Moderate hypothermia for severe cardiogenic shock (COOL Shock Study I & II)

Cardiogenic Shock Intravascular Cooling Trial (CHILL-SHOCK)

BACKGROUND

Cardiogenic shock (CS) is complicated by high mortality rates. Targeted temperature control (TTC) has been proposed as an adjunct therapy in CS. This study aims to examine the safety of TTC in patients presenting with CS.

METHODS AND RESULTS

In this open-label, randomized controlled pilot trial, 20 patients with hemodynamic criteria for CS were assigned to standard of care plus TTC vs standard of care alone. The primary outcome was a composite safety outcome, including well-described complications of TTC. Secondary outcomes included mortality at 90 days, invasive hemodynamic and echocardiographic parameters, electrocardiographic measurements, and inotrope dosing. There were no significant differences in the composite analysis of prespecified safety outcomes (3 events in the TTC group vs 0 events in the control group; P = 0.24). Patients randomized to TTC demonstrated a statistically significant increase in cardiac index and cardiac power index compared to the control group at 48-96 hours after randomization (3.6 [3.1, 3.9] L/min/m2 vs 2.6 [2.5, 3.15] L/min/m2; P = 0.029 and 0.61 [0.55, 0.7] W/m2 vs 0.53 [0.435, 0.565] W/m2; P = 0.029, respectively).

CONCLUSION

TTC may be a safe adjunct therapy for patients presenting with CS and may yield improvement in specific hemodynamic parameters.

External validation of the CREST model to predict early circulatory-etiology death after out-of-hospital cardiac arrest without initial ST-segment elevation myocardial infarction

BACKGROUND

The CREST model is a prediction model, quantitating the risk of circulatory-etiology death (CED) after cardiac arrest based on variables available at hospital admission, and intend to guide the triage of comatose patients without ST-segment-elevation myocardial infarction after successful cardiopulmonary resuscitation. This study assessed performance of the CREST model in the Target Temperature Management (TTM) trial cohort.

METHODS

We retrospectively analyzed data from resuscitated out-of-hospital cardiac arrest (OHCA) patients in the TTM-trial. Demographics, clinical characteristics, and CREST variables (history of coronary artery disease, initial heart rhythm, initial ejection fraction, shock at admission and ischemic time > 25 min) were assessed in univariate and multivariable analysis. The primary outcome was CED. The discriminatory power of the logistic regression model was assessed using the C-statistic and goodness of fit was tested according to Hosmer-Lemeshow.

RESULTS

Among 329 patients eligible for final analysis, 71 (22%) had CED. History of ischemic heart disease, previous arrhythmia, older age, initial non-shockable rhythm, shock at admission, ischemic time > 25 min and severe left ventricular dysfunction were variables associated with CED in univariate analysis. CREST variables were entered into a logistic regression model and the area under the curve for the model was 0.73 with adequate calibration according to Hosmer-Lemeshow test (p = 0.602).

CONCLUSIONS

The CREST model had good validity and a discrimination capability for predicting circulatory-etiology death after resuscitation from cardiac arrest without ST-segment elevation myocardial infarction. Application of this model could help to triage high-risk patients for transfer to specialized cardiac centers.

Outcomes of mild-to-moderate postresuscitation shock after non-shockable cardiac arrest and association with temperature management: a post hoc analysis of HYPERION trial data

BACKGROUND

Outcomes of postresuscitation shock after cardiac arrest can be affected by targeted temperature management (TTM). A post hoc analysis of the "TTM1 trial" suggested higher mortality with hypothermia at 33 °C. We performed a post hoc analysis of HYPERION trial data to assess potential associations linking postresuscitation shock after non-shockable cardiac arrest to hypothermia at 33 °C on favourable functional outcome.

METHODS

We divided the patients into groups with vs. without postresuscitation (defined as the need for vasoactive drugs) shock then assessed the proportion of patients with a favourable functional outcome (day-90 Cerebral Performance Category [CPC] 1 or 2) after hypothermia (33 °C) vs. controlled normothermia (37 °C) in each group. Patients with norepinephrine or epinephrine > 1 µg/kg/min were not included.

