Freezing and non-freezing cold weather injuries: a systematic review

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.

Freezing cold injuries among soldiers in the Norwegian Armed Forces - A cross sectional study

INTRODUCTION

Freezing cold injuries (FCI) are a common risk in extreme cold weather warfare operations. The Norwegian Armed Forces (NAF) have the expertise and capabilities in education and training for warfighting capabilities in the Arctic. Nevertheless, a substantial number of Norwegian soldiers sustain freezing cold injuries annually. The aim of this study was to describe the FCI in the NAF, the associated risk factors and clinical associations.

METHODOLOGY

The subjects for the study were soldiers registered with FCI in the Norwegian Armed Forces Health Registry (NAFHR) between January 1st 2004-July1st 2021. The soldiers answered a questionnaire regarding background, activities at the time of injury, description of the FCI, risk factors, medical treatment and any sequelae from their FCI.

RESULTS

FCI in the NAF were most frequently reported among young conscripts (mean20.5 years). Hands and feet are most often injured (90.9%). Only a minority (10.4%) received medical treatment. The majority (72.2%) report sequelae. Extreme weather conditions was the most important risk factor (62.5%).

CONCLUSIONS

Most soldiers had the knowledge to avoid FCI, but they were injured anyway. It is concerning that only one in 10 injured soldiers received medical treatment after diagnosed with FCI, increasing the risk of FCI sequelae.

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.

The classification of freezing cold injuries - a NATO research task group position paper

INTRODUCTION

Freezing cold injuries (FCI) are a common risk in extreme cold weather operations. Although the risks have long been recognised, injury occurrences tend to be sparse and geographically distributed, with relatively few cases to study in a systematic way. The first challenge to improve FCI medical management is to develop a common nomenclature for FCI classification. This is critical for the development of meaningful epidemiological reports on the magnitude and severity of FCI, for the standardisation of patient inclusion criteria for treatment studies, and for the development of clinical diagnosis and treatment algorithms.

METHODOLOGY

A scoping review of the literature using PubMed and cross-checked with Google Scholar, using search terms related to freezing cold injury and frostbite, highlighted a paucity of published clinical papers and little agreement on classification schemes.

RESULTS

A total of 74 papers were identified, and 28 were included in the review. Published reports and studies can be generally grouped into four different classification schemes that are based on (1) injury morphology; (2) signs and symptoms; (3) pathophysiology; and (4) clinical outcome. The nomenclature in the different classification systems is not coherent and the discrete classification limits are not evidence based.

CONCLUSIONS

All the classification systems are necessary and relevant to FCI medical management for sustainment of soldier health and performance in cold weather operations and winter warfare. Future FCI reports should clearly characterise the nature of the FCI into existing classification schemes for surveillance (morphology, symptoms, and appearance), identifying risk-factors, clinical guidelines, and agreed inclusion/exclusion criteria for a future treatment trial.

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.

Development of interactive guidance for cold exposure using a thermoregulatory model

For decades, the Wind Chill Temperature Index (WCT) and its various iterations have been used to assess the risk of frostbite on unclothed body parts. This paper presents an innovative knowledge-based Cold Weather Ensemble Decision Aid (CoWEDA) that can be used to guide the selection of the most appropriate cold weather ensemble(s) relative to anticipated mission physical activities and environmental conditions. CoWEDA consists of a validated six-cylinder thermoregulatory model, a database of clothing properties, algorithms for calculating the whole ensemble properties from individual garments and a graphical user interface. The user-friendly CoWEDA allows users to select from an inventory of clothing items to build an ensemble suitable for their needs. CoWEDA predicts the risks of both frostbite and hypothermia and ensures that a selected clothing ensemble will provide adequate protection to prevent cold injury. CoWEDA predictions provide not only estimates of frostbite risk similar to WCT tables but also hypothermia times and clothing required to prevent cold injuries. In addition, a CoWEDA model variant can predict survivability and clothing requirements during cold water immersion. Thus, CoWEDA represents a significant enhancement of the WCT-based guidance for cold weather safety and survival by providing greater individual fidelity in cold injury predictions.

