Therapeutic hypothermia after cardiac arrest in adults: mechanism of neuroprotection, phases of hypothermia, and methods of cooling

Temperature Control in Acute Brain Injury: An Update

Temperature control in severe acute brain injury (SABI) is a key component of acute management. This manuscript delves into the complex role of temperature management in SABI, encompassing conditions like traumatic brain injury (TBI), acute ischemic stroke (AIS), intracerebral hemorrhage (ICH), aneurysmal subarachnoid hemorrhage (aSAH), and hypoxemic/ischemic brain injury following cardiac arrest. Fever is a common complication in SABI and is linked to worse neurological outcomes due to increased inflammatory responses and intracranial pressure (ICP). Temperature management, particularly hypothermic temperature control (HTC), appears to mitigate these adverse effects primarily by reducing cerebral metabolic demand and dampening inflammatory pathways. However, the effectiveness of HTC varies across different SABI conditions. In the context of post-cardiac arrest, the impact of HTC on neurological outcomes has shown inconsistent results. In cases of TBI, HTC seems promising for reducing ICP, but its influence on long-term outcomes remains uncertain. For AIS, clinical trials have yet to conclusively demonstrate the benefits of HTC, despite encouraging preclinical evidence. This variability in efficacy is also observed in ICH, aSAH, bacterial meningitis, and status epilepticus. In pediatric and neonatal populations, while HTC shows significant benefits in hypoxic-ischemic encephalopathy, its effectiveness in other brain injuries is mixed. Although the theoretical basis for employing temperature control, especially HTC, is strong, the clinical outcomes differ among various SABI subtypes. The current consensus indicates that fever prevention is beneficial across the board, but the application and effectiveness of HTC are more nuanced, underscoring the need for further research to establish optimal temperature management strategies. Here we provide an overview of the clinical evidence surrounding the use of temperature control in various types of SABI.

Analysis of Epinephrine Dose, Targeted Temperature Management, and Neurologic and Survival Outcomes Among Adults With Out-of-Hospital Cardiac Arrest

IMPORTANCE

Epinephrine improves return of spontaneous circulation after out-of-hospital cardiac arrest (OHCA). These beneficial cardiac effects do not directly translate to better neurologic outcomes, possibly because of epinephrine-induced microvascular effects that produce critical brain ischemia.

OBJECTIVE

To examine whether targeted temperature management (TTM) modifies the adverse association between increasing prehospital epinephrine dose and neurologically favorable survival.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study assessed 14 612 adults from Seattle and King County, Washington, with nontraumatic OHCA between January 1, 2008, and December 31, 2018, and included those who achieved return of spontaneous circulation and were unconscious at hospital admission. Data analysis was performed from April 2021 to May 2022.

EXPOSURES

Epinephrine dose and TTM during prehospital resuscitation.

MAIN OUTCOMES AND MEASURES

Favorable neurologic survival (Cerebral Performance Category [CPC] 1 or 2) and survival to hospital discharge.

RESULTS

Of the 14 612 assessed adults, 5253 (median age, 63 years; IQR, 51-74 years; 3460 [65.8%] male) were eligible for the study. The median epinephrine dose was 2.0 mg (IQR, 1.0-3.0 mg); 3052 patients (58.1%) received TTM. In all, 1889 patients (36.0%) survived with CPC 1 to 2, and 2177 (41.4%) survived to discharge. Increasing doses of epinephrine were associated with a decreasing likelihood of CPC 1 to 2 (odds ratio [OR], 0.46; 95% CI 0.42-0.50 for each additional milligram of epinephrine) and survival (OR, 0.47; 95% CI, 0.43-0.51). The dose-dependent epinephrine association was modified by TTM. After adjusting for Utstein covariates, TTM was associated with a relative stepwise improvement in odds of CPC 1 to 2 (interaction OR, 1.36; 95% CI, 1.22-1.51) and survival (interaction OR, 1.37; 95% CI, 1.24-1.51). A significant interaction was also observed when the analysis was stratified according to initial rhythm among shockable OHCA and nonshockable OHCA (shockable interaction OR, 1.20; 95% CI, 1.04-1.39; and nonshockable interaction OR, 1.24, 95% CI, 1.07-1.45).

