Therapeutic hypothermia after cardiopulmonary resuscitation

The Effect of Prophylactic Anticoagulation with Heparin on the Brain Cells of Sprague-Dawley Rats in a Cardiopulmonary-Cerebral Resuscitation Model

After a cardiac arrest (CA) of 5 to 10 min, a marked activation of blood coagulation occurs and microthrombi are found in the cerebral vessels. These microcirculatory disturbances directly affect the outcome on cardiopulmonary resuscitation (CPR). The purpose of this study was to investigate the effects and potential mechanisms of prophylactic anticoagulation on rat brain cells after cerebral CPR. After setting up an asphyxial CA model, we monitored the basic parameters such as the vitals and survival rate of the rats and assessed the respective neurological deficit (ND) and histological damage (HD) scores of their brain tissues. We, furthermore, investigated the influence of heparin on the expressions of TNF-α, IL-1β, CD40, NF-κB, and HIF-1α after asphyxial CA. The results showed that anticoagulation with heparin could obviously improve the outcome and prognosis of brain ischemia, including improvement of neurological function recovery and prevention of morphological and immunohistochemical injury on the brain, while significantly increasing the success rate of CPR. Treatment with heparin significantly inhibited the upregulation of CD40, NF-κB, and HIF-1α induced by asphyxial CA. Thrombolysis treatment may improve the outcome and prognosis of CPR, and future clinical studies need to evaluate the efficacy of early heparin therapy after CA.

Prognostication in Anoxic Brain Injury

Cardiac arrest is a common cause of coma with frequent poor outcomes. Palliative medicine teams are often called upon to discuss the scope of treatment and future care in cases of anoxic brain injury. Understanding prognostic tools in this setting would help medical teams communicate more effectively with patients’ families and caregivers and may promote improved quality of life overall. This article reviews multiple tools that are useful in determining outcomes in the setting of postarrest anoxic brain injury.

Sudden cardiac death in South India: Incidence, risk factors and pathology

BACKGROUND

Sudden cardiac death (SCD) is a major cause of mortality secondary to coronary artery disease (CAD) in the industrialized societies. Although South Asians have a high prevalence of CAD, the frequency and underlying pathology of SCD among this population are unknown.

METHODS

Medical records of consecutive patients presenting with unexplained sudden death (USD) in a tertiary care center were reviewed. Patients with trauma, violent deaths, positive toxicology and non-cardiac pathology were excluded to determine sudden cardiac death (SCD). Cardiac pathological findings were analyzed by autopsy. SCD rate was estimated based on census and government vital statistics for the years studied.

RESULTS

During a two year period, 223 patients (mean age 55 + 10 yrs, 78.9% male, body mass index 26 + 4, 60% smokers, 39% known CAD, 46% hypertension, 43% diabetes) presented to hospital with USD. SCD was attributed to myocardial infarction (MI) in 87% of cases; 69% were acute (96% anterior MI); 76% were small/moderate infarct and 9.9% of the cohort had normal hearts. Based on official municipal vital statistics, the SCD rate in those >35 yrs of age was estimated as 39.7/100,000 with male/female ratio of 4.6.

CONCLUSIONS

SCD in this south Indian city occurred predominantly in men of relatively young age and was most frequently associated with small or moderate-sized acute MI. Improved health care access, preventive measures and enhanced emergency management may reduce SCD from acute MI in this locale.

The cooling tube: A novel small animal model of systemic hypothermia in awake Syrian Golden Hamsters (mesocricetus auratus)