Heat, Cold, and Environmental Emergencies in Athletes

With the increase in outdoor events, there is an inevitable rise in climate-related environmental emergencies. Heat exposure can place athletes at risk for life-threatening heatstroke which requires emergent diagnosis and rapid in-field management. Cold exposure can lead to hypothermia, frostbite, and other nonfreezing injuries that require prompt evaluation and management to minimize morbidity and mortality. Altitude exposure can lead to acute mountain sickness or other serious neurologic or pulmonary emergencies. Finally, harsh climate exposure can be life-threatening and require appropriate prevention and event planning.

The Effects of Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor Gel on Third-Degree Frostbite Wounds in Northeastern China: A Randomized Controlled Trial

The aim of the study was to investigate the effects of the rhGM-CSF gel on third-degree frostbite wounds. Sixty-two patients who had suffered third-degree frostbite on their hand or foot (91 wounds in total) were selected using a convenience sampling method and randomly allocated to two groups: the rhGM-CSF group(31patients,45 frostbite wounds) received the rhGM-CSF gel when wound dressing change daily; however, the control group (31patients, 46 frostbite wounds) received aloe glue. The wound healing time, the score of inflammation about the wound and the positive bacterial culture of wound secretions were used to measure outcomes, respectively. Data were analyzed using SPSS (25.0), Student's t test or Mann-Whitney U test and chi-square test or Fisher exact test were selected, as appropriate. The healing time of the rhGM-CSF group was (12.2 ± 5.0) days, which was significantly shorter than that of the control group (15.5 ± 4.7) days (P < .0001). The rhGM-CSF group's wound inflammation scores on the 7th and 14th day of treatment were (0.96 ± 0.21) and (1.88 ± 0.29), respectively, which were better than those of the control group (1.12 ± 0.24) and (1.38 ± 0.15) (both P < .0001). The positive bacterial culture of wound secretions in the rhGM-CSF group was also better than that in the control group on the 3rd, 7th, and 14th day after treatment (P = .027, .004, .030, respectively). According to the results, using rhGM-CSF gel considerably increases the speed of frostbite wounds healing, and have an effect on protecting third-degree frostbite wounds regarding the positive effects. Trial Registration: This trial was registered in the Chinese Clinical Trial Register, ChiCTR1900021299.

Frostbite: a systematic review on freezing cold injuries in a military environment

BACKGROUND

Military practice or deployment in extreme conditions includes risks, dangers and rare disorders. One of the challenges is frostbite; however, current literature does not provide an overview of this condition in a military context. This review aims to map the incidence, risk factors and outcome of frostbite in military casualties in the armed forces.

METHODS

A systematic literature search on frostbite (freezing cold injuries) in military settings from 1995 to the present was performed. A critical appraisal of the included articles was conducted. Data on incidence, risk factors, treatment and outcome were extracted.

RESULTS

Fourteen studies were included in our systematic review. Most studies of frostbite in a military setting were published nearly half a century ago. Frostbite incidence has declined from 7% to around 1% in armed forces in arctic regions but could be as high as 20% in small-scale arctic manoeuvres. Overall and military-specific risk factors for contracting frostbite were identified.

CONCLUSION

During inevitable arctic manoeuvres, frostbite is a frequently diagnosed injury in service members. Postfreezing symptoms often persist after severe frostbite injury, which decreases employability within the service. Over time, military practice has changed considerably, and modern protective materials have been introduced; therefore, re-evaluation and future study in the military field are appropriate, preferably with other North Atlantic Treaty Organization partners.

A numerical tool for assessing human thermal safety and thermal comfort in cold-weather activities

This paper describes a newly developed software tool to evaluate human thermal safety and thermal comfort in cold-weather activities aimed at guiding users to arrange activity plans and select appropriate clothing ensembles. The software inputs include conditions of activity, environment, human body, and clothing ensemble. It outputs physiological temperatures, cold injury risks, thermal sensations, and thermal comforts in intuitive ways like cloud maps and curves. The software tool is characterized by (1) integration of a thermoregulatory model that predicts human thermophysiological responses under exercise conditions in cold environments, (2) the functions of clothing ensemble database and individual parameter database, (3) the human centric outputs that directly reflect human physiological and mental status, and (4) the user-friendly operation interface and output interface, as well as a wide applicability. The software is validated with human test studies covering ambient temperatures from - 30.6 to 5 °C, clothing ensembles from 1.34 to 3.20 clo, and activity intensities from 2 to 9 Mets. The average prediction RMSEs of core temperature, mean skin temperature, thermal sensation, and thermal comfort are 0.16 °C, 0.45 °C, 0.58, and 1.41, respectively. The software is an advanced expansion to current standards and guidance of cold exposure assessment and a meaningful tool for the fields of occupational health care, cold protection, and environmental ergonomics.

