Therapeutic hypothermia for acute myocardial infarction and cardiac arrest

Impact of Mild Hypothermia As Adjunctive Therapy in Patients With ST-Elevation Myocardial Infarction: A Meta-Analysis and Trial Sequential Analysis of Randomized Controlled Trials

BACKGROUND

The prevention of reperfusion injury remains an unmet need in ST-elevation myocardial infarction (STEMI) patients. Several randomized controlled trials (RCTs) evaluated mild hypothermia as adjunctive therapy during STEMI, with conflicting results.

AIMS

To summarize the evidence about the efficacy and safety of mild hypothermia in patients with STEMI, as well as its conclusiveness through a trial sequential analysis (TSA).

METHODS

PubMed and Scopus electronic databases were screened for eligible studies until August 12, 2024. Efficacy endpoints were all-cause death, infarct size (IS), left ventricular ejection fraction (LVEF), the occurrence of microvascular obstruction (MVO), thrombolysis in myocardial infarction (TIMI) flow grade 3, and the resolution of ST-segment elevation (i.e., > 50-70% from baseline) after the procedure. Safety endpoints included: the incidence of atrial fibrillation (AF), infections, any bleeding, major bleeding, acute and subacute stent thrombosis (STh), cardiogenic shock/pulmonary oedema, and ventricular fibrillation/tachycardia. "Door-to-balloon time" was indicated as the procedural endpoint. Two pre-specified subgroup analyses were planned according to the mean ischemic time and the site of hypothermia induction (intra-coronary vs. extra-coronary). A TSA was run to explore whether the effect estimate of each efficacy outcome could be influenced by further studies.

RESULTS

Ten RCTs were included. Hypothermia did not provide a benefit for any of the specified efficacy endpoints. Furthermore, it enhanced the risk of infection, the risk of STh in patients with a mean ischemic time of less than 4 h, and the risk of AF in patients undergoing extra-coronary hypothermia. Finally, it was also associated with an increased "door-to-balloon time", and a trend toward an increased risk of any bleeding. No significant difference was found for the other endpoints. TSA showed conclusive evidence of an absence of benefit of hypothermia on IS, MVO, LVEF, and TIMI three flow.

CONCLUSIONS

Mild hypothermia is not beneficial and causes relevant delays in clinical management of STEMI patients, raising safety issues mainly related to the occurrence of STh, AF, and infections.

Therapeutic Hypothermia Inhibits Hypoxia-Induced Cardiomyocyte Apoptosis Via the MiR-483-3p/Cdk9 Axis

Background Therapeutic hypothermia has a beneficial effect on cardiac function after acute myocardial infarction, but the exact mechanism is still unclear. Recent research has suggested that microRNAs participate in acute myocardial infarction to regulate cardiomyocyte survival. This study aimed to explore the ability of hypothermia-regulated microRNA-483-3p (miR-483-3p) to inhibit hypoxia-induced myocardial infarction. Methods and Results Primary cardiomyocytes were cultured under hypoxia at 32 °C to mimic therapeutic hypothermia, and the differentially expressed microRNAs were determined by RNA sequencing. Therapeutic hypothermia recovered hypoxia-induced increases in apoptosis, decreases in ATP levels, and decreases in miR-483-3p expression. Overexpression of miR-483-3p exhibited effects similar to those of therapeutic hypothermia on hypoxia in the treatment of cardiomyocytes to associate with maintaining the mitochondrial membrane potential, and cyclin-dependent kinase 9 (Cdk9) was identified as a target gene with downregulated expression by miR-483-3p. Knockdown of Cdk9 also promoted cardiac survival, ATP production, and mitochondrial membrane potential stability under hypoxia. In vivo, the expression of miR-483-3p and Cdk9 was tested in the cardiac tissue of the mice with acute myocardial infarction, and the expression of miR-483-3p decreased and Cdk9 increased in the region of myocardial infarction. However, miR-483-3p was overexpressed with lentivirus, which suppressed apoptosis, infarct size (miR-483-3p, 22.00±4.04% versus negative control, 28.57±5.44%, P<0.05), and Cdk9 expression to improve cardiac contractility. Conclusions MiR-483-3p antagonizes hypoxia, leading to cardiomyocyte injury by targeting Cdk9, which is a new mechanism of therapeutic hypothermia.

