Therapeutic Hypothermia after Cardiac Arrest

Temperature Management in the ICU

OBJECTIVE

Temperature abnormalities are recognized as a marker of human disease, and the therapeutic value of temperature is an attractive treatment target. The objective of this synthetic review is to summarize and critically appraise evidence for active temperature management in critically ill patients.

DATA SOURCES

We searched MEDLINE for publications relevant to body temperature management (including targeted temperature management and antipyretic therapy) in cardiac arrest, acute ischemic and hemorrhagic stroke, traumatic brain injury, and sepsis. Bibliographies of included articles were also searched to identify additional relevant studies.

STUDY SELECTION

English-language systematic reviews, meta-analyses, randomized trials, observational studies, and nonhuman data were reviewed, with a focus on the most recent randomized control trial evidence.

DATA EXTRACTION

Data regarding study methodology, patient population, temperature management strategy, and clinical outcomes were qualitatively assessed.

DATA SYNTHESIS

Temperature management is common in critically ill patients, and multiple large trials have been conducted to elucidate temperature targets, management strategies, and timing. The strongest data concerning the use of therapeutic hypothermia exist in comatose survivors of cardiac arrest, and recent trials suggest that appropriate postarrest temperature targets between 33°C and 37.5°C are reasonable. Targeted temperature management in other critical illnesses, including acute stroke, traumatic brain injury, and sepsis, has not shown benefit in large clinical trials. Likewise, trials of pharmacologic antipyretic therapy have not demonstrated improved outcomes, although national guidelines do recommend treatment of fever in patients with stroke and traumatic brain injury based on observational evidence associating fever with worse outcomes.

CONCLUSIONS

Body temperature management in critically ill patients remains an appealing therapy for several illnesses, and additional studies are needed to clarify management strategies and therapeutic pathways.

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.

Therapeutic hypothermia application vs standard support care in post resuscitated out-of-hospital cardiac arrest patients

INTRODUCTION

Survival after cardiac arrest remains poor, especially when it occurs outside of hospital. In recent years, therapeutic hypothermia has been used to improve outcomes in patients who have experienced cardiac arrest, however, application to out-of-hospital cardiac arrest (OHCA) patients remains controversial.

METHODS

A total of 175 OHCA patients underwent therapeutic hypothermia (TH), which was performed using large volume ice crystalloid fluid (LVICF) infusions after ICU admission. Ice packs and conventional cooling blankets were used to maintain a core body temperature of 33°C, according to standard protocol for 36 hours. Patients in the control group received standard supportive care without TH. Hospital survival and neurologic outcomes were compared.

RESULTS

There was no significant difference between the groups with regards to patient characteristics, underlying etiologies, and length of hospital stays. The duration of cardiac pulmonary resuscitation (CPR) was also similar. In the 51 patients that received TH, 14 were alive at hospital discharge. In the 124 patients belonging to the supportive care group, only 15 were alive at hospital discharge (27.5% vs. 12.1%, p = 0.013). Approximately 7.9% of patients in the TH group had good neurologic outcomes (4 of 51) compared with the 1.7% (2 of 124) of patients in the supportive group (p = 0.04). There were no specific treatment-related complications.

CONCLUSION

Therapeutic hypothermia can be safely applied to OHCA patients and can improve their outcome. Further large scale studies are needed to verify our results.

Pathway for the management of survivors of out-of-hospital cardiac arrest

The estimated number of out-of-hospital care arrest cases is about 300,000 per year in the United States. Two landmark studies published in 2002 demonstrated that the use of therapeutic hypothermia after cardiac arrest decreased mortality and improved neurologic outcome. Based on these studies, the International Liaison Committee on Resuscitation and the American Heart Association recommended the use of therapeutic hypothermia after cardiac arrest. Therapeutic hypothermia is defined as a controlled lowering of core body temperature to 32 degrees C to 34 degrees C. This temperature goal represents the optimal balance between clinical effect and cardiovascular toxicity. Therapeutic hypothermia does require resources to implement-including device, close nursing care, and monitoring. It is important to select patients who have potential for benefit from this technique which is a limited resource and carries potential complications. A collaborative team approach involving physicians and nurses is critical for successful development and implementation of this kind of a protocol. In 2004, the "Advanced Cardiac Admission Program" was launched at the St. Luke's Roosevelt Hospital Center of Columbia University in New York. The program consists of a series of projects, which have been developed to bridge the gap between published guidelines and implementation during "real world" patient care. In this article, we are reporting our latest project for the comprehensive management of survivors of out-of-hospital cardiac arrest. The pathway is divided into 3 steps: Step I, From the field through the emergency department into the cardiac catherization laboratory and to the critical care unit; Step II, Induced invasive hypothermia protocol in the critical care unit (this step is divided into 3 phases: 1, invasive cooling for the first 24 hours; 2, rewarming; 3, maintenance); Step III, Management post the rewarming phase including the recommendation for out-of-hospital therapy and the ethical decision to define goal of care. We hope that this novel pathway will bridge the gap between the complex guidelines and the actual clinical practice and will improve the survival and neurologic condition of patients suffering cardiac arrest.