Health effects of voluntary exposure to cold water - a continuing subject of debate

This review is based on a multiple database survey on published literature to determine the effects on health following voluntary exposure to cold-water immersion (CWI) in humans. After a filtering process 104 studies were regarded relevant. Many studies demonstrated significant effects of CWI on various physiological and biochemical parameters. Although some studies were based on established winter swimmers, many were performed on subjects with no previous winter swimming experience or in subjects not involving cold-water swimming, for example, CWI as a post-exercise treatment. Clear conclusions from most studies were hampered by the fact that they were carried out in small groups, often of one gender and with differences in exposure temperature and salt composition of the water. CWI seems to reduce and/or transform body adipose tissue, as well as reduce insulin resistance and improve insulin sensitivity. This may have a protective effect against cardiovascular, obesity and other metabolic diseases and could have prophylactic health effects. Whether winter swimmers as a group are naturally healthier is unclear. Some of the studies indicate that voluntary exposure to cold water has some beneficial health effects. However, without further conclusive studies, the topic will continue to be a subject of debate.

Frostbite of The Extremities - Recognition, Evaluation and Treatment

OBJECTIVES

Frostbite refers to the freezing of body tissue which is caused by prolonged exposure to cold temperatures and results in tissue destruction. Tissue damage is due to both immediate cold-induced cell death and the more gradual development of localized inflammatory processes and tissue ischemia. A detailed treatment plan based on the current UpToDate literature is needed to decrease morbidity and mortality rates.

METHODS

The United States National Library of Medicine (PubMed/Medline), EMBASE, Web of Science, and the Cochrane Database of Systematic Reviews were systematically searched to identify publications relevant to this review.

CONCLUSION

In this review, we present the current knowledge on the diagnosis and treatment of frostbite injuries. We then provide an extended and detailed treatment plan, from first aid in the field to treatment of short and long-term complications .

Biopsychosocial factors associated with complications in patients with frostbite

Cold weather injuries can be devastating and life changing. Biopsychosocial factors such as homelessness and mental illness (especially substance use disorders [SUDs]) are known risk factors for incurring frostbite. Based on clinical experience in an urban level 1 trauma center, we hypothesized that complications following frostbite injury would be influenced by homelessness, SUDs, and other forms of mental illness. The aim of this study was to examine the relationship between biopsychosocial factors and both amputations and unplanned hospital readmissions after cold injuries. Patients admitted with a diagnosis of frostbite between the winters of 2009 and 2018 were included in this retrospective cohort study. Descriptive statistics and multivariable regression assessed factors associated with outcomes of interest. Of the 148 patients in the study, 40 had unplanned readmissions within 1 year. Readmitted patients were significantly less likely to have a stable living situation (48.7% vs 75.0%, P = .005) and more likely to have an SUD (85.0% vs 60.2%, P = .005) or other psychiatric disorder (70.0% vs 50.9%, P = .042). Homelessness and SUDs were independent predictors of unplanned readmission. Overall, 18% of frostbite injuries resulted in amputation. Any history of drug and/or alcohol use independently predicted amputations. The study results suggest that additional hospital and community resources may need to be marshaled to prevent vulnerable patients with biopsychosocial risk factors from having complications after frostbite. Complications place a high downstream burden on healthcare systems. Clinicians caring for frostbite patients with comorbid conditions can use these findings to inform care and discharge decisions.

Cardiovascular Stress and Characteristics of Cold-Induced Vasodilation in Women and Men during Cold-Water Immersion: A Randomized Control Study

Simple Summary

Cold-induced vasodilation is a phenomenon that refers to a paradoxical increase in finger temperature that sometimes occurs during cold exposure. Differences between sexes in cold-induced vasodilation have been explored in only a handful of studies. These studies investigated finger skin temperature but did not evaluate toe skin temperature, blood flow in the fingers or toes, clothing, as well as potential underlying mechanisms of cutaneous vasomotion. On the whole, our knowledge on the potential impacts of sex differences on CIVD is limited and this may have important implications for workers and how they cope with exposure to cold environments. The aim of the study was to investigate and compare cold-induced vasodilation and other cardiovascular responses between genders, during exposure to different environmental conditions. The present study demonstrated that women experienced elevated cardiovascular strain and higher frequency of CIVD reactions, particularly in the toes, compared to their male counterparts during cold-water immersion.

