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.

Iloprost for the treatment of frostbite: a scoping review

We performed a scoping review to identify the extent of the literature describing the use of iloprost in the treatment of frostbite. Iloprost is a stable synthetic analog of prostaglandin I₂. As a potent inhibitor of platelet aggregation and vasodilator, it has been used to address the post-rewarming reperfusion injury in frostbite. The search using iloprost and frostbite as key words and MeSH terms yielded 200 articles. We included in our review the literature examining iloprost for the treatment of frostbite in humans in the form of primary research, conference proceedings and abstracts. Twenty studies published from 1994 to 2022 were selected for analysis. The majority were retrospective case series consisting of a homogeneous population of mountain sport enthusiasts. A total of 254 patients and over 1000 frostbitten digits were included among the 20 studies. The larger case series demonstrated a decrease in amputation rates relative to untreated patients. Primary gaps in the literature include a paucity of randomised trials and relatively limited study populations to date. While the case evidence is promising, a multi-centre collaboration would be crucial to adequately power prospective randomised studies to definitively determine if iloprost has a role in the treatment of frostbite.

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.

Performance of a Chemical Heat Blanket in Dry, Damp, and Wet Conditions Inside a Mountain Rescue Hypothermia Wrap

INTRODUCTION

Casualties with accidental hypothermia are evacuated using multilayer wraps, typically including a chemical heat blanket (CHB), a vapor barrier, and an insulating outer bag. We investigated CHB performance against dry, damp, and wet fabric, in a multilayer wrap, in response to a case report indicating diminished performance when wet.

METHODS

We wrapped a torso manikin in a base layer, CHB, vapor barrier, casualty bag, and vacuum mattress, recording CHB panel temperatures at intervals of up to 7 h. Experimental conditions were dry, damp, and wet clothing, with 2 blankets tested in each condition. We subsequently used a forward-looking infrared camera to assess whether the panels heated evenly and heat flux sensors to quantify heat transfer across 2 dry, 1 damp, and 1 wet fleece under CHB panels.

RESULTS

Chemical heat blankets maintained heat output for >7 h inside the wraps. Median (IQR) panel steady state temperatures were 52°C (39-56°C) against dry fleece, 41°C (36-45°C) against damp fleece, and 30°C (29-33°C) against wet fleece. Peak panel temperature was 67°C. The heat flux results indicated that CHBs generated similar quantities of heat in dry and damp conditions, as the lower temperatures were compensated by more efficient transfer of heat across the moist clothing layer. Chemical heat blanket heat output was diminished in wet conditions.

CONCLUSIONS

Rescuers should cut off saturated clothing in a protected environment before wrapping casualties, but damp clothing need not be removed. Because of the high peak temperatures recorded on the surfaces of CHBs, they should not be placed directly against skin, and compression straps should not be placed directly over CHBs.

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.

Cold Weather Injury in a Special Operations Aviation Crew Member: A Case Report

As arctic warfare becomes a center focus within Special Operations, cold weather injury looms as both a medical and operational threat. While cold weather injury can range from pernio to hemodynamically unstable systemic hypothermia, the more minor injuries are far more common. However, these present a challenge in austere medical care and can drastically impact mission capability. We present a case of a Special Operations crew chief with cold weather digital injury while at the Arctic Isolation Course in Alaska and his subsequent clinical course. Prevention remains the key for mitigating these injuries, while the decision to rewarm must be made with both medical and tactical factors in mind as refreezing incurs significant morbidity. Other components of prehospital treatment include active rewarming, ibuprofen, aloe vera, and pain control.

The peripheral vascular responses in non-freezing cold injury and matched controls

NEW FINDINGS

What is the central question of this study? Does non-freezing cold injury (NFCI) alter normal peripheral vascular function? What is the main finding and its importance? Individuals with NFCI were more cold sensitive (rewarmed more slowly and felt more discomfort) than controls. Vascular tests indicated that extremity endothelial function was preserved with NFCI and that sympathetic vasoconstrictor response might be reduced. The pathophysiology underpinning the cold sensitivity associated with NFCI thus remains to be identified.

ABSTRACT

The impact of non-freezing cold injury (NFCI) on peripheral vascular function was investigated. Individuals with NFCI (NFCI group) and closely matched controls with either similar (COLD group) or limited (CON group) previous cold exposure were compared (n = 16). Peripheral cutaneous vascular responses to deep inspiration (DI), occlusion (PORH), local cutaneous heating (LH) and iontophoresis of acetylcholine and sodium nitroprusside were investigated. The responses to a cold sensitivity test (CST) involving immersion of a foot in 15°C water for 2 min followed by spontaneous rewarming, and a foot cooling protocol (footplate cooled from 34°C to 15°C), were also examined. The vasoconstrictor response to DI was lower in NFCI compared to CON (toe: 73 (28)% vs. 91 (17)%; P = 0.003). The responses to PORH, LH and iontophoresis were not reduced compared to either COLD or CON. During the CST, toe skin temperature rewarmed more slowly in NFCI than COLD or CON (10 min: 27.4 (2.3)°C vs. 30.7 (3.7)°C and 31.7 (3.9)°C, P < 0.05, respectively); however, no differences were observed during the footplate cooling. NFCI were more cold-intolerant (P < 0.0001) and reported colder and more uncomfortable feet during the CST and footplate cooling than COLD and CON (P < 0.05). NFCI showed a decreased sensitivity to sympathetic vasoconstrictor activation than CON and greater cold sensitivity (CST) compared to COLD and CON. None of the other vascular function tests indicated endothelial dysfunction. However, NFCI perceived their extremities to be colder and more uncomfortable/painful than the controls.