RESULTS

Of the 581 patients included in 25 ICUs in France and who did not withdraw consent, 339 had a postresuscitation shock and 242 did not. In the postresuscitation-shock group, 159 received hypothermia, including 14 with a day-90 CPC of 1-2, and 180 normothermia, including 10 with a day-90 CPC of 1-2 (8.81% vs. 5.56%, respectively; P = 0.24). After adjustment, the proportion of patients with CPC 1-2 also did not differ significantly between the hypothermia and normothermia groups (adjusted hazards ratio, 1.99; 95% confidence interval, 0.72-5.50; P = 0.18). Day-90 mortality was comparable in these two groups (83% vs. 86%, respectively; P = 0.43).

CONCLUSIONS

After non-shockable cardiac arrest, mild-to-moderate postresuscitation shock at intensive-care-unit admission did not seem associated with day-90 functional outcome or survival. Therapeutic hypothermia at 33 °C was not associated with worse outcomes compared to controlled normothermia in patients with postresuscitation shock. Trial registration ClinicalTrials.gov, NCT01994772.

Cardiovascular and pulmonary interactions: why Galen's misconceptions proved clinically useful for 1,300 years

The new generations of physicians are, to a large extent, unaware of the complex philosophical and biological concepts that created the bases of modern medicine. Building on the Hellenistic tradition of the four humors and their qualities, Galen (AD 129 to c. 216) provided a persuasive scheme of the structure and function of the cardiorespiratory system, which lasted, without serious contest, for 1,300 yr. Galen combined teleological concepts with careful clinical observation to defend a coherent and integrated system in which the fire-heart-flaming at the center of the body-interacts with lungs' air-pneuma to create life. Remarkably, however, he achieved these goals, despite failing to grasp the concept of systemic and pulmonary blood circulations, understand the source and destiny of venous and arterial blood, recognize the lung as the organ responsible for gas exchange, comprehend the actual events taking place in the left ventricle, and identify the source of internal heat. In this article, we outline the alternative theories Galen put forward to explain these complex phenomena. We then discuss how the final consequences of Galen's flawed anatomical and physiological conceptions do not differ substantially from those obtained if one applies modern concepts. Recognition of this state of affairs may explain why the ancient practitioner could achieve relative success, without harming the patient, to understand and treat a multitude of symptoms and illnesses.

Postresuscitation Care after Out-of-hospital Cardiac Arrest: Clinical Update and Focus on Targeted Temperature Management

Out-of-hospital cardiac arrest is a major cause of mortality and morbidity worldwide. With the introduction of targeted temperature management more than a decade ago, postresuscitation care has attracted increased attention. In the present review, we discuss best practice hospital management of unconscious out-of-hospital cardiac arrest patients with a special focus on targeted temperature management. What is termed post-cardiac arrest syndrome strikes all organs and mandates access to specialized intensive care. All patients need a secured airway, and most patients need hemodynamic support with fluids and/or vasopressors. Furthermore, immediate coronary angiography and percutaneous coronary intervention, when indicated, has become an essential part of the postresuscitation treatment. Targeted temperature management with controlled sedation and mechanical ventilation is the most important neuroprotective strategy to take. Targeted temperature management should be initiated as quickly as possible, and according to international guidelines, it should be maintained at 32° to 36°C for at least 24 h, whereas rewarming should not increase more than 0.5°C per hour. However, uncertainty remains regarding targeted temperature management components, warranting further research into the optimal cooling rate, target temperature, duration of cooling, and the rewarming rate. Moreover, targeted temperature management is linked to some adverse effects. The risk of infection and bleeding is moderately increased, as is the risk of hypokalemia and magnesemia. Circulation needs to be monitored invasively and any deviances corrected in a timely fashion. Outcome prediction in the individual patient is challenging, and a self-fulfilling prophecy poses a real threat to early prognostication based on clinical assessment alone. Therefore, delayed and multimodal prognostication is now considered a key element of postresuscitation care. Finally, modern postresuscitation care can produce good outcomes in the majority of patients but requires major diagnostic and therapeutic resources and specific training. Hence, recent international guidelines strongly recommend the implementation of regional prehospital resuscitation systems with integrated and specialized cardiac arrest centers.

Impact of hypothermia on cardiac performance during targeted temperature management after cardiac arrest

INTRODUCTION

Targeted temperature management (TTM) is a well-accepted neuro-protective intervention in the management of comatose survivors of cardiac arrest (CA). However, the impact of TTM on cardiac performance has not been adequately evaluated.