Abstract

Background: Cold-induced vasodilation (CIVD) is a phenomenon that refers to a paradoxical increase in finger temperature that sometimes occurs during cold exposure. The aim of this study was to compare CIVD responses between women and men, during exposure to different environmental conditions. Methods: Seven men and seven women participated in a matched controlled study consisting of a familiarization protocol followed by three experimental sessions (cool (10.8 °C WBGT), thermoneutral (17.2 °C WBGT), and hot (27.2 °C WBGT)). In each session, participants were asked to immerse their left hand and foot in warm water (35 ± 1 °C) for five minutes. Thereafter, the left hand and foot were immersed in cold water (8 ± 1 °C) for 40 min. After that, the left hand and foot were removed from the water and participants remained seated for five minutes. Results: For a matched thermal stress, women experienced an elevated cardiovascular strain (heart rate and in some cases mean arterial pressure) and higher frequency of CIVD reactions (men: 31 vs. women: 60) in comparison to their male counterparts. Conclusions: The present study demonstrated that women experienced elevated cardiovascular strain and higher frequency of CIVD reactions, particularly in the toes, compared to their male counterparts during cold-water immersion.

Early Use of Iloprost in Nonfreezing Cold Injury

Nonfreezing cold injury (NFCI) is caused by prolonged exposure to cold, usually wet conditions and represents a separate pathological entity from frostbite. The pathophysiology of NFCI is characterized by vasoconstriction and microcirculatory disturbance. Iloprost, a synthetic prostaglandin analogue with vasodilatory properties is a recognized adjuvant treatment in frostbite; however, its role in NFCI is unclear. We present a case of a 29-y-old man with severe NFCI to both forefeet after prolonged immersion in cold seawater. Initial treatment with passive rewarming, analgesia and aspirin was initiated. Infusion of iloprost was used within 24 h from presentation and was well tolerated. This resulted in reduced tissue loss compared to the apparent tissue damage documented during the initial assessment. Delayed surgical intervention allowed minor debridement and minor toe amputations, maintaining the patient's ability to ambulate. This case demonstrates the safe use of iloprost in acute NFCI and highlights the importance of delayed surgical intervention in patients presenting with severe NFCI.

Cold Weather Injuries: Initial Evaluation and Management

ABSTRACT

As more people take to extreme sporting activities and hobbies, the sports medicine physician should be proficient in early identification and initial sideline or field management of cold weather injuries. There is significant mortality and morbidity associated with these conditions. The most severe of these are hypothermia and frostbite, which have limited evidence for their field management. Nonfreezing cold injuries and chilblains are much rarer, although appropriate prevention and treatment strategies can be used to minimize harm to athletes. This article will provide the most updated recommendations for field or sideline evaluation and initial management of hypothermia, frostbite, nonfreezing cold injury, and chilblains.

Healthcare Utilization for Lateral Epicondylitis: A 9-Year Analysis of the 2010–2018 Health Insurance Review and Assessment Service National Patient Sample Data

This retrospective cross-sectional study examined healthcare utilization among 213,025 patients with lateral epicondylitis over a nine-year period using the 2010–2018 Health Insurance Review and Assessment Service (HIRA) data (ICD code M771). Healthcare utilization, types of treatment, and the route of the visit were analyzed with frequency analysis for Western medicine (WM) and Korean medicine (KM). The findings revealed that the number of patients visiting WM and KM facilities for lateral epicondylitis rose every year from 2010 to 2018. Over this period, the age distribution of patients was 45–54 years (39.93%), 55–64 (23.12%), and 35–44 years (21.07%), and there were slightly more female patients (53.66%) than male patients (46.34%). The number of claims for lateral epicondylitis tended to increase with decreasing average monthly temperature; an increased proportion of middle-aged patients (45–64 years) was the most evident. The most frequently performed interventions in WM were subcutaneous or intramuscular injection (injection), deep heat therapy (physical therapy), and spinal peripheral nerve block-axillary nerve block (treatment/operation); the most frequently performed intervention in KM was acupuncture (injection). For pharmacological treatment, analgesics and anti-inflammatory medications were most frequently prescribed. The findings can be useful for health policymakers and as foundational data for clinicians and researchers.

