Construction and validation of a risk prediction model for soldiers with frostbite in northeast China: a cross-sectional study.

BACKGROUND: One of the challenges of physical training in extreme condition is frostbite, especially in Northeast China. In this study, we aimed to construct a risk prediction model for frostbite among soldiers in Northeast China, and verify its effect. METHODS: 698 participants were selected via convenience sampling from Northeast China from December 2021 to January 2022 (winter). They were randomly divided into a training set (N = 479) and a testing set (N = 202) in a ratio of 7:3. All participants completed a researcher-made questionnaire on frostbite. The prediction model was constructed through the use of Logistic regression analysis, which was used to predict the independent risk factors for frostbite formation and screen significant indicators. The model's performance was assessed using the receiver operating characteristic (ROC) curve and decision curve analysis (DCA) to evaluate the prediction efficiency and goodness of fit. RESULTS: The incidence of frostbite in the training set was 19.83% (95 people), all of which were first-degree frostbite. Among them, frostbite in multiple parts was the most common (58.95%), followed by singular body parts like hands (24.21%), ears (11.58%) and feet (5.26%). Single factor logistic regression analyses showed that ambient temperature, ambient wind speed, outdoor stationary time, stationary status, and history of frostbite are independent risk factors that affect the occurrence of frostbite. Furthermore, we constructed the frostbite risk prediction model for soldiers in the northeastern region of China. The area under the receiver operating characteristic curve (AUC) for the risk of frostbite in the training set and testing set was 0.816 (95% CI, 0.770 ~ 0.862) and 0.787 (95% CI, 0.713 ~ 0.860), respectively. The Hosmer-Lemeshow test of the model showed χ2 = 11.328 and P = 0.184 (> 0.05). The DCA curve indicated that most of the clinical net benefits of the model are greater than 0, demonstrating good clinical usefulness. CONCLUSION: The constructed frostbite prediction model can effectively identify soldiers with a higher risk of frostbite. It provided theoretical support for commanders to take preventive measures to reduce the incidence of frostbite among soldiers and was of great clinical guiding significance.

Limb Salvage Using Microsurgical Free Tissue Transfer in Severe Frostbite.

PURPOSE: Frostbite is often managed conservatively; however, in severe cases, microsurgical free tissue transfer is required for soft tissue coverage and limb salvage. Given its rarity, the techniques and outcomes of these cases are not well described. The purpose of this report is to present the largest case series, to date, of frostbite injuries requiring microsurgical reconstruction for limb salvage. METHODS: A single-center retrospective review was conducted of all patients who underwent free tissue transfer by a single surgeon from 2008 to 2022. Patients of all ages were included if they suffered a frostbite injury requiring free tissue transfer. Demographics, operative details, and surgical outcomes were recorded. RESULTS: Eight patients with frostbite injuries were included in the report. Patients had frostbite injuries either to the lower extremities (n = 4) or to both upper and lower extremities (n = 4). Sixteen free flaps were done in total including four paired chimeric and eight single free flaps. Flap recipient sites included knees (n = 5), foot/ankle (n = 3), dorsal hands (n = 2), and thumbs (n = 2). All 16 flaps survived. Five patients had complications: four with major complications requiring operative management and two with minor complications requiring conservative management. Mean follow-up time was 505.7 days (range 115-1564). All lower extremity reconstructions were able to weight-bear at an average of 125.2 days post-injury (range 87-164). CONCLUSIONS: This case series demonstrates that free tissue transfer is a robust option for soft tissue coverage and functional limb salvage in patients with severe frostbite injuries to both upper and lower extremities.

Frostbite in the Pediatric Population: A Comprehensive Review and a Prospective Canadian Survey.

INTRODUCTION: Frostbite in the pediatric population, where skeletal maturity has not been achieved, can have important repercussions on subsequent growth. Yet, the optimal management of frostbite injuries in children remains vague. This review aims to summarize the current evidence for frostbite management in children and understand Canadian practice trends on this topic. METHODS: A review using Medline, Scopus, Web of Science, and gray literature was performed to identify relevant literature on the clinical manifestations, diagnostic methods, and treatment options in pediatric frostbite. An online survey was sent to plastic surgeons through the Canadian Society of Plastic Surgeons (CSPS) mailing list to further identify national practices and trends for pediatric frostbite management. RESULTS: A total of 109 articles were reviewed. No article provided a specific algorithm for pediatric frostbite, with existing recommendations suggesting the use of adult guidelines for treating children. Our survey yielded 9 responses and highlighted the rarity of pediatric frostbite cases, with no responder treating more than 10 cases per year. Most (55.6%) do not use a pediatric-specific treatment algorithm, whereas 30% apply adult guidelines. A conservative approach focusing on rewarming (55.6%), limb elevation (50%), and tetanus status verification (66.7%) was predominant. Imaging and surgical interventions seem to be reserved for severe cases. CONCLUSIONS: The current literature for pediatric frostbite management lacks specificity. Canadian practices vary, with a trend toward a conservative approach. The limited evidence and rarity of experience highlight the need for further research, ideally in a collaborative multicentric manner, to create a consensus for pediatric frostbite care.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2024 Update.

