Intra-arrest transnasal evaporative cooling: a randomized, prehospital, multicenter study (PRINCE: Pre-ROSC IntraNasal Cooling Effectiveness)

State-of-the-art paper: Therapeutic hypothermia in out of hospital cardiac arrest survivors

Out of hospital cardiac arrest (OHCA) is associated with an extremely poor survival rate, with mortality in most cases being related to neurological injury. Among patients who experience return of spontaneous circulation (ROSC), therapeutic hypothermia (TH) is the only proven intervention shown to reduce mortality and improve neurological outcome. First described in 1958, the field of TH has rapidly evolved in recent years. While recent technological advances in TH will likely improve outcomes in OHCA survivors, several fundamental questions remain to be answered including the optimal speed of cooling, which patients benefit from an early invasive strategy, and whether technological advances will facilitate application of TH in the field. An increased awareness and understanding of TH strategies, devices, monitoring, techniques, and complications will allow for a more widespread adoption of this important treatment modality.

Clinical trials in cardiac arrest and subarachnoid hemorrhage: lessons from the past and ideas for the future

Introduction. Elevated intracranial pressure that occurs at the time of cerebral aneurysm rupture can lead to inadequate cerebral blood flow, which may mimic the brain injury cascade that occurs after cardiac arrest. Insights from clinical trials in cardiac arrest may provide direction for future early brain injury research after subarachnoid hemorrhage (SAH). Methods. A search of PubMed from 1980 to 2012 and clinicaltrials.gov was conducted to identify published and ongoing randomized clinical trials in aneurysmal SAH and cardiac arrest patients. Only English, adult, human studies with primary or secondary mortality or neurological outcomes were included. Results. A total of 142 trials (82 SAH, 60 cardiac arrest) met the review criteria (103 published, 39 ongoing). The majority of both published and ongoing SAH trials focus on delayed secondary insults after SAH (70%), while 100% of cardiac arrest trials tested interventions within the first few hours of ictus. No SAH trials addressing treatment of early brain injury were identified. Twenty-nine percent of SAH and 13% of cardiac arrest trials showed outcome benefit, though there is no overlap mechanistically. Conclusions. Clinical trials in SAH assessing acute brain injury are warranted and successful interventions identified by the cardiac arrest literature may be reasonable targets of the study.

Prehospital therapeutic hypothermia after cardiac arrest: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Therapeutic hypothermia has been recommended for the treatment of cardiac arrest patients who remain comatose after the return of spontaneous circulation. However, the optimal time to initiate therapeutic hypothermia remains unclear. The objective of the present study is to assess the effectiveness and safety of prehospital therapeutic hypothermia after cardiac arrest.

METHODS

Databases such as MEDLINE, Embase, and Cochrane Library were searched from their establishment date to May of 2012 to retrieve randomized control trials on prehospital therapeutic hypothermia after cardiac arrest. Thereafter, the studies retrieved were screened based on predefined inclusion and exclusion criteria. Data were extracted and the quality of the included studies was evaluated. A meta-analysis was performed by using the Cochrane Collaboration Review Manager 5.1.6 software.

RESULTS

Five studies involving 633 cases were included, among which 314 cases were assigned to the treatment group and the other 319 cases to the control group. The meta-analysis indicated that prehospital therapeutic hypothermia after cardiac arrest produced significant differences in temperature on hospital admission compared with in-hospital therapeutic hypothermia or normothermia (patient data; mean difference=-0.95; 95% confidence interval -1.15 to -0.75; I(2)=0%). However, no significant differences were observed in the survival to the hospital discharge, favorable neurological outcome at hospital discharge, and rearrest. The risk of bias was low; however, the quality of the evidence was very low.

CONCLUSION

This review demonstrates that prehospital therapeutic hypothermia after cardiac arrest can decrease temperature on hospital admission. On the other hand, regarding the survival to hospital discharge, favorable neurological outcome at hospital discharge, and rearrest, our meta-analysis and review produces non-significant results. Using the Grading of Recommendations, Assessment, Development and Evaluation methodology, we conclude that the quality of evidence is very low.

Automated peritoneal lavage: an extremely rapid and safe way to induce hypothermia in post-resuscitation patients

Introduction

Mild therapeutic hypothermia (MTH) is a worldwide used therapy to improve neurological outcome in patients successfully resuscitated after cardiac arrest (CA). Preclinical data suggest that timing and speed of induction are related to reduction of secondary brain damage and improved outcome.

Methods

Aiming at a rapid induction and stable maintenance phase, MTH induced via continuous peritoneal lavage (PL) using the Velomedix^® Inc. automated PL system was evaluated and compared to historical controls in which hypothermia was achieved using cooled saline intravenous infusions and cooled blankets.