Peripheral sensory function in non-freezing cold injury patients and matched controls

NEW FINDINGS

What is the central question of this study? Is peripheral sensory function impaired in the chronic phase of non-freezing cold injury (NFCI)? What is the main finding and its importance? Warm and mechanical detection thresholds are elevated and intraepidermal nerve fibre density is reduced in individuals with NFCI in their feet when compared to matched controls. This indicates impaired sensory function in individuals with NFCI. Interindividual variation was observed in all groups, and therefore a diagnostic cut-off for NFCI has yet to be established. Longitudinal studies are required to follow NFCI progression from formation to resolution ABSTRACT: The aim of this study was to compare peripheral sensory neural function of individuals with non-freezing cold injury (NFCI) with matched controls (without NFCI) with either similar (COLD) or minimal previous cold exposure (CON). Thirteen individuals with chronic NFCI in their feet were matched with the control groups for sex, age, race, fitness, body mass index and foot volume. All undertook quantitative sensory testing (QST) on the foot. Intraepidermal nerve fibre density (IENFD) was assessed 10 cm above the lateral malleolus in nine NFCI and 12 COLD participants. Warm detection threshold was higher at the great toe in NFCI than COLD (NFCI 45.93 (4.71)°C vs. COLD 43.44 (2.72)°C, P = 0.046), but was non-significantly different from CON (CON 43.92 (5.01)°C, P = 0.295). Mechanical detection threshold on the dorsum of the foot was higher in NFCI (23.61 (33.59) mN) than in CON (3.83 (3.69) mN, P = 0.003), but was non-significantly different from COLD (10.49 (5.76) mN, P > 0.999). Remaining QST measures did not differ significantly between groups. IENFD was lower in NFCI than COLD (NFCI 8.47 (2.36) fibre/mm2 vs. COLD 11.93 (4.04) fibre/mm2 , P = 0.020). Elevated warm and mechanical detection thresholds may indicate hyposensitivity to sensory stimuli in the injured foot for individuals with NFCI and may be due to reduced innervation given the reduction in IENFD. Longitudinal studies are required to identify the progression of sensory neuropathy from the formation of injury to its resolution, with appropriate control groups employed.

Plasma biomarkers of endothelial function, inflammation and oxidative stress in individuals with non-freezing cold injury

NEW FINDINGS

What is the central question of this study? Are biomarkers of endothelial function, oxidative stress and inflammation altered by non-freezing cold injury (NFCI)? What is the main finding and its importance? Baseline plasma [interleukin-10] and [syndecan-1] were elevated in individuals with NFCI and cold-exposed control participants. Increased [endothelin-1] following thermal challenges might explain, in part, the increased pain/discomfort experienced with NFCI. Mild to moderate chronic NFCI does not appear to be associated with either oxidative stress or a pro-inflammatory state. Baseline [interleukin-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosis of NFCI.

ABSTRACT

Plasma biomarkers of inflammation, oxidative stress, endothelial function and damage were examined in 16 individuals with chronic NFCI (NFCI) and matched control participants with (COLD, n = 17) or without (CON, n = 14) previous cold exposure. Venous blood samples were collected at baseline to assess plasma biomarkers of endothelial function (nitrate, nitrite and endothelin-1), inflammation [interleukin-6 (IL-6), interleukin-10 (IL-10), tumour necrosis factor alpha and E-selectin], oxidative stress [protein carbonyl, 4-hydroxy-2-nonenal (4-HNE), superoxide dismutase and nitrotyrosine) and endothelial damage [von Willebrand factor, syndecan-1 and tissue type plasminogen activator (TTPA)]. Immediately after whole-body heating and separately, foot cooling, blood samples were taken for measurement of plasma [nitrate], [nitrite], [endothelin-1], [IL-6], [4-HNE] and [TTPA]. At baseline, [IL-10] and [syndecan-1] were increased in NFCI (P < 0.001 and P = 0.015, respectively) and COLD (P = 0.033 and P = 0.030, respectively) compared with CON participants. The [4-HNE] was elevated in CON compared with both NFCI (P = 0.002) and COLD (P < 0.001). [Endothelin-1] was elevated in NFCI compared with COLD (P < 0.001) post-heating. The [4-HNE] was lower in NFCI compared with CON post-heating (P = 0.032) and lower than both COLD (P = 0.02) and CON (P = 0.015) post-cooling. No between-group differences were seen for the other biomarkers. Mild to moderate chronic NFCI does not appear to be associated with a pro-inflammatory state or oxidative stress. Baseline [IL-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosing NFCI, but it is likely that a combination of tests will be required.

Horticultural Practices in Early Spring to Mitigate the Adverse Effect of Low Temperature on Fruit Set in 'Lapins' Sweet Cherry