Impaired neuromuscular function by conjoint actions of organophosphorus insecticide metabolites omethoate and cyclohexanol with implications for treatment of respiratory failure

BACKGROUND

Ingestion of agricultural organophosphorus insecticides is a significant cause of death in rural Asia. Patients often show acute respiratory failure and/or delayed, unexplained signs of neuromuscular paralysis, sometimes diagnosed as "Intermediate Syndrome". We tested the hypothesis that omethoate and cyclohexanol, circulating metabolites of one agricultural formulation, cause muscle weakness and paralysis.

METHODS

Acetylcholinesterase activity of insecticide components and metabolites was measured using purified enzyme from eel electroplaque or muscle homogenates. Mechanomyographic recording of pelvic limb responses to nerve stimulation was made in anaesthetized pigs and isometric force was recorded from isolated nerve-muscle preparations from mice. Omethoate and cyclohexanol were administered intravenously or added to physiological saline bathing isolated muscle. We also assessed the effect of MgSO₄ and cooling on neuromuscular function.

RESULTS

Omethoate caused tetanic fade in pig muscles and long-lasting contractions of the motor innervation zone in mouse muscle. Both effects were mitigated, either by i.v. administration of MgSO₄ in vivo or by adding 5 mM Mg²⁺ to the medium bathing isolated preparations. Combination of omethoate and cyclohexanol initially potentiated muscle contractions but then rapidly blocked them. Cyclohexanol alone caused fade and block of muscle contractions in pigs and in isolated preparations. Similar effects were observed ex vivo with cyclohexanone and xylene. Cyclohexanol-induced neuromuscular block was temperature-sensitive and rapidly reversible.

CONCLUSIONS

The data indicate a crucial role for organophosphorus and solvent metabolites in muscle weakness following ingestion of agricultural OP insecticide formulations. The metabolites omethoate and cyclohexanol acted conjointly to impair neuromuscular function but their effects were mitigated by elevating extracellular Mg²⁺ and decreasing core temperature, respectively. Clinical studies of MgSO₄ therapy and targeted temperature management in insecticide-poisoned patients are required to determine whether they may be effective adjuncts to treatment.

Targeted temperature management at 33°C or 36℃ induces equivalent myocardial protection by inhibiting HMGB1 release in myocardial ischemia/reperfusion injury

Acute myocardial infarction (AMI) is lethal and causes myocardial necrosis via time-dependent ischemia due to prolonged occlusion of the infarct-related artery. No effective therapy or potential therapeutic targets can prevent myocardial ischemia/reperfusion (I/R) injury. Targeted temperature management (TTM) may reduce peri-infarct regions by inhibiting the extracellular release of high mobility group box-1 (HMGB1) as a primary mediator of the innate immune response. We used a rat left anterior descending (LAD) coronary artery ligation model to determine if TTM at 33°C and 36°C had similar myocardial protective effects. Rats were divided into sham, LAD I/R+37°C normothermia, LAD I/R+33°C TTM, and LAD I/R+36°C TTM groups (n = 5 per group). To verify the cardioprotective effect of TTM by specifically inhibiting HMGB1, rats were assigned to sham, LAD I/R, and LAD I/R after pre-treatment with glycyrrhizin (known as a pharmacological inhibitor of HMGB1) groups (n = 5 per group). Different target temperatures of 33°C and 36°C caused equivalent reductions in infarct volume after myocardial I/R, inhibited the extracellular release of HMGB1 from infarct tissue, and suppressed the expression of inflammatory cytokines from peri-infarct regions. TTM at 33°C and 36°C significantly attenuated the elevation of cardiac troponin, a sensitive and specific marker of heart muscle damage, after injury. Similarly, glycyrrhizin alleviated myocardial damage by suppressing the extracellular release of HMGB1. TTM at 33°C and 36°C had equivalent myocardial protective effects by similar inhibiting HMGB1 release against myocardial I/R injury. This is the first study to suggest that a target core temperature of 36°C is applicable for cardioprotection.

Neurocritical Management of Traumatic Acute Subdural Hematomas

Acute subdural hematoma (ASDH) has been a major part of traumatic brain injury. Intracranial hypertension may be followed by ASDH and brain edema. Regardless of the complicated pathophysiology of ASDH, the extent of primary brain injury underlying the ASDH is the most important factor affecting outcome. Ongoing intracranial pressure (ICP) increasing lead to cerebral perfusion pressure (CPP) decrease and cerebral blood flow (CBF) decreasing occurred by CPP decrease. In additionally, disruption of cerebral autoregulation, vasospasm, decreasing of metabolic demand may lead to CBF decreasing. Various protocols for ICP lowering were introduced in neuro-trauma field. Usage of anti-epileptic drugs (AEDs) for ASDH patients have controversy. AEDs may reduce the risk of early seizure (<7 days), but, does not for late-onset epilepsy. Usage of anticoagulants/antiplatelets is increasing due to life-long medical disease conditions in aging populations. It makes a difficulty to decide the proper management. Tranexamic acid may use to reducing bleeding and reduce ASDH related death rate. Decompressive craniectomy for ASDH can reduce patient's death rate. However, it may be accompanied with surgical risks due to big operation and additional cranioplasty afterwards. If the craniotomy is a sufficient management for the ASDH, endoscopic surgery will be good alternative to a conventional larger craniotomy to evacuate the hematoma. The management plan for the ASDH should be individualized based on age, neurologic status, radiologic findings, and the patient's conditions.