Results

In 16 PL patients, time to reach the core target temperature of 32.5°C was 30 minutes (interquartile range (IQR): 19 to 60), which was significantly faster compare to 150 minutes (IQR: 112 to 240) in controls. The median rate of cooling during the induction phase in the PL group of 4.1°C/h (IQR: 2.2 to 8.2) was significantly faster compared to 0.9°C/h (IQR: 0.5 to 1.3) in controls. During the 24-hour maintenance phase mean core temperature in the PL patients was 32.38 ± 0.18°C (range: 32.03 to 32.69°C) and in control patients 32.46 ± 0.48°C (range: 31.20 to 33.63°C), indicating more steady temperature control in the PL group compared to controls. Furthermore, the coefficient of variation (VC) for temperature during the maintenance phase was lower in the PL group (VC: 0.5%) compared to the control group (VC: 1.5%). In contrast to 23% of the control patients, none of the PL patients showed an overshoot of hypothermia below 31°C during the maintenance phase. Survival and neurological outcome was not different between the two groups. Neither shivering nor complications related to insertion or use of the PL method were observed.

Conclusions

Using PL in post-CA patients results in a rapidly reached target temperature and a very precise maintenance, unprecedented in clinical studies evaluating MTH techniques. This opens the way to investigate the effects on neurological outcome and survival of ultra-rapid cooling compared to standard cooling in controlled trials in various patient groups.

Trial Registration

ClinicalTrials.gov: NCT01016236

See related letter by Esnault et al., http://ccforum.com/content/17/3/431

Current and future approaches to the therapy of human rabies

Human rabies has traditionally been considered a uniformly fatal disease. However, recent decades have seen several instances in which individuals have developed clinical signs of rabies, but survived, usually with permanent neurologic sequelae. Most of these patients had received prophylactic rabies vaccine before the onset of illness. The best outcomes have been seen in patients infected with bat viruses, which appear to be less virulent for humans than strains associated with other rabies vectors. In 2003, an article by rabies experts suggested that survival might be improved through a combination of vaccine, anti-rabies immunoglobulin, antiviral drugs and the anesthetic ketamine, which had shown benefit in an animal model. One year later, a girl in Milwaukee who developed rabies after bat exposure was treated with some of these measures, plus a drug-induced (therapeutic) coma, and survived her illness with mild neurologic sequelae. Although the positive outcome in this case has been attributed to the treatment regimen, it more likely reflects the patient's own brisk immune response, as anti-rabies virus antibodies were detected at the time of hospital admission, even though she had not been vaccinated. This conclusion is supported by the failure of the "Milwaukee Protocol" to prevent death in numerous subsequent cases. Use of this protocol should therefore be discontinued. Future research should focus on the use of animal models to improve understanding of the pathogenesis of rabies and for the development of new therapeutic approaches.

Overview of therapeutic hypothermia

OPINION STATEMENT

Therapeutic hypothermia has proven neuroprotective effects in global cerebral ischemia. Indications for hypothermia induction include cardiac arrest and neonatal asphyxia. The two general methods of induced hypothermia are either surface cooling or endovascular cooling. Hypothermia should be induced as early as possible to achieve maximum neuroprotection and edema blocking effect. Endovascular cooling has the benefit of shorter time to reach target temperature but catheter insertion requires expertise and training, which may be a barrier to widespread availability. The optimum method of cooling is yet to be determined but a multimodal approach is necessary to address three phases of cooling: induction, maintentance, and rewarm. Specifying core practitioners who are well-versed in established guidelines can help integrate the multidisciplinary team that is needed to successfully implement cooling protocols. Reducing shivering to make heat exchange more efficient with tighter temperature control enables quicker time to target temperature and avoids rewarming which can lead to inadvertent increase in intracranial pressure and cerebral edema. Promising applications but yet to be determined is whether hypothermia treatment can improve outcomes in acute ischemic stroke or traumatic brain injury.

Intra-arrest hypothermia during cardiac arrest: a systematic review

Introduction

Therapeutic hypothermia is largely used to protect the brain following return of spontaneous circulation (ROSC) after cardiac arrest (CA), but it is unclear whether we should start therapeutic hypothermia earlier, that is, before ROSC.

Methods

We performed a systematic search of PubMed, EMBASE, CINAHL, the Cochrane Library and Ovid/Medline databases using "arrest" OR "cardiac arrest" OR "heart arrest" AND "hypothermia" OR "therapeutic hypothermia" OR "cooling" as keywords. Only studies using intra-arrest therapeutic hypothermia (IATH) were selected for this review. Three authors independently assessed the validity of included studies and extracted data regarding characteristics of the studied cohort (animal or human) and the main outcomes related to the use of IATH: Mortality, neurological status and cardiac function (particularly, rate of ROSC).