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for the prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the guidelines published in 2019.

Oropharyngeal Swelling and Airway Obstruction from Environmental Cold Exposure: A Case Report.

A 19-year-old male presented with facial frostbite and severe oropharyngeal edema after prolonged riding of a snowmobile without any facial covering. The diffuse swelling eventually progressed to airway obstruction, requiring a surgical airway. No alternative explanation was found for his presentation, making this the first case found in the literature of airway obstruction secondary to environmental cold exposure.

Cold-Induced Vasodilation, Rewarming, and Dexterity Impairment Following Second-Degree Frostbite.

Frostbite, a severe cold injury resulting from exposure to subfreezing temperatures, damages the skin and underlying tissues of the affected area and ranges in severity from first to fourth degree. This case report investigates the impact of second-degree frostbite suffered by a marine during winter training on cold-induced vasodilation (CIVD). Comparisons of CIVD before and after the injury revealed significant alterations in CIVD responses. CIVD, a physiological mechanism characterized by blood vessel dilation in response to cold exposure, plays a crucial role in operating in cold-weather environments and enhancing dexterity. The marine exhibited prolonged CIVD onset time, lower finger temperatures, increased pain sensations, and diminished dexterity after the frostbite injury during follow-up CIVD testing. The findings suggest that the frostbite-induced damage possibly compromised the microvascular function, contributing to the observed changes in CIVD. The marine reported persistent cold sensitivity and difficulty in maintaining hand warmth when assessed postinjury. This case underscores the potential long-term consequences of frostbite on CIVD and manual dexterity, emphasizing the importance of understanding these physiological changes for individuals engaged in cold-weather activities, particularly for military and occupational personnel.

Prevention and Treatment of Nonfreezing Cold Injuries and Warm Water Immersion Tissue Injuries: Supplement to Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite.

We convened an expert panel to develop evidence-based guidelines for the evaluation, treatment, and prevention of nonfreezing cold injuries (NFCIs; trench foot and immersion foot) and warm water immersion injuries (warm water immersion foot and tropical immersion foot) in prehospital and hospital settings. The panel graded the recommendations based on the quality of supporting evidence and the balance between benefits and risks/burdens according to the criteria published by the American College of Chest Physicians. Treatment is more difficult with NFCIs than with warm water immersion injuries. In contrast to warm water immersion injuries that usually resolve without sequelae, NFCIs may cause prolonged debilitating symptoms, including neuropathic pain and cold sensitivity.

Convolutional neural network models for automatic diagnosis and graduation in skin frostbite.

The study aimed to develop and validate a convolutional neural network (CNN)-based deep learning method for automatic diagnosis and graduation of skin frostbite. A dataset of 71 annotated images was used for the training, the validation, and the testing based on ResNet-50 model. The performances were evaluated with the test set. The diagnosis and graduation performance of our approach was compared with two residents from burns department. The approach correctly identified all the frostbite of IV (18/18, 100%), but with respectively 1 mistake in the diagnosis of degree I (29/30, 96.67%), II (28/29, 96.55%) and III (37/38, 97.37%). The accuracy of the approach on the whole test set was 97.39% (112/115). The accuracy of the two residents were respectively 77.39% and 73.04%. Weighted Kappa of 0.583 indicates good reliability between the two residents (P = .445). Kendall's coefficient of concordance is 0.326 (P = .548), indicating differences in accuracy between the approach and the two residents. Our approach based on CNNs demonstrated an encouraging performance for the automatic diagnosis and graduation of skin frostbite, with higher accuracy and efficiency.

[Research progress on Huangqi Guizhi Wuwu Decoction and predictive analysis of quality markers].

Huangqi Guizhi Wuwu Decoction is a classic prescription in traditional Chinese medicine(TCM) and is known for its effects of tonifying Qi, warming the meridians, and promoting blood circulation to alleviate obstruction. It is primarily used to treat conditions characterized by Qi stagnation, Yang deficiency, and obstruction, and it exhibits pharmacological effects such as immune regulation, anti-inflammation, analgesia, protection of the cardiovascular and cerebrovascular systems, itch relief, reduction of frostbite symptoms, antioxidative stress, promotion of cell apoptosis, and kidney protection. In modern clinical practice, it is commonly used to treat acute myocardial infarction, sequelae of cerebral infarction, cervical spondylosis, frozen shoulder, lower limb arteriosclerosis, lower limb vascular disorders, peripheral neuropathy in diabetes, and lupus nephritis. Recent research has focused on the chemical components, pharmacological effects, and clinical applications of Huangqi Guizhi Wuwu Decoction. Based on the "five principles" of quality markers(Q-markers) in TCM, this study predicted and analyzed the Q-markers of Huangqi Guizhi Wuwu Decoction. It suggested that astragaloside Ⅳ, formononetin, kaempferol, quercetin, cinnamic acid, cinnamaldehyde, 6-gingerol, paeoniflorin, albiflorin, and gallic acid could serve as Q-markers for Huangqi Guizhi Wuwu Decoction. The findings of this study can provide references for quality control of Huangqi Guizhi Wuwu Decoction and the development of new Chinese medicinal formulations.