Effect of sub-hypothermia blood purification technique in cardiac shock after valvular disease surgery

To observe the effect of sub-hypothermia (HT) blood purification technique in the treatment of cardiac shock after heart valve disease.The patients were randomly divided into normothermic (NT) continuous blood purification (CBP) group (NT group) and HT CBP group (HT group). Observe the cardiac index (CI), the oxygen delivery (DO2) and oxygen consumption (VO2) ratio, Acute Physiology and Chronic Health Evaluation III(APACHE III) score, multiple organ dysfunction syndrome (MODS) score, dynamic monitoring of electrocardiograph, blood loss with or without muscle tremors, intensive care unit stay, mechanical ventilation time, CBP time, and the cases of infection and mortality at 0 day, 1 day, 2 day, 3 day; all above indicators were compared between 2 groups.Ninety-five patients were randomly assigned into HT group (48 cases) and NT group (47 cases); there were no significant differences between the 2 groups for age, gender, pre-operative cardiac function, cardiothoracic ratio, and type of valve replacement (P > .05). There were no significant differences among the 1 day, 2 day, 3 day after recruited for CI, DO2/VO2 ratio, APACHE III score, MODS score (P > .05). But in HT group, DO2/VO2 ratio had been significantly improved after treatment for 1 day (2.5 ± 0.7 vs 1.8 ± 0.4, P = .024), and CI (3.0 ± 0.5 vs 1.9 ± 0.7, P = .004), APACHE III score (50.6 ± 6.2 vs 77.5 ± 5.5 P = .022), MODS score (6.0 ± 1.5 vs 9.3 ± 3.4, P = .013) also had been significantly improved after treatment for 3 days. In clinical outcomes, there were no significant differences between 2 groups for blood loss (617.0 ± 60.7 ml vs 550.9 ± 85.2 ml, P = .203), infection ratio (54.17% vs 53.19%, P = .341), the incidence of ventricular arrhythmia (31.25% vs 36.17%, P = .237), and muscle tremors (14.58% vs 8.51%, P = .346), while there were significant differences between 2 groups for intensive care unit stay (6.9 ± 3.4 days vs 12.5 ± 3.5 days, P = .017,), mechanical ventilation time (4.2 ± 1.3 days vs 7.5 ± 2.7 days, P = .034,), CBP time (4.6 ± 1.4 days vs 10.5 ± 4.0 days, P = .019), mortality (12.50% vs 23.40%, P = .024). But the incidence of bradycardia in HT group was much higher than the NT group (29.16% vs 14.89%, P = .029).HT blood purification is a safer and more effective treatment than NT blood purification for patients who suffered from cardiac shock after valve surgery.

Recent Advances in Pharmacological and Non-Pharmacological Strategies of Cardioprotection

Ischemic heart diseases (IHD) are the leading cause of death worldwide. Although the principal form of treatment of IHD is myocardial reperfusion, the recovery of coronary blood flow after ischemia can cause severe and fatal cardiac dysfunctions, mainly due to the abrupt entry of oxygen and ionic deregulation in cardiac cells. The ability of these cells to protect themselves against injury including ischemia and reperfusion (I/R), has been termed “cardioprotection”. This protective response can be stimulated by pharmacological agents (adenosine, catecholamines and others) and non-pharmacological procedures (conditioning, hypoxia and others). Several intracellular signaling pathways mediated by chemical messengers (enzymes, protein kinases, transcription factors and others) and cytoplasmic organelles (mitochondria, sarcoplasmic reticulum, nucleus and sarcolemma) are involved in cardioprotective responses. Therefore, advancement in understanding the cellular and molecular mechanisms involved in the cardioprotective response can lead to the development of new pharmacological and non-pharmacological strategies for cardioprotection, thus contributing to increasing the efficacy of IHD treatment. In this work, we analyze the recent advances in pharmacological and non-pharmacological strategies of cardioprotection.

