British Military freezing cold injuries: a 13-year review

Cold Injury

Cold injury has been documented for centuries and remains a concern for military personnel, winter recreationalists, and urban homeless populations. Treatment advances in the last decades have included thrombolytic and prostaglandin therapies however the mainstay remains early recognition and rapid rewarming. This chapter focuses on frostbite, with a brief overview of other cold related conditions.

Designing suitable shoes to prevent foot frostbite through optimization of the geometric dimensions of the shoe and sock model

To prevent frostbite in cold environments, proper dimensions and materials for different parts of shoes along with the optimal design of shoe geometry were investigated. Furthermore, the optimal geometry of shoes was computed using an optimization algorithm to provide maximum thermal protection for the foot while having the lowest weight. The results showed that the length of the shoe sole and the thickness of the sock are the most effective parameters in foot protection against frostbite. Using thicker socks, which only increased the weight by roughly 11%, enhanced the minimum foot temperature by more than 2.3 times. HIGHLIGHTSOptimal design of shoe geometry is used to prevent frostbite in cold environments.A model of a biothermal nonlinear model is developed for the barefoot.Length of the shoe sole and the thickness of the sock are the most effective parameters in protecting the foot against frostbite.For the selected weather conditions, the toes are most likely to have frostbite.The best shoe for the selected weather conditions is the shoe that has the highest amount of thermal insulation in the toe area.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

Can iloprost be used for treatment of cold weather injury at the point of wounding in a forward operating environment? A literature review

INTRODUCTION

Cold Weather Injury (CWI) represents a spectrum of pathology, the two main divisions being Freezing Cold Injury (FCI) and Non-Freezing Cold Injury (NFCI). Both are disabling conditions associated with microvascular and nerve injury often treated hours after initial insult when presenting to a healthcarestablishment. Given that iloprost is used for the treatment of FCI, could it be used in a forward operating environment to mitigate treatment delay? Is there a role for its use in the forward treatment of NFCI? This review sought to evaluate the strength of evidence for the potential use of iloprost in a forward operating environment.

METHODS

Literature searches were undertaken using the following question for both FCI and NFCI: in [patients with FCI/NFCI] does [the use of iloprost] compared to [standard care] reduce the incidence of [long-term complications]. Medline, CINAHL and EMBASE databases were searched using the above question and relevant alternative terminology. Abstracts were reviewed before full articles were requested.

RESULTS

The FCI search yielded 17 articles that were found to refer to the use of iloprost and FCI. Of the 17, one referred to pre-hospital treatment of frostbite at K2 base camp; however, this was utilising tPA. No articles referred to pre-hospital use in either FCI or NFCI.

DISCUSSION

Although evidence exists to support the use of iloprost in the treatment of FCI, its use to date has been in hospital. A common theme is delayed treatment due to the challenges of evacuating casualties from a remote location. There may be a role for iloprost in the treatment of FCI; however, further study is required to better understand the risk of its use.

A preliminary study of the thermal strain experienced by dive support boat personnel

Anecdotal evidence indicated some British military dive support boat personnel suffer from uncomfortably cold hands and feet, which could impair their performance and be associated with reductions in core body temperature. This study collected preliminary data on thermal stress and cognitive performance of personnel taking part in a cold-weather training exercise. Six men were monitored during four boat transits in a range of climatic conditions (air temperature +1.2°C to -10.5°C, wind chill -4.5°C to 19.3°C). Core body temperature was measured with a radio pill and 12 skin sites (ISO 9886 plus hand, finger, foot and toe) with iButtons or thermistors. Self-reported thermal comfort and thermal sensation was also recorded. Reaction time and selective attention were measured pre- and post-transit. Participants' physical characteristics and personal clothing ensembles were recorded. No participant became hypothermic. Most participants' hand, foot and digit temperatures fell to below 15°C, indicating a risk of impaired dexterity, in addition to that arising from gloves. During the trial, hand and digit temperatures occasionally fell below 10°C. The limited data collected showed personal clothing choices could provide adequate thermal protection for these conditions and temperatures, and highlighted inter-individual variation and the need to allow for significant variation of day-to-day environmental conditions.

Experiences of frostbite injury from recreational use of nitrous oxide canisters in a UK burns center: Not a laughing matter

Nitrous oxide is used as a recreational drug. Contact frostbite injury from compressed gas canisters has previously been described in the literature, but an increased number of such cases has been noted in our busy regional burns center in the UK. A single-center prospective case series of all patients referred and treated for frostbite injury secondary to misuse of nitrous oxide compressed gas canisters between January and December 2022 is presented. Data collection was performed through a referral database and patient case notes. Sixteen patients, of which 7 were male and 9 were female, satisfied the inclusion criteria. Mean patient age was 22.5 years. The median TBSA was 1%. In total, 50% of patients in the cohort had a delayed initial presentation to A&E of greater than 5 days. Eleven patients were reviewed at our burns center for further assessment and management. In total, 11 patients had bilateral inner thigh frostbite injuries, of which 8 had necrotic full-thickness injury, including subcutaneous fat. Seven patients were reviewed at our burns center and offered excision and split-thickness skin graft. Four patients presented with contact frostbite injury to the hand and one patient to the lower lip. This subgroup was managed successfully with conservative management alone. The reproducible pattern of frostbite injury secondary to the abuse of nitrous oxide compressed gas canisters is demonstrated in our case series. The distinct pattern of injury, patient cohort, and anatomical area affected presents an opportunity for targeted public health intervention in this group.

