Snakebite or frostbite: what are we doing? An evaluation of cryotherapy for envenomation.
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Cryosurgery↗
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The consequences of frostbite.
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Amputation, Surgical↗
[Medical aspects of avalanche accidents: hypothermia and frostbite].
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Accidents↗
Face cooling by cold wind in walking subjects.
The effects of low to moderate wind speeds on face temperature, thermal and pain sensations while subjects walked on a treadmill during cold exposure were studied in eight healthy men. The purpose of the study was to evaluate further the risk of frostbite at different activity levels. The walking speed was 2.8 km h(-1) and two inclination levels were used, 0 degrees and 6 degrees. The subjects were exposed to -10 degrees C and 0, 1 or 5 m s(-1) wind for 60 min dressed in cold-protective clothing with only the face unprotected. Results from previous experiments with the same subjects standing for 30 min were included in the analysis of the data. Each individual was exposed to all combinations of air velocity and activity level. The exposure to -10 degrees C and the highest wind speed used would carry no risk of frostbite according to the wind chill index. Cold lowered the skin temperature of the face significantly and wind further increased skin cooling. The activity level did not affect forehead and cheek temperatures, but the average nose skin temperature was higher and pain sensations were reduced at a higher work rate. The predicted risk of frostbite in the nose, based on average responses, would thus be less at a higher work rate. However, the results indicate that exercise does not necessarily protect all individuals from frostbite at moderate air speeds, since the nose skin temperature of 25% of the subjects dropped to 0 degrees C at 5 m s(-1) during both standing and walking. Thus the potential individual risk of frostbite in the nose is similar during light exercise and standing. Moreover, the risk of frostbite seems to be underestimated by the wind chill index under the conditions tested in this study.
Adult↗
Early and late functional and histopathological perturbations in the rabbit ear-artery following local cold injury.
BACKGROUND: These experiments aimed to study the in vivo short and long term neurovascular regeneration after frostbite. METHODS: The rabbit central ear-artery was used as the experimental model. The effects on the noradrenergic innervation of the artery were measured in isolated vascular ring segments the first day and 2, 3-4, and 8-10 or 10-20 weeks following freezing at -9 degrees C or -18 degrees C for 15 min with slow rewarming for 7 min at room temperature. RESULTS: Two days after freezing the sympathetic nerves were completely degenerated, as observed with glyoxylic acid-induced fluorescence. The vascular isometric tension responses to exogenous noradrenaline and endogenously released noradrenaline by electrical stimulation in vitro were abolished. A varying degree of necrosis of the vascular wall was observed. Two weeks after freezing at -18 degrees C in vitro responses to exogenous noradrenaline and electrical stimulation were still abolished, then gradually approaching control levels after 10-20 weeks of in vivo regeneration. Eight and 10 weeks after injury at -9 degrees C increased vascular tension responses to exogenous noradrenaline was found. In spite of a long regeneration period the total uptake and the spontaneous and K+ (75 mM) evoked releases of [3H]noradrenaline were persistently decreased after frostbite at -18 degrees C, but they were regenerated to control levels already 10-20 weeks after -9 degrees C. Regeneration of noradrenergic nerve function, expressed as [3H]noradrenaline uptake and release and responsiveness to electrical stimulation, expressed as vascular contraction, was slower than the regeneration of the vascular smooth muscle. Myointimal hyperplasia developed in response to -9 degrees C and -18 degrees C frostbite. The uptake and the K+ evoked release of [3H]noradrenaline were particularly sensitive parameters for autonomic nerve function. CONCLUSIONS: The present findings may demonstrate important neurovascular reactions to local frostbite and may explain human sequelae following frostbite.
Adrenergic Fibers↗
Changes in adrenergic nerves and tissue perfusion after freezing injury to the ear skin of rabbits.
The aim of the present study was to investigate by a combined trypan blue and catecholamine fluorescence technique the sequential changes in cutaneous adrenergic nerves, the distribution of blood flow, and vascular permeability at the demarcation line that occurred after experimental cold injury. Nine New Zealand white rabbits weighing 4.0-4.4 kg had frostbite induced by pressing the bottom of a glass bottle 2 cm in diameter filled with liquid nitrogen against the shaved skin of the ear. All the rabbits were anaesthetised with ketamine hydrochloride (Ketamine) and xylazine hydrochloride (Rompun). Specimens were taken one and three days, and two weeks after frostbite. Control samples were taken from the opposite normal ear. Trypan blue was injected into a saphenous vein just before the specimens were taken. The specimens were always taken in the same way and selected so that the probable demarcation line of the frostbite ran across the middle. The glyoxylic acid-induced fluorescence method was used to show the adrenergic nerves. There were no adrenergic nerves around the vessels and no arteriovenous anastomoses in the central area of the injury after one day, but catecholamines had started to accumulate in the adrenergic nerve endings at the margins of the injured area. This accumulation was still more obvious three days after frostbite. Some fluorescent regenerating adrenergic nerves could already be seen at the probable demarcation line two weeks after frostbite. There was increased trypan blue fluorescence near the margin of the injured area after one day, indicating extravasation and vascular damage.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Eicosanoids and inflammatory cells in frostbitten tissue: prostacyclin, thromboxane, polymorphonuclear leukocytes, and mast cells.