Hypothermia is increasingly used as a therapeutic strategy in a diversity of clinical scenarios. Its impact on mammalian physiology, particularly on the microcirculatory changes of critical organ systems, are, however, incompletely understood. Close examination of the literature reveals a marked paucity of small animal models of rapid systemic hypothermia. All published models introduce important microvascular confounders by investigating either local cooling processes or using anaesthetised animals. Here we present the first rapid systemic hypothermia model in an awake hamster. We developed a waterstream cooled copper tube system for standardized systemic temperature control. With this novel system core body temperature (Tc) in 14 awake animals could be precisely stabilised at temperatures of 30°C and 18°C (7 animals, respectively) within 10-20 min. Rewarming was achieved over 10-15 min. Tolerance of the procedure was excellent. Hamsters did not show any behavioural changes in the mild hypothermia group. In the deep hypothermia group 6 of 7 animals regained normal behaviour within 2-11 hs. As hypothermia was induced in dorsal skinfold chamber bearing animals this model seems suitable for investigation of microcirculatory purposes.Advantages over previously established experimental hypothermia models are significant. Amongst these, the possibility of visualization of microcirculation, the lack of microcirculation confounding factors such as anaesthetic drugs, the ability for precise Tc control and rapid induction of hypothermia are prominent.

Mild Hypothermia as a Cardioprotective Approach for Acute Myocardial Infarction: Laboratory to Clinical Application

In many animal models, mild therapeutic hypothermia is a powerful intervention, reducing myocardial infarct size, reducing the no-reflow phenomenon, and improving healing after infarction. Cooling in these models has been produced by various means including whole-body hypothermia, synchronized hypothermic coronary venous retro-perfusion, heat exchangers, and regional hypothermia targeting the heart alone. However, in humans, the most widely used techniques are surface cooling and cooling by endovascular heat-exchange catheters. The reduction in temperature necessary to produce cardioprotection is mild (32-34°C), appears to have no detrimental effects on left ventricular function or regional myocardial blood flow, and may improve microvascular reflow to previously ischemic heart tissue. It has been shown in experimental and clinical studies that for therapeutic hypothermia to be effective it must be (1) initiated as early as possible after the onset of ischemia and (2) initiated before reperfusion. This may require initiation of hypothermia in the ambulance, well before mechanical reperfusion occurs. The mechanisms of protection produced by hypothermia have yet to be conclusively determined but may include a decrease in tissue metabolic rate, preservation of high energy phosphates, a reduction in tissue apoptosis or induction of heat shock proteins.

Intravenous infusion of bone marrow mesenchymal stem cells improves brain function after resuscitation from cardiac arrest

OBJECTIVE

Allogeneic bone marrow mesenchymal stem cells were previously shown to improve myocardial function when administered intravenously after resuscitation from cardiac arrest in rats. Coincidental evidence of improved brain function prompted the present study.

DESIGN

Prospective, randomized, controlled study.

SETTING

University-affiliated research institute.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Using an established model in 20 male Sprague-Dawley rats in which 6 mins of untreated cardiac arrest was followed by cardiopulmonary resuscitation, animals were randomized to receive 5 x 10(6) mesenchymal stem cells labeled with PKH26 in phosphate buffer solution or phosphate buffer solution alone as a placebo at 2 hrs after restoration of spontaneous circulation. The stem cells or buffer diluent were injected into a catheter advanced from the jugular vein into the right atrium.

MEASUREMENTS AND MAIN RESULTS

Outcome measurements in addition to 35-day survival included somatosensor testing of capability for removal of an adhesive patch applied to both front paws, testing of motor function using a rotating cylinder, and observational scoring of the severity of neurologic impairment. Labeled mesenchymal stem cells were subsequently identified and counted in 5 microm sections obtained from defined sites in the harvested brain. Immunohistochemistry was used to identify neural cells differentiation of mesenchymal stem cells. Adhesive removal, motor function test, neurologic severity score, and 35-day survival were each significantly improved in comparison with control animals. Labeled mesenchymal stem cells were identified in the hippocampus, cortex, pons, medulla, and cerebellum and expressed protein markers phenotypic neural cells.

CONCLUSIONS

Mesenchymal stem cells injected into the right atrium of rats after resuscitation from cardiac arrest were identified in brains harvested 35 days later. Brain function was significantly improved. Accordingly, venous injection of mesenchymal stem cells after cardiopulmonary resuscitation has promise of minimizing the severity of postresuscitation neurologic impairment.