Antioxidant defense and protection against cardiac arrhythmias: lessons from a mammalian hibernator (the woodchuck)

Hibernating animals show resistance to hypothermia-induced cardiac arrhythmias. However, it is not clear whether and how mammalian hibernators are resistant to ischemia-induced arrhythmias. The goal of this investigation was to determine the susceptibility of woodchucks ( Marmota monax) to arrhythmias and their mechanisms after coronary artery occlusion at the same room temperature in both winter, the time for hibernation, and summer, when they do not hibernate. By monitoring telemetric electrocardiograms, we found significantly higher arrhythmia scores, calculated as the severity of arrhythmias, with incidence of ventricular tachycardia, ventricular fibrillation, and thus sudden cardiac death (SCD) in woodchucks in summer than they had in winter. The level of catalase expression in woodchuck hearts was significantly higher, whereas the level of oxidized Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) was lower in winter than it was in summer. Ventricular myocytes isolated from woodchucks in winter were more resistant to H₂O₂-induced early afterdepolarizations (EADs) compared with myocytes isolated from woodchucks in summer. The EADs were eliminated by inhibiting CaMKII (with KN-93), l-type Ca current (with nifedipine), or late Na⁺ current (with ranolazine). In woodchucks, in the summer, the arrhythmia score was significantly reduced by overexpression of catalase ( via adenoviral vectors) or the inhibition of CaMKII (with KN-93) in the heart. This study suggests that the heart of the mammalian hibernator is more resistant to ischemia-induced arrhythmias and SCD in winter. Increased antioxidative capacity and reduced CaMKII activity may confer resistance in woodchuck hearts against EADs and arrhythmias during winter. The profound protection conferred by catalase overexpression or CaMKII inhibition in this novel natural animal model may provide insights into clinical directions for therapy of arrhythmias.-Zhao, Z., Kudej, R. K., Wen, H., Fefelova, N., Yan, L., Vatner, D. E., Vatner, S. F., Xie, L.-H. Antioxidant defense and protection against cardiac arrhythmias: lessons from a mammalian hibernator (the woodchuck).

Selective brain hypothermia

Selective brain hypothermia is a powerful concept for neuroprotection that has been successfully investigated in a variety of animal models of global and focal ischemia. Its major advantages over systemic hypothermia include rapid induction of cooling, ability to achieve profound target brain temperatures, organ-selective cooling, and temperature control. Clinical systems and devices are available or are currently under development that utilize conductive (surface-cooling pads, closed-loop catheters), convective (transnasal coolant delivery), or mass and energy transport (cold intra-arterial infusion) methods to achieve and maintain selective brain hypothermia. The "ideal" brain-cooling system that is characterized by rapid cooling to profound hypothermia, its ability to maintain selective cooling over several days, and is noninvasive in nature, remains unrealistic. Instead, systems may be identified by their distinct advantages to meet a specific need in the care of a patient. This involves the consideration of the timing of ischemic injury (preischemic, intraischemic, postischemic), extent of ischemic damage (excitotoxicity, inflammation, necrosis, edema), and type and setting of therapeutic intervention (intensive care, interventional therapy, surgery). The successful translation of these systems into clinical practice will depend on smart engineering, safety and efficacy, and usability in current clinical work flow.

Feasibility Study of a Novel High-Flow Cold Air Cooling Protocol of the Porcine Brain Using MRI Temperature Mapping

Early, prehospital cooling seeks to reduce and control the body temperature as early as possible to protect the brain and improve patient outcome in cardiac arrest, stroke, and traumatic brain injury. In this study, we investigate the feasibility of localized cooling of the porcine brain by using a novel high-flow cold air protocol, which utilizes the close proximity between the nasal cavity and the brain. Five adult pigs were anesthetized and temperature change was mapped before, during, and after cooling by using the proton resonance frequency method on a 3 T Siemens Magnetom Skyra system. Cooling was performed by inserting a tube blowing high-flow (250 L/min) cold air (-10°C) through the nasal cavity for 5-20 minutes. The brain temperature change was measured by using an MRI phase mapping technique utilizing the temperature-dependent proton resonance frequency change. MRI maps showed significant temperature reduction of the porcine brain. On average, a mean whole-brain cooling effect of -0.33°C ± 0.30°C was found after 5 minutes of cooling. The anterior part of the brain was directly exposed to the cold and showed a significantly larger temperature drop (-0.83°C ± 0.51°C) than the posterior part (-0.03°C ± 0.21°C). However, a large variability of the temperature drop was observed between the animals. This variability may be caused by not well-controlled factors confounding the MRI temperature mapping, for example, subject movement, or cooling effectiveness, for example, core temperature or nasal patency. The results indicate that the proposed high-flow cold air protocol allows for localized cooling of the frontal porcine brain, which may be clinically relevant for traumatic injuries of the frontal brain where systemic cooling is unfavorable.