CONCLUSIONS AND RELEVANCE

This cohort study found an interaction between TTM and epinephrine dose such that the beneficial association of TTM increased with increasing epinephrine dose, suggesting that TTM may attenuate the adverse effects of higher-dose epinephrine.

Outcomes of Targeted Temperature Management for In-Hospital and Out-Of-Hospital Cardiac Arrest: A Matched Case-Control Study Using the National Database of Taiwan Network of Targeted Temperature Management for Cardiac Arrest (TIMECARD) Registry

BACKGROUND This study aimed to compare outcomes of targeted temperature management (TTM) for patients with in-hospital and out-of-hospital cardiac arrest using the national database of TaIwan network of targeted temperature ManagEment for CARDiac arrest (TIMECARD) registry. MATERIAL AND METHODS A retrospective, matched, case-control study was conducted. Patients with in-hospital cardiac arrest (IHCA) treated with TTM after the return of spontaneous circulation (ROSC) were selected as the case group and controls were defined as the same number of patients with out-of-hospital cardiac arrest (OHCA), matched for sex, age, Charlson comorbidity index, and cerebral performance category. Neurological outcome and survival at hospital discharge were the primary outcome measures. RESULTS Data of 103 patients with IHCA and matched controls with OHCA were analyzed. Patients with IHCA were more likely to experience witnessed arrest and bystander cardiopulmonary resuscitation (CPR). The duration from collapse to the beginning of CPR, CPR time, and the duration from ROSC to initiation of TTM were shorter in the IHCA group but their initial arterial blood pressure after ROSC was lower. Overall, 88% of patients survived to completion of TTM and 43% survived to hospital discharge. Hospital survival (42.7% vs 42.7%, P=1.00) and favorable neurological outcome at discharge (19.4% vs 12.7%, P=0.25) did not differ between the 2 groups. CONCLUSIONS The findings from the national TIMECARD registry showed that clinical outcomes following TTM for patients with IHCA were not significantly different from OHCA when baseline factors were matched.

Targeted Temperature Management at 33 Versus 36 Degrees: A Retrospective Cohort Study

OBJECTIVES

To determine the association between targeted temperature management goal temperature of 33°C versus 36°C and neurologic outcome after out-of-hospital cardiac arrest.

DESIGN

This was a retrospective, before-and-after, cohort study.

SETTING

Urban, academic, level 1 trauma center from 2010 to 2017.

PATIENTS

Adults with nontraumatic out-of-hospital cardiac arrest who received targeted temperature management.

INTERVENTIONS

Our primary exposure was targeted temperature management goal temperature, which was changed from 33°C to 36°C in April of 2014 at the study hospital. Primary outcome was neurologically intact survival to discharge. Secondary outcomes included hospital mortality and care processes.

MEASUREMENTS AND MAIN RESULTS

Of 782 out-of-hospital cardiac arrest patients transported to the study hospital, 453 (58%) received targeted temperature management. Of these, 258 (57%) were treated during the 33°C period (targeted temperature management 33°C) and 195 (43%) were treated during the 36°C period (targeted temperature management 36°C). Patients treated during targeted temperature management 33°C were older (57 vs 52 yr; p < 0.05) and had more arrests of cardiac etiology (45% vs 35%; p < 0.05), but otherwise had similar baseline characteristics, including initial cardiac rhythm. A total of 40% of patients treated during targeted temperature management 33°C survived with favorable neurologic outcome, compared with 30% in the targeted temperature management 36°C group (p < 0.05). After adjustment for demographic and cardiac arrest characteristics, targeted temperature management 33°C was associated with increased odds of neurologically intact survival to discharge (odds ratio, 1.79; 95% CI, 1.09-2.94). Targeted temperature management 33°C was not associated with significantly improved hospital mortality. Targeted temperature management was implemented faster (1.9 vs 3.5 hr from 911 call; p < 0.001) and more frequently in the emergency department during the targeted temperature management 33°C period (87% vs 55%; p < 0.001).

