RISKS OF HYPOTHERMIA

Even though Global Warming is melting our glaciers, there is still a risk of becoming hypothermic, especially for those SASlers involved in skiing and mountaineering. Major progress has been made and discussed during the 7 th International Symposium on Accidental Hypothermia in Lausanne in 2022 regarding prognosis and treatment of victims of accidental hypothermia, and thanks also to the International Hypothermia Registry (IHR).

Beat Walpoth l MD, Emeritus, Cardiovascular Surgery in Geneva & Founder of the International Hypothermia Registry.

Louis Marxer l MD, GRIMM, Sion

Amélie Dupasquier l Medical Student, Lausanne

Paradigm shift

Forty years ago, a mountain guide fell into a crevasse and suffered deep accidental hypothermia until the rescue team could recover him, at which time he was found without any vital signs. He was transported by helicopter to the nearest hospital where the doctors diagnosed a very low body temperature (< 23°C) and a cardiac arrest, not compatible with survival. He was declared "dead".

At the same time, in the 1980’s, cardiac surgery for complex, congenital defects in children was performed in specialized centres in deep hypothermic cardiac arrest, giving the surgeon about 30’ to operate the defect in a total standstill without neurologic deficits after rewarming to 37°C. As you may well know, a cardiac arrest of more than 3-5’ may lead to irreversible brain damage in normothermia. Hypothermia slows down the metabolism enough to give an opportunity of normal survival after rewarming. Therefore, the team of Prof. Althaus, at the Inselspital in Bern, in which I was involved, decided to attempt rewarming of such hypothermic victims by heart-lung machine (Figure 1), as used during cardiac surgery for blood perfusion, oxygenation and rewarming of the body.

The operation was successful and it opened a new era of treatment for such victims. However, as these accidents are very rare, we performed a Swiss Multi-Centre Study with a follow-up of the patients five years after their survival to assess their physical and intellectual conditions. I directed this study and we achieved a 47% long-term survival rate after accidental deep hypothermic cardiac arrest. At follow-up, five years after the accident, all the 15 survivors had recovered their normal life and were sequelae-free. These findings were published in the New England Journal of Medicine, the world’s leading medical journal and from there on, this new rewarming and reviving treatment of patients in hypothermic cardiac arrest is used worldwide and therefore represents an innovation in medicine.

International Hypothermia Registry (IHR)

As not all international centres reported similar good results of a survival of about 50% as described in our study, and the fact that deep accidental hypothermia with cardiac arrest is rare with concomitant factors playing a role for survival, I initiated, together with Dr. Marie Meyer at the University Hospital in Geneva, the IHR in 2010. This Registry now contains data from more than 250 patients from all five continents and over 50 international centres actively participate. Recently an analysis of these data from the last 10 years was published in the journal Resuscitation and focuses on negative and positive survival predictors thus aiming at improving the outcome of the patient and helping the rescue teams on-site and hospital teams to make right decision. www.hypothermia-registry.org

Danger of winter sports

Besides many dangers of winter sports such as ski accidents and sometimes avalanches as related in the last SAS News, hypothermia may also represent a danger which can lead to death. Hypothermia is when the body core temperature falls below 36°C and is divided into mild, moderate, and severe stages. Mild hypothermia consists mainly of cold sensation, shivering and can be treated with warm clothes and drinks. Moderate hypothermia already represents a danger zone and medical help should be sought. Severe hypothermia (with body temperature below 28°C) is a lifethreatening condition and most of the victims are comatose, with or without cardiac arrest, and need to be transported immediately to a centre where they can be rewarmed by extra-corporeal life support using a heart-lung machine. (Figure 2)

The world’s deepest hypothermic survivor was a young Norwegian doctor who was found after a skiing accident with a temperature of 13.7°C. She was rewarmed with our method, followed by a long rehabilitation leading to normal professional and recreational life. Several factors influence the chance of survival of such patients, namely if the victim had some vital signs before rescue. To the contrary, victims of an avalanche may succumb early due to asphyxia (impossible to breathe under the avalanche).

Major advance in the treatment of deep accidental hypothermia victims in cardiac arrest has been achieved with prolonged use of a modified heart-lung machine (ECMO), with the possibility to support the patient’s circulation and respiration for a longer period than the conventional heart-lung machine as used in cardiac surgery.

7th International Symposium on Accidental Hypothermia

In order to foster the knowledge of accidental hypothermia treatment, we created a biannual meeting which involves mainly medical doctors such as emergency, anaesthesia and surgery specialists, as well as terrestrial and air-borne rescue services. Last year’s meeting was the first post-pandemic event and brought together around 200 participants from all over the world and was organized by Mathieu Pasquier, MD, Evelien Cools, MD and myself, from the Universities of Lausanne and Geneva. The SASlers, Dr. Louis Marxer, emergency physician, representing GRIMM, a rescue organization from the Valais, as well as Amélie Dupasquier, medical student from Lausanne, both participated actively in the meeting. ( Figure 3 ) During the meeting not only results from the IHR were presented but also the

HOPE Score which is a multi-variable predictor for survival to be used when victims arrive at the hospital.

For more information on this subject, please also consult the 2018 Schneehase.

1 Heart-lung machine used to rewarm the blood of hypothermic victims.

2 Rescue of a hypothermic crevasse victim.

3 & 4 Beat Walpoth with Louis Marxer and Amélie Dupasquier at the 7th International Symposium on Accidental Hypothermia in Lausanne

Louis Marxer

«C'est un honneur pour nous, jeunes médecins travaillant dans le domaine des urgences, des soins intensifs et au sein du GRIMM (Groupe de Recherche et d'Intervention médical en montagne (www.grimm-vs.ch) d'avoir accès au Symposium sur l'hypothermie, tel que celui organisé par Beat et son équipe en 2022 à Lausanne. Les résultats des recherches portés à notre connaissance permettent une adaptation préclinique et clinique de la prise en charge de nos patients, notamment en Valais et dans le domaine du secours en montagne, en gardant à l'esprit que nous pouvons tous être touchés par cette problématique médicale.»

"The symposium on accidental hypothermia was a great opportunity to get closer to mountain medicine, which fascinates me. My master thesis is about hypothermic patient in cardiac arrest at the hospital in Sion. Taking part in this symposium immersed me in the subject, seeing the progress of the research and the questions that still arise. It is motivating to see all these people passionate about the same subject."