Editor's Choice- Inside the cold heart: A review of therapeutic hypothermia cardioprotection

Targeted temperature management has been originally used to reduce neurological injury and improve outcome in patients after out-of-hospital cardiac arrest. Myocardial infarction remains a major cause of death in the world and several investigators are studying the effect of mild therapeutic hypothermia during an acute cardiac ischemic injury. A search on MEDLINE, Scopus and EMBASE databases was conducted to obtain data regarding the cardioprotective properties of therapeutic hypothermia. Preclinical studies have shown that therapeutic hypothermia provides a cardioprotective effect in animals. The proposed pathways for the cardioprotective effects of therapeutic hypothermia include stabilization of mitochondrial permeability, production of nitric oxide, equilibration of reactive oxygen species, and calcium channels homeostasis. Clinical trials in humans have yielded controversial results. Current trials are therefore seeking to combine therapeutic hypothermia with other treatment modalities in order to improve the outcomes of patients with acute ischemic injury. This article provides a review of the hypothermia effects on the cardiovascular system, from the basic science of physiological changes in the human body and molecular mechanisms of cardioprotection to the bench of clinical trials with therapeutic hypothermia in patients with acute ischemic injury.

Pramipexole-Induced Hypothermia Reduces Early Brain Injury via PI3K/AKT/GSK3β pathway in Subarachnoid Hemorrhage rats

Previous studies have shown neuroprotective effects of hypothermia. However, its effects on subarachnoid hemorrhage (SAH)-induced early brain injury (EBI) remain unclear. In this study, a SAH rat model was employed to study the effects and mechanisms of pramipexole-induced hypothermia on EBI after SAH. Dose-response experiments were performed to select the appropriate pramipexole concentration and frequency of administration for induction of mild hypothermia (33–36 °C). Western blot, neurobehavioral evaluation, Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and Fluoro-Jade B (FJB) staining were used to detect the effects of pramipexole-induced hypothermia on SAH-induced EBI, as well as to study whether controlled rewarming could attenuate these effects. Inhibitors targeting the PI3K/AKT/GSK3β pathway were administered to determine whether the neuroprotective effect of pramipexole-induced hypothermia was mediated by PI3K/AKT/GSK3β signaling pathway. The results showed that intraperitoneal injection of pramipexole at 0.25 mg/kg body weight once per 8 hours was found to successfully and safely maintain rats at mild hypothermia. Pramipexole-induced hypothermia ameliorated SAH-induced brain cell death, blood-brain barrier damage and neurobehavioral deficits in a PI3K/AKT/GSK3β signaling-dependent manner. Therefore, we may conclude that pramipexole-induced hypothermia could effectively inhibit EBI after SAH in rats via PI3K/AKT/GSK3β signaling pathway.

Therapeutic Hypothermia for Cardioprotection in Acute Myocardial Infarction

Mild therapeutic hypothermia of 32-35°C improved neurologic outcomes in outside hospital cardiac arrest survivor. Furthermore, in experimental studies on infarcted model and pilot studies on conscious patients with acute myocardial infarction, therapeutic hypothermia successfully reduced infarct size and microvascular resistance. Therefore, mild therapeutic hypothermia has received an attention as a promising solution for reduction of infarction size after acute myocardial infarction which are not completely solved despite of optimal reperfusion therapy. Nevertheless, the results from randomized clinical trials failed to prove the cardioprotective effects of therapeutic hypothermia or showed beneficial effects only in limited subgroups. In this article, we reviewed rationale for therapeutic hypothermia and possible mechanisms from previous studies, effective methods for clinical application to the patients with acute myocardial infarction, lessons from current clinical trials and future directions.

Hypothermia in the setting of experimental acute myocardial infarction: a comprehensive review

A door-to-balloon time of less than 90 minutes is the gold standard for reperfusion therapy to treat acute myocardial infarction (MI). Because 30-day mortality remains ∼ 10%, new methods must be cultivated to limit myocardial injury. Therapeutic hypothermia has long been experimentally used to attenuate myocardial necrosis during MI with promising results, but the treatment has yet to gain popularity among most clinicians. Hypothermia, in the basic science setting, has been achieved using many techniques. In our review, we examine past and current methods of inducing hypothermia, benefits and setbacks of such methods, current and future clinical trials, and potential mechanisms.