Yield of sweet cherry (Prunus avium L.) is determined by fruit set, a developmental stage sensitive to variable spring environmental conditions. To sustain fruit production and enhance crop climate resilience, it is important to understand the impacts of abiotic stresses and the effectiveness of horticultural mitigations in the spring on the critical developmental processes during fruit set. In this study, flowering phenology, pistil browning and percent fruit set of 'Lapins' were monitored at five sites of different elevation and frost risk in the Okanagan Valley, British Columbia, Canada, in 2019 and 2022. At Site 1 in Summerland Research and Development Centre ("SuRDC1"), where a 'Lapins' on Krymsk 5 planting was located in a frost pocket where the crops were exposed to high risk of cold damage in the spring, a series of experiments were conducted to investigate the floral organ viability and percent fruit set under low temperatures, and under the effects of four spring horticultural mitigation measures. Installation of polyethylene sleeves and FAME spray (fatty acid methyl esters-based plant growth regulator, WAIKEN, SST Australia) were implemented in 2019; boric acid spray and postponed irrigation were tested in 2022. Low fruit set at SuRDC1 in both years was associated with severe pistil browning after night temperature dropped below -4 °C in late April. In 2019, the semi-enclosure of polyethylene sleeves led to an increase in the surface temperature (T_surfae) of floral buds by 2-4 °C, which prolonged the stage of first bloom, delayed petal fall and prevented frost damage on pistils, but led to the decrease in percent fruit set by 77%, due to ovule abortion or cessation of fruitlet development. The early and late sprays of FAME had no significant influence on either abundance of germinated pollen tubes or percent fruit set; however, the potential of late spray in improving pollen abundance and reducing pistil browning requires further investigation. In 2022, the spray of 0.01% boric acid solution led to a decrease in fruit set by 6.95%. Six-week postponement of irrigation starting from full bloom decreased soil moisture, but increased soil temperature and improved fruit set by 7.61%. The results improved our understanding about the damages of adverse spring air temperatures on pistils and ovules, and suggested the potential of irrigation adjustment in regulating soil moisture and temperature and improving fruit set in the cool and moist spring.

A prospective study on local cold injuries in northern Sweden

The study aimed to determine the prevalence and incidence proportion of local cold injuries in northern Sweden, and identify associated factors. It was based on prospective data from surveys in 2015 and 2021 sent to a population-based sample in northern Sweden. Multiple binary logistic regression was performed. The study included 5,017 subjects (response rate 44.4%). The prevalence of cold injuries in the hands was 11.4%, feet 12.6%, and face 19.9%, while the incidence proportion was 1.0%, 1.0%, and 0.9%, respectively. Male gender was associated with incident cold injuries in the hands (OR 1.69; 95% CI 1.31-1.28), feet (OR 1.34; 95% CI 1.04-1.73), and face (OR 1.53; 95% CI 1.15-2.03); mental stress with cold injuries in the hands (OR 1.55; 95% CI 1.16-2.05) and feet (OR 1.39; 95% CI 1.04-1.88); previous stroke with cold injuries in the hands (OR 2.64; 95% CI 1.09-6.40) and face (OR 3.09; 95% CI 1.26-7.56); and Raynaud's phenomenon with cold injuries in the hands (OR 2.48; 95% CI 1.80-3.41) and feet (OR 2.07; 95% CI 1.50-2.87). We conclude that male gender, mental stress, previous stroke, and Raynaud's phenomenon increased the probability of contracting local cold injuries.

Antagonist of sphingosine 1-phosphate receptor 3 reduces cold injury of rat donor hearts for transplantation

Cold storage is widely used to preserve an organ for transplantation; however, a long duration of cold storage negatively impacts graft function. Unfortunately, the mechanisms underlying cold exposure remain unclear. Based on the sphingosine-1-phosphate (S1P) signal involved in cold tolerance in hibernating mammals, we hypothesized that S1P signal blockage reduces damage from cold storage. We used an in vitro cold storage and rewarming model to evaluate cold injury and investigated the relationship between cold injury and S1P signal. Compounds affecting S1P receptors (S1PR) were screened for their protective effect in this model and its inhibitory effect on S1PRs was measured using the NanoLuc Binary Technology (NanoBiT)-β-arrestin recruitment assays. The effects of a potent antagonist were examined via heterotopic abdominal rat heart transplantation. The heart grafts were transplanted after 24-hour preservation and evaluated on day 7 after transplantation. Cold injury increased depending on the cold storage time and was induced by S1P. The most potent antagonist strongly suppressed cold injury consistent with the effect of S1P deprivation in vitro. In vivo, this antagonist enabled 24-hour preservation, and drastically improved the beating score, cardiac size, and serological markers. Pathological analysis revealed that it suppressed the interstitial edema, inflammatory cell infiltration, myocyte lesion, TUNEL-positive cell death, and fibrosis. In conclusion, S1PR3 antagonist reduced cold injury, extended the cold preservation time, and improved graft viability. Cold preservation strategies via S1P signaling may have clinical applications in organ preservation for transplantation and contribute to an increase in the donor pool.

Isolation and Identification of Ice Nucleation Active Fusarium Strains from Rapid Apple Declined Trees in Korea

In biological particles such as Fusarium species, ice nucleation activity (INA) has been observed. Fusarium strains isolated from apple declined trees in Korea were identified with a multilocus sequence analysis using the tef1 and rpb1 genes. Droplet-freezing and tube-freezing assays were used to determine the INA of the strains, using Pseudomonas syringae pv. syringae KACC 21200 as a positive control and resulting in seven INA+ fungal strains that were identified as F. tricinctum (KNUF- 21-F17, KNUF-21-F18, KNUF-21-F29, KNUF-21-F32, KNUF-21-F38, KNUF-21-F43, and KNUF-21-F44). The effect of Fusarium INA+ KNUF-21-F29 was compared to that of INA- strains on Chrysanthemum morifolium cv. Shinma explants. A higher callus formation and noshoot formation were observed, suggesting that fungal INA could play a role in cold injuries and be a factor to consider in rapid apple decline. To the best of our knowledge, this is the first report of INA fungal strains isolated in Korea.