Results

A total of 23 animal studies (level of evidence (LOE) 5) and five human studies, including one randomized controlled trial (LOE 1), one retrospective and one prospective controlled study (LOE 3), and two prospective studies without a control group (LOE 4), were identified. IATH improved survival and neurological outcomes when compared to normothermia and/or hypothermia after ROSC. IATH was also associated with improved ROSC rates and with improved cardiac function, including better left ventricular function, and reduced myocardial infarct size, when compared to normothermia.

Conclusions

IATH improves survival and neurological outcome when compared to normothermia and/or conventional hypothermia in experimental models of CA. Clinical data on the efficacy of IATH remain limited.

Therapeutic Hypothermia after Perioperative Cardiac Arrest in Cardiac Surgical Patients

BACKGROUND: Therapeutic hypothermia (TH) has been established as an effective treatment for preserving neurological function after out of hospital cardiac arrest (CA). Use of TH has been limited in cardiac surgery patients in particular because of concern about adverse effects such as hemorrhage and dysrhythmia. Little published data describe efficacy or safety of TH in cardiac surgical patients who suffer unintentional CA. However, the benefits of TH are such as may suggest clinical equipoise, even in this high risk patient population. OBJECTIVE: To report a series of three patients in our institution's cardiac surgery intensive care unit who suffered unintentional CA within 48 hours of cardiac surgery and were treated with TH. METHODS: After institutional review board approval, study patients were identified by diagnosis of undesired intraoperative CA or arrest on ICU days 1-2, as well as having documented TH. The institution's electronic medical record and the Society of Thoracic Surgeons database were retrospectively reviewed for demographic information, comorbid diagnoses, surgical procedure, and outcomes including hemorrhage, re-warming dysrhythmias, infection, in-hospital mortality, and neurologic outcome were assessed. TH was initiated and monitored using active cooling pads according to written institutional protocol. RESULTS: Four patients received TH after perioperative arrest. One patient was inadequately cooled and had massive surgical bleeding, and was therefore excluded from this review. The remaining three patients had a predicted mortality of 14.6% (±13.3) based on Euroscore calculation, and were cooled for 17.6±4.0 hours after CA. Coagulopathy, hypovolemia, severe electrolyte abnormalities, and re-warming dysrhythmias were not identified in any patient. 2 patients were discharged home and 1 was discharged to a long-term care facility. CONCLUSION: Herein we report the safe and successful use of TH after unintentional perioperative CA in 3 cardiac surgery patients. These data suggest that further investigation of this therapy may be warranted given the potential benefit and apparent safety in a small series.

Hypothermia for neuroprotection in adults after cardiopulmonary resuscitation

BACKGROUND

Good neurologic outcome after cardiac arrest is hard to achieve. Interventions during the resuscitation phase and treatment within the first hours after the event are critical. Experimental evidence suggests that therapeutic hypothermia is beneficial, and a number of clinical studies on this subject have been published. This review was originally published in 2009.

OBJECTIVES

We performed a systematic review and meta-analysis to assess the effectiveness of therapeutic hypothermia in patients after cardiac arrest. Neurologic outcome, survival and adverse events were our main outcomes. We aimed to perform individual patient data analysis, if data were available, and to form subgroups according to the cardiac arrest situation.

SEARCH METHODS

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2001, Issue 7); MEDLINE (1971 to July 2011); EMBASE (1987 to July 2011); CINAHL (1988 to July 2011); PASCAL (2000 to July 2011); and BIOSIS (1989 to July 2011). The original search was performed in January 2007.

SELECTION CRITERIA

We included all randomized controlled trials assessing the effectiveness of therapeutic hypothermia in patients after cardiac arrest, without language restrictions. Studies were restricted to adult populations cooled with any cooling method, applied within six hours of cardiac arrest.

DATA COLLECTION AND ANALYSIS

Validity measures, the intervention, outcomes and additional baseline variables were entered into a database. Meta-analysis was only done for a subset of comparable studies with negligible heterogeneity. For these studies, individual patient data were available.

MAIN RESULTS

We included four trials and one abstract reporting on 481 patients in the systematic review. The updated search resulted in no new studies to include. Quality of the included studies was good in three out of five studies. For the three comparable studies on conventional cooling methods all authors provided individual patient data. With conventional cooling methods, patients in the hypothermia group were more likely to reach a best cerebral performance categories (CPC) score of one or two (five point scale: 1 = good cerebral performance, to 5 = brain death) during the hospital stay (individual patient data; RR 1.55; 95% CI 1.22 to 1.96) and were more likely to survive to hospital discharge (individual patient data; RR 1.35; 95% CI 1.10 to 1.65) compared to standard post-resuscitation care. Across all studies, there was no significant difference in reported adverse events between hypothermia and control.