Temperature modulation with an esophageal heat transfer device - a pediatric swine model study

Background

An increasing number of conditions appear to benefit from control and modulation of temperature, but available techniques to control temperature often have limitations, particularly in smaller patients with high surface to mass ratios. We aimed to evaluate a new method of temperature modulation with an esophageal heat transfer device in a pediatric swine model, hypothesizing that clinically significant modulation in temperature (both increases and decreases of more than 1°C) would be possible.

Methods

Three female Yorkshire swine averaging 23 kg were anesthetized with inhalational isoflurane prior to placement of the esophageal device, which was powered by a commercially available heat exchanger. Swine temperature was measured rectally and cooling and warming were performed by selecting the appropriate external heat exchanger mode. Temperature was recorded over time in order to calculate rates of temperature change. Histopathology of esophageal tissue was performed after study completion.

Results

Average swine baseline temperature was 38.3°C. Swine #1 exhibited a cooling rate of 3.5°C/hr; however, passive cooling may have contributed to this rate. External warming blankets maintained thermal equilibrium in swine #2 and #3, demonstrating maximum temperature decrease of 1.7°C/hr. Warming rates averaged 0.29°C/hr. Histopathologic analysis of esophageal tissue showed no adverse effects.

Conclusions

An esophageal heat transfer device successfully modulated the temperature in a pediatric swine model. This approach to temperature modulation may offer a useful new modality to control temperature in conditions warranting temperature management (such as maintenance of normothermia, induction of hypothermia, fever control, or malignant hyperthermia).

Myocardial ischemic protection in natural mammalian hibernation

Hibernating myocardium is an important clinical syndrome protecting the heart with chronic myocardial ischemia, named for its assumed resemblance to hibernating mammals in winter. However, the effects of myocardial ischemic protection have never been studied in true mammalian hibernation, which is a unique strategy for surviving extreme winter environmental stress. The goal of this investigation was to test the hypothesis that ischemic stress may also be protected in woodchucks as they hibernate in winter. Myocardial infarction was induced by coronary occlusion followed by reperfusion in naturally hibernating woodchucks in winter with and without hibernation and in summer, when not hibernating. The ischemic area at risk was similar among groups. Myocardial infarction was significantly less in woodchucks in winter, whether hibernating or not, compared with summer, and was similar to that resulting after ischemic preconditioning. Whereas several genes were up or downregulated in both hibernating woodchuck and with ischemic preconditioning, one mechanism was unique to hibernation, i.e., activation of cAMP-response element binding protein (CREB). When CREB was upregulated in summer, it induced protection similar to that observed in the woodchuck heart in winter. The cardioprotection in hibernation was also mediated by endothelial nitric oxide synthase, rather than inducible nitric oxide synthase. Thus, the hibernating woodchuck heart is a novel model to study cardioprotection for two major reasons: (1) powerful cardioprotection occurs naturally in winter months in the absence of any preconditioning stimuli, and (2) it resembles ischemic preconditioning, but with novel mechanisms, making this model potentially useful for clinical translation.

ST elevation myocardial infarction: recent advances and updates

ST elevation myocardial infarction (STEMI) remains a leading cause of morbidity, mortality and disability worldwide. Statistically, a trend towards improvements in morbidity and mortality has been consistent over the years, which is attributed primarily to the modification of risk factors, healthier lifestyles, treatment advances and better management of door-to-balloon times via STEMI systems. However, a major challenge in the coming years will be the baby boomers (born between the years 1946 and 1964) coming into old age. The first baby boomers turned 65 in year 2011. As the baby boomers age in the coming years, the incidence of coronary heart disease is likely to increase, and so there will be a greater need to have major advances in the management of coronary heart disease in order to deal with this additional incidence. The scope of this article is to review recent advances in the management of STEMI and to provide an updated overview.

Hypothermia after cardiac arrest as a novel approach to increase survival in cardiopulmonary cerebral resuscitation: a review

Context:

The aim of this review study was to evaluate therapeutic mild hypothermia, its complications and various methods for induced mild hypothermia in patients following resuscitation after out-of-hospital cardiac arrest.

Evidence Acquisition:

Studies conducted on post-cardiac arrest cares, history of induced hypothermia, and therapeutic hypothermia for patients with cardiac arrest were included in this study. We used the valid databases (PubMed and Cochrane library) to collect relevant articles.

Results:

According to the studies reviewed, induction of mild hypothermia in patients after cardiopulmonary resuscitation would lead to increased survival and better neurological outcome; however, studies on the complications of hypothermia or different methods of inducing hypothermia were limited and needed to be studied further.

