Hypothermia for neuroprotection after cardiac arrest: systematic review and individual patient data meta-analysis

Hypoxia-induced cell damage is reduced by mild hypothermia and postconditioning with catalase in-vitro: application of an enzyme based oxygen deficiency system

Mild hypothermia and pharmacological postconditioning are widespread therapeutical treatment options that positively influence the clinical outcome after tissue hypoxia. In the study presented, a two-enzyme based in-vitro oxygen deficiency model in combination with cultured HT-1080 fibrosarcoma cells was employed to mimic the in-vivo situation of hypoxia and to evaluate the influence of mild hypothermia and postconditioning with catalase on hypoxia-mediated cell damage. Using the in-vitro oxygen deficiency model, partial pressure of oxygen was rapidly reduced to levels below 5mmHg in the culture media and cells responded with an increased expression of hypoxia inducible factor-1 on protein level. Hypoxia resulted in significant cell rounding and retraction of cytoplasmic cell extensions. Evaluation of cytotoxicity revealed a 3.5-fold increase in lactate dehydrogenase levels which was accompanied by 40-fold elevated levels of hydrogen peroxide. The hypoxia-induced increase of lactate dehydrogenase was 2.5-fold reduced in the hypothermia group, although morphological correlates of cytotoxicity were still visible. Hypothermia did not significantly influence hydrogen peroxide concentrations in the culture media. Pharmacological postconditioning with catalase however dose-dependently decreased hypoxia-induced lactate dehydrogenase release. This cytoprotective effect was accompanied by a dose-dependent, up to 50-fold reduction of hydrogen peroxide concentrations and retention of normal cell morphology. We suggest that the described in-vitro oxygen deficiency model is a convenient and simple culture system for the investigation of cellular and subcellular events associated with oxygen deficiency. Moreover, our in-vitro results imply that catalase postconditioning may be a promising approach to attenuate hypoxia-induced and hydrogen peroxide-mediated cell and tissue damage.

Predictors of survival from out-of-hospital cardiac arrest: a systematic review and meta-analysis

BACKGROUND

Prior studies have identified key predictors of out-of-hospital cardiac arrest (OHCA), but differences exist in the magnitude of these findings. In this meta-analysis, we evaluated the strength of associations between OHCA and key factors (event witnessed by a bystander or emergency medical services [EMS], provision of bystander cardiopulmonary resuscitation [CPR], initial cardiac rhythm, or the return of spontaneous circulation). We also examined trends in OHCA survival over time.

METHODS AND RESULTS

An electronic search of PubMed, EMBASE, Web of Science, CINAHL, Cochrane DSR, DARE, ACP Journal Club, and CCTR was conducted (January 1, 1950 to August 21, 2008) for studies reporting OHCA of presumed cardiac etiology in adults. Data were extracted from 79 studies involving 142 740 patients. The pooled survival rate to hospital admission was 23.8% (95% CI, 21.1 to 26.6) and to hospital discharge was 7.6% (95% CI, 6.7 to 8.4). Stratified by baseline rates, survival to hospital discharge was more likely among those: witnessed by a bystander (6.4% to 13.5%), witnessed by EMS (4.9% to 18.2%), who received bystander CPR (3.9% to 16.1%), were found in ventricular fibrillation/ventricular tachycardia (14.8% to 23.0%), or achieved return of spontaneous circulation (15.5% to 33.6%). Although 53% (95% CI, 45.0% to 59.9%) of events were witnessed by a bystander, only 32% (95% CI, 26.7% to 37.8%) received bystander CPR. The number needed to treat to save 1 life ranged from 16 to 23 for EMS-witnessed arrests, 17 to 71 for bystander-witnessed, and 24 to 36 for those receiving bystander CPR, depending on baseline survival rates. The aggregate survival rate of OHCA (7.6%) has not significantly changed in almost 3 decades.

