Therapeutic hypothermia following resuscitation

Survival and Neurologic Outcomes From Pharmacologic Peptide Administration During Cardiopulmonary Resuscitation of Pulseless Electrical Activity

BACKGROUND

Outcomes from cardiopulmonary resuscitation (CPR) following sudden cardiac arrest are suboptimal. Postresuscitation targeted temperature management has been shown to have benefit in subjects with sudden cardiac arrest due to ventricular fibrillation, but there are few data for outcomes from sudden cardiac arrest due to pulseless electrical activity. In addition, intra-CPR cooling is more effective than postresuscitation cooling. Physical cooling is associated with increased protein kinase B activity. Therefore, our group developed a novel peptide, TAT-PHLPP9c, which regulates protein kinase B. We hypothesized that when given during CPR, TAT-PHLPP9c would improve survival and neurologic outcomes following pulseless electrical activity arrest.

METHODS AND RESULTS

In 24 female pigs, pulseless electrical activity was induced by inflating balloon catheters in the right coronary and left anterior descending arteries for ≈7 minutes. Advanced life support was initiated. In 12 control animals, epinephrine was given after 1 and 3 minutes. In 12 peptide-treated animals, 7.5 mg/kg TAT-PHLPP9c was also administered at 1 and 3 minutes of CPR. The balloons were removed after 2 minutes of support. Animals were recovered and neurologically scored 24 hours after return of spontaneous circulation. Return of spontaneous circulation was more common in the peptide group, but this difference was not significant (8/12 control versus 12/12 peptide; P=0.093), while fully intact neurologic survival was significantly more common in the peptide group (0/12 control versus 11/12 peptide; P<0.00001). TAT-PHLPP9c significantly increased myocardial nicotinamide adenine dinucleotide levels.

CONCLUSIONS

TAT-PHLPP9c resulted in improved survival with full neurologic function after sudden cardiac arrest in a swine model of pulseless electrical activity, and the peptide shows potential as an intra-CPR pharmacologic agent.

CPR and ECMO: The Next Frontier

Cardiopulmonary resuscitation (CPR) is a first-line therapy for sudden cardiac arrest, while extracorporeal membrane oxygenation (ECMO) has traditionally been used as a means of countering circulatory failure. However, new advances dictate that CPR and ECMO could be complementary for support after cardiac arrest. This review details the emerging science, technology, and clinical application that are enabling the new paradigm of these iconic circulatory support modalities in the setting of cardiac arrest.

Left Ventricle Function During Therapeutic Hypothermia with Beta1-Adrenergic Receptor Blockade

Therapeutic hypothermia is an established treatment in patients resuscitated from cardiac arrest. It is usually well-tolerated circulatory, but hypothermia negatively effects myocardial contraction and relaxation velocities and increases diastolic filling restrictions. A significant proportion of resuscitated patients are treated with long-acting beta-receptor blocking agents' prearrest, but the combined effects of hypothermia and beta-blockade on left ventricle (LV) function are not previously investigated. We hypothesized that beta₁-adrenergic receptor blockade (esmolol infusion) exacerbates the negative effects of hypothermia on active myocardial motions, affecting both systolic and diastolic LV function. A pig (n = 10) study was performed to evaluate the myocardial effects of esmolol during hypothermia (33°C) and during normothermia, at spontaneous and pacing-increased heart rates (HRs). LV function was assessed by a LV pressure transducer, an epicardial ultrasonic transducer (wall thickness, wall thickening/thinning velocity) and an aortic ultrasonic flow-probe (stroke volume, cardiac output). The data were compared using a paired two-tailed Students t-test, and also analyzed using a linear mixed model to handle dependencies introduced by repeated measurements within each subject. The significance level was p ≤ 0.05. The effects of hypothermia and beta blockade were distinct and additive. Hypothermia reduced myocardial motion velocities and increased diastolic filling restrictions, but end-systolic wall thickness increased, and stroke volume and dP/dt_max (pumping function) were maintained. In contrast, esmolol predominantly affected systolic pumping function, by a negative inotropic effect. In combination, hypothermia and esmolol reduced myocardial velocities in systole and diastole by ∼40%, compared with normothermia without esmolol, inducing in combination both systolic and diastolic LV function impairment. The cardiac dysfunction deteriorated at increased HRs during hypothermia. Beta₁-adrenergic receptor blockade (esmolol) exacerbates the negative effects of hypothermia on active myocardial contraction and relaxation. The combination of hypothermia with beta-blockade induces both systolic and diastolic LV function impairment.