A 3-D virtual human model for simulating heat and cold stress

In this study, we extended our previously developed anatomically detailed three-dimensional (3-D) thermoregulatory virtual human model for predicting heat stress to allow for predictions of heat and cold stress in one unified model. Starting with the modified Pennes bioheat transfer equation to estimate the spatiotemporal temperature distribution within the body as the underlying modeling structure, we developed a new formulation to characterize the spatial variation of blood temperature between body elements and within the limbs. We also implemented the means to represent heat generated from shivering and skin blood flow that apply to air exposure and water immersion. Then, we performed simulations and validated the model predictions with experimental data from nine studies, representing a wide range of heat- and cold-stress conditions in air and water and physical activities. We observed excellent agreement between model predictions and measured data, with average root mean squared errors of 0.2 °C for core temperature, 0.9 °C for mean skin temperature, and 27 W for heat from shivering. We found that a spatially varying blood temperature profile within the limbs was crucial to accurately predict core body temperature changes during very cold exposures. Our 3-D thermoregulatory virtual human model consistently predicted the body's thermal state accurately for each of the simulated hot and cold environmental conditions and exertional heat stress. As such, it serves as a reliable tool to assess whole-body, localized tissue, and, potentially, organ-specific injury risks, helping develop injury prevention and mitigation strategies in a systematic and expeditious manner.

Cold Stress, Freezing Adaptation, Varietal Susceptibility of Olea europaea L.: A Review

Olive (Olea europaea L.) is an evergreen xerophytic tree characterizing vegetative landscape and historical-cultural identity of the Mediterranean Basin. More than 2600 cultivars constitute the rich genetic patrimony of the species cultivated in approximately 60 countries. As a subtropical species, the olive tree is quite sensitive to low temperatures, and air temperature is the most critical environmental factor limiting olive tree growth and production. In this present review, we explored the detrimental effects caused of low temperatures on olive cultivars, and analyzed the most frequently experimental procedures used to evaluate cold stress. Then, current findings freezing stress physiology and gene are summarized in olive tree, with an emphasis on adaptive mechanisms for cold tolerance. This review might clear the way for new research on adaptive mechanisms for cold acclimation and for improvement of olive growing management.

Acral skin vasoreactivity and thermosensitivity to hand cooling following 5 days of intermittent whole-body cold exposure

We sought to examine whether short-term whole-body cold acclimation would modulate finger vasoreactivity and thermosensitivity to localized cooling. Fourteen men were equally assigned to either the experimental (CA) or the control (CON) group. The CA group was immersed to the chest in 14°C water for ≤120 min daily over a 5-day period, while the skin temperature of the right-hand fingers was clamped at ~35.5°C. The CON group was instructed to avoid any cold exposure during this period. Before and after the intervention, both groups performed, on two different consecutive days, a local cold provocation trial consisting of a 30-min hand immersion in 8°C water, while immersed to the chest once in 21°C (mild-hypothermic trial; 0.5°C fall in rectal temperature from individual pre-immersion values) and on the other occasion in 35.5°C (normothermic trial). In the CA group, the cold-induced reduction in finger temperature was less (mild-hypothermic trial: P = 0.05; normothermic trial: P = 0.02), and the incidence of the cold-induced vasodilation episodes was greater (in normothermic trials: P = 0.04) in the post than in the pre-acclimation trials. The right-hand thermal discomfort was also attenuated (mild-hypothermic trial: P = 0.04; normothermic trial: P = 0.01). The finger temperature responses of the CON group did not vary between testing periods. Our findings suggest that repetitive whole-body exposure to severe cold within a week, may attenuate finger vasoreactivity and thermosensitivity to localized cooling. These regional thermo-adaptions were ascribed to central neural habituation produced by the iterative, generalized cold stimulation.

A Combination of Synthetic Molecules Acts as Antifreeze for the Protection of Skin against Cold-Induced Injuries

Seasonal and occupational exposure of the human body to extreme cold temperatures can result in cell death in the exposed area due to the formation of ice crystals. This leads to superficial or deep burn injury and compromised functionality. Currently available therapeutics can be ineffective in extreme cases, and thus, it is necessary to develop prophylactic strategies. In this study, we have devised a combination of known synthetic cryopreservative agents (termed SynAFP) and evaluated their potential antifreeze applications on skin. The prophylactic activity of SynAFP in vitro is indicated by improved cellular revival and cell viability, retention of the cytoskeleton, and normal cell cycle progression even after cold stress. A comprehensive whole-cell proteomic approach revealed that in the presence of SynAFP, cold-induced downregulation of proteins involved in cell-cell adhesion and upregulation of those related to mitochondrial stress were ameliorated. Pre-application of SynAFP in mice facing a frostbite challenge prevents their skin from incurring significant injury as confirmed through macroscopic and histological examination. Moreover, multiple applications of SynAFP on mouse skin at room temperature did not compromise skin integrity. SynAFP was also formulated in anAloe vera-based cream (referred to as fSynAFP), which offered similar protection under cold stress conditions. Thus, SynAFP can be considered as a potential candidate for formulating a topical intervention for protection from cold-induced injuries to skin.

Long-Term Sequelae of Frostbite-A Scoping Review

Frostbite is tissue damage caused by freezing temperatures and constitutes an important cause of morbidity in cold climate zones and high altitude. The direct effects of sub-zero temperatures lead to tissue freezing, electrolyte shifts and pH alterations, microvascular damage, and eventually to cell death. Upon rewarming, inflammatory reperfusion injury and thrombosis may lead to further tissue damage. Several studies and various case reports show that many patients suffer from long-term sequelae such as vasomotor disturbances (associated with susceptibility to refreezing), and neuropathic and nociceptive pain, as well as damage to skeletal structures. There are still many uncertainties regarding the pathophysiology of these sequelae. It has been shown that the transient receptor potential channel (TRP) family plays a role in cold allodynia. Botulinum Toxin type A (BTX-A) injections have been reported to be beneficial in vasomotor and neuropathic disturbances secondary to frostbite. Epidural sympathetic block has been used for short-term treatment of frostbite induced chronic pain. Furthermore, amitriptyline, gabapentinoids, and duloxetine may have some benefits. Frostbite arthritis clinically resembles regular osteoarthritis. In children there is a risk of epiphyseal cartilage damage leading to bone deformities. Despite some promising therapeutic concepts, the scarcity of data on frostbite long-term sequelae in the literature indicates the need of more in-depth studies of this pathology in all its aspects.