CONCLUSIONS

Comatose, adult out-of-hospital cardiac arrest patients treated during the targeted temperature management 33°C period had higher odds of neurologically intact survival to hospital discharge compared with those treated during the targeted temperature management 36°C period. There was no significant difference in hospital mortality.

Increased protocol adherence and safety during controlled normothermia as compared to hypothermia after cardiac arrest

PURPOSE

This study aims to compare protocol adherence, neurological outcome and adverse effects associated with a controlled hypothermia versus a controlled normothermia protocol in patients successfully resuscitated after cardiac arrest.

METHODS

In this retrospective single-center study in a university intensive care unit in Switzerland, post-cardiac arrest patients were compared before and after a protocol change from targeted temperature management at 33 °C (TTM-33) to 36 °C (TTM-36) using an intravascular cooling device. Protocol adherence was assessed as the primary outcome. Secondary outcomes were in-hospital mortality, neurological outcome and adverse effects.

RESULTS

373 patients after cardiac arrest were screened, of whom a total of 133 patients were included. Protocol adherence was lower in the TTM-33 group (47% vs 87% of patients, p < 0.01). In-hospital mortality (59% vs 45%, p = 0.15) and neurological outcome (modified Rankin Score < 4 in 33% vs 39% and CPC-Score < 3 in 33% vs 39% of patients, p = 0.60 and 0.97) were similar. Overall incidence of adverse effects was comparable, with bradycardic arrhythmias occurring more frequently in the TTM-33 group.

CONCLUSION

Protocol adherence was higher in the TTM-36 group. In-hospital mortality and neurological outcome were similar, while bradycardic arrhythmias were encountered more often in TTM-33.

Hypothermia prevents hippocampal oxidative stress and apoptosis via the GSK-3β/Nrf2/HO-1 signaling pathway in a rat model of cardiac arrest-induced brain damage

OBJECTIVES

The present study was undertaken to investigate the effects and related mechanisms of hypothermia on oxidative stress and apoptosis caused by cardiac arrest (CA)-induced brain damage in rats.

METHODS

The CA/CPR model was initiated by asphyxia. Body temperature in the normothermia and hypothermia groups was maintained at 37°C ± 0.2°C and 34°C ± 0.2°C, respectively, by surface cooling with an ice pack. First, neurological deficit scores (NDSs) were assessed, and then hippocampus samples were collected at 24 and 72 h after return of spontaneous circulation (ROSC).

RESULTS

The NDSs of rats were significantly reduced after CA, and hypothermia ameliorated neurological deficits. Varying degrees of changes in cellular nuclei and mitochondria were observed in the hippocampus following CA; however, morphological changes became less apparent after therapeutic hypothermia. Malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were higher in the hippocampus at 24 h after ROSC. In contrast, hypothermia did not alter MDA content, while SOD activity further increased. Furthermore, hypothermia reversed the caspase-3 enhancement observed in the normothermia group at 24 h after ROSC. CA also inhibited GSK-3β phosphorylation, promoted Nrf2 translocation to the nucleus, and downregulated HO-1 expression. However, hypothermia significantly reversed these CA-induced changes in GSK-3β phosphorylation, Nrf2 translocation, and HO-1 expression.

CONCLUSION

Hypothermia attenuated CA-induced neurological deficits and hippocampal morphology changes in rats. The protective effect of hypothermia following CA may have been related to inhibition of oxidative stress and apoptosis, and its underlying mechanisms may have been due, at least in part, to activation of the GSK-3β/Nrf2/HO-1 pathway.