[Endovascular or surface cooling?: therapeutic hypothermia after cardiac arrest]

INTRODUCTION

Time course, time necessary to achieve the target temperature and stable maintenance, as well as a controlled rewarming period are important factors influencing the outcome of patients after successful cardiopulmonary resuscitation.

METHODS

After successful cardiopulmonary resuscitation a total of 49 patients were cooled via an endovascular or external cooling device to a target temperature of 33 degrees C. Relevant cooling parameters, such as time between admission and initiation of cooling, achievement of target temperature and stable maintenance of cooling therapy, were compared between both groups.

RESULTS

In the endovascular cooling group the target temperature was reached significantly faster (154 +/- 97 min vs. 268 +/- 95 min, p = 0.0002) and showed stable and controlled maintenance of cooling therapy (deviation from target temperature: 0.189 +/- 0.23 degrees C vs 0.596 +/- 0.61 degrees C, p = 0.00006). The rewarming phase was better controlled and length of ICU stay was shorter in the group with endovascular cooling (8.8 +/- 3 vs. 12.9 +/- 6 days).

CONCLUSION

Endovascular cooling offers the possibility to reach the target temperature significantly faster and a stable maintenance of therapeutic hypothermia. It is capable of a more controlled rewarming period and shortens the length of ICU stay.

Prognostication after out-of-hospital cardiac arrest, a clinical survey

Background

Numerous parameters and tests have been proposed for outcome prediction in comatose out-of-hospital cardiac arrest survivors. We conducted a survey of clinical practice of prognostication after therapeutic hypothermia (TH) became common practice in Norway.

Methods

By telephone, we interviewed the consultants who were in charge of the 25 ICUs admitting cardiac patients using 6 structured questions regarding timing, tests used and medical specialties involved in prognostication, as well as the clinical importance of the different parameters used and the application of TH in these patients.

Results

Prognostication was conducted within 24–48 hours in the majority (72%) of the participating ICUs.

The most commonly applied parameters and tests were a clinical neurological examination (100%), prehospital data (76%), CCT (56%) and EEG (52%). The parameters and tests considered to be of greatest importance for accurate prognostication were prehospital data (56%), neurological examination (52%), and EEG (20%).

In 76% of the ICUs, a multidisciplinary approach to prognostication was applied, but only one ICU used a standardised protocol. Therapeutic hypothermia was in routine use in 80% of the surveyed ICUs.

Conclusion

Despite the routine use of TH, outcome prediction was performed early and was mainly based on prehospital information, neurological examination and CCT and EEG evaluation. Somatosensory evoked potentials appear to be underused and underrated, while the importance of prehospital data, CCT and EEG to appear to be overrated as methods for making accurate predictions.

More evidence-based protocols for prognostication in cardiac arrest survivors, as well as additional studies on the effect of TH on known prognostic parameters are needed.

Induction of Thioredoxin and Mitochondrial Survival Proteins Mediates Preconditioning-Induced Cardioprotection and Neuroprotection