Microwave Treatment of Cold Injuries

In spite of the fact that extremity frostbites are a widespread type of injuries in many countries, specialized equipment for frostbite treatment is lacking. Treatment is carried out by conservative methods. The best results are obtained by using thermal isolation of injured tissues and activation of internal warming. It is proposed to initiate deep warming of frostbitten extremities on exposure to low-power microwave radiation. A microwave chamber has been developed to implement this technique. The efficiency of the approach was earlier demonstrated on animals. An example is given of successful treatment of a cold injury of patient hands and feet that allowed amputation to be avoided.

Social determinants of poor outcomes following frostbite injury: a study of the National Inpatient Sample

Severe frostbite injury can result in significant disability from amputation of limbs and digits which may be mitigated through prompt medical care. The reported rates of amputation vary widely between centers. Our aim is to describe the incidence and factors associated with amputation secondary to frostbite injury in the United States using a national sample of hospitalizations. Admissions for frostbite injury were identified in the National Inpatient Sample (2016-18). Factors associated with amputation were assessed by multivariable logistic regression and clustered by hospital. The overall incidence of frostbite injury in the U.S. is 0.83/100,000 people. Of the social factors associated with frostbite injury, homelessness and Black race were independently associated with a higher likelihood of amputation at the primary admission. Diagnosis of cellulitis was a predictor of amputation. Homeless frostbite patients more frequently discharged AMA and were less likely to discharge with supportive medical care, despite having a higher rate of more severe injury. Disability from amputation following frostbite injury impacts at least 20% of frostbite injured patients and disproportionally impacts the homeless population. Further study is needed to ascertain the decision-making that leads to early amputation following frostbite injury, especially in the homeless and Black population. Outreach and education efforts should be initiated to promote salvage of functional limb length following frostbite injury.

High Cost and Resource Utilization of Frostbite Readmissions in the United States

BACKGROUND

Frostbite is a high morbidity, high-cost injury that can lead to digit or limb necrosis requiring amputation. Our primary aim is to describe the rate of readmission following frostbite injury. Our secondary aims are to describe the overall burden of care, cost, and characteristics of repeat hospitalizations of frostbite-injured people.

METHODS

Hospitalizations following frostbite injury (index and readmissions) were identified in the 2016 and 2017 Nationwide Readmission Database. Multivariable logistic regression was clustered by hospital and additionally adjusted for severe frostbite injury, gender, year, payor group, severity, and comorbidity index. Population estimates were calculated and adjusted for by using survey weight, sampling clusters, and stratum.

RESULTS

In the two-year cohort, 1,065 index hospitalizations resulted in 1,907 total hospitalizations following frostbite injury. Most patients were male (80.3%), lived in metropolitan/urban areas (82.3%), and nearly half were insured with Medicaid (46.4%). Of the 842 readmissions, 53.7% were associated with complications typically associated with frostbite injury. Overall, 29% of frostbite injuries resulted in at least one amputation. The average total cost and total LOS of readmissions was $236,872 and 34.7 days. Drug or alcohol abuse, homelessness, Medicaid insurance, and discharge AMA were independent predictors of unplanned readmission. Factors associated with multiple readmissions include discharge AMA and Medicare Insurance, but not drug or alcohol abuse or homelessness. The population-based estimated unplanned readmission rate following frostbite injury was 35.4% (95% CI 32.2 - 38.6%).

CONCLUSIONS

This is the first study examining readmissions following frostbite injury on a national level. Drug or alcohol abuse, homelessness, Medicaid insurance, and discharge AMA were independent predictors of unplanned readmission, while only AMA discharge and Medicare insurance were associated with multiple readmissions. Supportive resources (community and hospital-based) may reduce unplanned readmissions of frostbite injured patients with those additional risk factors.

In pursuit of the unicorn

This short review was prompted by The Physiological Society's recent online symposium on variability. It does not deal with a specific methodology, but rather with the myth that certain environmentally-induced clinical conditions can be identified, quantified, simplified and monitored with a single methodology. Although this might be possible with some clinical conditions, others resist the prevailing reductionist approach of minimizing rather than exploring variation in pathogenesis and pathology, and will not be understood fully until the variation in cause and effect are embraced. This is likely to require comprehensive methodologies and collaboration.

Self-inflicted finger cold injury leading to amputation: Report of a case

A cold injury can result in devastating outcomes, leading to significant morbidity and loss of distal extremities. Amputations are common after severe frostbite injuries with delayed presentation, often mediated by post-injury arterial thrombosis. Ischemic injuries are managed according to the ischemia time. The most controversial aspect of treating a salvage injury is the time of surgical intervention, which used to be based on the previous management dogma freeze in January, amputate in July. Recently, the paradigm has shifted to early surgical management if the level of viability of the deep structure can be ascertained using 99mTc pertechnetate scintigraphy (99mTc bone scans). We present a case of a finger amputation resulting from a cold injury secondary to a crush injury.