Effects of regional body temperature variation during asphyxial cardiac arrest on mortality and brain damage in a rat model

To date, hypothermia has focused on improving rates of resuscitation to increase survival in patients sustaining cardiac arrest (CA). Towards this end, the role of body temperature in neuronal damage or death during CA needs to be determined. However, few studies have investigated the effect of regional temperature variation on survival rate and neurological outcomes. In this study, adult male rats (12 week-old) were used under the following four conditions: (i) whole-body normothermia (37 ± 0.5 °C) plus (+) no asphyxial CA, (ii) whole-body normothermia + CA, (iii) whole-body hypothermia (33 ± 0.5 °C)+CA, (iv) body hypothermia/brain normothermia + CA, and (v) brain hypothermia/body normothermia + CA. The survival rate after resuscitation was significantly elevated in groups exposed to whole-body hypothermia plus CA and body hypothermia/brain normothermia plus CA, but not in groups exposed to whole-body normothermia combined with CA and brain hypothermia/body normothermia plus CA. However, the group exposed to hypothermia/brain normothermia combined with CA exhibited higher neuroprotective effects against asphyxial CA injury, i.e. improved neurological deficit and neuronal death in the hippocampus compared with those involving whole-body normothermia combined with CA. In addition, neurological deficit and neuronal death in the group of rat exposed to brain hypothermia/body normothermia and CA were similar to those in the rats subjected to whole-body normothermia and CA. In brief, only brain hypothermia during CA was not associated with effective survival rate, neurological function or neuronal protection compared with those under body (but not brain) hypothermia during CA. Our present study suggests that regional temperature in patients during CA significantly affects the outcomes associated with survival rate and neurological recovery.

Targeted Temperature Management and Multimodality Monitoring of Comatose Patients After Cardiac Arrest

Out-of-hospital cardiac arrest (CA) remains a leading cause of sudden morbidity and mortality; however, outcomes have continued to improve in the era of targeted temperature management (TTM). In this review, we highlight the clinical use of TTM, and provide an updated summary of multimodality monitoring possible in a modern ICU. TTM is neuroprotective for survivors of CA by inhibiting multiple pathophysiologic processes caused by anoxic brain injury, with a final common pathway of neuronal death. Current guidelines recommend the use of TTM for out-of-hospital CA survivors who present with a shockable rhythm. Further studies are being completed to determine the optimal timing, depth and duration of hypothermia to optimize patient outcomes. Although a multidisciplinary approach is necessary in the CA population, neurologists and neurointensivists are central in selecting TTM candidates and guiding patient care and prognostic evaluation. Established prognostic tools include clinal exam, SSEP, EEG and MR imaging, while functional MRI and invasive monitoring is not validated to improve outcomes in CA or aid in prognosis. We recommend that an evidence-based TTM and prognostication algorithm be locally implemented, based on each institution's resources and limitations. Given the high incidence of CA and difficulty in predicting outcomes, further study is urgently needed to determine the utility of more recent multimodality devices and studies.

Nutritional and Bioenergetic Considerations in Critically Ill Patients with Acute Neurological Injury

The brain, due to intensive cellular processes and maintenance of electrochemical gradients, is heavily dependent on a constant supply of energy. Brain injury, and critical illness in general, induces a state of increased metabolism and catabolism, which has been proven to lead to poor outcomes. Of all the biochemical interventions undertaken in the ICU, providing nutritional support is perhaps one of the most undervalued, but potentially among the safest, and most effective interventions. Adequate provisions of calories and protein have been shown to improve patient outcomes, and guidelines for the nutritional support of the critically ill patient are reviewed. However, there are no such specific guidelines for the critically ill patient with neurological injury. Patients with primary or secondary neurological disorders are frequently undernourished, while data suggest this population would benefit from early and adequate nutritional support, although comprehensive clinical evidence is lacking. We review the joint recommendations from the Society for Critical Care Medicine and the American Society for Parenteral and Enteral Nutrition, as they pertain to neurocritical care, and assess the recommendations for addressing nutrition in this patient population.

Hypothermia and brain inflammation after cardiac arrest

The cessation (ischemia) and restoration (reperfusion) of cerebral blood flow after cardiac arrest (CA) induce inflammatory processes that can result in additional brain injury. Therapeutic hypothermia (TH) has been proven as a brain protective strategy after CA. In this article, the underlying pathophysiology of ischemia-reperfusion brain injury with emphasis on the role of inflammatory mechanisms is reviewed. Potential targets for immunomodulatory treatments and relevant effects of TH are also discussed. Further studies are needed to delineate the complex pathophysiology and interactions among different components of immune response after CA and identify appropriate targets for clinical investigations.

