Cold physiology: What to do in case of hypothermia?

Two CERG post doctors, Trine Karlsen and Svein Erik Gaustad are spending this week at the enjoy the cold physiology class in Ny-Ålesund, Spitsbergen, a research station run by the Kings Bay company at 79 degrees north. The class is organized by the hyperbaric research group at Department of Circulation and Medical Imaging at NTNU, with participants from the Norwegian and Swedish armies, Norwegian petroleum companies and departments, the University of Tromsø and NTNU. The class is a mixture of theoretical and practical training in how to plan and behave when exposed to the artic climate. For the oil and shipping industry this is vital knowledge for the coming artic expansion.

Hypothermia and circulation
A person is hypothermic when core temperature drops below 35 degrees Celsius. At this temperature the body is unable to increase body temperature by self-produced heat when remaining in the cold environment. At core temperatures of 28 degrees, severe hypothermia is present and is associated with unconsciousness and cardiac arrhythmias.  Individuals may reach exhaustion already at mild to moderate hypothermia due to increased bodily stress.

The respiratory rate increases significantly, and heart rate may be close to maximum early during core cooling.  When core temperature continues to decrease to 25°C degrees, heart rate decreases dramatically to values as low as 25 beats per minutes. At this point the risk of ventricular fibrillation and cardiac arrest increases dramatically, and must be accounted for when transporting and treating severely hypothermic individuals.

How to rescue a hypothermic individual
To rescue a hypothermic individual, observation of breathing frequency is critical. Remember, you will not be able to feel any peripheral pulse. In severe hypothermia, breathing frequency may be as low as 2-3 breaths per minute. To rescue hypothermic individuals call 113 (In Norway) and request medical assistance and transport to hospital. If you cannot detect proper breathing, start immediate CPR (30 by 2) and continue CPR until the patient is admitted to a hospital that can offer rewarming by heart-lung machine.

While waiting for medical assistance, keep the hypothermic individual in the supine position (lying down, face up) to maintain blood pressure and the circulation of blood through the heart. Do not change position to sitting or standing! While waiting for medical assistance, prevent further heat loss in the individual by removing wet clothing, but take great care to avoid rapid movement of body parts or position. In general, treat the individual as your most precious crystal glass in order to prevent arrhythmias from occurring.

Rewarming a hypothermic patient is critical and requires medical expertise as cardiac problems with re-warming shock and and a high incidence of cardiac arrest is common. At the University of Tromsø, world-leading research on rewarming in hypothermic animals is currently being done to improve medical treatment.

Thanks to Professor Torkjel Tveita  at the University of Tromsø and UNN for summarizing the facts of heart function in hypothermia. 

Written by Trine Karlsen, Post Doc at CERG.