Abstracts from The Cold Weather Operations Conference 2021

A common effort for both military and civil healthcare is to achieve knowledge-based health care in cold weather injuries and fatal accidents in harsh arctic environment. The Cold Weather Operations Conference in November 2021, having more than 300 participants from 20 countries, was addressing the prevention and treatment of injuries and trauma care in cold weather conditions and the challenges for military prehospital casualty care. The intention of the programme was to stimulate further research and systematic knowledge-based clinical work. The abstracts from the conference present cold weather research and clinical experience relevant for readers of the International Journal of Circumpolar Health.

Pharmacokinetics and tissue distribution of Trans-ferulic acid-4-β-glucoside in rats by UPLC-MS/MS

Trans-ferulic acid-4-β-glucoside (FAG) is a monomer extracted from Radix Aconiti Lateralis Preparata, which is a potential candidate for the prevention and treatment of the cold injury. To determine the concentration FAG in rats, it is essential to develop an ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method. The chromatographic separation was achieved by ACQUITY UPLC BEH C18 column(2.1×50mm, 1.7μm). A Xevo triple quadrupole tandem mass spectrometer was used to quantitative determination of FAG in the negative ion mode. The standard calibration curve was linear over the concentration range of 0.1-100 μg/mL and 0.0626-31.28 μg/g for rat plasma and liver tissue homogenates samples, separately. The inter-and intra-batch precision (RSD%) of the assay was ≤ 8.29% and accuracy (RE%) ranged from -7.41 to 10.99%. The matrix effect was between 92.99 and 102.39%. The oral absolute bioavailability of FAG was obtained as 1.80%. The results of tissue distribution suggested that FAG spread rarely in liver and brown adipose, which was not propitious to exert its ability to treat cold injury. In general, the above studies were significant to provide necessary information for further study.

ACSM Expert Consensus Statement: Injury Prevention and Exercise Performance during Cold-Weather Exercise

ABSTRACT

Cold injury can result from exercising at low temperatures and can impair exercise performance or cause lifelong debility or death. This consensus statement provides up-to-date information on the pathogenesis, nature, impacts, prevention, and treatment of the most common cold injuries.

Frostbite injuries: independent predictors of outcomes

Objectives

Frostbite injuries are important causes of morbidity and mortality after trauma. Epidemiology, injury patterns, and outcomes after frostbite among patients presenting to trauma centers are incompletely defined. The purpose of this study was to delineate patient demographics, clinical characteristics, and independent predictors of outcomes after frostbite.

Material and Methods

Patients with frostbite injury were identified from the National Trauma Data Bank (NTDB) (2007-2014). Demographics, clinical/injury data, and outcomes were collected. Patients were dichotomized into study groups based on intensive care unit (ICU) admission. Univariate analysis was performed with the Mann-Whitney U, Fisher's exact, or Chi-Square test as appropriate. Multivariate analysis using logistic regression determined independent predictors of outcomes.

Results

Over the study period, 241 patients were identified. Median body temperature on admission was 36.3⁰C (IQR 33.4-36.7). Mortality was 3% (n= 7). ICU admission was required in 101 (42%) patients and 48 (20%) underwent surgical intervention. On multivariate analyses, mortality was predicted by lower admission GCS (p= 0.027) and amputation by higher HR (p= 0.013). Need for ICU admission was predicted by older age (p= 0.010), male gender (p= 0.040), higher HR (p= 0.031) and ISS (p <0.001), and lower GCS (p= 0.001). Prolonged hospital LOS was predicted by higher heart rate (p <0.001) and ISS (p <0.001).

Conclusion

Frostbite injuries are uncommon but can necessitate surgical intervention and cause mortality. Lower GCS and higher heart rate, but not body temperature, portend poor outcomes. These findings can be used to triage patients appropriately upon admission and to better inform prognosis after frostbite injuries.

Ski-Everest (8848 m) Expedition: Digit Skin Temperature Responses to Cold Immersion May Reflect Susceptibility to Cold Injury

INTRODUCTION

We tested the hypothesis that individual susceptibility to freezing cold injury might be reflected in an attenuated cold-induced vasodilatation (CIVD) response by comparing the CIVD responses of an elite alpinist with a history of freezing cold injury in the feet (case alpinist) with those of an age- and ability- matched noninjured alpinists control group (controls). According to this hypothesis, the vasomotor responses to a CIVD test of the case alpinist would represent a pathophysiological response when compared with the normal physiological response of a noninjured cohort.

METHODS

The case alpinist and the controls in the cohort group conducted a cold water immersion test comprising sequential immersion of a hand and foot for 5 min in 35°C water, followed by a 30-min immersion in 8°C water and a 10-min recovery period in room air. During this test we monitored the finger and toe skin temperatures.

RESULTS

The case alpinist had a significantly attenuated CIVD response and a lower skin temperature in all injured and noninjured digits during immersion (∼2°C lower than in the control group) and an attenuated recovery of finger skin temperatures (∼6°C lower than in the control group).

CONCLUSIONS

The attenuated CIVD response of the case alpinist may reflect a previously unrecognized enhanced susceptibility to frostbite. In addition to the poor vasomotor response observed in the injured toes, he also exhibited a poor vasomotor response in his noninjured fingers. The results of the present study indicate that a test of vasomotor activity during thermal stress may identify individuals predisposed to cold injury.