Conclusions:

This study provides strategic issues concerning the induction of mild hypothermia, its complications, and different ways of performing it on patients; using this method helps to increase patients’ neurological survival rate.

Rapid Induction of Hypothermia by the ThermoSuit System Profoundly Reduces Infarct Size and Anatomic Zone of No Reflow Following Ischemia-Reperfusion in Rabbit and Rat Hearts

INTRODUCTION

Although hypothermia reduces myocardial infarct size, noninvasive and rapid cooling methods are lacking. This study tests the effectiveness of a novel cooling apparatus on myocardial infarct size and no-reflow area in 2 models of coronary artery occlusion (CAO).

METHODS AND RESULTS

Animals were randomized to normothermic (N) or hypothermic (H) groups after isolation of a proximal coronary artery. Animals were subjected to 30 minutes CAO and 3 hours reperfusion. In protocol 1 (rabbit, n = 8 per group), hypothermia was initiated, using the ThermoSuit apparatus (convective-immersion cooling), 5 minutes after the onset of CAO to a goal temperature of ∼32°C. In protocol 2 (rat, n = 5 per group), hypothermia was initiated 2 minutes after the onset of CAO to a goal temperature of ∼30°C. Goal temperature was reached in ∼20 minutes. In protocol 1, hypothermia caused an 82% reduction in infarct size as a percentage of the ischemic risk zone (N, 44% ± 5%; H; 8% ± 2%, P < 0.001) and an 89% reduction in the no-reflow area (N, 44% ± 4%; H, 5% ± 1%, P < 0.001). In protocol 2, hypothermia caused a 73% infarct size reduction (N, 51% ± 5%; H, 14% ± 6%, P < 0.01) and a 99% reduction in the no-reflow area (N, 33% ± 5%; H, 0.4% ± 0.3%, P < 0.01).

CONCLUSION

The ThermoSuit device induced rapid hypothermia and limited infarct size and no reflow to the greatest extent ever observed in this laboratory with a single intervention.

Early MEK1/2 inhibition after global cerebral ischemia in rats reduces brain damage and improves outcome by preventing delayed vasoconstrictor receptor upregulation

Background

Global cerebral ischemia following cardiac arrest is associated with increased cerebral vasoconstriction and decreased cerebral blood flow, contributing to delayed neuronal cell death and neurological detriments in affected patients. We hypothesize that upregulation of contractile ET_B and 5-HT_1B receptors, previously demonstrated in cerebral arteries after experimental global ischemia, are a key mechanism behind insufficient perfusion of the post-ischemic brain, proposing blockade of this receptor upregulation as a novel target for prevention of cerebral hypoperfusion and delayed neuronal cell death after global cerebral ischemia. The aim was to characterize the time-course of receptor upregulation and associated neuronal damage after global ischemia and investigate whether treatment with the MEK1/2 inhibitor U0126 can prevent cerebrovascular receptor upregulation and thereby improve functional outcome after global cerebral ischemia. Incomplete global cerebral ischemia was induced in Wistar rats and the time-course of enhanced contractile responses and the effect of U0126 in cerebral arteries were studied by wire myography and the neuronal cell death by TUNEL. The expression of ET_B and 5-HT_1B receptors was determined by immunofluorescence.

Results

Enhanced vasoconstriction peaked in fore- and midbrain arteries 3 days after ischemia. Neuronal cell death appeared initially in the hippocampus 3 days after ischemia and gradually increased until 7 days post-ischemia. Treatment with U0126 normalised cerebrovascular ET_B and 5-HT_1B receptor expression and contractile function, reduced hippocampal cell death and improved survival rate compared to vehicle treated animals.

Conclusions

Excessive cerebrovascular expression of contractile ET_B and 5-HT_1B receptors is a delayed response to global cerebral ischemia peaking 3 days after the insult, which likely contributes to the development of delayed neuronal damage. The enhanced cerebrovascular contractility can be prevented by treatment with the MEK1/2 inhibitor U0126, diminishes neuronal damage and improves survival rate, suggesting MEK1/2 inhibition as a novel strategy for early treatment of neurological consequences following global cerebral ischemia.