METHODS

We reviewed data on consecutive CA survivors undergoing TTM at a quaternary cardiac intensive care unit between January 2015 and June 2017. Enrollment was restricted to cases with invasive hemodynamics (iHDs) at TTM initiation, every 8 h at target temperature (32-34 °C) and at completion of rewarming (>36 °C), unless precluded by mortality. Cardiac index and cardiac index-derived variables were adjusted for a decreased oxygen consumption during hypothermia. We assessed the serial impact of cooling on iHDs and cardiac performance utilizing longitudinal data analysis accounting for the effects of time as surrogate for the expected change from the post arrest syndrome and instituted treatments. A Frank-Starling construct was used to evaluate changes in cardiac contractility.

RESULTS

We evaluated the effects of cooling on iHDs and cardiac performance in 46 CA survivors. Heart rate decreased with cooling (p < 0.001), to return to baseline after rewarming (p = 0.6). Mean arterial pressure and pulmonary wedge pressure decreased by cooling (p < 0.001 for both), with sustained improvement after rewarming (p < 0.001 for both). Systemic vascular resistance was unaffected by hypothermia (p > 0.05). Left stroke work index increased with cooling (p < 0.001), with return to baseline after rewarming (p = 0.6). Cooling was associated with a left-upward shift in the Frank-Starling curve indicative of increased contractility.

CONCLUSION

Mild hypothermia in CA survivors appears associated to positive changes in iHDs and cardiac performance, including a potential increase in cardiac contractility. Larger studies are needed to conclusively confirm these findings.

Successful Re-Initiation of Therapeutic Hypothermia as Adjunctive Salvage Therapy in a Case of Refractory Cardiogenic Shock Due to Acute Myocardial Infarction

BACKGROUND Acute myocardial infarction (AMI) complicated by cardiogenic shock has a high mortality rate, despite prompt revascularization, advanced medical therapy and the use of mechanical circulatory support devices. Therapeutic hypothermia is associated with physiological cellular changes in the ischemic myocardium, and a trend towards improved hemodynamics in patients with AMI and cardiogenic shock, but is currently not considered to be a therapeutic modality. A case is presented that supports the role of therapeutic hypothermia as salvage therapy in patients with cardiogenic shock following AMI. CASE REPORT A 37-year-old man who presented with cardiac arrest following an anterior wall AMI due to occlusion of the left anterior descending coronary artery complicated by cardiogenic shock, underwent emergent percutaneous revascularization with placement of a stent, a percutaneous left ventricular-assist device (LVAD), and a pulmonary artery catheter. Therapeutic hypothermia was initiated to achieve a target core body temperature of between 32-34°C for 24 hours, followed by slow re-warming. However, after rewarming, the patient developed refractory cardiogenic shock, despite revascularization, pharmacological and mechanical circulatory support. A second cycle of therapeutic hypothermia was initiated as salvage therapy, leading to clinical improvement. The patient had a favorable outcome, was discharged from hospital and was able to return to work. CONCLUSIONS The first successful case is described in which therapeutic hypothermia was re-initiated as salvage therapy for cardiogenic shock where no other hemodynamic support resources were available.

Assessing structural and functional response of murine vasculature to acute β-adrenergic stimulation in vivo during hypothermic and hyperthermic conditions

Background: Because of the importance of adrenoreceptors in regulating the cardiovascular (CV) system and the role of the CV system in thermoregulation, understanding the response to these two stressors is of interest. The purpose of this study was to assess changes of arterial geometry and function in vivo during thermal and β-adrenergic stress induced in mice and quantified by MRI.Methods: Male mice were anesthetized and imaged at 7 T. Anatomical and functional data were acquired from the neck (carotid artery), torso (suprarenal and infrarenal aorta and iliac artery) and periphery (femoral artery). Intravenous dobutamine (tail vein catheter, 40 µg/kg/min, 0.12 mL/h) was used as β-adrenergic stressor. Baseline and dobutamine data were acquired at minimally hypothermic (35 °C) and minimally hyperthermic (38 °C) core temperatures. Cross-sectional vessel area and maximum cyclic strain were measured across the cardiac cycle.Results: Vascular response varied by location and by core temperature. For minimally hypothermic conditions (35 °C), average, maximum and minimum areas decreased with dobutamine only at the suprarenal aorta (avg: -17.9%, max: -13.5%, min: -21.4%). For minimally hyperthermic conditions (38 °C), vessel areas decreased between baseline and dobutamine at the carotid (avg: -19.6%, max: -15.5%, min: -19.3%) and suprarenal aorta (avg: -24.2%, max: -17.4%, min: -17.3%); whereas, only the minimum vessel area decreased for the iliac artery (min: -14.4%). Maximum cyclic strain increased between baseline and dobutamine at the iliac artery for both conditions and at the suprarenal aorta at hyperthermic conditions.Conclusions: At hypothermic conditions, the vessel area response to dobutamine is diminished compared to hyperthermic conditions where the vessel area response mimics normothermic dobutamine conditions. The varied response emphasizes the need to monitor and control body temperature during medical conditions or treatments that may be accompanied by hypothermia, especially when vasoactive agents are used.