The role of nitrous oxide in stroke

Stroke that is caused by poor blood flow into the brain results in cell death, including ischemia stroke due to lack of blood into brain tissue, and hemorrhage due to bleeding. Both of them will give rise to the dysfunction of brain. In general, the signs and symptoms of stroke are the inability of feeling or moving on one side of body, sometimes loss of vision to one side. Above symptoms will appear soon after the stroke has happened. If the symptoms and signs happen in 1 or 2 hours, we often call them as transient ischemic attack. Moreover, hemorrhagic stroke often leads to severe headache. It is known that neuronal death can happen after stroke, and it depends upon the activation of N-methyl-D-aspartate (NMDA) excitatory glutamate receptor which is the goal for a lot of neuroprotective agents. Nitrous oxide was discovered by Joseph Priestley in 1772, and then he and his friends, including the poet Coleridge and Robert Sauce, experimented with the gas. They found this gas could make patients loss the sense of pain and still maintain consciousness after inhalation. Shortly the gas was used as an anesthetic, especially in the field of dentists. Now, accroding to theme of Helene N. David and other scientists, both of nitrous oxide at 75 vol% and xenon at 50 vol% could reduce ischemic neuronal death in the cortex by 70% and decrease NMDA-induced Ca²⁺ influx by 30%. Therefore, more clinical and experimental studies are important to illuminate the mechanisms of how nitrous oxide protects brain tissue and to explore the best protocol of this gas in stroke treatment.

Two Negative-Strand RNA Viruses Identified in Watermelon Represent a Novel Clade in the Order Bunyavirales

Two novel negative-sense, single-stranded (ss) RNA viruses were identified in watermelon plants and named watermelon crinkle leaf-associated virus 1 and 2 (WCLaV-1 and -2), respectively. The multipartite genomes consist of three RNA molecules of ~6.8, 1.4, and 1.3 kb. The genomes and the deduced proteins of RNA1 and RNA3 show features resembling those of members in the genus Phlebovirus and Tenuivirus; however, the predicted proteins encoded by RNA2 are related to the movement protein (MP) in the genus Ophiovirus and Emaravirus. Furthermore, these two viruses define a novel clade in the family Phenuiviridae, order Bunyavirales, which is phylogenetically related to the viruses in the above four genera. Moreover, after mechanical inoculation with WCLaV-1 seedlings of the natural host watermelon plants develop crinkling similar to those observed in the field. These findings enhance our understanding of the evolution and the classification of ssRNA viruses.

Neuroprotective effect of epidermal growth factor plus growth hormone-releasing peptide-6 resembles hypothermia in experimental stroke

BACKGROUND

Combined therapy with epidermal growth factor (EGF) and growth hormone-releasing peptide 6 (GHRP-6) in stroke models has accumulated evidence of neuroprotective effects from several studies, but needs further support before clinical translation. Comparing EGF + GHRP-6 to hypothermia, a gold neuroprotection standard, may contribute to this purpose.

OBJECTIVES

The aims of this study were to compare the neuroprotective effects of a combined therapy based on EGF + GHRP-6 with hypothermia in animal models of (a) global ischemia representing myocardial infarction and (b) focal brain ischemia representing ischemic stroke.

METHODS

(a) Global ischemia was induced in Mongolian gerbils by a 15-min occlusion of both carotid arteries, followed by reperfusion. (b) Focal brain ischemia was achieved by intracerebral injection of endothelin 1 in Wistar rats. In each experiment, three ischemic treatment groups - vehicle, EGF + GHRP-6, and hypothermia - were compared to each other and to a sham-operated control group. End points were survival, neurological scores, and infarct volume.