AUTHORS' CONCLUSIONS

Conventional cooling methods to induce mild therapeutic hypothermia seem to improve survival and neurologic outcome after cardiac arrest. Our review supports the current best medical practice as recommended by the International Resuscitation Guidelines.

Hyperinvasive approach to out-of hospital cardiac arrest using mechanical chest compression device, prehospital intraarrest cooling, extracorporeal life support and early invasive assessment compared to standard of care. A randomized parallel groups comparative study proposal. "Prague OHCA study"

Background

Out of hospital cardiac arrest (OHCA) has a poor outcome. Recent non-randomized studies of ECLS (extracorporeal life support) in OHCA suggested further prospective multicenter studies to define population that would benefit from ECLS. We aim to perform a prospective randomized study comparing prehospital intraarrest hypothermia combined with mechanical chest compression device, intrahospital ECLS and early invasive investigation and treatment in all patients with OHCA of presumed cardiac origin compared to a standard of care.

Methods

This paper describes methodology and design of the proposed trial. Patients with witnessed OHCA without ROSC (return of spontaneous circulation) after a minimum of 5 minutes of ACLS (advanced cardiac life support) by emergency medical service (EMS) team and after performance of all initial procedures (defibrillation, airway management, intravenous access establishment) will be randomized to standard vs. hyperinvasive arm. In hyperinvasive arm, mechanical compression device together with intranasal evaporative cooling will be instituted and patients will be transferred directly to cardiac center under ongoing CPR (cardiopulmonary resuscitation). After admission, ECLS inclusion/exclusion criteria will be evaluated and if achieved, veno-arterial ECLS will be started. Invasive investigation and standard post resuscitation care will follow. Patients in standard arm will be managed on scene. When ROSC achieved, they will be transferred to cardiac center and further treated as per recent guidelines.

Primary outcome

6 months survival with good neurological outcome (Cerebral Performance Category 1–2). Secondary outcomes will include 30 day neurological and cardiac recovery.

Discussion

Authors introduce and offer a protocol of a proposed randomized study comparing a combined “hyperinvasive approach” to a standard of care in refractory OHCA. The protocol is opened for sharing by other cardiac centers with available ECLS and cathlab teams trained to admit patients with refractory cardiac arrest under ongoing CPR. A prove of concept study will be started soon. The aim of the authors is to establish a net of centers for a multicenter trial initiation in future.

Ethics and registration

The protocol has been approved by an Institutional Review Board, will be supported by a research grant from Internal Grant Agency of the Ministry of Health, Czech Republic NT 13225-4/2012 and has been registered under ClinicalTrials.gov identifier: NCT01511666.

Therapeutic hypothermia for acute myocardial infarction and cardiac arrest

This report focuses on cardioprotection and describes the advantages and disadvantages of various methods of inducing therapeutic hypothermia (TH) with regard to neuroprotection and cardioprotection for patients with cardiac arrest and ST-segment elevation myocardial infarction (STEMI). TH is recommended in cardiac arrest guidelines. For patients resuscitated after out-of-hospital cardiac arrest, improvements in survival and neurologic outcomes were observed with relatively slow induction of TH. More rapid induction of TH in patients with cardiac arrest might have a mild to modest incremental impact on neurologic outcomes. TH drastically reduces infarct size in animal models, but achievement of target temperature before reperfusion is essential. Rapid initiation of TH in patients with STEMI is challenging but attainable, and marked infarct size reductions are possible. To induce TH, a variety of devices have recently been developed that require additional study. Of particular interest is transcoronary induction of TH using a catheter or wire lumen, which enables hypothermic reperfusion in the absence of total-body hypothermia. At present, the main methods of inducing and maintaining TH are surface cooling, endovascular heat-exchange catheters, and intravenous infusion of cold fluids. Surface cooling or endovascular catheters may be sufficient for induction of TH in patients resuscitated after out-of-hospital cardiac arrest. For patients with STEMI, intravenous infusion of cold fluids achieves target temperature very rapidly but might worsen left ventricular function. More widespread use of TH would improve survival and quality of life for patients with out-of-hospital cardiac arrest; larger studies with more rapid induction of TH are needed in the STEMI population.