CONCLUSIONS

Overall survival from OHCA has been stable for almost 30 years, as have the strong associations between key predictors and survival. Because most OHCA events are witnessed, efforts to improve survival should focus on prompt delivery of interventions of known effectiveness by those who witness the event.

Hypothermia and postconditioning after cardiopulmonary resuscitation reduce cardiac dysfunction by modulating inflammation, apoptosis and remodeling

BACKGROUND

Mild therapeutic hypothermia following cardiac arrest is neuroprotective, but its effect on myocardial dysfunction that is a critical issue following resuscitation is not clear. This study sought to examine whether hypothermia and the combination of hypothermia and pharmacological postconditioning are cardioprotective in a model of cardiopulmonary resuscitation following acute myocardial ischemia.

METHODOLOGY/PRINCIPAL FINDINGS

Thirty pigs (28-34 kg) were subjected to cardiac arrest following left anterior descending coronary artery ischemia. After 7 minutes of ventricular fibrillation and 2 minutes of basic life support, advanced cardiac life support was started according to the current AHA guidelines. After successful return of spontaneous circulation (n = 21), coronary perfusion was reestablished after 60 minutes of occlusion, and animals were randomized to either normothermia at 38 degrees C, hypothermia at 33 degrees C or hypothermia at 33 degrees C combined with sevoflurane (each group n = 7) for 24 hours. The effects on cardiac damage especially on inflammation, apoptosis, and remodeling were studied using cellular and molecular approaches. Five animals were sham operated. Animals treated with hypothermia had lower troponin T levels (p<0.01), reduced infarct size (34+/-7 versus 57+/-12%; p<0.05) and improved left ventricular function compared to normothermia (p<0.05). Hypothermia was associated with a reduction in: (i) immune cell infiltration, (ii) apoptosis, (iii) IL-1beta and IL-6 mRNA up-regulation, and (iv) IL-1beta protein expression (p<0.05). Moreover, decreased matrix metalloproteinase-9 activity was detected in the ischemic myocardium after treatment with mild hypothermia. Sevoflurane conferred additional protective effects although statistic significance was not reached.

CONCLUSIONS/SIGNIFICANCE

Hypothermia reduced myocardial damage and dysfunction after cardiopulmonary resuscitation possible via a reduced rate of apoptosis and pro-inflammatory cytokine expression.

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.

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 outcome parameters. We aimed to perform individual patient data analysis if data were available, and to from subgroups according to the cardiac arrest situation.

SEARCH STRATEGY

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2007 Issue 1); MEDLINE (1971 to January 2007); EMBASE (1987 to January 2007); CINAHL (1988 to January 2007); PASCAL (2000 to January 2007); and BIOSIS (1989 to January 2007).

SELECTION CRITERIA

We included all randomized controlled trials assessing the effectiveness of the 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, outcome parameters and additional baseline variables were entered into the 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

Four trials and one abstract reporting on 481 patients were included in the systematic review. Quality of the included studies was good in three out of five included 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 score of one or two (CPC, five point scale; 1= good cerebral performance, to 5 = brain death) during 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.

Application of Induced Hypothermia for Neuroprotection after Cardiac Arrest: A Systematic Review

The dismal outcome after cardiac arrest calls for novel therapeutic approaches. Therapeutic hypothermia is a promising therapeutic modality. In this article we review the evidence for therapeutic hypothermia, for the best methods for cooling available and for the safety of therapeutic hypothermia.