RESULTS

(a) In global ischemia, neurological score at 48-72 h, infarct volume, and neuronal density of hippocampal CA1 zone in gerbils treated with EGF + GHRP-6 were similar to the hypothermia-treated group. (b) In focal ischemia, the neurologic score and infarct volume of rats receiving EGF + GHRP-6 were also similar to animals in the hypothermia group.

DISCUSSION

With hypothermia being a good standard neuroprotectant reference, these results provide additional proof of principle for EGF and GHRP-6 co-administration as a potentially neuroprotective stroke therapy.

The Association Between Arterial Oxygen Tension and Neurological Outcome After Cardiac Arrest

A number of observational studies have evaluated the association between arterial oxygen tensions and outcome after cardiac arrest with variable results. The objective of this study is to determine the association between arterial oxygen tension and neurological outcome after cardiac arrest. A retrospective cohort analysis was performed using the Penn Alliance for Therapeutic Hypothermia registry. Adult patients who experienced return of spontaneous circulation after in-hospital or out-of-hospital cardiac arrest (OHCA) and had a partial pressure of arterial oxygen (PaO₂) recorded within 48 hours were included. Our primary exposure of interest was PaO₂. Hyperoxemia was defined as PaO₂ > 300 mmHg, hypoxemia as PaO₂ < 60 mmHg, and optimal oxygenation as PaO₂ 60-300 mmHg. The primary outcome was neurological function at hospital discharge among survivors, as described by the cerebral performance category (CPC) score, dichotomized into "favorable" (CPCs 1-2) and "unfavorable" (CPCs 3-5). Secondary outcomes included in-hospital mortality. A total of 544 patients from 13 institutions were included. Average age was 61 years, 56% were male, and 51% were white. A total of 64% experienced OHCA, 81% of arrests were witnessed, and pulseless electrical activity was the most common initial rhythm (40%). More than 72% of the patients had cardiac etiology for their arrests, and 55% underwent targeted temperature management. A total of 38% of patients survived to hospital discharge. There was no significant association between PaO₂ at any time interval and neurological outcome at hospital discharge. Hyperoxemia at 12 hours after cardiac arrest was associated with decreased odds of survival (OR 0.17 [0.03-0.89], p = 0.032). There was no significant association between arterial oxygen tension measured within the first 48 hours after cardiac arrest and neurological outcome.

Efficacy of mild hypothermia for the treatment of patients with cardiac arrest

BACKGROUND

Therapeutic hypothermia has been recommended for the treatment of cardiac arrest patients who remain comatose after the return of spontaneous circulation. The aim of this study was to evaluate the effectiveness and safety of mild hypothermia on patients with cardiac arrest by conducting a meta-analysis.

METHODS

The relevant trials were searched in Cochrane Library, PubMed, Web of Science, Embase, CNKI and Wan Fang Data from the date of their establishment to October 2014. 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 conducted using the Cochrane Collaboration Review Manager 5.2 software.

RESULTS

Six randomized controlled trials involving 531 cases were included, among which 273 cases were assigned to the treatment group and the other 258 cases to the control group. The meta-analysis indicated that mild hypothermia therapy after cardiac arrest produced significant differences in survival rate (relative risk [RR] =1.23, 95% confidence interval [CI]: 1.02-1.48, P = 0.03) and neurological function (RR = 1.33, 95% CI: 1.08-1.65, P = 0.007) after 6 months compared with normothermia therapy. However, no significant differences were observed in the survival to the hospital discharge (RR = 1.35, 95% CI: 0.87-2.10, P = 0.18), favorable neurological outcome at hospital discharge (RR = 1.53, 95% CI: 0.95-2.45, P = 0.08) and adverse events.

CONCLUSIONS

The meta-analysis demonstrated that mild hypothermia can improve the survival rate and neurological function of patients with cardiac arrest after 6 months. On the other hand, regarding the survival to hospital discharge, favorable neurological outcome at hospital discharge, and adverse events, our meta-analysis produced nonsignificant results.