Intranasal post-cardiac arrest treatment with orexin-A facilitates arousal from coma and ameliorates neuroinflammation

Cardiac arrest (CA) entails significant risks of coma resulting in poor neurological and behavioral outcomes after resuscitation. Significant subsequent morbidity and mortality in post-CA patients are largely due to the cerebral and cardiac dysfunction that accompanies prolonged whole-body ischemia post-CA syndrome (PCAS). PCAS results in strong inflammatory responses including neuroinflammation response leading to poor outcome. Currently, there are no proven neuroprotective therapies to improve post-CA outcomes apart from therapeutic hypothermia. Furthermore, there are no acceptable approaches to promote cortical or cognitive arousal following successful return of spontaneous circulation (ROSC). Hypothalamic orexinergic pathway is responsible for arousal and it is negatively affected by neuroinflammation. However, whether activation of the orexinergic pathway can curtail neuroinflammation is unknown. We hypothesize that targeting the orexinergic pathway via intranasal orexin-A (ORXA) treatment will enhance arousal from coma and decrease the production of proinflammatory cytokines resulting in improved functional outcome after resuscitation. We used a highly validated CA rat model to determine the effects of intranasal ORXA treatment 30-minute post resuscitation. At 4hrs post-CA, the mRNA levels of proinflammatory markers (IL1β, iNOS, TNF-α, GFAP, CD11b) and orexin receptors (ORX1R and ORX2R) were examined in different brain regions. CA dramatically increased proinflammatory markers in all brain regions particularly in the prefrontal cortex, hippocampus and hypothalamus. Post-CA intranasal ORXA treatment significantly ameliorated the CA-induced neuroinflammatory markers in the hypothalamus. ORXA administration increased production of orexin receptors (ORX1R and ORX2R) particularly in hypothalamus. In addition, ORXA also resulted in early arousal as measured by quantitative electroencephalogram (EEG) markers, and recovery of the associated behavioral neurologic deficit scale score (NDS). Our results indicate that intranasal delivery of ORXA post-CA has an anti-inflammatory effect and accelerates cortical EEG and behavioral recovery. Beneficial outcomes from intranasal ORXA treatment lay the groundwork for therapeutic clinical approach to treating post-CA coma.

A Combination of Three Repurposed Drugs Administered at Reperfusion as a Promising Therapy for Postischemic Brain Injury

Cerebral ischemia leads to multifaceted injury to the brain. A polytherapeutic drug that can be administered immediately after reperfusion may increase protection to the brain by simultaneously targeting multiple deleterious cascades. This study evaluated efficacy of the combination of three clinically approved drugs: lamotrigine, minocycline, and lovastatin, using two mouse models: global and focal cerebral ischemia induced by transient occlusion of the common carotid arteries or the middle cerebral artery, respectively. In vitro, the combination drug, but not single drug, protected neurons against oxygen-glucose deprivation (OGD)-induced cell death. The combination drug simultaneously targeted cell apoptosis and DNA damage induced by ischemia. Besides acting on neurons, the combination drug suppressed inflammatory processes in microglia and brain endothelial cells induced by ischemia. In a transient global ischemia model, the combination drug, but not single drug, suppressed microglial activation and inflammatory cytokine production, and reduced neuronal damage. In a transient focal ischemia model, the combination drug, but not single drug, attenuated brain infarction, suppressed infiltration of peripheral neutrophils, and reduced neurological deficits following ischemic stroke. In summary, the combination drug confers a broad-spectrum protection against ischemia/reperfusion (I/R) injury and could be a promising approach for early neuroprotection after out-of-hospital cardiac arrest or ischemic stroke.

Does therapeutic hypothermia during extracorporeal cardiopulmonary resuscitation preserve cardiac function?

Background

Extracorporeal cardiopulmonary resuscitation (E-CPR) is increasingly used as a rescue method in the management of cardiac arrest and provides the opportunity to rapidly induce therapeutic hypothermia. The survival after a cardiac arrest is related to post-arrest cardiac function, and the application of therapeutic hypothermia post-arrest is hypothesized to improve cardiac outcome. The present animal study compares normothermic and hypothermic E-CPR considering resuscitation success, post-arrest left ventricular function and magnitude of myocardial injury.