Safety and Feasibility of a Sheath Cryoprobe for Bronchoscopic Transbronchial Biopsy: The FROSTBITE Trial.

BACKGROUND: Bronchoscopic lung biopsy is typically performed using transbronchial forceps. However, this method is limited by small sample size and presence of crush artifact. Cryobiopsy offers the potential to overcome these limitations with larger artifact-free samples but has not been widely adopted due to concerns over increased rates of bleeding and pneumothorax. A new, smaller 1.1-mm cryoprobe has been developed that operates in a similar fashion to forceps, though the safety profile of this cryoprobe has not yet been prospectively studied. OBJECTIVE: The aim of this study was to investigate the safety of transbronchial biopsy using a novel 1.1-mm cryoprobe. METHODS: This prospective, single-arm study enrolled patients referred for transbronchial biopsy. All procedures were performed using the 1.1-mm cryoprobe with oversheath. The primary outcome was the composite of significant complications related to the cryobiopsy procedure (bleeding Grade ≥3, pneumothorax Grade ≥2, and respiratory failure). Bleeding and pneumothorax were graded according to previously published scales. RESULTS: Fifty participants from two academic medical centers underwent transbronchial cryobiopsy. Indications for biopsy included evaluation of lung transplant allograft (50%), diffuse lung disease (44%), and pulmonary parenchymal lesion (6%). There were two pneumothoraces (4%), neither of which required aspiration or chest tube placement. There were no Grade 3 or 4 bleeding events. Mild bleeding (Grade ≤2) was observed in 25 cases (50%). No complications occurred that met the a priori primary outcome of bleeding Grade ≥3, pneumothorax Grade ≥2, and respiratory failure. CONCLUSIONS: Transbronchial cryobiopsy using a 1.1-mm cryoprobe is feasible with an acceptable safety profile.

Clinical utilization of a sous vide device in the acute rewarming of frostbitten extremities.

The current standard of care for acute frostbite rewarming is the use of a circulating warm water bath at a temperature of 37 °C to 39 °C. There is no standardized method to achieve this. Manual management of a warm water bath can be inefficient and time consuming. This case describes the clinical use of a sous vide cooking device to create and maintain a circulating warm water bath to rewarm acute frostbite. A 34 year-old male presented to the emergency department with acute frostbite. Each of the patient's feet were placed in a water bath with a sous vide device attached to the side of the basin and set to 38 °C. Temperatures were recorded every 2 m from 2 thermometers. Once target temperature was achieved, the extremities were rewarmed for 30 m. The water baths required an average of 25 m to reach target temperature and maintained the target temperature within ±1 °C for the duration of the rewarming. The extremities were clinically thawed in one session and there were no adverse events. The patient was seen by plastic and vascular surgery and admitted to the hospital for conservative management. He was discharged on hospital day 3 and did not require any amputations. A sous vide device can be used clinically to heat and maintain a water bath and successfully rewarm frostbitten extremities in one 30 m cycle. No adverse events were reported and providers rated this as a convenient method of water bath management.

The role of hyperbaric oxygen for acute traumatic ischemias.

Acute traumatic ischemias are an array of disorders that range from crush injuries to compartment syndromes, from burns to frostbite and from threatened flaps to compromised reimplantations. Two unifying components common to these conditions are a history of trauma be it physical, thermal, or surgical coupled with ischemia to the traumatized tissues. Their pathophysiology resolves around the self-perpetuating cycle of edema and ischemia, and their severity represents a spectrum from mild, almost non-existent, to tissue death. Since ischemia is a fundamental component of the traumatic ischemias and hypoxia is a consequence of ischemia, hyperbaric oxygen is a logical intervention for those conditions where tissue survival, infection control and healing is at risk. Unfortunately, even with mechanisms of hyperbaric oxygen that strongly support its usefulness in traumatic ischemias coupled with supportive clinical data, clinicians are disinclined to utilize it for these conditions. This focuses on the orthopedic aspects of the traumatic ischemias, namely crush injury and compartment syndrome, and show how hyperbaric oxygen treatments can mitigate their severity.

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.

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.

Frostbite injury: an unknown risk when using nitrous oxide as a party drug.