Therapeutic hypothermia in acute ischemic stroke

Induced hypothermia has been used for neuroprotection in cardiac and neurovascular procedures. Experimental and translational studies provide evidence for its utility in the treatment of ischemic cerebrovascular disease. Over the past decade, these principles have been applied to the clinical management of acute stroke. Varying induction methods, time windows, clinical indications, and adjuvant therapies have been studied. In this article the authors review the mechanisms and techniques for achieving therapeutic hypothermia in the setting of acute stroke, and they outline pertinent side effects and complications. The manuscript summarizes and examines the relevant clinical trials to date. Despite a reasonable amount of existing data, this review suggests that additional trials are warranted to define the optimal time window, temperature regimen, and precise clinical indications for induction of therapeutic hypothermia in the setting of acute stroke.

[Prehospital cardiac arrest. Therapeutic hypothermia in adults]

Therapeutic hypothermia is one of the few advances in recent years that has improved survival and neurological outcome of survivors of cardiac arrest. Therapeutic hypothermia is part of current guidelines and, therefore, should be part of the routine procedure in postresuscitation care of patients still comatose after primarily successful resuscitation. Early induction of hypothermia may be achieved even in the prehospital setting with different cooling techniques which, however, are less suitable to maintain a constant temperature and additionally do not allow precisely controlled re-warming. To achieve the goal of a target temperature of 32-34°C for 12-24 h, controlled feedback systems are more reliable and also can be used for patients during percutaneous coronary intervention. The optimal time point to start cooling is not well defined, even if theoretical considerations and animal experiments are in favor of beginning early. Another question is whether therapeutic hypothermia is of benefit for patients with cardiac arrest due to asystole and pulseless electrical activity in contrast to patients with ventricular fibrillation where it is of proven value.

Optimizing outcome after cardiac arrest

PURPOSE OF REVIEW

To discuss recent data relating to survival rates after cardiac arrest and interventions that can be used to optimize outcome.

RECENT FINDINGS

A recent analysis of 70 studies indicates that following out-of-hospital cardiac arrest (OHCA), 7.6% of patients will survive to hospital discharge (95% confidence interval 6.7-8.4). Following in-hospital cardiac arrest, 18% of patients will survive to hospital discharge. Survival may be optimized by increasing the rate of bystander cardiopulmonary resuscitation (CPR), which can be achieved by improving recognition of cardiac arrest, simplifying CPR and training more of the community. Feedback systems improve the quality of CPR but this has yet to be translated into improved outcome. One study has shown improved survival following OHCA with active compression-decompression CPR combined with an impedance-threshold device. In those who have no obvious extracardiac cause of OHCA, 70% have at least one significant coronary lesion demonstrable by coronary angiography. Although generally reserved for those with ST-elevation myocardial infarction, primary percutaneous coronary intervention may also benefit OHCA survivors with ECG patterns other than ST elevation. The term 'mild therapeutic hypothermia' has been replaced by the term 'targeted temperature management'; its role in optimizing outcome after cardiac arrest continues to be defined.

SUMMARY

In several centres, survival rates following OHCA are increasing. All links in the chain of survival must be optimized if a good-quality neurological outcome is to be achieved.

The relevance of severity scores in predicting outcome after cardiac arrest

Cardiac arrest is a major health and economic problem, with a mortality rate remaining unacceptably high. Prediction of outcome in this setting, especially if determined in the early phase after hospital admission, would allow clinicians to prioritize rapid therapeutic interventions, to better stratify patients' severity of illness, to reconsider the intensity of care and to readdress resource utilization. This article focuses on the possibility of using a severity-of-illness score, combining the Sequential Organ Failure Assessment score and the Full Outline of Unresponsiveness score, to predict morbidity and mortality after cardiac arrest.

Clinically useful cardioprotection: ischemic preconditioning then and now

Ischemic preconditioning (IP) is the most effective, reproducible form of protection against myocardial cell death yet described. The mechanism of classic IP has not been identified, but recent investigations have focused on the mitochondrial permeability transition pore (mPTP). Similarly, the mechanism of the "second window of protection" (SWOP) is not known but thought to involve increased expression of important gene products. Currently, IP in the clinical arena is limited to cardiac surgery, planned angioplasty, and organ preservation protocols. To move preconditioning into a broader clinical arena will require resolution of important fundamental yet stubborn problems involving both basic and clinical science. Important unresolved issues include the mechanisms involved in the transition from reversible to irreversible injury, the amount of potential salvageable myocardium present at the onset of reperfusion, the identity and signaling of the mPTP, the optimization of protocols, the identity of end effectors (SWOP), and the identification of the best experimental model systems. From a clinical standpoint, important issues include the influence of comorbidities on cardioprotection, identification of appropriate animal models, the lack of a biologic marker of the cardioprotective state, the influence of coexistent therapeutic drugs, potential toxicity of pharmacologic mimics, and the window of opportunity for significant protection. Ischemic preconditioning has yielded promising results in other organs including the brain as well as tissue preservation for certain surgical procedures that will require definition of the underlying mechanism(s) to be fully exploited clinically. Over the past 25 years, the scientific community has learned much regarding the biology and potential mechanisms of IP and the concept has been expanded to many other organ systems in many other clinically relevant scenarios. To realize the full clinical potential will require continued investigation into the mechanism.