Therapeutic hypothermia post-cardiac arrest: a clinical nurse specialist initiative in Pakistan

PURPOSE

The purpose of this project was to assess the feasibility of an evidence-based therapeutic hypothermia protocol in adult post-cardiac arrest (CA) patients in a university hospital in Pakistan.

BACKGROUND

Cardiac arrest has a deleterious effect on neurological function, and survival is associated with significant morbidity. The International Liaison Committee of Cardiopulmonary Resuscitation and the American Heart Association recommend the use of mild hypothermia in post-CA victims to mitigate brain injury caused by anoxia. In Pakistan, the survival rate in CA victims is poor. At present, there are no hospitals in the country that use the evidence-based hypothermia intervention in adult post-CA victims.

DESCRIPTION

This pilot project of therapeutic hypothermia in adult post-CA patients was implemented in a university hospital in Pakistan by a clinical nurse specialist in collaboration with the cardiopulmonary resuscitation committee and the nursing leadership of the hospital. Various clinical nurse specialist competencies and roles were used to address the 3 spheres of influence: patient, nurses, and system, while executing an evidence-based hypothermia protocol. Process and outcome indicators were monitored to evaluate the effectiveness and feasibility of hypothermia intervention in this setting.

OUTCOME

The hypothermia protocol was successfully implemented in 3 adult post-CA patients using cost-effective measures. All 3 patients were extubated within 72 hours after CA, and 2 patients were discharged home with good neurological outcome.

CONCLUSION

Adoption of an evidence-based hypothermia protocol for adult CA patients is feasible in the intensive care setting of a university hospital in Pakistan.

IMPLICATIONS

The process used in the project can serve as a road map to other hospitals in resource-limited countries such as Pakistan that are motivated to improve post-CA outcomes. This experience reveals that advanced practice nurses can be instrumental in translation of evidence into practice in a healthcare system in Pakistan.

Therapeutic benefits of mild hypothermia in patients successfully resuscitated from cardiac arrest: A meta-analysis

BACKGROUND

Good neurological outcome after cardiac arrest (CA) is hard to achieve for clinicians. Experimental and clinical evidence suggests that therapeutic mild hypothermia is beneficial. This study aimed to assess the effectiveness and safety of therapeutic mild hypothermia in patients successfully resuscitated from CA using a meta-analysis.

METHODS

We searched the MEDLINE (1966 to April 2012), OVID (1980 to April 2012), EMBASE (1980 to April 2012), Chinese bio-medical literature & retrieval system (CBM) (1978 to April 2012), Chinese medical current contents (CMCC) (1995 to April 2012), and Chinese medical academic conference (CMAC) (1994 to April 2012). Studies were included if 1) the study design was a randomized controlled trial (RCT); 2) the study population included patients successfully resuscitated from CA, and received either standard post-resuscitation care with normothermia or mild hypothermia; 3) the study provided data on good neurologic outcome and survival to hospital discharge. Relative risk (RR) and 95% confidence interval (CI) were used to pool the effect.

RESULTS

The study included four RCTs with a total of 417 patients successfully resuscitated from CA. Compared to standard post-resuscitation care with normothermia, patients in the hypothermia group were more likely to have good neurologic outcome (RR=1.43, 95% CI 1.14-1.80, P=0.002) and were more likely to survive to hospital discharge (RR=1.32, 95% CI 1.08-1.63, P=0.008). There was no significant difference in adverse events between the normothermia and hypothermia groups (P>0.05), nor heterogeneity and publication bias.

CONCLUSION

Therapeutic mild hypothermia improves neurologic outcome and survival in patients successfully resuscitated from CA.

