Historically, hypothermia, cold injuries and frostbite have claimed many human lives and inflicted debilitating injuries on a considerable number of military personnel. In the Great Northern War in the 18th century, cold weather was probably the greatest challenge during General Armfeld's retreat, later known as the 'Death March', where half of his army succumbed to the cold (1). In 1982, a considerable number of British special forces personnel sustained frostbite during the Falklands War (2).
Today, the Norwegian Armed Forces act as a centre of excellence in relation to frostbite within NATO, Center of Excellence – Cold Weather Operations (3), and a large number of foreign troops undertake winter training in Norway, including in the Armed Forces School of Winter Operations. Army personnel and conscripts nevertheless sustain frostbite during exercises and other service. Although the quality of equipment and clothing is excellent, the Armed Forces' annual reports confirm that a considerable number of injuries and health problems occur as a result of military activity, especially winter exercises (4).
Published literature on the diagnosis of cold injuries and frostbite has a varying level of precision. The confusion around terminology has a number of reasons. For example, cold injuries and frostbite are divided among several specialties, little research has been undertaken in this area and there is little correspondence between the terminology used in different countries. The distinction between different types of injuries, the degree of severity, treatment and prognosis is made even more challenging since the term 'cold weather injury' (CWI) is commonly used in international medical literature.
The term 'cold weather injury' is imprecise and sometimes encompasses three quite different injuries (5):
frostbite (tissue temperature below -0.55 °C)
cold injury (hypothermic peripheral tissue, but with temperatures above the freezing point of the tissue: -0.55 °C)
general hypothermia (the core temperature of the body falls below 35.0 °C).
In principle, frostbite occurs in temperatures below the freezing point of the tissue, which is -0.55 °C (6, 7). Below this temperature cell damage occurs with a subsequent inflammation process and disruption of the local microcirculation. Local frostbite with a specific 'frostbite pathophysiology' does not occur in temperatures above the freezing point of the tissue. International medical literature uses the term 'frostbite' and 'freezing cold injuries' (FCI) to denote such injuries. In the Norwegian nomenclature, we should use 'frostskade' (frostbite) consistently wherever symptoms and findings indicate that the tissue temperature has dropped below -0.55 °C.
Cold injuries develop when the peripheral skin on the extremities is exposed to high levels of moisture in combination with cooling, commonly approaching but not falling below the freezing point of the tissue (8). Cold injuries commonly occur at temperatures down to 0 °C. However, lengthy exposure to moisture in combination with ambient temperatures as high as 20 °C may also result in 'cold-injury pathophysiology', especially neuropathy. Cold injuries may in principle affect any part of the body, but occurs most frequently on the feet, hence the historical names of 'trench foot' or 'lifeboat foot'. International medical literature tends to use the term 'non-freezing cold injuries' (NFCI) to refer to cold injuries. In the Norwegian nomenclature we should be specific and use the term 'kuldeskade' (cold injury) where symptoms and findings indicate that the tissue temperature has been lowered, but not below the freezing point of tissue.
Hypothermia is defined as a lowering of the body's core temperature to below 35 °C. Traditionally, hypothermia has been divided into mild, moderate and severe forms (9). A lowering of the body's core temperature by 1–2 degrees may cause drowsiness and disruption of bodily functions, while a lowering by 4–5 degrees may be fatal (10). Severe hypothermia may frequently be life-threatening (arrhythmia) in otherwise healthy patients. In case of trauma or other co-morbidity, mild hypothermia will often be life-threatening, for example as a result of bleeding. New clinical recommendations for treatment of patients with lowered core temperature emphasise reporting of consciousness, shivering, respiration and pulse rate for selection of an appropriate level of treatment (11). The new clinical recommendations are divided into four levels (mild, moderate, severe, deep) and comply with international standards (12).
When tissue is exposed to temperatures below the freezing point of the skin (-0.55 °C), ice crystals may form within the cells. The ice crystals rupture the cells and blood vessels and cause cell death. When only the skin surface is frozen, a white patch ('chilblain') is observed, which normally will be a Grade 1 frostbite (13). If the frostbite continues, deeper layers of the skin can become affected and oedemas and blisters may appear, possibly indicating a Grade 2 frostbite. If the injury develops further, a deeper frostbite will occur in tissue below the level of the skin (14).
A considerable proportion of patients with peripheral frostbite suffer permanent changes in their microcirculation and disruption of neurological functions. Depending on the extent of injury, general functioning and ability to work may be impaired by vasospasm, hypersensitivity to cold, pain and hyperhidrosis (15). Permanent paraesthesia involving sensations of electric shock (16), growth-plate disruptions and osteoarthritis may exacerbate the course of illness (13, 17).
A possible challenge in diagnosing mild frostbite (Grade 1) could be that the symptoms fluctuate, making an exact diagnosis difficult. For severe frostbite (Grades 2–4), somewhat clearer clinical criteria are provided (16) (Table 1).
Clinical criteria and levels of frostbite (7, 14, 16)
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Symptoms and findings
Reddish skin, swelling, numbness, stinging discomfort ('frostnip'), white patches ('chilblains')
Partial intradermal frostbite
Pronounced hyperaemia, blisters filled with clear fluid, superficial erosions, severe pain (gradually reduced sense of pain)
Complete dermal frostbite
Blisters filled with bloody fluid, bluish-white discoloration of the skin, necrosis, significantly reduced sensation of pain
Injury down to the subcutaneous tissue
Deep red/bluish-black discoloration of the skin, skin is firm and immobile, full- thickness oedema, tissue necrosis, no sensation of pain
Injury to muscles and bone
In addition to preventive measures, the literature also describes initial emergency treatment and recommendations for further clinical follow-up and therapy. However, the prognosis and long-term course of severe frostbite has not previously been investigated in larger cohorts.
The Armed Forces Health Registry is a central health registry (18) that contains data from Armed Forces personnel (9), including conscripts as well as civilian and military staff employed by the Armed Forces. The objective of the registry is to identify risks linked to the different services and provide a basis for research and statistics on the health of Armed Forces personnel. The types of personal data that can be processed are defined by Section 1–8 of the Regulations concerning the collection and processing of information in the Armed Forces Health Registry (19).
Pursuant to the regulations, the registry may contain personal information, administrative information, medical information and workplace information. The information in the Armed Forces Health Registry is drawn from Armed Forces medical records and HR systems, as well as internal health surveys. The Ministry of Defence is the data controller and the Armed Forces Medical Services is the data processor. Medical and operational responsibility lies with the Institute of Military Medicine and Epidemiology, Norwegian Armed Forces Joint Medical Service, at Sessvollmoen camp.
Data from the health registry contribute increasingly to research seeking to identify health injuries during, or as a consequence of, military service (20–22). A separate module of the SANDOK patient records system has been developed to collect data on illness, injury and death.
In this study, we will investigate how many of those who are registered in the Armed Forces Health Registry with frostbite that occurred during military service can confirm that they sustained this injury. Furthermore, we will investigate the degree of frostbite, the location of the injury, activities at the time of injury and the long-term course of illness.