Extracorporeal Life Support in Accidental Hypothermia with Cardiac Arrest—A Narrative Review

Swol, Justyna*; Darocha, Tomasz†; Paal, Peter‡; Brugger, Hermann§; Podsiadło, Paweł¶; Kosiński, Sylweriusz‖; Puślecki, Mateusz#,**; Ligowski, Marcin**; Pasquier, Mathieu††. Extracorporeal Life Support in Accidental Hypothermia with Cardiac Arrest—A Narrative Review. ASAIO Journal 68(2):p 153-162, February 2022. | DOI: 10.1097/MAT.0000000000001518

Summary of "Extracorporeal Life Support in Accidental Hypothermia with Cardiac Arrest—A Narrative Review"

Abstract

• Overview: This narrative review explores the management of patients experiencing cardiac arrest (CA) due to severe accidental hypothermia. It emphasizes the potential for good neurological recovery in such patients when treated with extracorporeal life support (ECLS). The review also addresses patient selection, prognostication, and the specific pathophysiological changes associated with hypothermic cardiac arrest.

Introduction

• Background: Accidental hypothermia, defined as a core temperature below 35°C, can lead to cardiac arrest, especially when temperatures drop below 30°C in healthy individuals or 32°C in elderly, multimorbid patients. The management of hypothermic CA is complicated by logistical challenges and a lack of awareness, particularly in regions where hypothermia is rare.

• Objective: The review aims to provide guidance on recognizing and treating hypothermic CA, with a focus on the use of ECLS for rewarming and cardiovascular stabilization.

Pathophysiology

• Hypothermic Effects: Hypothermia causes a progressive decrease in brain oxygen requirements and metabolic activity, which can prolong the survivability of CA at lower temperatures. The cardiovascular system becomes increasingly irritable, with the risk of arrhythmias and decreased cardiac output. These changes necessitate a specialized approach to resuscitation and rewarming in hypothermic patients.

Outcomes of Hypothermic CA After ECLS Rewarming

• Survival Rates: Survival rates for patients with hypothermic CA who receive ECLS vary from 20% to 100%, with a significant proportion of survivors achieving good neurological outcomes. However, outcomes are generally worse for avalanche victims and drowning patients.

• HOPE Score: The Hypothermia Outcome Prediction After ECLS (HOPE) score is a tool used to predict survival probabilities for hypothermic CA patients undergoing ECLS. It is based on six covariates and has been validated for clinical use, providing a negative predictive value of 97%.

Problems and Pitfalls in Patient Selection and Qualification for ECLS

• Challenges: Prehospital recognition of hypothermia and appropriate triage to ECLS centers are crucial for patient survival. Misdiagnosis or delay in treatment can lead to poor outcomes. ECLS is indicated in hypothermic CA with a potential for reversibility, and the absence of signs of life should not be used to declare death in these patients until they are rewarmed.

• Patient Management: Core temperature measurement and blood sampling are essential at hospital admission to confirm hypothermia and assess eligibility for ECLS rewarming using the HOPE score.

Indications for ECLS Rewarming

• Eligibility: ECLS rewarming is indicated in hypothermic CA with a HOPE score of ≥10%. Special considerations are given to children, who may have higher chances of survival.

• Contraindications: While there are no absolute contraindications for ECLS rewarming, factors such as severe trauma and futile comorbidities may influence the decision-making process.

Practical Information on the Management of Patients During ECLS Rewarming

• Initial Management: Immediate continuation of chest compressions until sufficient ECLS flow is achieved is recommended. Core temperature monitoring and fluid resuscitation are critical during rewarming to maintain cerebral perfusion and avoid complications.

• Rewarming Goals: Slow and controlled rewarming is associated with better neurological outcomes. The target rewarming rate is ≤5°C/h, with careful monitoring of temperature gradients to prevent complications such as cerebral overheating.

• Weaning: Weaning from ECLS is considered once normothermia and stable hemodynamic and pulmonary function are achieved. Repetitive echocardiography is recommended to assess cardiac function during the weaning process.

Conclusions

• Key Points: Accidental hypothermia-related CA is underdiagnosed and undertreated, particularly in regions where hypothermia is rare. Proper diagnosis, timely initiation of ECLS, and adherence to rewarming protocols are critical for achieving favorable outcomes. The use of the HOPE score is recommended for assessing patient eligibility for ECLS rewarming, and a multidisciplinary approach is essential for optimal patient management.

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Discussion Questions

1. How can the HOPE score be further integrated into clinical practice to improve outcomes in patients with accidental hypothermia-related cardiac arrest?

2. What are the key challenges in the prehospital recognition and management of hypothermic cardiac arrest, and how can these be addressed?

3. How might advancements in ECLS technology and protocols impact the survival and neurological outcomes of hypothermic cardiac arrest patients?

Javier Amador-Castañeda, BHS, RRT, FCCM

Interprofessional Critical Care Network (ICCN)

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