Extracellular vesicles from human hepatic progenitor cells accelerate deep frostbite wound healing by promoting fibroblasts proliferation and inhibiting apoptosis

Frostbites are cold tissue damages frequently observed at high altitudes and under extremely cold conditions. Though their incidence rate is low, the resulting impact in affected patients can be very serious, often leading to amputations. Clinical management and the prediction of outcome can be of utmost importance to frostbite patients. A possible use of stem cell-derived extracellular vesicles (EVs) has been suggested for cutaneous wound healing and we, therefore, tested their use for the treatment of deep frostbite wound. To this end, the impacts of hHPC-derived EVs were evaluated in an in vivo animal model comprising of Kunming female mice as well as studied in vitro for the mechanism. We first characterized the EVs and these hHPC-derived EVs, when applied to treat frostbite wounds, accelerated wound healing in the in vivo animal model, as assessed by wound closure, re-epithelization thickness, collagen density and the expression of Collagen I and α-SMA. The proliferation and migration of human skin fibroblasts was also found to be increased by EVs in the in vitro experiments. The H₂O₂-induced apoptosis cell model, established to simulate the post-frostbite injury, was inhibited by EVs, with concomitant increase in the expression of Bcl-2 and decreased expression of Bax, further confirming the findings. Our novel results indicate that the application of EVs might be a promising strategy for deep frostbite wound healing.

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.

A digital tool for prevention and management of cold weather injuries-Cold Weather Ensemble Decision Aid (CoWEDA)

This paper describes a Cold Weather Ensemble Decision Aid (CoWEDA) that provides guidance for cold weather injury prevention, mission planning, and clothing selection. CoWEDA incorporates current science from the disciplines of physiology, meteorology, clothing, and computer modeling. The thermal performance of a cold weather ensemble is defined by endurance times, which are the time intervals from initial exposure until the safety limits are reached. These safety limits correspond to conservative temperature thresholds that provide a warning of the approaching onset of frostbite and/or hypothermia. A validated six-cylinder thermoregulatory model is used to predict human thermal responses to cold while wearing different ensembles. The performance metrics, model, and a database of clothing properties were integrated into a user-friendly software application. CoWEDA is the first tool that allows users to build their own ensembles from the clothing menu (i.e., jackets, footwear, and accessories) for each body region (i.e., head, torso, lower body, hands, feet) and view their selections in the context of physiological strain and the operational consequences. Comparison of predicted values to skin and core temperatures, measured during 17 cold exposures ranging from 0 to -40°C, indicated that the accuracy of CoWEDA prediction is acceptable, and most predictions are within measured mean ± SD. CoWEDA predicts the risk of frostbite and hypothermia and ensures that a selected clothing ensemble is appropriate for expected weather conditions and activities. CoWEDA represents a significant enhancement of required clothing insulation (IREQ, ISO 11079) and wind chill index-based guidance for cold weather safety and survival.

Increased cold injuries and the effect of body mass index in patients with peripheral vascular disease

Background

Exposure to extremely or moderate low temperatures is associated with increased morbidity and mortality risk. Peripheral vascular disease (PVD) is a slow and progressive circulation disorder. Given that cold temperature causes constriction of the small arteries and veins in the skin, patients who suffer from peripheral circulation problems, like PVD, may be vulnerable to cold injuries. This study aimed to investigate the association between PVD and cold-induced injuries in the winter among Korean adults. We further analyzed the association stratified by body mass index (BMI) classification.

Methods

We used the 2002–2015 National Health Insurance Service-National Sample Cohort data and included a total of 535,186 adults as the study population. Patients with underlying PVD were identified by ICD-10 code I73. Cold-related illnesses were defined by ICD-10 codes (T690, T691, T698, T699, T330 ~ T339, T340 ~ T349, and T350 ~ T357). Body mass index (BMI) was categorized into underweight, normal weight, overweight, and obese.

