration are warranted.

Capillary transit time heterogeneity and flow-metabolism coupling after traumatic brain injury

Most patients who die after traumatic brain injury (TBI) show evidence of ischemic brain damage. Nevertheless, it has proven difficult to demonstrate cerebral ischemia in TBI patients. After TBI, both global and localized changes in cerebral blood flow (CBF) are observed, depending on the extent of diffuse brain swelling and the size and location of contusions and hematoma. These changes vary considerably over time, with most TBI patients showing reduced CBF during the first 12 hours after injury, then hyperperfusion, and in some patients vasospasms before CBF eventually normalizes. This apparent neurovascular uncoupling has been ascribed to mitochondrial dysfunction, hindered oxygen diffusion into tissue, or microthrombosis. Capillary compression by astrocytic endfeet swelling is observed in biopsies acquired from TBI patients. In animal models, elevated intracranial pressure compresses capillaries, causing redistribution of capillary flows into patterns argued to cause functional shunting of oxygenated blood through the capillary bed. We used a biophysical model of oxygen transport in tissue to examine how capillary flow disturbances may contribute to the profound changes in CBF after TBI. The analysis suggests that elevated capillary transit time heterogeneity can cause critical reductions in oxygen availability in the absence of 'classic' ischemia. We discuss diagnostic and therapeutic consequences of these predictions.

Stem cell therapy for neonatal hypoxic-ischemic encephalopathy

Treatments for neonatal hypoxic-ischemic encephalopathy (HIE) have been limited. The aim of this paper is to offer translational research guidance on stem cell therapy for neonatal HIE by examining clinically relevant animal models, practical stem cell sources, safety and efficacy of endpoint assays, as well as a general understanding of modes of action of this cellular therapy. In order to do so, we discuss the clinical manifestations of HIE, highlighting its overlapping pathologies with stroke and providing insights on the potential of cell therapy currently investigated in stroke, for HIE. To this end, we draw guidance from recommendations outlined in stem cell therapeutics as an emerging paradigm for stroke or STEPS, which have been recently modified to Baby STEPS to cater for the “neonatal” symptoms of HIE. These guidelines recognized that neonatal HIE exhibit distinct disease symptoms from adult stroke in need of an innovative translational approach that facilitates the entry of cell therapy in the clinic. Finally, new information about recent clinical trials and insights into combination therapy are provided with the vision that stem cell therapy may benefit from available treatments, such as hypothermia, already being tested in children diagnosed with HIE.

Revisiting therapeutic hypothermia for severe traumatic brain injury... again

Improved understanding of the molecular mechanisms of secondary brain injury has informed the optimum depth and duration of cooling and led to increased clinical interest in the therapeutic moderate hypothermia for severe traumatic brain injury over the past two decades. Although several large multi-center clinical trials have not found a treatment effect, multiple single-center trials have, and a recent meta-analysis by Crossley and colleagues now finds that the cumulative findings of those single-center trials dilute the multi-center trial results and show an overall reduction in mortality and poor outcomes associated with cooling. The need for consistent support of key physiologic parameters during cooling is emphasized by this finding.