Sniff of coke breaks the heart: cocaine-induced coronary vasospasm aggravated by therapeutic hypothermia and vasopressors after aborted sudden cardiac death: a case report

Introduction

Coronary vasospasm and sudden cardiac death are a frequently reported complication of cocaine abuse. We present a case with uniquely severe clinical and angiographic presentation.

Case presentation

A 39-year-old patient was presented to the cath lab after out-of-hospital cardiac arrest. Coronary angiography revealed focal coronary vasospasm in the proximal LCx, well responsive for intracoronary nitrates. Accordingly, no coronary intervention was performed and the patient was transferred to the cardiac intensive care unit. There, after systematically cooling sudden haemodynamic deterioration and massive ST-elevation was observed. Repeated coronary angiography revealed subocclusive LAD and LCx vasospasm, which again recovered after intracoronary injection of nitric oxide.

Discussion

Coronary-spastic effect of cocaine and its potentially dreadful clinical consequences are well-described phenomena. As novelty this case emphasizes that standard of care, including systematic hypothermia and vasopressor administration after out-of-hospital cardiac arrest can potentiate cocaine-induced coronary spasm with dramatic outcomes.

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.

Targeted temperature management in the ICU: Guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term "targeted temperature management" (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de réanimation de langue française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société francaise d'anesthésie réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société française de médecine d'urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe francophone de réanimation et urgences pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association nationale de neuro-anesthésie réanimation française [ANARLF]), and the French Neurovascular Society (Société française neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts' opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

Targeted temperature management in the ICU: guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term “targeted temperature management” (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de Réanimation de Langue Française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société Francaise d’Anesthésie Réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société Française de Médecine d’Urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe Francophone de Réanimation et Urgences Pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association Nationale de Neuro-Anesthésie Réanimation Française [ANARLF]), and the French Neurovascular Society (Société Française Neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts’ opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

Recent developments in the management of patients resuscitated from cardiac arrest

Cardiac arrest is the leading cause of death in Europe and the United States. Many patients who are initially resuscitated die in the hospital, and hospital survivors often have substantial neurologic dysfunction. Most cardiac arrests are caused by coronary artery disease; patients with coronary artery disease likely benefit from early coronary angiography and intervention. After resuscitation, cardiac arrest patients remain critically ill and frequently suffer cardiogenic shock and multiorgan failure. Early cardiopulmonary stabilization is important to prevent worsening organ injury. To achieve best patient outcomes, comprehensive critical care management is needed, with primary goals of stabilizing hemodynamics and preventing progressive brain injury. Targeted temperature management is frequently recommended for comatose survivors of cardiac arrest to mitigate the neurologic injury that drives outcomes. Accurate neurologic assessment is central to managing care of cardiac arrest survivors and should combine physical examination with objective neurologic testing, with the caveat that delaying neurologic prognosis is essential to avoid premature withdrawal of supportive care. A combination of clinical findings and diagnostic results should be used to estimate the likelihood of functional recovery. This review focuses on recent advances in care and specific cardiac intensive care strategies that may improve morbidity and mortality for patients after cardiac arrest.

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.

[Early onset pneumonia after successful resuscitation : Incidence after mild invasive hypothermia therapy]

BACKGROUND

Targeted temperature management (TTM) represents an effective therapy to improve neurologic outcome in patients who survive an out-of-hospital cardiac arrest (OHCA). First publications about this therapy reported a higher incidence of infections in patients who underwent TTM induced by external cooling devices. Whether intravascular cooling devices are also associated with an increased infection rate has not been investigated so far.