Results

A total of 23.21% (n = 124,224) were PVD patients, and 0.59% (n = 3154) had cold-induced injuries. PVD patients were more likely to be diagnosed with cold injuries, but it was valid only in the underweight or normal weight groups. After adjusting for age, sex, income, cigarette smoking, alcohol consumption, regular exercise, high blood pressure, and hyperglycemia, PVD patients had a significantly increased odds ratio (OR) for cold injuries [adjusted OR = 1.11; 95% confidence intervals (95% CI): 1.01–1.21]. Increased OR for cold injuries in PVD patients was also observed in adults (adjusted OR = 1.14; 95% CI: 1.03–1.25 in Model 2), but not in the elderly. When we classified study subjects into the four BMI groups, the adjusted OR of cold injuries in PVD patients was significant in the underweight group (OR = 1.83; 95% CI, 1.26–2.66) and normal weight group (OR = 1.15; 95% CI, 1.03–1.27), not in those with overweight and obese. In adults, a consistent result was found in adults in the underweight group (OR = 1.63; 95% CI, 1.08–2.47 in Model 2) and normal weight group (OR = 1.19; 95% CI, 1.07–1.33 in Model 2). In the elderly, the adjusted OR for cold injuries was only significant in the underweight group (OR = 3.37; 95% CI, 1.08–10.53 in Model 2).

Conclusions

We found a significant association between PVD and cold-induced injuries in the general population. BMI modified the association. Thus, the association observed appears to be clinically applicable to PVD patients being low to normal BMI.

Expert consensus on the prevention, diagnosis and treatment of cold injury in China, 2020

Cold injury refers to local or systemic injury caused by a rapid, massive loss of body heat in a cold environment. The incidence of cold injury is high. However, the current situation regarding the diagnosis and treatment of cold injury in our country is not ideal. To standardize and improve the level of clinical diagnosis and treatment of cold injury in China, it is necessary to make a consensus that is practical and adapted to the conditions in China. We used the latest population-level epidemiological and clinical research data, combined with relevant literature from China and foreign countries. The consensus was developed by a joint committee of multidisciplinary experts. This expert consensus addresses the epidemiology, diagnosis, on-site emergency procedures, in-hospital treatment, and prevention of cold injury.

Using Intra-arterial tPA for Severe Frostbite Cases. An Observational Comparative Retrospective Study

Frostbite causes tissue damage through five major mechanisms, out of which two are amenable to treatment. The first-line treatment is rapid rewarming therapy using water at 40°C to 42°C, which addresses the formation of ice crystals in the intra and extra cellular compartments. The second mechanism is progressive tissue ischemia after rewarming and is only accessible to a second-line therapy represented by thrombolysis. This study aimed to determine the efficacy of thrombolysis. This is a single-center retrospective cohort study, where it was aimed to evaluate two groups of patients. A total of 18 patients were included in this study. Mean times between injury to thrombolytic therapy and admission to thrombolytic therapy was 26.04 hours (SD 13.6) and 9.65 hours (SD 9.89), respectively. All patients suffered injuries ranging from second-degree deep to third degree. The rate of patients having complete, partial, and no angiographic responses were 55.6%, 11.1%, and 33.3%, respectively. The main outcome of interest showed that 11 (61.1%) patients in total had amputations at different levels. Results showed that in the intervention group, five (55.6%) of the patients had amputations compared with six (66.7%) from the control group (P = .6) at comparable levels of amputation. The literature supports that the use of intra-arterial tissue plasminogen activator might be beneficial for severe cases of frostbites; however, it lacks of studies of major significance and results are often controversial. Our study has not shown statistically significant results on amputation levels and cannot support the hypothesis of efficacy of thrombolytic therapy.

Frostbite: Current status and advancements in therapeutics

Frostbite is a severe ischemic injury which occurs due to the tissue vascular damage after sub-zero temperature tissue exposure. Deep frostbite can result in necrosis and may need amputation of affected tissue. Though a serious injury, it is not very well understood, and further scientific exploration is needed. This work explores the current understanding of the pathophysiology of frostbite. We reviewed the current status of the diagnostics, the drugs, the therapies and the surgical practices for prevention and management of frostbite. Advances in nanotechnology and drug delivery had improved the therapeutic outcomes significantly. This review also explored the latest advancements and researches done for development of newer therapeutics and diagnostics for frostbite care.