In recent years nitrous oxide has become a popular party drug. Large cylinders filled with nitrous oxide are used to fill balloons for recreational use. We present two patients with severe third-degree cold burns on their thighs after clamping a large cylinder between their legs while filling balloons. During filling, large amounts of nitrous oxide are inhaled, which causes the pain to be numbed. As nitrous oxide is discharged from the cylinder, the cylinder becomes ice cold. Due to direct contact with the icecold cylinder and numbness, third-degree frostbite wounds occur. In both cases presented, the burn wounds had to be debrided and treated with split-thickness skin transplants. Awareness is needed as at first presentation as the burns look superficial, but can rapidly develop into third-degree burn wounds. Close follow-up and aggressive treatment is necessary to prevent infections and to regain a good functional outcome of the affected limb.

Pediatric Environmental Cold Injuries.

Cold weather injuries are relevant concerns for children during winter sports and outdoor activities. To mitigate the risk of cold injury in this high-risk population, providers can educate parents on proper outdoor attire as well as the added risks of wind and water exposure. There are 2 types of environmental cold injuries: freezing injuries and nonfreezing injuries. Frostbite is a freezing injury from direct contact with cold air or surfaces. The extent of injury depends on the depth to which the freezing extends. Treatment involves rewarming the frozen tissue with warm water baths and considering analgesia. Hypothermia is a nonfreezing cold injury, and it can occur even when ambient temperatures are above freezing. When there is a decrease in the body's core temperature, hypothermia progresses from mild to severe symptoms. Treatment of hypothermia is threefold but is also dependent on the core body temperature, as colder core temperatures will require more aggressive warming techniques. Hypothermia treatment involves passive protection from further heat loss (ie, removing wet clothing), which helps the body to warm itself. Treatment also involves active external rewarming wherein a heat source, such as a heated blanket, is used to increase body temperature. Active internal rewarming is the delivery of heat inside the patient's body, such as warmed intravenous fluids.

A Tibetan adolescent girl suffered frostbite on the journey of pilgrimage: A case report.

Frostbite in Southwestern China has been overlooked due to its low incidence, relatively mild temperature and lack of literature published before. However, it needs to be further studied for religious diversity and distinct geomorphology. In this article, we reported an 18-year-old Tibetan girl who suffered from blizzard attack during pilgrimage. Her feet and several fingers showed mummified gangrene upon physical examination with poor movement. She was diagnosed with 3rd to 4th degree of frostbite. The girl was given oral ibuprofen, debridement and other regular treatment daily, but she was eventually amputated due to insufficient thrombolytic management in primary hospital, delayed informing consent in the referral hospital and ethnic conflict between religion and guidelines. This case enriched the experience of managing complex frostbite in Tibetan population and alarms that efforts should be integrated to protect pilgrims and mountaineers in the Tibetan region.

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.

Effects of 7 Consecutive Systematic Applications of Cryotherapy With Compression.

CONTEXT: Postsurgical and acute orthopedic patients are frequently treated with consecutive systematic cryotherapy despite the void of data to support treatment safety or effectiveness. The purpose of this study was to examine the occurrence of frostbite and measure skin temperatures during the systematic application of 2 cryocompression protocols. DESIGN: A repeated-measures design guided this study. METHODS: Nine healthy, college-aged participants (4 men and 5 women; age = 20.7 [1.2] y; height = 174 [11.01] cm; mass = 74 [14] kg) received both cryocompression protocols separated by ≥ 1 week. The static cryocompression protocol consisted of seven 40-minute "on" cycles of cryotherapy (4.4°C) with 45 mm Hg of compression, each followed by a 30-minute "off" cycle (no cryotherapy, compression set at 5 mm Hg). The intermittent cryocompression protocol consisted of seven 40-minute "on" cycles of cryotherapy (4.4°C) with compression alternating between 5 and 45 mm Hg, each followed by a 30-minute "off" cycle (no cryotherapy, compression set at 5 mmHg). At the end of each "on" and "off" cycle, we used a checklist to assess for frostbite, a PT-6 thermocouple to measure skin temperature (in degrees Celsius), and a 10-cm Likert scale to assess comfort. RESULTS: None of the participants experienced any signs or symptoms of frostbite. There were no differences in skin temperature between the compression conditions over time (F14,112 = 1.43; P = .149) nor were there any differences between the 2 compression conditions (F1,8 = 3.75; P = .087; 1-ß = 0.40). The skin temperatures were statistically different over the course of all 7 "on" and "off" cycles (F14,112 = 95.12; P < .001). There was no difference between the skin temperatures produced at the end of each "on" cycle. CONCLUSIONS: The application of 7 consecutive cryotherapy treatments with compression did not result in any signs or symptoms of frostbite and produced similar skin temperatures with each "on" cycle.

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.