Therapeutic mild hypothermia improves outcome after out-of-hospital cardiac arrest

Purpose. Therapeutic mild hypothermia (TMH) is indicated for comatose survivors of an out-ofhospital cardiac arrest (OHCA) to improve general outcome. Although widely used, there are not many reports on its use on a critical care unit (CCU) or on the comparison of cooling methods.Methods. In a retrospective analysis covering January 2005 to December 2006, 75 consecutive comatose subjects post-OHCA due to ventricular fibrillation and nonventricular fibrillation rhythms (asystole/pulseless electrical activity) were studied in a single tertiary PCI centre. Subjects treated with conventional post-resuscitation care without TMH served as controls (n=26; Jan 2005-Sep 2005). Outcome from controls at hospital discharge was compared with subjects treated with TMH (n=49; Oct 2005-Dec 2006). During the study period, TMH was induced by either external (n=25; Oct 2005-Feb 2006) or endovascular (n=24; Mar 2006-Dec 2006) approach.Results. Besides more females in the control group, there were no major differences in baseline characteristics present between all groups. TMH improved survival (OR 0.36 [0.13-0.95], p<0.05) and neurological outcome (OR 0.23 [0.07-0.70], p<0.01). After subanalysis, TMH-improved outcome did not differ between the two cooling methods used. However, the times to reach TMH and normothermia were shorter with the endovascular approach.Conclusion. TMH induced on a CCU improves survival and neurological outcome after post-OHCA coma. TMH by endovascular approach was more feasible compared with external cooling, but the two cooling methods did not result in a different outcome. (Neth Heart J 2009;17:378-84.).

Effect of hypothermia therapy after outpatient cardiac arrest due to ventricular fibrillation

BACKGROUND

Several investigators have emphasized the positive effect of hypothermia therapy on patients who have suffered from cardiac arrest. Salvaging patients from circulatory collapse is a pivotal task, but it is unclear whether additional hypothermia can practically contribute to an improvement in the neurological outcome.

METHODS AND RESULTS

Since December 2005, our hospital has been using hypothermia therapy. Forty-six comatose patients after recovery of spontaneous circulation were consecutively enrolled in the present study. Twenty-five of the enrolled patients received hypothermia therapy and 21 did not because they were treated prior to 2005. The time from collapse to spontaneous circulation (P=0.09), the rates of performance of bystander CPR (P=0.370) and presence of a witnessed collapse (P=0.067) were not significantly different between the recovery group (n=28) and the non-recovery group (n=18). The additional hypothermia therapy was an independent predictor of neurological recovery (P=0.005, OR 6.5, 95%CI 1.74-24.27). The recovery rate was significantly higher in patients who received hypothermia therapy (80%) compared to those who did not (38%).

CONCLUSIONS

Hypothermia therapy is very useful for treating patients who have had an out-of-hospital cardiac arrest; it should be induced rapidly and smoothly.

Outcome, timing and adverse events in therapeutic hypothermia after out-of-hospital cardiac arrest

BACKGROUND

Therapeutic hypothermia (TH) after cardiac arrest protects from neurological sequels and death and is recommended in guidelines. The Hypothermia Registry was founded to the monitor outcome, performance and complications of TH.

METHODS

Data on out-of-hospital cardiac arrest (OHCA) patients admitted to intensive care for TH were registered. Hospital survival and long-term outcome (6-12 months) were documented using the Cerebral Performance Category (CPC) scale, CPC 1-2 representing a good outcome and 3-5 a bad outcome.

RESULTS

From October 2004 to October 2008, 986 TH-treated OHCA patients of all causes were included in the registry. Long-term outcome was reported in 975 patients. The median time from arrest to initiation of TH was 90 min (interquartile range, 60-165 min) and time to achieving the target temperature (< or =34 degrees C) was 260 min (178-400 min). Half of the patients underwent coronary angiography and one-third underwent percutaneous coronary intervention (PCI). Higher age, longer time to return of spontaneous circulation, lower Glasgow Coma Scale at admission, unwitnessed arrest and initial rhythm asystole were all predictors of bad outcome, whereas time to initiation of TH and time to reach the goal temperature had no significant association. Bleeding requiring transfusion occurred in 4% of patients, with a significantly higher risk if angiography/PCI was performed (2.8% vs. 6.2%P=0.02).