Calcium maintained higher quality and enhanced resistance against chilling stress by regulating enzymes in reactive oxygen and biofilm metabolism of Chinese winter jujube fruit

The postharvest senescence of Chinese winter jujube fruit can be effectively delayed by refrigerated storage. However, chilling injury often occurs in jujube fruit during cold storage. In this study, Chinese winter jujubes were sprayed with CaCl₂ (4%) 3 times at intervals of 2 hr on the day of refrigeration. The results presented that maximum difference of 2.7 N firmness, 3.42% TAC, and 0.8 OD₂₈₀ /g polyphenol content were detected in calcium-treated fruit during cold storage, but the levels of O 2 - , MDA, hydrogen peroxide, browning rate, electrolyte leakage, and weight loss rate were significantly inhibited (p < .05). The maximum difference of enzymes activity of CAT, POD, SOD was 2.1, 10.8, and 40.6 mol h^-1 kg^-1 respectively, but 21.1 mol h^-1 kg^-1 PPO was restrained in the treated group. In conclusion, the results provided a reliable method for inhibiting cold injury and explained the internal molecular mechanism of the fruit regulated by calcium. PRACTICAL APPLICATIONS: Refrigerated storage is an important method for extending the storage time of Chinese winter jujube fruit. However, cold damage may occur when the jujubes are stored at low temperature for long-term. It is, therefore, of great significance to find a new method and reveal the molecular mechanism. We believe that our study makes a significant contribution to the literature because it provides an effective method of maintaining higher quality and mechanistic insights into the resistance against the chilling stress of jujubes.

Pedicled Abdominal Flaps for Enhanced Digital Salvage After Severe Frostbite Injury

Extremities are the area of the body most commonly affected by frostbite, which can also affect the face, ears, perineum, or genitals. Optimum management has moved away from early amputation and debridement toward maximizing tissue preservation and delaying surgical intervention. Increasing length of digit amputation increases morbidity, in terms of loss of hand function, experienced by patients. Reconstruction of affected digits is limited by bone necrosis, which often leads to shortened residual stumps and limited functional outcomes. This case describes the management of a severe frostbite injury affecting both hands and feet in a 39-y-old man, sustained during descent of Mount Everest. The use of a pedicled abdominal flap to provide soft-tissue cover permitted optimized digit length and function and sensate digits. The case highlights the benefits of early multidisciplinary team involvement in the management of severe frostbite to optimize functional outcome.

AP-1 and the injury response of the GFAP gene

Increased GFAP gene expression is a common feature of CNS injury, resulting in its use as a reporter to investigate mechanisms producing gliosis. AP-1 transcription factors are among those proposed to participate in mediating the reactive response. Prior studies found a consensus AP-1 binding site in the GFAP promoter to be essential for activity of reporter constructs transfected into cultured cells, but to have little to no effect on basal transgene expression in mice. Since cultured astrocytes display some properties of reactive astrocytes, these findings suggested that AP-1 transcription factors are critical for the upregulation of GFAP in injury, but not for its resting level of expression. We have examined this possibility by comparing the injury response in mice of lacZ transgenes driven by human GFAP promoters that contain the wild-type AP-1 binding site to those in which the site is mutated. An intact AP-1 site was found critical for a GFAP promoter response to the three different injury models used: physical trauma produced by cryoinjury, seizures produced by kainic acid, and chronic gliosis produced in an Alexander disease model. An unexpected additional finding was that the responses of the lacZ transgenes driven by the wild-type promoters were substantially less than that of the endogenous mouse GFAP gene. This suggests that the GFAP gene has previously unrecognized injury-responsive elements that reside further upstream of the transcription start site than the 2.2 kb present in the GFAP promoter segments used here.

Cold exposure causes cell death by depolarization-mediated Ca2+ overload in a chill-susceptible insect

Cold tolerance of insects is arguably among the most important traits defining their geographical distribution. Even so, very little is known regarding the causes of cold injury in this species-rich group. In many insects it has been observed that cold injury coincides with a cellular depolarization caused by hypothermia and hyperkalemia that develop during chronic cold exposure. However, prior studies have been unable to determine if cold injury is caused by direct effects of hypothermia, by toxic effects of hyperkalemia, or by the depolarization that is associated with these perturbations. Here we use a fluorescent DNA-staining method to estimate cell viability of muscle and hindgut tissue from Locusta migratoria and show that the cellular injury is independent of the direct effects of hypothermia or toxic effects of hyperkalemia. Instead, we show that chill injury develops due to the associated cellular depolarization. We further hypothesized that the depolarization-induced injury was caused by opening of voltage-sensitive Ca²⁺ channels, causing a Ca²⁺ overload that triggers apoptotic/necrotic pathways. In accordance with this hypothesis, we show that hyperkalemic depolarization causes a marked increase in intracellular Ca²⁺ levels. Furthermore, using pharmacological manipulation of intra- and extracellular Ca²⁺ concentrations as well as Ca²⁺ channel conductance, we demonstrate that injury is prevented if transmembrane Ca²⁺ flux is prevented by removing extracellular Ca²⁺ or blocking Ca²⁺ influx. Together these findings demonstrate a causal relationship between cold-induced hyperkalemia, depolarization, and the development of chill injury through Ca²⁺-mediated necrosis/apoptosis.

Frostbite Injuries in the Austrian Alps: A Retrospective 11-Year National Registry Study

OBJECTIVES

Frostbite is a cold injury mostly affecting the extremities. The objective of this study was to reveal the incidence of frostbite injuries in the Austrian Alps, to search for frostbite risk factors, and thereby optimize prevention and treatment.

METHODS

Out-of-hospital data in the National Registry of Alpine Accidents from January 1, 2005, to December 31, 2015, were screened for frostbite injuries. Cases in the registry were merged with clinical data from the major trauma center in western Austria, Innsbruck Medical University Hospital, and statistically analyzed.