Methods

After a 15-min untreated ventricular fibrillation, the pigs (n = 20) were randomized to either normothermic (38 °C) or hypothermic (32–33 °C) E-CPR. Defibrillation terminated ventricular fibrillation after 5 min of E-CPR, and extracorporeal support continued for 2 h, followed by warming, weaning and a stabilization period. Magnetic resonance imaging and left ventricle pressure measurements were used to assess left ventricular function pre-arrest and 5 h post-arrest. Myocardial injury was estimated by serum concentrations of cardiac TroponinT and Aspartate transaminase (ASAT).

Results

E-CPR resuscitated all animals and the hypothermic strategy induced therapeutic hypothermia within minutes without impairment of the resuscitation success rate. All animals suffered a severe global systolic left ventricular dysfunction post-arrest with 50–70% reductions in stroke volume, ejection fraction, wall thickening, strain and mitral annular plane systolic excursion. Serum concentrations of cardiac TroponinT and ASAT increased considerably post-arrest. No significant differences were found between the two groups.

Conclusions

Two-hour therapeutic hypothermia during E-CPR offers an equal resuscitation success rate, but does not preserve the post-arrest cardiac function nor reduce the magnitude of myocardial injury, compared to normothermic E-CPR.

Trial registration FOTS 4611/13 registered 25 October 2012

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1099-y) contains supplementary material, which is available to authorized users.

A novel pharmacological strategy by PTEN inhibition for improving metabolic resuscitation and survival after mouse cardiac arrest

Sudden cardiac arrest (SCA) is a leading cause of death in the United States. Despite return of spontaneous circulation, patients die due to post-SCA syndrome that includes myocardial dysfunction, brain injury, impaired metabolism, and inflammation. No medications improve SCA survival. Our prior work suggests that optimal Akt activation is critical for cooling protection and SCA recovery. Here, we investigate a small inhibitor of PTEN, an Akt-related phosphatase present in heart and brain, as a potential therapy in improving cardiac and neurological recovery after SCA. Anesthetized adult female wild-type C57BL/6 mice were randomized to pretreatment of VO-OHpic (VO) 30 min before SCA or vehicle control. Mice underwent 8 min of KCl-induced asystolic arrest followed by CPR. Resuscitated animals were hemodynamically monitored for 2 h and observed for 72 h. Outcomes included heart pressure-volume loops, energetics (phosphocreatine and ATP from (31)P NMR), protein phosphorylation of Akt, GSK3β, pyruvate dehydrogenase (PDH) and phospholamban, circulating inflammatory cytokines, plasma lactate, and glucose as measures of systemic metabolic recovery. VO reduced deterioration of left ventricular maximum pressure, maximum rate of change in the left ventricular pressure, and Petco2 and improved 72 h neurological intact survival (50% vs. 10%; P < 0.05). It reduced plasma lactate, glucose, IL-1β, and Pre-B cell colony enhancing factor, while increasing IL-10. VO increased phosphorylation of Akt and GSK3β in both heart and brain, and cardiac phospholamban phosphorylation while reducing p-PDH. Moreover, VO improved cardiac bioenergetic recovery. We concluded that pharmacologic PTEN inhibition enhances Akt activation, improving metabolic, cardiovascular, and neurologic recovery with increased survival after SCA. PTEN inhibitors may be a novel pharmacologic strategy for treating SCA.