Management and Outcome of Feet Deep Frostbite Injury (III and IV Degrees): A Series Report of 36 Cases

Deep feet frostbite is a severe trauma and often leads to amputation due to full-thickness skin necrosis and subcutaneous tissue damage. A retrospective analysis was performed between June 2013 and June 2019 to review the management measures and outcomes of clinical treatment, and available data had been collected including demographic characteristics, risk factors, and injury environment record. Treatment protocols, wound management, and outcomes were also presented. There were 36 patients diagnosed with deep feet frostbite with a mean age of 51.5 years; the ratio for male to female is 5:1. Drunk and mental disorders were the main risk behaviors for frostbite occurrence. As for the injury environment, mean temperature and wind speed were -20.5 °C and 3.3 m/s, respectively. Fourteen cases achieved wound healing without surgery intervention, 5 cases received skin graft, and 17 cases received amputation. Most amputations (12 cases) were restricted at toe level; only 1 case received whole feet amputation. Our finding indicated that feet deep frostbite in our hospital showed a male predominant and older age including various risk behaviors and coexistence risk factors. Clinical management based on pathology mechanism needs further improvement, as the amputation rate was still high. How to avoid amputation and lower the amputation level are the focus of future efforts.

Atypical replantation and reconstruction of frozen ear: A case report

RATIONALE

The first successful ear replantation was performed by Pennigton in 1980 in Sydney. At least 84 ear replantations have been described in the literature over a period of 37 years since the first case. The authors have not found any previous case of frozen ear replantation in the literature.

PATIENT CONCERNS

We report the case of a 38-year-old man, who had an injury to the head while working with a machine.

DIAGNOSIS

The patient suffered total traumatic avulsion of the left ear. The ear was wrapped in moistened, sterile gauze and was transported on dry ice. At the time of admission to our department, the amputated ear was frozen to stiff, solid nonelastic matter.

INTERVENTIONS

We attempted replantation. Despite repeated arterial thrombosis during surgery, the ear was successfully replanted with arterial and venous anastomosis.

OUTCOMES

Venous congestion occurred within 9 h of surgery and was treated using leeches. Freezing cold injury developed during reattachment. The radix and proximal parts of the helix exhibited necrosis and so were reconstructed by contralateral conchal cartilage graft, which was wrapped with a local subauricular skin flap. On completion of treatment, a satisfactory shape was achieved, although the replanted and reconstructed left auricle slightly was smaller than the contralateral auricle.

LESSONS LEARNED

Our report confirms that the replantation of a frozen, amputated ear is possible, and we suggest that ear replantation should be the method of choice for the treatment of ear loss even under these conditions.

Cold Weather Conditions and Risk of Hypothermia Among People Experiencing Homelessness: Implications for Prevention Strategies

Hypothermia is a preventable condition that disproportionately affects individuals who experience homelessness, yet limited data exist to inform the response to cold weather. To fill this gap, we examined the association between meteorological conditions and the risk of hypothermia among homeless individuals. Hypothermic events were identified from emergency department charts and coroner's records between 2004 and 2015 in Toronto, Canada. A time-stratified case-crossover design with conditional logistic regression was used to assess the relationship between the meteorological conditions (minimum temperature and precipitation) and the risk of hypothermia. There were 97 hypothermic events identified: 79 injuries and 18 deaths. The odds of experiencing a hypothermic event increased 1.64-fold (95% CI: 1.30-2.07) with every 5 °C decrease in the minimum daily temperature and 1.10-fold (95% CI: 1.03-1.17) with every 1 mm increase in precipitation. The risk of hypothermia among individuals experiencing homelessness increased with declining temperature; however, most cases occurred during periods of low and moderate cold stress. 72% occurred when the minimum daily temperatures were warmer than -15 °C. These findings highlight the importance of providing a seasonal cold weather response to prevent hypothermia, complemented by an alert-based response on extremely cold days.

Acute Compartment Syndrome of the Foot Due To Frostbite: Literature Review and Case Report

Acute compartment syndrome of the foot and ankle is a relatively rare clinical finding. Lower extremity compartment syndrome is customarily due to vascular or orthopedic traumatic limb-threatening pathologic issues. Clinical correlation and measurement of intracompartmental pressure are paramount to efficient diagnosis and treatment. Delayed treatment can lead to local and systemically adverse consequences. Frostbite, a comparatively more common pathologic entity of the distal extremities, occurs when tissues are exposed to freezing temperatures. Previously found in military populations, frostbite has become increasingly prevalent in the general population, leading to more clinical presentations to foot and ankle specialists. We present a review of the published data of acute foot compartment syndrome and pedal frostbite, with pathogenesis, treatment, and subsequent sequelae. A case report illustrating 1 example of bilateral foot, atraumatic compartment syndrome, is highlighted in the present report. The patient presented with changes consistent with distal bilateral forefoot frostbite, along with gangrenous changes to the distal tuft of each hallux. At admission and evaluation, the patient had increasing rhabdomyolysis with no other clear etiology. Compartment pressures were measured in the emergency room and were >100 mm Hg in the medial compartment and 50 mm Hg dorsally. The patient was taken to the operating room urgently for bilateral pedal compartment release. Both pathologic entities have detrimental outcomes if not treated in a timely and appropriate manner, with amputation rates increasing with increasing delay.

