Outcomes of Extracorporeal Life Support Use in Accidental Hypothermia: A Systematic Review

Environmental Hypothermia

Although a rare diagnosis in the Emergency Department, hypothermia affects patients in all environments, from urban to mountainous settings. Classic signs of death cannot be interpreted in the hypothermic patient, thus resulting in the mantra, "No one is dead until they're warm and dead." This comprehensive review of environmental hypothermia covers the clinical significance and pathophysiology of hypothermia, pearls and pitfalls in the prehospital management of hypothermia (including temperature measurement techniques and advanced cardiac life support deviations), necessary Emergency Department diagnostics, available rewarming modalities including extracorporeal life support, and criteria for termination of resuscitation.

Delayed Rewarming Thrombocytopenia: A Suggested Preventable and Treatable Cause of Rewarming Deaths

The lack of a consensus of accepted prognostic factors in hypothermia suggests an additional factor has been overlooked. Delayed rewarming thrombocytopenia (DRT) is a novel candidate for such a role. At body temperature, platelets undergoing a first stage of aggregation are capable of progression to a second irreversible stage of aggregation. However, we have shown that the second stage of aggregation does not occur below 32°C and that this causes the first stage to become augmented (first-stage platelet hyperaggregation). In aggregometer studies performed below 32°C, the use of quantities of ADP that cause a marked first-stage hyperaggregation can cause an augmented second-stage activation of the platelets during rewarming (second-stage platelet hyperaggregation). In vivo, after 24 hours of hypothermia, platelets on rewarming seem to undergo second-stage hyperaggregation, from ADP released from erythrocytes, leading to life-threatening thrombocytopenia. This hyperaggregation is avoidable if heparin is given before the hypothermia or if aspirin, alcohol or platelet transfusion is given during the hypothermia before reaching 32°C on rewarming. Many of the open questions existing in this field are explained by DRT. Prevention and treatment of DRT could be of significant value in preventing rewarming deaths and some cases of rescue collapse. Performing platelet counts during rewarming will demonstrate potentially fatal thrombocytopenia and enable treatment with platelet infusions aspirin or alcohol.

The Beginning of an ECLS Center: First Successful ECPR in an Emergency Department in Romania-Case-Based Review

According to the latest international resuscitation guidelines, extracorporeal cardiopulmonary resuscitation (ECPR) involves the utilization of extracorporeal membrane oxygenation (ECMO) in specific patients experiencing cardiac arrest, and it can be considered in situations where standard cardiopulmonary resuscitation efforts fail if they have a potentially reversible underlying cause, among which we can also find hypothermia. In cases of cardiac arrest, both witnessed and unwitnessed, hypothermic patients have higher chances of survival and favorable neurological outcomes compared to normothermic patients. ECPR is a multifaceted procedure that requires a proficient team, specialized equipment, and comprehensive multidisciplinary support within a healthcare system. However, it also carries the risk of severe, life-threatening complications. With the increasing use of ECPR in recent years and the growing number of centers implementing this technique outside the intensive care units, significant uncertainties persist in both prehospital and emergency department (ED) settings. Proper organization is crucial for an ECPR program in emergency settings, especially given the challenges and complexities of these treatments, which were previously not commonly used in ED. Therefore, within a narrative review, we have incorporated the initial case of ECPR in an ED in Romania, featuring a successful resuscitation in the context of severe hypothermia (20 °C) and a favorable neurological outcome (CPC score of 1).

[Extracorporeal Life Support in Critical Care Medicine]

Veno-arterial extracorporeal life support (ECLS) may be indicated in patients with refractory heart failure. The list of conditions in which ECLS is successfully used is growing and includes cardiogenic shock following myocardial infarction, refractory cardiac arrest, septic shock with low cardiac output and severe intoxication. Femoral ECLS is the most common and often preferred ECLS-configuration in the emergency setting. Although femoral access is usually quick and easy to establish, it is also associated with specific adverse haemodynamic effects due to the direction of blood flow and access-site complications are inherent. Femoral ECLS provides adequate oxygen delivery and compensates for impaired cardiac output. However, retrograde blood flow into the aorta increases left ventricular afterload and may worsen left ventricular stroke work. Therefore, femoral ECLS is not equivalent to left ventricular unloading. Daily haemodynamic assessments are crucial and should include echocardiography and laboratory tests determining tissue oxygenation. Common complications include the harlequin-phenomenon, lower limb ischaemia or cerebral events and cannula site or intracranial bleeding. Despite a high incidence of complications and high mortality, ECLS is associated with survival benefits and better neurological outcomes in selected patient groups.

Outcome of extracorporeal membrane oxygenation use in severe accidental hypothermia with cardiac arrest and circulatory instability: A multicentre, prospective, observational study in Japan (ICE-CRASH study)

AIM

To elucidate the effectiveness of extracorporeal membrane oxygenation (ECMO) in accidental hypothermia (AH) patients with and without cardiac arrest (CA), including details of complications.

METHODS

This study was a multicentre, prospective, observational study of AH in Japan. All adult (aged ≥18 years) AH patients with body temperature ≤32 °C who presented to the emergency department between December 2019 and March 2022 were included. Among the patients, those with CA or circulatory instability, defined as severe AH, were selected and divided into the ECMO and non-ECMO groups. We compared 28-day survival and favourable neurological outcomes at discharge between the ECMO and non-ECMO groups by adjusting for the patients' background characteristics using multivariable logistic regression analysis.