Therapeutic hypothermia and prevention of acute kidney injury: a meta-analysis of randomized controlled trials

BACKGROUND

Therapeutic hypothermia has been shown to reduce neurological morbidity and mortality in the setting of out-of-hospital cardiac arrest and may be beneficial following brain injury and cardiopulmonary bypass. We conducted a systematic review to ascertain the effect of therapeutic hypothermia on development of acute kidney injury (AKI) and mortality.

METHODS

We searched for randomized controlled trials in MEDLINE through February 2011. We included trials comparing hypothermia to normothermia that reported kidney-related outcomes including, development of AKI, dialysis requirement, changes in serum creatinine, and mortality. We performed Peto fixed-effect and random-effects model meta-analyses, and meta-regressions.

RESULTS

Nineteen trials reporting on 2218 patients were included; in the normothermia group, the weighted rate of AKI was 4.2%, dialysis requirement 3.7%, and mortality 10.8%. By meta-analysis, hypothermia was not associated with a lower odds of AKI (odds ratio [OR] 1.01, 95% confidence interval [CI] 0.68, 1.51; P=0.95) or dialysis requirement (OR 0.81; 95% CI 0.30, 2.19; P=0.68); however, by meta-regression, a lower target cooling temperature was associated with a lower odds of AKI (P=0.01). Hypothermia was associated with lower mortality (OR 0.69; 95% CI 0.51, 0.92; P=0.01).

CONCLUSIONS

In trials that ascertained kidney endpoints, therapeutic hypothermia prevented neither the development of AKI nor dialysis requirement, but was associated with lower mortality. Different definitions and rates of AKI, differences in mortality rates, and concerns about the optimal target cooling temperature preclude definitive conclusions.

Hypothermia and Ischemic Stroke

OPINION STATEMENT: The use of tissue plasminogen activator (tPA) is the major treatment method for acute ischemic stroke, but it reaches only a very limited number of stroke patients. Although neuroprotectants may be useful in stroke patients in principle, promising animal data have not yet been successfully transferred to stroke patients. However, many arguments favor the successful translation of therapeutic hypothermia (TH) to stroke patients: it is a multimodal method, there is a strong correlation between fever and outcome in stroke patients, and TH has been shown to be beneficial in other kinds of acute brain injury (resuscitation, perinatal asphyxia). In addition, it is useful in controlling intracranial pressure caused by brain edema. So far, available data from clinical studies are not sufficient to recommend TH for the routine treatment of acute ischemic stroke. The quality of trials and the number of stroke patients treated by TH are far too low to prove efficacy or futility, but multicenter randomized controlled clinical trials are on their way. Studies in awake stroke patients will use TH very early in the clinical setting, which implies certain problems. The use of TH in awake individuals requires methods to suppress cold-induced vegetative responses such as shivering and sympathic activation, clinically relevant side effects that need to be monitored and treated carefully. In mass-occupying ischemic stroke, randomized trials will evaluate the neuroprotective effects of controlling edema and intracranial pressure. Because the optimal depth, duration, and methods of cooling are not clear, only large randomized controlled trials will set the baseline from which TH as a neuroprotective therapy can be optimized and brought successfully to stroke patients.

Therapeutic hypothermia for acute neurological injuries

Therapeutic hypothermia (TH) is the intentional reduction of core body temperature to 32°C to 35°C, and is increasingly applied by intensivists for a variety of acute neurological injuries to achieve neuroprotection and reduction of elevated intracranial pressure. TH improves outcomes in comatose patients after a cardiac arrest with a shockable rhythm, but other off-label applications exist and are likely to increase in the future. This comprehensive review summarizes the physiology and cellular mechanism of action of TH, as well as different means of TH induction and maintenance with potential side effects. Indications of TH are critically reviewed by disease entity, as reported in the most recent literature, and evidence-based recommendations are provided.