METHODS

In a single center retrospective study, the incidence of early onset pneumonia (EOP) in OHCA patients with or without intravascular TTM at 33 °C target temperature for 24 h who survived at least 24 h after admission was analyzed.

RESULTS

A total of 68 OHCA survivors (mean age 65 ± 15 years) were included in this analysis. The most common causes of OHCA were myocardial infarction (35 %), primary ventricular fibrillation (24 %), asystole (15 %), and pulmonary embolism (7 %). Of those, 32 patients (48 %) received TTM. The overall incidence of EOP was 38 %. Incidence of EOP did not differ significantly between groups, was more frequent in the group without TTM (42 % vs. 34 %, p = 0.57) and had no impact on mortality (hazard ratio = 1.02; 95 % confidence interval 0.25-4.16; p = 0.97).

CONCLUSION

Intravascular TTM at 33 °C with a cooling catheter is not associated with more infective complications in OHCA patients. This finding underscores the safety of TTM.

Electrocardiographic Manifestations in three Psychiatric patients with Hypothermia - Case Report

Hypothermia occurs when the core body temperature falls below 35°C, which, in severe cases, can lead to electrocardiographic changes. Several conditions that occur in the psychiatric population increase the risk of hypothermia. This risk can be further increased by the use of several classes of medications such as antipsychotics, beta-adrenergic antagonists and benzodiazepines. We report on three psychiatric patients who were admitted for hypothermia and developed electrocardiographic manifestations (sinus bradycardia, QT prolongation and Osborn waves), which completely resolved after treatment.

Inotropic Effects of Experimental Hyperthermia and Hypothermia on Left Ventricular Function in Pigs-Comparison With Dobutamine

OBJECTIVES

The results from the recent Targeted Temperature Management trial raised the question whether cooling or merely the avoidance of fever mediates better neurologic outcome in resuscitated patients. As temperature per se is a major determinant of cardiac function, we characterized the effects of hyperthermia (40.5°C), normothermia (38.0°C), and mild hypothermia (33.0°C) on left ventricular contractile function in healthy pigs and compared them with dobutamine infusion.

DESIGN

Animal study.

SETTING

Large animal facility, Medical University of Graz, Graz, Austria.

SUBJECTS

Nine anesthetized and mechanically ventilated closed-chest Landrace pigs (67 ± 2 kg).

INTERVENTIONS

Core body temperature was controlled using an intravascular device. At each temperature step, IV dobutamine was titrated to double maximum left ventricular dP/dt (1.8 ± 0.1 µg/kg/min at normothermia). Left ventricular pressure-volume relationships were assessed during short aortic occlusions. Left ventricular contractility was assessed by the calculated left ventricular end-systolic volume at an end-systolic left ventricular pressure of 100 mm Hg.

MEASUREMENTS AND MAIN RESULTS

Heart rate (98 ± 4 vs 89 ± 4 vs 65 ± 2 beats/min; all p < 0.05) and cardiac output (6.7 ± 0.3 vs 6.1 ± 0.3 vs 4.4 ± 0.2 L/min) decreased with cooling from hyperthermia to normothermia and mild hypothermia, whereas left ventricular contractility increased (left ventricular end-systolic volume at a pressure of 100 mm Hg: 74 ± 5 mL at hyperthermia, 52 ± 4 mL at normothermia, and 41 ± 3 mL at mild hypothermia; all p < 0.05). The effect of cooling on left ventricular end-systolic volume at a pressure of 100 mm Hg (hyperthermia to normothermia: -28% ± 3% and normothermia to mild hypothermia: -20% ± 5%) was of comparable effect size as dobutamine at a given temperature (hyperthermia: -28% ± 4%, normothermia: -27% ± 6%, and mild hypothermia: -27% ± 9%).

CONCLUSIONS

Cooling from hyperthermia to normothermia and from normothermia to mild hypothermia increased left ventricular contractility to a similar degree as a significant dose of dobutamine in the normal porcine heart. These data indicate that cooling can reduce the need for positive inotropes and that lower rather than higher temperatures are appropriate for the resuscitated failing heart.