Severe carbon monoxide poisoning complicated by hypothermia: a case report

It is proposed that the significant elevation of interleukin-6 (>400 pg/mL) in cerebrospinal fluid during the early phase of carbon monoxide poisoning may be a predictive biomarker for the development of delayed encephalopathy. A 52-year-old man presented to the emergency department with severe carbon monoxide poisoning. On arrival, the patient was comatose with decorticate rigidity (Glasgow Coma Scale, E1V1M3). His core body temperature, measured in the urinary bladder, was 32.4°C. Laboratory blood analysis revealed elevated CO-Hb (36.0%) and metabolic acidosis with elevated lactate (pH 7.081; base excess [BE], -19.2 mmol/L; HCO3, -9.8 mmol/L; lactate, 168.8 mg/dL). After treatment with hyperbaric oxygen and several different rewarming techniques, he became alert and his core body temperature increased to normal. Interleukin-6 in cerebrospinal fluid at 5.5 hours after his last exposure to carbon monoxide was significantly elevated (752 pg/mL). However, he did not develop delayed encephalopathy. In this case, hypothermia in the range of therapeutic hypothermia (32°C to 34°C) may have suppressed formation of reactive oxygen species and subsequent lipid peroxydation, preventing the development of delayed encephalopathy. Therapeutic hypothermia initiated soon after the last exposure to carbon monoxide may be an effective prophylactic method for preventing the development of delayed encephalopathy.

Prehospital resuscitated cardiac arrest patients: role for induced hypothermia

This article is a support paper for the National Association of EMS Physicians' position paper on induced therapeutic hypothermia in resuscitated cardiac arrest patients. Induced hypothermia is one of the newest treatments aimed at increasing the dismal neurologically intact survival rate for out-of-hospital cardiac arrest patients. Two landmark studies published in 2002 by the New England Journal of Medicine led to the American Heart Association (AHA) Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care IIa recommendation of cooling unconscious adult patients with return of spontaneous circulation after out-of-hospital cardiac arrest due to ventricular fibrillation to 32 degrees C to 34 degrees C for 12 to 24 hours. Despite many limitations of those studies, the AHA also suggests that this therapy may be beneficial for patients with non-ventricular fibrillation arrests. However, the literature is lacking in answers with regard to the best methods to utilize in cooling patients. While avoiding delay in the initiation of cooling seems logical, the literature is also lacking evidence indicating the ideal time at which to implement cooling. Furthermore, it remains unclear as to which patients may benefit from induced hypothermia. Finally, the literature provides no evidence to support mandating induced hypothermia in the prehospital setting. Given limited prehospital resources, sometimes consisting of only two providers, attention first needs to be given to providing the basic care with the utmost skill. Once the basics are being delivered expertly, consideration can be given to the use of prehospital cooling for the resuscitated cardiac arrest patient in the setting of continued cooling in the hospital.

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.

Hypothermia after cardiac arrest: expanding the therapeutic scope

Therapeutic hypothermia for 12 to 24 hrs following resuscitation from out-of-hospital cardiac arrest is now recommended by the American Heart Association for the treatment of neurological injury when the initial cardiac rhythm is ventricular fibrillation. However, the role of therapeutic hypothermia is uncertain when the initial cardiac rhythm is asystole or pulseless electrical activity, or when the cardiac arrest is primarily due to a noncardiac cause, such as asphyxia or drug overdose. Given that survival rate in these latter conditions is very low, it is unlikely that clinical trials will be undertaken to test the efficacy of therapeutic hypothermia in this setting because of the very large sample size that would be required to detect a significant difference in outcomes. Therefore, in patients with anoxic brain injury after nonventricular fibrillation cardiac arrest, clinicians will need to balance the possible benefit of therapeutic hypothermia with the possible side effects of this therapy. Given that the side effects of therapeutic hypothermia are generally easily managed in the critical care setting, and there is benefit for anoxic brain injury demonstrated in laboratory studies, consideration may be given to treat comatose post-cardiac arrest patients with therapeutic hypothermia in this setting. Because the induction of therapeutic hypothermia has become more feasible with the development of simple intravenous cooling techniques and specialized equipment for improved temperature control in the critical care unit, it is expected that therapeutic hypothermia will become more widely used in the management of anoxic neurological injury whatever the presenting cardiac rhythm.

Practical pharmacologic aspects of therapeutic hypothermia after cardiac arrest

Abstract Therapeutic hypothermia has emerged as an effective means of improving neurologic outcomes among cardiac arrest survivors. To achieve optimal results, clinicians must understand and anticipate potential adverse effects of cooling and provide rigorous monitoring and/or pharmacologic interventions as appropriate. Using pharmacotherapy to counter adverse effects of cooling or to treat an intrinsic process under hypothermic conditions requires understanding how hypothermia will influence the clinical effects of the drug, including the drug's pharmacokinetics and pharmacodynamics. The pharmacologic aspects of therapeutic hypothermia in relation to physiology and adverse effects are reviewed.

Hypothermia for cardiac arrest

Therapeutic hypothermia for cardiac arrest survivors has emerged as a highly effective means of improving neurologic outcome. There are a number of purported mechanisms by which it is felt to be effective, but the exact mechanism is unknown. This article reviews the biochemical mechanisms of injury occurring in cardiac arrest, as well as the avenues that hypothermia takes to combat this injury. It also reviews the animal model data in support of this, as well as the newer animal studies that may help to improve the field. Several human studies of hypothermia in cardiac arrest have been performed, and this article reviews these for their methods and shortcomings. Our currently recommended guidelines for performing therapeutic hypothermia are presented. With therapeutic hypothermia comes potential risks to the patient, primarily affecting cardiac, metabolic, and hematologic systems, and these risks and their management are discussed. Multiple methods of cooling exist, including selective cranial as well as systemic cooling by internal or external approaches. Finally, the article discusses the current research in the field of hypothermia for cardiac arrest and implications for future practice.