CONCLUSIONS

Half of the patients survived, with >90% having a good neurological function at long-term follow-up. Factors related to the timing of TH had no apparent association to outcome. The incidence of adverse events was acceptable but the risk of bleeding was increased if angiography/PCI was performed.

The use of pre-hospital mild hypothermia after resuscitation from out-of-hospital cardiac arrest

Hypothermia has emerged as a potent neuroprotective modality following resuscitation from cardiac arrest. Although delayed hospital cooling has been demonstrated to improve outcome after cardiac arrest, in-field cooling begun immediately following the return of spontaneous circulation may be more beneficial. Cooling in the field following resuscitation, however, presents new challenges, in that the cooling method has to be portable, safe, and effective. Rapid infusion of intravenous fluid at 4 degrees C, the use of a cooling helmet, and cooling plates have all been proposed as methods for field cooling, and are all in various stages of clinical and animal testing. Whether field cooling will improve survival and neurologic outcome remains an important unanswered clinical question.

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.

Hospital-based use of therapeutic hypothermia after cardiac arrest in adults

Improving survival and brain function after initial resuscitation from cardiac arrest remains a critical challenge with few therapeutic options. The publication of several randomized controlled trials supporting the use of therapeutic hypothermia in cardiac arrest survivors has provided a remarkable opportunity to reduce mortality and neurologic disability from this leading cause of death. On the strength of these trials, therapeutic hypothermia has now been incorporated in the American Heart Association guidelines for post-resuscitation care. This review will focus on the hospital-based application of therapeutic hypothermia in adult cardiac arrest survivors, with special attention to practical aspects of cooling, protocol development, and evaluation of recent data from "real world" experiences using hypothermia as a treatment option. Finally, remaining research questions and directions for future improvements in therapy will be discussed.

Successful resuscitation of a patient in asystole after a TASER injury using a hypothermia protocol

New studies have shown the benefit of initiating a hypothermia protocol in the survivors of cardiac arrest. Although the data have shown an improved neurologic end point in patients initially in ventricular fibrillation or pulseless ventricular tachycardia, there is still debate about whether patients initially in other rhythms would benefit from hypothermia after return of spontaneous circulation. This is a report of a 17-year-old male found to be in asystole after sustaining a TASER injury, who was treated with a hypothermia protocol after return of spontaneous circulation and left the hospital with intact neurologic function.

Post-cardiac arrest syndrome: Epidemiology, pathophysiology, treatment, and prognostication: A scientific statement from the International Liaison Committee on Resuscitation; the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; the Council on Stroke (Part 1)

AIM OF THE REVIEW

To review the epidemiology, pathophysiology, treatment and prognostication in relation to the post-cardiac arrest syndrome.

METHODS

Relevant articles were identified using PubMed, EMBASE and an American Heart Association EndNote master resuscitation reference library, supplemented by hand searches of key papers. Writing groups comprising international experts were assigned to each section. Drafts of the document were circulated to all authors for comment and amendment.

RESULTS

The 4 key components of post-cardiac arrest syndrome were identified as (1) post-cardiac arrest brain injury, (2) post-cardiac arrest myocardial dysfunction, (3) systemic ischaemia/reperfusion response, and (4) persistent precipitating pathology.

CONCLUSIONS

A growing body of knowledge suggests that the individual components of the postcardiac arrest syndrome are potentially treatable.

Can a simple blood test quantify brain injury?

Despite significant advances in neurocritical care, it remains difficult to precisely measure the extent of neurological injury in patients affected by stroke, trauma, or cardiac arrest. In the intensive care unit the extent of primary and secondary injury often eludes clinicians, making prognostication imprecise and difficult. Derwall and colleagues present their findings on the dynamics of serum S-100B protein levels in out-of-hospital cardiac arrest survivors. Their study suggests that elevation of S-100B reflects the severity of the primary hypoxic-ischemic insult.