Optimal protective hypothermia in arrested mammalian hearts

Many therapeutic hypothermia recommendations have been reported, but the information supporting them is sparse, and reveals a need for the data of target therapeutic hypothermia (TTH) from well-controlled experiments. The core temperature ≤35°C is considered as hypothermia, and 29°C is a cooling injury threshold in pig heart in vivo. Thus, an optimal protective hypothermia (OPH) should be in the range 29-35°C. This study was conducted with a pig cardiopulmonary bypass preparation to decrease the core temperature to 29-35°C range at 20 minutes before and 60 minutes during heart arrest. The left ventricular (LV) developed pressure, maximum of the first derivative of LV (dP/dtmax), cardiac power, heart rate, cardiac output, and myocardial velocity (Vmax) were recorded continuously via an LV pressure catheter and an aortic flow probe. At 20 minutes of off-pump during reperfusion after 60 minutes arrest, 17 hypothermic hearts showed that the recovery of Vmax and dP/dtmax established sigmoid curves that consisted of two plateaus: a good recovery plateau at 29-30.5°C, the function recovered to baseline level (BL) (Vmax=118.4%±3.9% of BL, LV dP/dtmax=120.7%±3.1% of BL, n=6); another poor recovery plateau at 34-35°C (Vmax=60.2%±2.8% of BL, LV dP/dtmax=28.0%±5.9% of BL, p<0.05, n=6; ), which are similar to the four normothermia arrest (37°C) hearts (Vmax=55.9%±4.8% of BL, LV dP/dtmax=24.5%±2.1% of BL, n=4). The 32-32.5°C arrest hearts showed moderate recovery (n=5). A point of inflection (around 30.5-31°C) existed at the edge of a good recovery plateau followed by a steep slope. The point presented an OPH that should be the TTH. The results are concordant with data in the mammalian hearts, suggesting that the TTH should be initiated to cool core temperature at 31°C.

Cardiac condition during cooling and rewarming periods of therapeutic hypothermia after cardiopulmonary resuscitation

BACKGROUND

Hypothermia has been used in cardiac surgery for many years for neuroprotection. Mild hypothermia (MH) [body temperature (BT) kept at 32-35°C] has been shown to reduce both mortality and poor neurological outcome in patients after cardiopulmonary resuscitation (CPR). This study investigated whether patients who were expected to benefit neurologically from therapeutic hypothermia (TH) also had improved cardiac function.

METHODS

The study included 30 patients who developed in-hospital cardiac arrest between September 17, 2012, and September 20, 2013, and had return of spontaneous circulation (ROSC) following successful CPR. Patient BTs were cooled to 33°C using intravascular heat change. Basal BT, systolic artery pressure (SAP), diastolic artery pressure (DAP), mean arterial pressure (MAP), heart rate, central venous pressure, cardiac output (CO), cardiac index (CI), global end-diastolic volume index (GEDI), extravascular lung water index (ELWI), and systemic vascular resistance index (SVRI) were measured at 36°C, 35°C, 34°C and 33°C during cooling. BT was held at 33°C for 24 hours prior to rewarming. Rewarming was conducted 0.25°C/h. During rewarming, measurements were repeated at 33°C, 34°C, 35°C and 36°C. A final measurement was performed once patients spontaneously returned to basal BT. We compared cooling and rewarming cardiac measurements at the same BTs.

RESULTS

SAP values during rewarming (34°C, 35°C and 36°C) were lower than during cooling (P < 0.05). DAP values during rewarming (basal temperature, 34°C, 35°C and 36°C) were lower than during cooling. MAP values during rewarming (34°C, 35°C and 36°C) were lower than during cooling (P < 0.05). CO and CI values were higher during rewarming than during cooling. GEDI and ELWI did not differ during cooling and rewarming. SVRI values during rewarming (34°C, 35°C, 36°C and basal temperature) were lower than during cooling (P < 0.05).

CONCLUSIONS

To our knowledge, this is the first study comparing cardiac function at the same BTs during cooling and rewarming. In patients experiencing ROSC following CPR, TH may improve cardiac function and promote favorable neurological outcomes.

Managing the Complications of Mild Therapeutic Hypothermia in the Cardiac Arrest Patient

Mild therapeutic hypothermia (MTH) is used to lower the core body temperature of cardiac arrest (CA) patients to 32°C from 34°C to provide improved survival and neurologic outcomes after resuscitation from in-hospital or out-of-hospital CA. Despite the improved benefits of MTH, there are potentially unforeseen complications associated during management. Although the adverse effects are transient, the clinician should be aware of the associated complications when managing the patient receiving MTH. We aim to provide the medical community comprehensive information related to the potential complications of survivors of CA receiving MTH, as it is imperative for the clinician to understand the physiologic changes that take place in the patient receiving MTH and how to prepare for them and manage them if they do occur. We hope to provide information of how to manage these potential complications through both a review of the current literature and a reflection of our own experience.