A systematic review of neuroprotective strategies after cardiac arrest: from bench to bedside (part II-comprehensive protection)

Neurocognitive deficits remain a significant source of morbidity in survivors of cardiac arrest. We conducted a literature review of treatment protocols designed to evaluate neurologic outcome and survival following global cerebral ischemia associated with cardiac arrest. The search was limited to investigational therapies that were implemented either during cardiopulmonary resuscitation or after return of spontaneous circulation in studies that included assessment of impact on neurologic outcome. Given that complex pathophysiology underlies global brain hypoxic ischemia following cardiac arrest, neuroprotective strategies targeting multiple stages of neuropathologic cascades should promise to improve survival and neurologic outcomes in cardiac arrest victims. In Part II of this review, we discuss several approaches that can provide comprehensive protection against global brain injury associated with cardiac arrest, by modulating multiple targets of neuropathologic cascades. Pharmaceutical approaches include adenosine and growth factors/hormones including brain-derived neurotrophic factor, insulin-like growth factor-1 and glycine-proline-glutamate, granulocyte colony stimulating factor and estrogen. Preclinical studies of these showed some benefit but were inconclusive in models of global brain injury involving systemic ischemia. Several medical gases that can mediate neuroprotection have been evaluated in experimental settings. These include hydrogen sulfide, hyperbaric oxygen and molecular hydrogen. Hyperbaric oxygen and molecular hydrogen showed promising results; however, further investigation is required prior to clinical application of these agents in cardiac arrest patients.

XENON in medical area: emphasis on neuroprotection in hypoxia and anesthesia

Xenon is a medical gas capable of establishing neuroprotection, inducing anesthesia as well as serving in modern laser technology and nuclear medicine as a contrast agent. In spite of its high cost, its lack of side effects, safe cardiovascular and organoprotective profile and effective neuroprotective role after hypoxic-ischemic injury (HI) favor its applications in clinics. Xenon performs its anesthetic and neuroprotective functions through binding to glycine site of glutamatergic N-methyl-D-aspartate (NMDA) receptor competitively and blocking it. This blockage inhibits the overstimulation of NMDA receptors, thus preventing their following downstream calcium accumulating cascades. Xenon is also used in combination therapies together with hypothermia or sevoflurane. The neuroprotective effects of xenon and hypothermia cooperate synergistically whether they are applied synchronously or asynchronously. Distinguishing properties of Xenon promise for innovations in medical gas field once further studies are fulfilled and Xenon’s high cost is overcome.

Ex vivo rehabilitation of non-heart-beating donor lungs in preclinical porcine model: delayed perfusion results in superior lung function

OBJECTIVES

Ex vivo lung perfusion (EVLP) is a promising modality for the evaluation and treatment of marginal donor lungs. The optimal timing of EVLP initiation and the potential for rehabilitation of donor lungs with extended warm ischemic times is unknown. The present study compared the efficacy of different treatment strategies for uncontrolled non-heart-beating donor lungs.

METHODS

Mature swine underwent hypoxic arrest, followed by 60 minutes of no-touch warm ischemia. The lungs were harvested and flushed with 4°C Perfadex. Three groups (n = 5/group) were stratified according to the preservation method: cold static preservation (CSP; 4 hours of 4°C storage), immediate EVLP (I-EVLP: 4 hours EVLP at 37°C), and delayed EVLP (D-EVLP; 4 hours of CSP followed by 4 hours of EVLP). The EVLP groups were perfused with Steen solution supplemented with heparin, methylprednisolone, cefazolin, and an adenosine 2A receptor agonist. The lungs then underwent allotransplantation and 4 hours of recipient reperfusion before allograft assessment for resultant ischemia-reperfusion injury.

RESULTS

The donor blood oxygenation (partial pressure of oxygen/fraction of inspired oxygen ratio) before death was not different between the groups. The oxygenation after transplantation was significantly greater in the D-EVLP group than in the I-EVLP or CSP groups. The mean airway pressure, pulmonary artery pressure, and expression of interleukin-8, interleukin-1β, and tumor necrosis factor-α were all significantly reduced in the D-EVLP group. Post-transplant oxygenation exceeded the acceptable clinical levels only in the D-EVLP group.

CONCLUSIONS

Uncontrolled non-heart-beating donor lungs with extended warm ischemia can be reconditioned for successful transplantation. The combination of CSP and EVLP in the D-EVLP group was necessary to obtain optimal post-transplant function. This finding, if confirmed clinically, will allow expanded use of nonheart-beating donor lungs.