Intracerebral monitoring in comatose patients treated with hypothermia after a cardiac arrest

BACKGROUND

Induced mild hypothermia (32-34 degrees C) has proven to reduce ischemic brain injury and improve outcome after a cardiac arrest (CA). The aim of this investigation was to study the occurrence of increased intracranial pressure (ICP) and neurochemical metabolic changes indicating cerebral ischemia, after CA and cardiopulmonary resuscitation (CPR), when induced hypothermia was applied.

METHODS

ICP, brain chemistry and brain temperature were monitored during induced hypothermia and re-warming in four adult unconscious patients with restoration of spontaneous circulation after CA and CPR.

RESULTS

ICP was occasionally above 20 mmHg. Neurochemical changes indicating cerebral ischemia (increased lactate/pyruvate ratio) and excitoxicity (increased glutamate) were found after CA, and signs of ischemia were also observed during the re-warming phase. A biphasic increase in glycerol was seen, which may have been a result of both membrane degradation and overspill from the general circulation.

CONCLUSIONS

Intracerebral microdialysis and ICP monitoring may be used in selected patients not requiring anticoagulants and PCI to obtain information regarding the common disturbances of intracranial dynamics after CA. The results of this study underline the importance of inducing hypothermia quickly after CA and emphasize the need for developing tools for guidance of the re-warming.

Improving the outcome of in-hospital cardiac arrest: the importance of being EARNEST

Cardiopulmonary resuscitation techniques were introduced more than 50 years ago, yet the rate of survival from cardiac arrest, particularly in the hospital setting, remains dismally low. This article reviews the prevalence, etiology, and outcome of in-hospital cardiac arrest, with a focus on the determinants of outcome that are amenable to improvement. These include principally components of basic life support that may be supported by either prompting or mechanical assistance (eg, chest compression, ventilation, and defibrillation). Also reviewed are preevent and postevent effectors such as medical staff skills and recognition of impending arrest, induction of mild hypothermia, and stabilization after return of spontaneous circulation.

Update on cardiopulmonary resuscitation and emergency cardiovascular care guidelines

PURPOSE

The key changes included in the 2005 cardiopulmonary resuscitation (CPR) and emergency cardiac care (ECC) guidelines are reviewed. Advances since publication of the current guidelines are also discussed.

SUMMARY

The 2005 CPR and ECC guidelines include several key changes from the previous version published in 2000. The new guidelines place an increased emphasis on chest compressions and recommend a compression:ventilation (C:V) ratio of 30:2. Current knowledge on defibrillation has also been incorporated by recommending that Emergency Medical Service (EMS) rescuers give two minutes of CPR before defibrillation when the response interval is greater than four to five minutes and EMS responders did not witness the arrest. Another major change is the recommendation for a single shock to be administered followed immediately by CPR with no check of the cardiac rhythm until two minutes of CPR has been performed postdefibrillation. The 2005 guidelines recommend that an automated external defibrillator should be implemented in public locations where there is a relatively high likelihood of witnessed cardiac arrest. In addition, the most recent guidelines highlight the shift from primary-rhythm-based therapies and resuscitation to a focus on neurologic outcomes.

CONCLUSION

Several evidence-based changes were included in the 2005 CPR and ECC guidelines, including a C:V ratio of 30:2 and mitigation of hands-off time, early defibrillation, administration of a single shock versus a three-shock sequence, use of public-access defibrillators, and a shift from primary-rhythm-based therapies to a focus on neurologic outcomes.

The clinical research enterprise in critical care: what's right, what's wrong, and what's ahead?

Intensivists have been remarkably successful in using randomized controlled trials to assess aspects of current practice. Unfortunately, this success has not been mirrored in trials of new pharmacotherapy, despite convincing pathophysiological rationales and encouraging preliminary studies. Misunderstandings of biological processes and flawed early clinical studies have led to the almost universal failure of fundamentally new treatments subjected to large phase III trials, despite their sound methodology. Compounding these problems is the tendency for new approaches to be either implemented widely on the basis of relatively poor studies or ignored despite strong supporting evidence. Having mastered the principles of evidence-based medicine in assessing existing therapy, intensivists have established a strong foundation. Critical care medicine must now embrace the challenge of translating a more solid understanding of basic disease mechanisms into widely implemented treatments.