RESULTS

Among the 499 patients in this study, 242 patients with severe AH were included in the analysis: 41 in the ECMO group and 201 in the non-ECMO group. Multivariable analysis showed that the ECMO group was significantly associated with better 28-day survival and favourable neurological outcomes at discharge in patients with CA compared to the non-ECMO group (odds ratio [OR] 0.17, 95% confidence interval [CI]: 0.05-0.58, and OR 0.22, 95%CI: 0.06-0.81). However, in patients without CA, ECMO not only did not improve 28-day survival and neurological outcomes, but also decreased the number of event-free days (ICU-, ventilator-, and catecholamine administration-free days) and increased the frequency of bleeding complications.

CONCLUSIONS

ECMO improved survival and neurological outcomes in AH patients with CA, but not in AH patients without CA.

Accidental Hypothermia: 2021 Update

Accidental hypothermia is an unintentional drop of core temperature below 35 °C. Annually, thousands die of primary hypothermia and an unknown number die of secondary hypothermia worldwide. Hypothermia can be expected in emergency patients in the prehospital phase. Injured and intoxicated patients cool quickly even in subtropical regions. Preventive measures are important to avoid hypothermia or cooling in ill or injured patients. Diagnosis and assessment of the risk of cardiac arrest are based on clinical signs and core temperature measurement when available. Hypothermic patients with risk factors for imminent cardiac arrest (temperature < 30 °C in young and healthy patients and <32 °C in elderly persons, or patients with multiple comorbidities), ventricular dysrhythmias, or systolic blood pressure < 90 mmHg) and hypothermic patients who are already in cardiac arrest, should be transferred directly to an extracorporeal life support (ECLS) centre. If a hypothermic patient arrests, continuous cardiopulmonary resuscitation (CPR) should be performed. In hypothermic patients, the chances of survival and good neurological outcome are higher than for normothermic patients for witnessed, unwitnessed and asystolic cardiac arrest. Mechanical CPR devices should be used for prolonged rescue, if available. In severely hypothermic patients in cardiac arrest, if continuous or mechanical CPR is not possible, intermittent CPR should be used. Rewarming can be accomplished by passive and active techniques. Most often, passive and active external techniques are used. Only in patients with refractory hypothermia or cardiac arrest are internal rewarming techniques required. ECLS rewarming should be performed with extracorporeal membrane oxygenation (ECMO). A post-resuscitation care bundle should complement treatment.

Intensive care with extracorporeal membrane oxygenation rewarming in accident severe hypothermia (ICE-CRASH) study: a protocol for a multicentre prospective, observational study in Japan

INTRODUCTION

Accidental hypothermia (AH) is a rare but critical disease, leading to death in severe cases. In recent decades, extracorporeal membrane oxygenation (ECMO) has been successfully used to rewarm hypothermic patients with cardiac arrest or circulation instability. However, data on the efficacy of rewarming using ECMO for patients with AH are limited. Therefore, a large-scale, multicentre, prospective study is warranted. The primary objective of this study will be to clarify the effectiveness of rewarming using ECMO for patients with AH. Our secondary objectives will be to compare the incidence of adverse effects between ECMO rewarming and non-ECMO rewarming and to identify the most appropriate management of ECMO for AH.

METHODS AND ANALYSES

The Intensive Care with ExtraCorporeal membrane oxygenation Rewarming in Accidentally Severe Hypothermia study is taking place in 35 tertiary emergency medical facilities in Japan. The inclusion criteria are patients ≥18 years old with a body temperature ≤32°C. We will include patients with AH who present to the emergency department from December 2019 to March 2022. The research personnel at each hospital will collect several variables, including patient demographics, rewarming method, ECMO data and complications. Our primary outcome is to compare the 28-day survival rate between the ECMO and non-ECMO (other treatments) groups among patients with severe AH. Our secondary outcomes are to compare the following values between the ECMO and non-ECMO groups: length of stay in the intensive-care unit and complications. Furthermore, in patients with cardiac arrest, the Cerebral Performance Category score at discharge will be compared between both groups.

ETHICS AND DISSEMINATION

This study received research ethics approval from Asahikawa Medical University (18194 and 19115). The study was approved by the institutional review board of each hospital, and the requirement for informed consent was waived due to the observational nature of the study.

TRIAL REGISTRATION NUMBER

UMIN000036132.

Hypothermic Cardiac Arrest - Retrospective cohort study from the International Hypothermia Registry

AIM

The International Hypothermia Registry (IHR) was created to increase knowledge of accidental hypothermia, particularly to develop evidence-based guidelines and find reliable outcome predictors. The present study compares hypothermic patients with and without cardiac arrest included in the IHR.

METHODS

Demographic, pre-hospital and in-hospital data, method of rewarming and outcome data were collected anonymously in the IHR between 2010 and 2020.

RESULTS

Two hundred and one non-consecutive cases were included. The major causeof hypothermia was mountain accidents, predominantly in young men. Hypothermic Cardiac Arrest (HCA) occurred in 73 of 201 patients. Core temperature was significantly lower in the patients in cardiac arrest (25.0 vs. 30.0 °C, p < 0.001). One hundred and fifteen patients were rewarmed externally (93% with ROSC), 53 by extra-corporeal life support (ECLS) (40% with ROSC) and 21 with invasive internal techniques (71% with ROSC). The overall survival rate was 95% for patients with preserved circulation and 36% for those in cardiac arrest. Witnessed cardiac arrest and ROSC before rewarming were positive outcome predictors, asphyxia, coagulopathy, high potassium and lactate negative outcome predictors.

CONCLUSIONS

This first analysis of 201 IHR patients with moderate to severe accidental hypothermia shows an excellent 95% survival rate for patients with preserved circulation and 36% for HCA patients. Witnessed cardiac arrest, restoration of spontaneous circulation, low potassium and lactate and absence of asphyxia were positive survival predictors despite hypothermia in young, healthy adults after mountaineering accidents. However, accidental hypothermia is a heterogenous entity that should be considered in both treatment strategies and prognostication.