Autonomic regulation of brown adipose tissue thermogenesis in health and disease: potential clinical applications for altering BAT thermogenesis

From mouse to man, brown adipose tissue (BAT) is a significant source of thermogenesis contributing to the maintenance of the body temperature homeostasis during the challenge of low environmental temperature. In rodents, BAT thermogenesis also contributes to the febrile increase in core temperature during the immune response. BAT sympathetic nerve activity controlling BAT thermogenesis is regulated by CNS neural networks which respond reflexively to thermal afferent signals from cutaneous and body core thermoreceptors, as well as to alterations in the discharge of central neurons with intrinsic thermosensitivity. Superimposed on the core thermoregulatory circuit for the activation of BAT thermogenesis, is the permissive, modulatory influence of central neural networks controlling metabolic aspects of energy homeostasis. The recent confirmation of the presence of BAT in human and its function as an energy consuming organ have stimulated interest in the potential for the pharmacological activation of BAT to reduce adiposity in the obese. In contrast, the inhibition of BAT thermogenesis could facilitate the induction of therapeutic hypothermia for fever reduction or to improve outcomes in stroke or cardiac ischemia by reducing infarct size through a lowering of metabolic oxygen demand. This review summarizes the central circuits for the autonomic control of BAT thermogenesis and highlights the potential clinical relevance of the pharmacological inhibition or activation of BAT thermogenesis.

Cellular mechanism underlying hypothermia-induced ventricular tachycardia/ventricular fibrillation in the setting of early repolarization and the protective effect of quinidine, cilostazol, and milrinone

BACKGROUND

Hypothermia has been reported to induce ventricular tachycardia and fibrillation (VT/VF) in patients with early repolarization (ER) pattern. This study examines the cellular mechanisms underlying VT/VF associated with hypothermia in an experimental model of ER syndrome and examines the effectiveness of quinidine, cilostazol, and milrinone to prevent hypothermia-induced arrhythmias.

METHODS AND RESULTS

Transmembrane action potentials were simultaneously recorded from 2 epicardial and 1 endocardial site of coronary-perfused canine left ventricular wedge preparations, together with a pseudo-ECG. A combination of NS5806 (3-10 μmol/L) and verapamil (1 μmol/L) was used to pharmacologically model the genetic mutations responsible for ER syndrome. Acetylcholine (3 μmol/L) was used to simulate increased parasympathetic tone, which is known to promote ER. In controls, lowering the temperature of the coronary perfusate to induce mild hypothermia (32°C-34°C) resulted in increased J-wave area on the ECG and accentuated epicardial action potential notch but no arrhythmic activity. In the setting of ER, hypothermia caused further accentuation of the epicardial action potential notch, leading to loss of the action potential dome at some sites but not others, thus creating the substrate for development of phase 2 reentry and VT/VF. Addition of the transient outward current antagonist quinidine (5 μmol/L) or the phosphodiesterase III inhibitors cilostazol (10 μmol/L) or milrinone (5 μmol/L) diminished the ER manifestations and prevented the hypothermia-induced phase 2 reentry and VT/VF.

CONCLUSIONS

Hypothermia leads to VT/VF in the setting of ER by exaggerating repolarization abnormalities, leading to development of phase 2 reentry. Quinidine, cilostazol, and milrinone suppress the hypothermia-induced VT/VF by reversing the repolarization abnormalities.

Extracorporeal membrane oxygenation for resuscitation and cardiac arrest management

This article reviews the potential application of extracorporeal membrane oxygenation (ECMO) technology to cardiopulmonary resuscitation for in and out-of-hospital cardiac arrest and discusses the current evidence on the subject. The possible strategies for organ protection during ECMO and the concept of ECMO networks are also reviewed.

Review article: the anesthesiologist's role in the prevention of surgical site infections

PURPOSE

To highlight the role of anesthesiologists in the prophylaxis of surgical site infections (SSIs) and to recognize the central role they play in quality improvement initiatives for the prevention of SSIs.

SOURCE

The medical literature was searched with a focus on three interventions affecting the risk of SSIs: preoperative antibiotic administration, perioperative normothermia, and perioperative hyperoxia. The literature was also searched for examples of initiatives in patient safety and quality improvement that highlight the role of anesthesiologists in preventing SSIs.

PRINCIPAL FINDINGS

The timely administration of preoperative antibiotics and the maintenance of perioperative normothermia have been shown to reduce the risk of SSI significantly. Perioperative hyperoxia in the prevention of SSIs remains controversial but may improve outcomes in specific subsets of the surgical population. Initiatives in quality improvement show the challenges faced by many centres to improve upon these processes of care, but they also highlight the role of anesthesiologists as champions in the multidisciplinary efforts for the prevention of SSIs.

CONCLUSIONS

Anesthesiologists are responsible for many of the processes of care shown to impact the risk for SSIs, and they play an important role in the prevention of SSIs. Their leadership in the multidisciplinary efforts to improve the quality of the surgical patient is of critical importance.