Cooling therapy for acute stroke

BACKGROUND

Increased body temperatures are common in patients with acute stroke and are associated with poor outcome. In animal models of focal cerebral ischaemia, temperature-lowering therapy reduces infarct volume. In patients with acute stroke, lowering temperature may therefore improve outcome. This is an update of a Cochrane review first published in 1999.

OBJECTIVES

To assess the effects of pharmacological and physical strategies to reduce body or brain temperature in patients with acute stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register (last searched December 2007). In addition, we searched MEDLINE and EMBASE (January 1998 to December 2007). We scanned references and contacted authors of included trials. For the previous version of this review, the authors contacted pharmaceutical companies and manufactures of cooling equipment in this field.

SELECTION CRITERIA

We considered all completed randomised or non-randomised controlled clinical trials, published or unpublished, where pharmacological or physical strategies or both to reduce temperature were applied in patients with acute ischaemic stroke or intracerebral haemorrhage. Outcome measures were death or dependency (modified Rankin Scale score >/= 3) at the end of follow up, and adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria, assessed trial quality, and extracted and cross-checked the data.

MAIN RESULTS

We included five pharmacological temperature reduction trials and three physical cooling trials involving a total of 423 participants. We found no statistically significant effect of pharmacological or physical temperature-lowering therapy in reducing the risk of death or dependency (odds ratio (OR) 0.9, 95% confidence interval (CI) 0.6 to 1.4) or death (OR 0.9, 95% CI 0.5 to 1.5). Both interventions were associated with a non-significant increase in the occurrence of infections.

AUTHORS' CONCLUSIONS

There is currently no evidence from randomised trials to support routine use of physical or pharmacological strategies to reduce temperature in patients with acute stroke. Large randomised clinical trials are needed to study the effect of such strategies.

The use of induced hypothermia after cardiac arrest: a survey of Canadian emergency physicians

OBJECTIVE

Inducing mild hypothermia in survivors of cardiac arrest has been demonstrated to improve outcomes. Despite this, other studies have found that few resuscitation physicians have used hypothermia in clinical practice. The objective of this study was to characterize the use of induced hypothermia by Canadian emergency physicians.

METHODS

An internet-based survey was distributed to all members of the Canadian Association of Emergency Physicians (CAEP). Participants were asked about their experience with, methods for and barriers to inducing hypothermia.

RESULTS

Of the 1328 CAEP members surveyed, 247 (18.6%) responded, with the majority working in academic centres (60.3%). Ninety-five out of 202 respondents (47.0%, 95% confidence interval [CI] 40.8%-53.2%) indicated that they had induced hypothermia in clinical practice and 86 of 212 (40.6%, 95% CI 34.0%-47.2%) worked in a department that had a policy or protocol for the use of induced hypothermia. The presence of a departmental policy or protocol was strongly associated with the use of induced hypothermia (unadjusted odds ratio 10.5, 95% CI 5.3-20.8). Barriers against induced hypothermia cited by respondents included a lack of institutional policies and protocols (38.9%), and of resources (29.4%). Lack of support from consultants was relatively uncommon (8.7%) in Canadian practice.

CONCLUSION

Only one-half of Canadian emergency physicians report that they have used therapeutic hypothermia in practice. Emergency departments should develop policies or protocols for inducing hypothermia in cardiac arrest survivors to optimize patient outcomes.