Myocardial Dysfunction and Shock after Cardiac Arrest

Postarrest myocardial dysfunction includes the development of low cardiac output or ventricular systolic or diastolic dysfunction after cardiac arrest. Impaired left ventricular systolic function is reported in nearly two-thirds of patients resuscitated after cardiac arrest. Hypotension and shock requiring vasopressor support are similarly common after cardiac arrest. Whereas shock requiring vasopressor support is consistently associated with an adverse outcome after cardiac arrest, the association between myocardial dysfunction and outcomes is less clear. Myocardial dysfunction and shock after cardiac arrest develop as the result of preexisting cardiac pathology with multiple superimposed insults from resuscitation. The pathophysiology involves cardiovascular ischemia/reperfusion injury and cardiovascular toxicity from excessive levels of inflammatory cytokine activation and catecholamines, among other contributing factors. Similar mechanisms occur in myocardial dysfunction after cardiopulmonary bypass, in sepsis, and in stress-induced cardiomyopathy. Hemodynamic stabilization after resuscitation from cardiac arrest involves restoration of preload, vasopressors to support arterial pressure, and inotropic support if needed to reverse the effects of myocardial dysfunction and improve systemic perfusion. Further research is needed to define the role of postarrest myocardial dysfunction on cardiac arrest outcomes and identify therapeutic strategies.

The impact of therapeutic hypothermia on on-treatment platelet reactivity and clinical outcome in cardiogenic shock patients undergoing primary PCI for acute myocardial infarction: Results from the ISAR-SHOCK registry

INTRODUCTION

Mild therapeutic hypothermia (TH) is standard of care after cardiac arrest of any cause. However, its impact on on-treatment platelet reactivity and clinical outcome in patients with acute myocardial infarction (AMI) complicated by cardiogenic shock and undergoing PCI with P2Y12 receptor inhibitor treatment is less clear.

METHODS AND RESULTS

For the ISAR-SHOCK registry, 145 patients with AMI, cardiogenic shock and primary PCI in two centers (Deutsches Herzzentrum München and Klinikum rechts der Isar, Technical University Munich) between January 2009-May 2012 were analysed. Of these, 64 (44%) patients received TH treatment. The median [IQR] ADP-induced platelet aggregation following thienopyridine loading dose administration (clopidogrel in 95 and prasugrel in 50 patients) did not differ between the two groups (419 [283-684] for TH vs. 355 [207-710] AU x min for non-TH patients, P=0.22). After 30days follow-up, no significant differences were observed between both groups for mortality (42 vs. 44 %, HR: 0.93, 95% CI [0.56-1.53], p=0.77), MI (6 vs. 6%, HR: 0.99 95% CI [0.27-3.7], p=0.99) and TIMI minor bleedings (17 vs. 17%, HR 0.99 95% CI [0.45-2.18], p=0.98). TIMI major bleedings were numerically higher in the TH vs. non-TH cohort (25 % vs. 12 %, HR: 2.1 95% CI [0.95-4.63], p=0.07). Three definite stent thrombosis (ST) were observed in this registry and all STs occurred in the TH group of patients (p=0.09).

CONCLUSION

Results of this registry suggest that TH does not negatively impact on platelet reactivity in shock patients receiving either clopidogrel or prasugrel. The numerically higher rate of major bleedings and the clustering of STs in the TH cohort warrant further investigation.

Mild hypothermia induces incomplete left ventricular relaxation despite spontaneous bradycardia in pigs

AIM

Mild hypothermia (MH) decreases left ventricular (LV) end-diastolic capacitance. We sought to clarify whether this results from incomplete relaxation.

METHODS

Ten anaesthetized pigs were cooled from normothermia (NT, 38 °C) to MH (33 °C). LV end-diastolic pressure (LVPed), volume (LVVed) and pressure-volume relationships (EDPVRs) were determined during stepwise right atrial pacing. LV capacitance (i.e. LVVed at LVPed of 10 mmHg, LV VPed10) was derived from the EDPVR. Pacing-induced changes of diastolic indices (LVPed, LVVed and LV VPed10) were analysed as a function of (i) heart rate and (ii) the ratio between diastolic time interval (t-dia) and LV isovolumic relaxation constant τ, which was calculated using a logistic fit (τL ) and monoexponential fit with zero asymptote (τZ ) and nonzero asymptote (τNZ ).