Delayed cardio- and neuroprotection are observed following a preconditioning procedure evoked by a brief and nontoxic oxidative stress due to deprivation of oxygen, glucose, serum, trophic factors, and/or antioxidative enzymes. Preconditioning protection can be observed in vivo and is under clinical trials for preservation of cell viability following organ transplants of liver. Previous studies indicated that ischemic preconditioning increases the expression of heat-shock proteins (HSPs) and nitric oxide synthase (NOS). Our pilot studies indicate that the treatment of neuronal NOS inhibitor (7-nitroindazole) and 6Br-cGMP blocks and mimics, respectively, preconditioning protection in human neuroblastoma SH-SY5Y cells. This minireview focuses on nitric oxide-mediated cellular adaptation and the related cGMP/PKG signaling pathway in a compensatory mechanism underlying preconditioning-induced hormesis. Both preconditioning and 6Br-cGMP increase the induction of human thioredoxin (Trx) mRNA and protein for cytoprotection, which is largely prevented by transfection of cells with Trx antisense but not sense oligonucleotides. Cytosolic Trx1 and mitochondrial Trx2 suppress free radical formation, lipid peroxidation, oxidative stress, and mitochondria-dependent apoptosis; knock out/down of either Trx1 or Trx2 is detrimental to cell survival. Other recent findings indicate that a transgenic increase of Trx in mice increases tolerance against oxidative nigral injury caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Trx1 can be translocated into nucleus and phosphoactivated CREB for a delayed induction of mitochondrial anti-apoptotic Bcl-2 and antioxidative MnSOD that is known to increase vitality and survival of cells in the brain and the heart. In conclusion, preconditioning adaptation or a brief oxidative stress induces a delayed nitric oxide-mediated compensatory mechanism for cell survival and vitality in the central nervous system and the cardiovascular system. Preconditioning-induced adaptive tolerance may be signaling through a cGMP-dependent induction of cytosolic redox protein Trx1 and subsequently mitochondrial proteins such as Bcl-2, MnSOD, and perhaps Trx2 or HSP70.

The Role of Thermoregulation in Cardiac Resuscitation

Regulating a patient's body temperature has long been within the scope of practice of the critical care nurse. Different measures and modalities have been used to achieve normothermia in the past. Recent research has demonstrated how crucial body temperature can be, not only because of its potential for neuroprotection but also because of its effects on all body systems. The general consensus of current literature is that maintaining mild hypothermia at 32 degrees to 34 degrees C (89.6 degrees-93.2 degrees F) for 12 to 24 hours after cardiac arrest may provide optimal neuroprotection with minimal complications for patients.

Brain function after resuscitation from cardiac arrest

PURPOSE OF REVIEW

In industrial countries the incidence of cardiac arrest is still increasing. Almost 80% of cardiac arrest survivors remains in coma for varying lengths of time and full cerebral recovery is still a rare event. After successful cardiopulmonary resuscitation, cerebral recirculation disturbances and complex metabolic postreflow derangements lead to death of vulnerable neurons with further deterioration of cerebral outcome. This article discusses recent research efforts on the pathophysiology of brain injury caused by cardiac arrest and reviews the beneficial effect of therapeutic hypothermia on neurologic outcome along with the recent approach to prognosticate long-term outcome by electrophysiologic techniques and molecular markers of brain injury.

RECENT FINDINGS

Recent experimental studies have brought new insights to the pathophysiology of secondary postischemic anoxic encephalopathy demonstrating a time-dependent cerebral oxidative injury, increased neuronal expression, and activation of apoptosis-inducing death receptors and altered gene expression with long-term changes in the molecular phenotype of neurons. Recently, nuclear MR imaging and MR spectroscopic studies assessing cerebral circulatory recovery demonstrated the precise time course of cerebral reperfusion after cardiac arrest. Therapeutic hypothermia has been shown to improve brain function after resuscitation from cardiac arrest and has been introduced recently as beneficial therapy in ventricular fibrillation cardiac arrest.

SUMMARY

Electrophysiologic techniques and molecular markers of brain injury allow the accurate assessment and prognostication of long-term outcome in cardiac arrest survivors. In particular, somatosensory evoked potentials have been identified as the method with the highest prognostic reliability. A recent systematic review of 18 studies analyzed the predictive ability of somatosensory evoked potentials performed early after onset of coma and found that absence of cortical somatosensory evoked potentials identify patients not returning from anoxic coma with a specificity of 100%.

Hypoxia tolerance in mammalian heterotherms

Heterothermic mammals tolerate severe hypoxia, as well as a variety of central nervous system insults, better than homeothermic mammals. Tolerance to hypoxia may stem from adaptations associated with the ability to survive hibernation and periodic arousal thermogenesis. Here, we review evidence and mechanisms of hypoxia tolerance during hibernation, euthermy and arousal in heterothermic mammals and consider potential mechanisms for regenerative-like processes, such as synaptogenesis, observed within hours of hypoxic stress associated with arousal thermogenesis.