RESULTS

Documented in the National Registry are 114,595 injured persons in the 11-year study period. Thirty-one frostbite cases were documented nationwide, 18 (58%) of which occurred in the western states of Austria and were therefore potentially referred to the Innsbruck Medical University Hospital. Six (19.6%) patients were female. Frostbite was almost exclusively related to fingers and toes (90% of cases).

CONCLUSIONS

Frostbite injuries in the Austrian Alps are rare. With an incidence of 0.07/100,000, three to four clinically relevant frostbite injuries occur annually. Men are at greater risk for frostbite injuries than women. Fingers and toes are at greatest risk. Proper preparation of outdoor activities and cold-protective gear can help prevent frostbite injuries.

A new treatment for frostbite sequelae; Botulinum toxin

Frostbite sequelae are a relevant occupational injury outcome for soldiers in arctic environments. A Caucasian male soldier suffered frostbite to both hands during a military winter exercise. He developed sensory-motor disturbances and cold hypersensitivity. Angiography and thermography revealed impaired blood flow while Quantitative Sensory Testing indicated impaired somato-sensory nerve function. Two years after the initial event, he received an off label treatment with Botulinum toxin distributed around the neurovascular bundles of each finger. After treatment, cold sensitivity was reduced while blood flow and somato-sensory nerve function improved. The successful treatment enabled the soldier to successfully pursue his career in the army.

Concurrent effects of cold and hyperkalaemia cause insect chilling injury

Chilling injury and death are the ultimate consequence of low temperature exposure for chill susceptible insects, and low temperature tolerance is considered one of the most important factors determining insect distribution patterns. The physiological mechanisms that cause chilling injury are unknown, but chronic cold exposure that causes injury is consistently associated with elevated extracellular [K(+)], and cold tolerant insects possess a greater capacity to maintain ion balance at low temperatures. Here, we use the muscle tissue of the migratory locust (Locusta migratoria) to examine whether chill injury occurs during cold exposure or following return to benign temperature and we specifically examine if elevated extracellular [K(+)], low temperature, or a combination thereof causes cell death. We find that in vivo chill injury occurs during the cold exposure (when extracellular [K(+)] is high) and that there is limited capacity for repair immediately following the cold stress. Further, we demonstrate that that high extracellular [K(+)] causes cell death in situ, but only when experienced at low temperatures. These findings strongly suggest that that the ability to maintain ion (particularly K(+)) balance is critical to insect low temperature survival, and highlight novel routes of study in the mechanisms regulating cell death in insects in the cold.

Overexpression of the long noncoding RNA TUG1 protects against cold-induced injury of mouse livers by inhibiting apoptosis and inflammation

Hepatic injury provoked by cold storage is a major problem affecting liver transplantation, as exposure to cold induces apoptosis in hepatic tissues. Long noncoding RNAs (lncRNAs) are increasingly understood to regulate apoptosis, but the contribution of lncRNAs to cold-induced liver injury remains unknown. Using RNA-seq, we determined the differential lncRNA expression profile in mouse livers after cold storage and found that expression of the lncRNA TUG1 was significantly down-regulated. Overexpression of TUG1 attenuated cold-induced apoptosis in mouse hepatocytes and liver sinusoidal endothelial cells LSECs, in part by blocking mitochondrial apoptosis and endoplasmic reticulum (ER) stress pathways. Moreover, TUG1 attenuated apoptosis, inflammation, and oxidative stress in vivo in livers subjected to cold storage. Overexpression of TUG1 also improved hepatocyte function and prolonged hepatic graft survival rates in mice. These results suggest that the lncRNA TUG1 exerts a protective effect against cold-induced liver damage by inhibiting apoptosis in mice, and suggests a potential role for TUG1 as a target for the prevention of cold-induced liver damage in liver transplantation.

DATABASES

RNA-seq data are available from GEO using accession number GSE76609.

Reactive oxygen species (ROS) mediates non-freezing cold injury of rat sciatic nerve

Non-freezing cold injury is an injury characterized by neuropathy, developing when patients expose to cold environments. Reactive oxygen species (ROS) has been shown as a contributing factor for the non-freezing cold nerve injury. However, the detailed connections between non-freezing cold nerve injury and ROS have not been described. In order to investigate the relationship between non-freezing cold nerve injury and reactive oxygen species, we study the effects of two cooling methods-the continuous cooling and the intermittent cooling with warming intervals-on rat sciatic nerves. Specifically, we assess the morphological changes and ROS production of the sciatic nerves underwent different cooling treatments. Our data shows both types of cooling methods cause nerve injury and ROS production. However, despite of identical cooling degree and duration, the sciatic nerves processed by intermittent cooling with warming intervals present more ROS production, severer reperfusion injury and pathological destructions than the sciatic nerves processed by continuous cooling. This result indicates reactive oxygen species, as a product of reperfusion, facilitates non-freezing cold nerve injury.

Effects of Two Short-Term, Intermittent Hypoxic Training Protocols on the Finger Temperature Response to Local Cold Stress

The study examined the effects of two short-term, intermittent hypoxic training protocols, namely exercising in hypoxia and living in normoxia (LL-TH; n=8), and exercising in normoxia preceded by a series of brief intermittent hypoxic exposures at rest (IHE+NOR; n=8), on the finger temperature response during a sea-level local cold test. In addition, a normoxic group was assigned as a control group (NOR; n=8). All groups trained on a cycle-ergometer 1 h/day, 5 days/week for 4 weeks at 50% of peak power output. Pre, post, and 11 days after the last training session, subjects immersed their right hand for 30 min in 8°C water. In the NOR group, the average finger temperature was higher in the post (+2.1°C) and 11-day after (+2.6°C) tests than in the pre-test (p≤0.001). Conversely, the fingers were significantly colder immediately after both hypoxic protocols (LL-TH: -1.1°C, IHE+NOR: -1.8°C; p=0.01). The temperature responses returned to the pre-training level 11 days after the hypoxic interventions. Ergo, present findings suggest that short-term intermittent hypoxic training impairs sea-level local cold tolerance; yet, the hypoxic-induced adverse responses seem to be reversible within a period of 11 days.