RESULTS

Mild hypothermia decreased heart rate (85 ± 4 to 68 ± 3 bpm), increased τL (22 ± 1 to 57 ± 4 ms), τZ (26 ± 2 to 56 ± 5 ms) and τNZ (41 ± 1 to 96 ± 5 ms), decreased t-dia/τ ratios, and shifted the EDPVR leftwards compared to NT (all P < 0.05). During NT, pacing at ≥140 bpm shifted the EDPVR progressively leftwards. During MH, relationships between diastolic indices and heart rate were shifted towards lower heart rates compared to NT. However, relationships between diastolic indices and t-dia/τ during NT and MH were superimposable.

CONCLUSION

We conclude that the loss of LV end-diastolic capacitance during MH can be explained at least in part by slowed LV relaxation. MH thereby is an example of incomplete LV relaxation at a spontaneous low heart rate. Caution may be advised, when heart rate is increased in patients treated with MH.

Systolic left ventricular function is preserved during therapeutic hypothermia, also during increases in heart rate with impaired diastolic filling

Background

Systolic left ventricular function during therapeutic hypothermia is found both to improve and to decline. We hypothesized that this discrepancy would depend on the heart rate and the variables used to assess systolic function.

Methods

In 16 pigs, cardiac performance was assessed by measurements of invasive pressures and thermodilution cardiac output and with 2D strain echocardiography. Left ventricle (LV) volumes, ejection fraction (EF), transmitral flow, and circumferential and longitudinal systolic strain were measured. Miniaturized ultrasonic transducers were attached to the epicardium of the LV to obtain M-mode images, systolic thickening, and diastolic thinning velocities and to determine LV pressure-wall dimension relationships. Preload recruitable stroke work (PRSW) was calculated. Measurements were performed at 38 and 33°C at spontaneous and paced heart rates, successively increased in steps of 20 up to the toleration limit. Effects of temperature and heart rate were compared in a mixed model analysis.

Results

Hypothermia reduced heart rate from 87 ± 10 (SD) to 76 ± 11 beats/min without any changes in LV stroke volume, end-diastolic volume, EF, strain values, or PRSW. Systolic wall thickening velocity (S′) and early diastolic wall thinning velocity decreased by approximately 30%, making systolic duration longer through a prolonged and slow contraction and changing the diastolic filling pattern from predominantly early towards late. Pacing reduced diastolic duration much more during hypo- than during normothermia, and combined with slow myocardial relaxation, incomplete relaxation occurred with all pacing rates. Pacing did not affect S′ or PRSW at physiological heart rates, but stroke volume, end-diastolic volume, and strain were reduced as a consequence of reduced diastolic filling and much more accentuated during hypothermia. At the ultimate tolerable heart rate during hypothermia, S′ decreased, probably as a consequence of myocardial hypoperfusion due to sustained ventricular contraction throughout a very short diastole.

Conclusions

Systolic function was maintained at physiological heart rates during therapeutic hypothermia. Reduced tolerance to increases in heart rate was caused by lack of ventricular filling due to diastolic dysfunction and shorter diastolic duration.

Bradycardia during therapeutic hypothermia is associated with good neurologic outcome in comatose survivors of out-of-hospital cardiac arrest

OBJECTIVE

Comatose patients resuscitated after out-of-hospital cardiac arrest receive therapeutic hypothermia. Bradycardia is frequent during therapeutic hypothermia, but its impact on outcome remains unclear. We explore a possible association between bradycardia during therapeutic hypothermia and neurologic outcome in comatose survivors of out-of-hospital cardiac arrest.

DESIGN

Retrospective cohort study, from January 2009 to January 2011.

SETTING

University hospital medical and cardiac ICUs.

PATIENTS

One hundred eleven consecutive comatose out-of-hospital cardiac arrest patients treated with therapeutic hypothermia.

INTERVENTIONS

Patients treated with standardized treatment protocol after cardiac arrest.