Therapeutic hypothermia in stroke and traumatic brain injury

Therapeutic hypothermia (TH) is considered to improve survival with favorable neurological outcome in the case of global cerebral ischemia after cardiac arrest and perinatal asphyxia. The efficacy of hypothermia in acute ischemic stroke (AIS) and traumatic brain injury (TBI), however, is not well studied. Induction of TH typically requires a multimodal approach, including the use of both pharmacological agents and physical techniques. To date, clinical outcomes for patients with either AIS or TBI who received TH have yielded conflicting results; thus, no adequate therapeutic consensus has been reached. Nevertheless, it seems that by determining optimal TH parameters and also appropriate applications, cooling therapy still has the potential to become a valuable neuroprotective intervention. Among the various methods for hypothermia induction, intravascular cooling (IVC) may have the most promise in the awake patient in terms of clinical outcomes. Currently, the IVC method has the capability of more rapid target temperature attainment and more precise control of temperature. However, this technique requires expertise in endovascular surgery that can preclude its application in the field and/or in most emergency settings. It is very likely that combining neuroprotective strategies will yield better outcomes than utilizing a single approach.

Early- versus late-initiation of therapeutic hypothermia after cardiac arrest: preliminary observations from the experience of 17 Italian intensive care units

OBJECTIVES

Mild therapeutic hypothermia (TH) has been shown to improve neurologic outcome in patients experiencing cardiac arrest after return of spontaneous circulation (ROSC). The best timing to initiate TH is currently not known. The aim of this study by the ICE (Italian Cooling Experience) group was to investigate the relationship between the timing of initiation of therapeutic hypothermia (TH) and both patient survival and neurologic outcome.

METHODS

In this observational prospective clinical study we collected data on cardiac arrest patients admitted, after ROSC, to any of the 17 participating Italian intensive care units. Patients were managed according to routine clinical practice, including, in a group of patients, therapeutic hypothermia. Patients who underwent TH were classified, arbitrarily, into an early-initiation group (TH started <2 h since cardiac arrest) and a late-initiation group (TH started >2 h since cardiac arrest).

RESULTS

Intensive care unit (ICU) mortality was 47.4% for the early-initiation group and 23.8% for the late-initiation group (P=0.01). Six-month mortality was 60.8% for the early-initiation group and 40.5% for the late-initiation group (P=0.04). Cerebral performance category (CPC, a measure of neuro-cognitive outcome) at ICU discharge was 1 [1-2] for the early-initiation group and 1 [1-3] for the late-initiation group (P=0.57). At 6 months, CPC was 1 [1-1] for the early-initiation group and 1 [1-2] for the late-initiation group.

DISCUSSION

Despite similar neurologic outcomes at every time point, mortality was significantly higher when therapeutic hypothermia was started within 2h of cardiac arrest than when it was started later. Due to the lack of possibility to control several putative confounding factors, such results should be considered as preliminary observations warranting further research.

Surface cooling after cardiac arrest: effectiveness, skin safety, and adverse events in routine clinical practice

BACKGROUND

Effectiveness of cooling and adverse events (AEs) involving skin have not been intensively evaluated in cardiac arrest survivors treated with therapeutic hypothermia (TH) when induced and maintained with a servomechanism-regulated surface cooling system.

METHODS

Retrospective review of sixty-nine cardiac arrest survivor-events admitted from April 2006-September 2008 who underwent TH using the Medivance Arctic Sun Temperature Management System. A TH database and medical records were reviewed, and nursing interviews conducted. Primary endpoint was time from initiation to target temperature (TT; 32-34 °C). Secondary endpoints were cooling rate, percentage of hypothermia maintenance phase at TT, effect of body-mass index (BMI) on rate of cooling, and AEs.

RESULTS

Mean time to the target temperature (TT) was 2.78 h; 80% of patients achieved TT within 4 h; all did within 8 h. Patients were at TT for 96.7% of hypothermia maintenance; 17% of patients had >1 hourly temperature measurement outside TT range. Mean cooling rate during induction phase was 1.1 °C/h, and was not associated with BMI. Minor skin injury occurred in 14 (20%) patients; 4 (6%) were device-related. Skin injuries were associated with shock (P = 0.04), and decubitus ulcers were associated with left ventricular ejection fraction <45% (P = 0.004). AEs included shivering (94%), hypokalemia (81%), hyperglycemia (57%), pneumonia (23%), bleeding (22%), post-cooling fever (17%), and bacteremia (9%).

CONCLUSIONS

The Arctic Sun Temperature Management System was an effective means of performing therapeutic hypothermia after cardiac arrest. Infrequent skin injuries were associated with vasopressor use and low ejection fraction.