Frostbite of the hand

Frostbite is damage caused by the freezing of tissue owing to exposure to extreme cold. Clinically, it is often difficult to identify the severity of frostbite injury. There may be a wide discrepancy between the extent of damage to the skin versus that to the deeper structures. The initial clinical impression is usually worse than actual tissue damage. In addition to physical examination, diagnostic imaging, especially triple-phase bone scan, has been proposed to help differentiate between superficial and deep damage. Principles of treatment involve rapid rewarming to thaw the tissues and halt direct cellular damage, methods to minimize progressive dermal ischemia, and active wound care to promote timely healing. Pharmacological adjuncts, such as fibrinolytics, have been proposed to minimize tissue damage. Surgical therapy is postponed until there is clear demarcation between healthy and necrotic tissue.

Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress

The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8°C water, during which they were inspiring either room air (Fio2: 0.21; AIR), or a hypoxic gas mixture (Fio2: 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 ± 0.5°C, HYPO: 10.0 ± 0.5°C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 ± 3.4°C; HYPO: 22.0 ± 3.8°C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.

Using thrombolytics in frostbite injury

Until recently, the treatment of frostbite injuries has been limited to supportive care only, with mediocre outcomes. The use of thrombolytic therapy has been presented in a limited fashion in the literature since 2005. This case study describes the work-up and treatment of a patient with severe frostbite injury who received tPA. We then discuss thrombolytic therapy in more detail, with particular attention to the two studies outlining different treatment regimens.

Dynamic thermal time model of cold hardiness for dormant grapevine buds

BACKGROUND AND AIMS

Grapevine (Vitis spp.) cold hardiness varies dynamically throughout the dormant season, primarily in response to changes in temperature. The development and possible uses of a discrete-dynamic model of bud cold hardiness for three Vitis genotypes are described.

METHODS

Iterative methods were used to optimize and evaluate model parameters by minimizing the root mean square error between observed and predicted bud hardiness, using up to 22 years of low-temperature exotherm data. Three grape cultivars were studied: Cabernet Sauvignon, Chardonnay (both V. vinifera) and Concord (V. labruscana). The model uses time steps of 1 d along with the measured daily mean air temperature to calculate the change in bud hardiness, which is then added to the hardiness from the previous day. Cultivar-dependent thermal time thresholds determine whether buds acclimate (gain hardiness) or deacclimate (lose hardiness).

KEY RESULTS

The parameterized model predicted bud hardiness for Cabernet Sauvignon and Chardonnay with an r(2) = 0·89 and for Concord with an r(2) = 0·82. Thermal time thresholds and (de-)acclimation rates changed between the early and late dormant season and were cultivar dependent but independent of each other. The timing of these changes was also unique for each cultivar. Concord achieved the greatest mid-winter hardiness but had the highest deacclimation rate, which resulted in rapid loss of hardiness in spring. Cabernet Sauvignon was least hardy, yet maintained its hardiness latest as a result of late transition to eco-dormancy, a high threshold temperature required to induce deacclimation and a low deacclimation rate.

CONCLUSIONS

A robust model of grapevine bud cold hardiness was developed that will aid in the anticipation of and response to potential injury from fluctuations in winter temperature and from extreme cold events. The model parameters that produce the best fit also permit insight into dynamic differences in hardiness among genotypes.

Effect of alpha-trinositol on interstitial fluid pressure, oedema generation and albumin extravasation in experimental frostbite in the rat

1. The anti-inflammatory effect of alpha-trinositol (D-myo-inositol-1,2,6-trisphosphate) on oedema formation, microvascular protein leakage and interstitial fluid pressure (Pif) in rat skin after frostbite injury, was investigated. Alpha-trinositol (40 mg kg body weight(-1)) was administered intravenously as a bolus both before and/or in the interval between freezing and thawing of the tissue. 2. Pif was measured in rat paw skin with micropipettes connected to a servo-controlled counterpressure system. Oedema formation was estimated by measuring the increase in total tissue water content (wet weight minus dry weight divided by dry weight). Albumin extravasation (i.e., the difference between the plasma equivalent space for 125I- and 131I-human serum albumin (HSA) circulating for different time intervals) was used to estimate the microvascular leakage. 3. Compared to untreated animals, alpha-trinositol given pre- and/or post-freeze reduced total tissue water and albumin extravasation as well as the fall in Pif in injured tissue significantly (P<0.05). Alpha-trinositol given only post-freeze reduced total tissue water and albumin extravasation from 4.46+/-0.93 and 2.37+/-1.12 to 2.51+/-0.29 and 0.36+/-0.18 ml g dry weight(-1), respectively (P<0.05). 4. Pif fell from -0.8+/-0.2 mmHg pre-freeze to -3.4+/-1.0 mmHg (P<0.05) at 20 min after tissue injury (circulatory arrest) and was attenuated by treatment with alpha-trinositol. 5. We conclude that alpha-trinositol exerts its anti-oedematous effect by acting on the extracellular matrix, attenuating the lowering of Pif as well as on the microvascular wall, thereby decreasing the protein extravasation.