MEASUREMENTS AND MAIN RESULTS

All out-of-hospital cardiac arrest patients' records were reviewed. Hemodynamic data were obtained every fourth hour during the first days. The patients were in temperature target range (32-34°C) 8 hours after out-of-hospital cardiac arrest and dichotomized into bradycardia and nonbradycardia groups depending on their actual heart rate less than or equal to 60 beats/min or more than 60 beats/min at that time. Primary endpoint was Cerebral Performance Category score at hospital discharge. More nonbradycardia group patients received epinephrine during resuscitation and epinephrine and norepinephrine in the early in-hospital period. They also had lower base excess at admission. Survival rate with favorable outcome was significantly higher in the bradycardia than the nonbradycardia group (60% vs 37%, respectively, p = 0.03). For further heart rate quantification, patients were divided into quartiles: less than or equal to 49 beats/min, 50-63 beats/min, 64-77 beats/min, and more than or equal to 78 beats/min, with respective proportions of patients with good outcome at discharge of 18 of 27 (67%), 14 of 25 (56%), 12 of 28 (43%), and 7 of 27 (26%) (p = 0.002). Patients in the lowest quartile had significantly better outcome than the higher groups (p = 0.027), whereas patients in the highest quartile had significantly worse outcome than the lower three groups (p = 0.013).

CONCLUSIONS

Bradycardia during therapeutic hypothermia was associated with good neurologic outcome at hospital discharge. Our data indicate that bradycardia should not be aggressively treated in this period if mean arterial pressure, lactate clearance, and diuresis are maintained at acceptable levels. Studies, both experimental and clinical, are warranted.

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.

Impact of intensified postresuscitation treatment on outcome of comatose survivors of out-of-hospital cardiac arrest according to initial rhythm

AIM

We investigated the impact of intensified postresuscitation treatment in comatose survivors of out-of-hospital cardiac arrest (OHCA) of presumed cardiac etiology according to the initial rhythm at the emergency medical team arrival.

METHODS

Interventions and survival with Cerebral Performance Category (CPC) 1-2 within each group were retrospectively compared between the periods of conservative (1995-2003) and intensified (2004-2012) postresuscitation treatment.

RESULTS

In shockable group, therapeutic hypothermia (TH) increased from 1 to 93%, immediate invasive coronary strategy from 28 to 78%, intraaortic balloon pump from 4 to 21%, vasopressors/inotropes from 47 to 81% and antimicrobial agents from 65 to 86% during the intensified period as compared to conservative period (p<0.001). This was associated with increased survival with CPC 1-2 from 27 to 47% (p<0.001). After adjusting for age, sex and prehospital confounders, TH (OR=2.12, 95% CI 1.25-3.61), percutaneous coronary intervention (OR 1.77, 95% CI 1.15-2.73) and antimicrobial agents (OR=12.21, 95% CI 5.13-29.08) remained associated with survival with CPC 1-2. In non-shockable patients, TH also significantly increased from 1 to 74%, immediate invasive coronary strategy from 8 to 51%, intraaortic balloon pump from 2 to 9% and vasopressors/inotropes from 56 to 84% during intensified period without concomitant increase in survival with CPC 1-2 (7% vs. 9%; p=0.27). After adjustment, only antimicrobial agents (OR=8.43, 95% CI: 1.05-67.72) remained associated with survival with CPC 1-2.

CONCLUSION

Intensified postresuscitation treatment was associated with doubled survival in comatose survivors of OHCA with shockable rhythm. Such association could not be demonstrated in patients with non-shockable rhythm.

Advances in monitoring and management of shock

Early recognition and treatment of pediatric shock, regardless of cause, decreases mortality and improves outcome. In addition to the conventional parameters (eg, heart rate, systolic blood pressure, urine output, and central venous pressure), biomarkers and noninvasive methods of measuring cardiac output are available to monitor and treat shock. This article emphasizes how fluid resuscitation is the cornerstone of shock resuscitation, although the choice and amount of fluid may vary based on the cause of shock. Other emerging treatments for shock (ie, temperature control, extracorporeal membrane oxygenation/ventricular assist devices) are also discussed.

State-of-the-art paper: Therapeutic hypothermia in out of hospital cardiac arrest survivors

Out of hospital cardiac arrest (OHCA) is associated with an extremely poor survival rate, with mortality in most cases being related to neurological injury. Among patients who experience return of spontaneous circulation (ROSC), therapeutic hypothermia (TH) is the only proven intervention shown to reduce mortality and improve neurological outcome. First described in 1958, the field of TH has rapidly evolved in recent years. While recent technological advances in TH will likely improve outcomes in OHCA survivors, several fundamental questions remain to be answered including the optimal speed of cooling, which patients benefit from an early invasive strategy, and whether technological advances will facilitate application of TH in the field. An increased awareness and understanding of TH strategies, devices, monitoring, techniques, and complications will allow for a more widespread adoption of this important treatment modality.