Impact of therapeutic hypothermia onset and duration on survival, neurologic function, and neurodegeneration after cardiac arrest

OBJECTIVE

Post-cardiac-arrest therapeutic hypothermia improves outcomes in comatose cardiac arrest survivors. This study tests the hypothesis that the efficacy of post-cardiac-arrest therapeutic hypothermia is dependent on the onset and duration of therapy.

DESIGN

Prospective randomized laboratory investigation.

SETTING

University research laboratory.

SUBJECTS

A total of 268 male Long Evans rats.

INTERVENTIONS

Post-cardiac-arrest therapeutic hypothermia.

MEASUREMENTS AND MAIN RESULTS

Adult male Long Evans rats that achieved return of spontaneous circulation after a 10-min asphyxial cardiac arrest were block randomized to normothermia (37°C ± 1°C) or therapeutic hypothermia (33°C ± 1°C) initiated 0, 1, 4, or 8 hrs after return of spontaneous circulation and maintained for 24 or 48 hrs. Therapeutic hypothermia initiated 0, 1, 4, and 8 hrs after return of spontaneous circulation resulted in 7-day survival rates of 45%*, 36%*, 36%*, and 14%, respectively, compared to 17% for normothermic controls and survival with good neurologic function rates of 24%*, 24%*, 19%*, and 0%, respectively, compared to 2% for normothermic controls (*p < .05 vs. normothermia). These outcomes were not different when therapeutic hypothermia was maintained for 24 vs. 48 hrs. In contrast, hippocampal CA1 pyramidal neuron counts were 53% ± 27%*, 53% ± 19%*, 51% ± 24%*, and 65% ± 16%* of normal, respectively, when therapeutic hypothermia was initiated 0, 1, 4, or 8 hrs after return of spontaneous circulation compared to 9% in normothermic controls (*p < .01 vs. normothermia). Furthermore, surviving neuron counts were greater when therapeutic hypothermia was maintained for 48 hrs compared to 24 hrs (68% ± 15%* vs. 42% ± 22%, *p < .0001).

CONCLUSIONS

In this study, post-cardiac-arrest therapeutic hypothermia resulted in comparable improvement of survival and survival with good neurologic function when initiated within 4 hrs after return of spontaneous circulation. However, histologic assessment of neuronal survival revealed a potentially broader therapeutic window and greater neuroprotection when therapeutic hypothermia was maintained for 48 vs. 24 hrs.

Local brain temperature reduction through intranasal cooling with the RhinoChill device: preliminary safety data in brain-injured patients

BACKGROUND AND PURPOSE

Hypothermia is neuroprotectant but currently available cooling methods are laborious, invasive, and require whole-body cooling. There is a need for less invasive cooling of the brain. This study was conducted to assess the safety and efficacy of temperature reduction of the RhinoChill transnasal cooling device.

METHODS

We conducted a prospective single-arm safety and feasibility study of intubated patients for whom temperature reduction was indicated. After rhinoscopy, the device was activated for 1 hour. Brain, tympanic, and core temperatures along with vital signs and laboratory studies were recorded. All general and device-related adverse events were collected for the entire hypothermia treatment.

RESULTS

A total of 15 patients (mean age, 50.3 ± 17.1 years) were enrolled. Brain injury was caused by intracerebral hemorrhage, trauma, and ischemic stroke in equal numbers. Hypothermia was induced for fever control in 9 patients and for neuroprotection/intracranial pressure control in 6. Core temperature, brain temperature, and tympanic temperature were reduced an average of 1.1 ± 0.6°C (range, 0.3 to 2.1°C), 1.4 ± 0.4°C (range, 0.8 to 5.1°C), and 2.2 ± 2°C (range, 0.5 to 6.5°C), respectively. Only 2 patients did not achieve the goal of ≥1°C decrease in temperature. Brain temperature, tympanic temperature, and core temperature reductions were similar between the afebrile and febrile patients. There were no unanticipated adverse events and only 1 anticipated adverse event: hypertension in 1 subject that led to discontinuation of cooling after 30 minutes. There were no nasal complications.

CONCLUSIONS

Intranasal cooling with the RhinoChill device appears safe and effectively lowers brain and core temperatures. Further study is warranted to assess the efficacy of hypothermia through intranasal cooling for brain-injured patients.

Is faster still better in therapeutic hypothermia?

The rapid institution of therapeutic hypothermia after cardiac arrest has become an accepted practice. In the previous issue of Critical Care, Haugk and colleagues present a retrospective analysis of 13 years of experience with therapeutic hypothermia at their center that suggests an association between rate of cooling and less favorable neurological outcomes. The association most likely reflects easier cooling in patients more severely brain injured by their initial cardiac arrest, and should not lead clinicians to abandon or slow their efforts to achieve post-resuscitative cooling.