Extended therapeutic hypothermia for several days during extracorporeal membrane-oxygenation after drowning and cardiac arrest Two cases of survival with no neurological sequelae

Drowning associated with hypothermia and cardiopulmonary resuscitation has a very poor prognosis. We report two such cases, where impossible oxygenation due to severe pulmonary oedema was treated with extracorporeal membrane-oxygenation (ECMO). Following cardiac arrest, mild therapeutic hypothermia for 24h was maintained as recommended, but subsequent rewarming precipitated additional pulmonary oedema. Little is currently known about how long to maintain therapeutic hypothermia to optimize neurological outcome and suppress reperfusion injury. In our patients, therapeutic hypothermia during veno-venous ECMO-treatment was extended for up to 6 days. Both patients survived with no neurological sequelae. We speculate that prolonged hypothermia was not only neuroprotective, but also minimized reperfusion injury including pulmonary oedema. Extension of hypothermia for several days seems safe and feasible in selected cases.

[Recent treatment of postischaemic anoxic brain damage after cardiac arrest by using therapeutic hypothermia]

Organ injury caused by ischaemia and anoxia during prolonged cardiac arrest is compounded by reperfusion injury that occurs when spontaneous circulation is restored. Mild hypothermia (32-35 degrees C) is neuroprotective through several mechanisms, including suppression of apoptosis, reduced production of excitotoxins and free radicals, and anti-inflammatory actions. Experimental studies show that hypothermia is more effective the earlier it is started after return of spontaneous circulation (ROSC). Two randomised clinical trials show improved survival and neurological outcome in adults who remained comatose after initial resuscitation from prehospital VF cardiac arrest, and who were cooled after ROSC. Different strategies can be used to induce hypothermia. Optimal timing of therapeutic hypothermia for cardiac ischaemia is unknown. In patients who failed to respond to standard cardiopulmonary resuscitation, intra-arrest cooling using ice-cold intravenous (i.v.) fluid improved the chance of survival. Recently, fasudil, a Rho kinase inhibitor, was reported to prevent cerebral ischaemia in vivo by increasing cerebral blood flow and inhibiting inflammatory responses. In future, two different kinds of protective therapies, BCL-2 overexpression and hypothermia,will both inhibit aspects of apoptotic cell death cascades, and that combination treatment can prolong the temporal "therapeutic window" for gene therapy.

Therapeutic hypothermia for cardiac arrest: a practical approach

Therapeutic hypothermia (TH), which prevents and ameliorates the cascade of secondary neurologic injury after the return of spontaneous circulation, is the most effective neuroprotective therapy for encephalopathic survivors of cardiac arrest. Acute management of patients with severe hypoxic-ischemic encephalopathy requires rapid and well-coordinated efforts involving emergency medicine, neurology, cardiology, critical care medicine, and palliative care. This effort is complex, and broad implementation of TH has been slow in the United States and Europe. This review summarizes recent developments in the practical application of TH, reviews the role of the neurologist, and suggests an algorithm for coordination of care of cardiac arrest survivors by physicians of divergent subspecialties, with the goals of maximizing neurologic and cardiac recovery.

Hypothermia attenuates protective effects of ginkgolides on astrocytes from ischemia/reperfusion injury

The neuroprotective roles of both hypothermia and ginkgolides have been well confirmed. We first examined whether hypothermia (32 or 28 degrees C) or ginkgolides have a protective effect on astrocytes against ischemia and reperfusion-induced injury. We demonstrated that ginkgolides, but not hypothermia, have a significantly time- and concentration-dependent protective role in ischemic astrocytes. We then investigated whether co-treatment with hypothermia and ginkgolides has a synergistic role to protect astrocytes against ischemia and reperfusion-induced injury. Cells were incubated with 18.75, 37.5 or 75 microg/ml of ginkgolides at 37, 32 or 28 degrees C for 24, 48 or 72 h before exposure to ischemia (24h) and then reperfusion (24h). Data showed that the co-treatment induced a significant decrease, rather than an increase as we had expected, in their cellular viabilities and anti-apoptotic abilities as compared with the cells treated by ginkgolides only. Western blot analysis demonstrated that hypothermia (32 or 28 degrees C for 24h) has no effect on the expression of Hypoxia-inducible factor-1 alpha (HIF-1 alpha) protein, suggesting that HIF-1 alpha is not associated with the adverse effect of hypothermia on ginkgolides. The findings imply the importance of further investigating the effects of hypothermia on the pharmacological role or therapeutic efficacy of drugs commonly used clinically.