Pediatric frostbite: A 10-year single-center retrospective study

OBJECTIVE

To describe frostbite (freezing cold injured tissue) in children and intrinsic (psychological and behavioral) and extrinsic (meteorological and safety hazard) factors related to the injury.

METHODS

Retrospective chart review of children <18 years old referred to a regional pediatric hospital for frostbite, to determine the demographics, environment, and risk factors related to injuries.

RESULTS

47 patients met the inclusion criteria. Median age was 15 years (IQR 12-16). All injuries occurred between November and March. 49% were admitted to the hospital and frostbite was associated with use of alcohol (53%), cigarettes (34%), marijuana (23%), and symptoms of depression (with and without suicidal ideation) (32%). Frostbite injury treated with conservative wound management presented at <-6°C and injury that underwent surgical procedures occurred at temperatures ≤-23°C (p=0.001). Longer exposure duration also significantly increased the likelihood of a surgical procedure (p<0.001). Intoxication and lack of supervision were two common factors, with lack of supervision at time of injury most common among patients 0-12 years (64%), and intoxication most common among patients ages 13-17 (61%).

CONCLUSION

Frostbite injuries in children begins at temperatures <-6°C; with risk of tissue loss increasing at temperatures below -23°C. Lack of supervision and intoxication are major risk factors for frostbite in children. Two-thirds of younger children were unsupervised, whereas intoxication was frequently related to frostbite in adolescents. Both of these factors can be addressed through an education-based prevention program.

Cold Susceptibility of Digit Stumps Resulting from Amputation After Freezing Cold Injury in Elite Alpinists

Gorjanc, Jurij, Shawnda A. Morrison, Rok Blagus, and Igor B. Mekjavic. Cold susceptibility of digit stumps resulting from amputation after freezing cold injury in elite alpinists. High Alt Med Biol. 19:185-192, 2018.

AIM

The aim of the study was to assess whether previous freezing cold injury in fingers and/or toes might predispose alpinists to greater risk of further freezing cold injury, primarily due to a greater vasoconstrictor response to cold, resulting in a lower perfusion, reflected in lower skin temperature.

METHODS

Ten elite alpinists (N = 10; 8 male and 2 female) with amputations after freezing cold injury participated in a cold-water (8°C) immersion stress test of the hands and feet. Digit skin temperatures of amputated digits, their noninjured counterparts, noninjured digits of the affected side and noninjured digits of the corresponding side were measured. The skin temperatures were compared during three consecutive phases of the cold stress test: prewarming, cold water immersion, and passive heating.

RESULTS

Amputated toes cooled much faster compared to their uninjured counterparts (n = 26, p < 0.001), and attained lower skin temperatures during the cold exposure test (n = 26, p < 0.001). Higher cooling rate was observed in all the toes on the injured limb compared with the toes on the uninjured limb (n = 40, p < 0.001). In contrast to the toes, the fingers on the injured limb after freezing cold injury were warmer during cooling phase compared to uninjured fingers (n = 15, p < 0.001).

CONCLUSIONS

The lower digit temperatures observed in affected toe stumps during the cold stress test compared to the nonamputated toes may indicate a heightened risk of future freezing cold injury with subsequent cold exposures, as a consequence of less perfusion, reflected in the lower skin temperature. This relationship was not confirmed in the fingers.

Cold Injuries

New treatments of frostbite have led to unprecedented salvage of extremities including fingers and toes. Success is predicated on prompt institution of time-sensitive protocols initiated soon after rewarming, particularly the use of thombolytics. Unfortunately, in the urban setting, most patients are not candidates for these treatment modalities. Triple-phase bone scans have allowed for early determination of devitalized parts that need amputation. Reconstructive surgical techniques are typically used to salvage limb length in these devastating injuries.