[Therapeutic hypothermia]

The use of therapeutic hypothermia has been shown to improve survival and neurological outcome following cardiac arrest. Patients with traumatic brain injury or ischemic stroke also responded positively to therapeutic hypothermia, which may be induced by various procedures including surface cooling, endovascular cooling catheter and cold infusion. Possible side effects include infection and hemorrhage, as well as changes in water and electrolyte levels. It is the aim of this article to provide an overview of studies to date, as well as practical guidance for the application of therapeutic hypothermia.

Post-cardiac arrest syndrome: epidemiology, pathophysiology, treatment, and prognostication. A Scientific Statement from the International Liaison Committee on Resuscitation; the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; the Council on Stroke

AIM OF THE REVIEW

To review the epidemiology, pathophysiology, treatment and prognostication in relation to the post-cardiac arrest syndrome.

METHODS

Relevant articles were identified using PubMed, EMBASE and an American Heart Association EndNote master resuscitation reference library, supplemented by hand searches of key papers. Writing groups comprising international experts were assigned to each section. Drafts of the document were circulated to all authors for comment and amendment.

RESULTS

The 4 key components of post-cardiac arrest syndrome were identified as (1) post-cardiac arrest brain injury, (2) post-cardiac arrest myocardial dysfunction, (3) systemic ischaemia/reperfusion response, and (4) persistent precipitating pathology.

CONCLUSIONS

A growing body of knowledge suggests that the individual components of the post-cardiac arrest syndrome are potentially treatable.

The pituitary-adrenal axis is activated more in non-survivors than in survivors of cardiac arrest, irrespective of therapeutic hypothermia

OBJECTIVE

To investigate the effect of therapeutic hypothermia in the prognostic value of the pituitary-adrenal axis in comatose patients after cardiac arrest.

DESIGN

Prospective observational study in intensive care units (ICU) of a university and an affiliated regional hospital.

PATIENTS

Twenty-nine consecutive patients, in coma after cardiac arrest, admitted to the ICU and treated by hypothermia.

MEASUREMENTS

On ICU-admission (T=1), at reaching the target of 32-33 degrees C during therapeutic hypothermia (T=2), at the end of hypothermia (T=3) and 48h later (T=4), plasma adrenocorticotrophic hormone (ACTH), serum cortisol, albumin and corticosteroid-binding globulin (CBG) were measured. A short 250 microg ACTH test was performed at each time-point, except at T=1. The free cortisol index (FCI) and free cortisol calculated by Coolens method were also evaluated.

RESULTS

The ICU mortality was 59%, including withdrawal of life-sustaining treatment in 45% because of negative somatosensory evoked potentials. ACTH and (free) cortisol levels (mean 13.1 pmol/L vs. 6.0 pmol/L and 1250 nmol/L vs. 596 nmol/L, respectively) were higher in non-survivors than in survivors. Levels decreased in time, but the relative difference between outcome groups was maintained until T=4. The cortisol response to ACTH was lower in non-survivors at T=3 (P=0.047) only.

CONCLUSIONS

In comatose patients resuscitated from cardiac arrest, the pituitary-adrenal axis is activated particularly in those dying in the ICU, irrespective of therapeutic hypothermia. Hence, activation of the axis may be a marker of fatal cerebral damage. There is no firm evidence for relative adrenal insufficiency associated with death and a transiently blunted cortisol response to ACTH in non-survivors may be attributed to higher baseline values.