The pathophysiology of cold injury is still controversial. An inflammatory process has been implicated as the underlying mechanism and certain anti-inflammatory substances such as ibuprofen and acetylsalicylic acid have been used in the clinical treatment of frostbite injury. It has been postulated that the progressive ischemic necrosis is secondary to excessive thromboxane A2 production, which upsets the normal balance between prostacyclin (prostaglandin I2) and thromboxane A2. It was aimed to clarify the pathophysiology of cold injury in this study. Twenty-one New Zealand White rabbits, each weighing 1.2 to 2.9 kg, were divided into control (n = 10) and frostbitten (n = 11) groups the randomly. The rabbit ears in the frostbitten group were subjected to cold injury, and the levels of thromboxane A2 (as thromboxane B2) and of prostaglandin I2 (as 6-keto-prostaglandin F1alpha) and the number of inflammatory cells (polymorphonuclear leukocytes and mast cells) were measured in normal and frostbitten skin of rabbit ears. The levels of 6-keto prostaglandin F1alpha and thromboxane B2, the stable metabolites of prostaglandin I2 and thromboxane A2, respectively, were increased in a statistically significant way (p < 0.002) by frostbite injury; however, thromboxane B2 increased more than 6-keto prostaglandin F1alpha. Polymorphonuclear leukocytes and mast cells, absent in normal skin, were present in the frostbitten skin. There was a statistically significant (p < 0.01) correlation between the time a rabbit ear was maintained at below -10 degrees C and skin survival and between the weights of rabbits and skin survival (p < 0.024). All these findings suggest that inflammation is involved in frostbite injury; a decrease in prostaglandin I2/thromboxane A2 ratio could be one of the factors leading to necrosis; the bigger the animal, the better its ability to counter frostbite.
6-Ketoprostaglandin F1 alpha↗
Basal cell carcinomas of the auricular region: a study of 23 cases.
Basal cell carcinomas (BCCs) of the auricular region are not frequently reported, especially in the Japanese literature. Predisposing conditions such as sun exposure or frostbite are possibly involved in their development. In this study, we report our cases of auricular BCCs, discussing the obtained results, the possible significance of predisposing conditions, and the correlation with the histologic subtypes involved. Among 1094 patients with BCCs, auricular tumors were observed in 23 patients (2.1%), 4 women and 19 men. All of them were present on the external sun-exposed auricular side. Histologic patterns were nodular and micronodular (13 cases) and infiltrative (10 cases). No differences were observed between sexes. The relative degree of elastosis was higher in men than in women. Frostbite was recorded in 4 cases. The ear is an anatomical region that is heavily exposed to sun-light and equally prone to frostbite. Our data showed that all the lesions were located on the auricular region more or less exposed to sunlight. There was a recorded previous history of predisposing factors in most cases, and the high degree of elastosis suggests the involvement of these predisposing factors. Moreover, the high prevalence of infiltrative subtypes observed in our survey suggests a possible correlation between some histologic subtypes, sun-exposure, and frostbite. The differences between the relatively high number of auricular BCCs reported in the literature in contrast with the Japanese observations suggest the involvement of social or local conditions.
Age Distribution↗
The epidemiology of cold injury in Antarctica.
METHOD: A retrospective study was performed of 10 yr of medical records to determine the type, severity, etiological factors and treatment of cold injury experienced by members of the British Antarctic Survey between 1986-95. RESULTS: There were 61 new consultations for cold injury. These comprised 2.5% of all new consultations with an incidence of 65.6 per 1000 per year. Cold injuries seen were frostbite (95%), hypothermia (3%) and trench foot (2%). Superficial frostbite was the most common injury (74% of cases) with the face the most frequently affected area (47% of injuries). No cases of frostbite severe enough to cause permanent tissue loss were seen. The prevalence of cold injury increased with falling temperature to a maximum between -25 and -35 degrees C, despite these temperatures occurring infrequently. The relationship with windchill is not as clear cut with frequency of injury tending to follow the frequency of windchill values except at higher windchill values. Neither temperature nor windchill were found to significantly influence the severity of frostbite. Prior cold injury was shown to be significantly (chi2 p < 0.001) associated with further cold injury. Most injuries (78%) occurred during recreation; skiing and snowmobile driving were often implicated. CONCLUSIONS: Cold injury is uncommon in Antarctica. Despite this, it warrants a continued high profile as under most circumstances it may be regarded as an entirely preventable occurrence.
Antarctic Regions↗
Cold exposure injuries and the winter athlete.
The winter athlete is faced with the hazards of injuries from exposure to low temperatures. Physicians who treat winter sports trauma must be prepared to manage the spectrum of these injuries including hypothermia, frostbite, and the combination of both. Hypothermia is primarily a problem of mortality, which can be lowered by gentle handling, close cardiac and electrolyte monitoring, and appropriate rewarming. Frostbite, a problem of morbidity from local tissue loss, can be treated most effectively with rapid rewarming in a water bath of 40 degrees-42 degrees. Spontaneous thawing with further injury to insensitive frostbitten members and refreezing injuries give a poor prognosis. The management of hypothermia and frostbite is directed first to hypothermia to lessen mortality and second to frostbite to decrease the morbidity.
Amputation, Surgical↗
Windchill and the risk of tissue freezing.
Low air temperatures and high wind speeds are associated with an increased risk of freezing of the exposed skin. P. A. Siple and C. F. Passel (Proc. Am. Phil. Soc. 89: 177-199, 1945) derived their windchill index from cooling experiments on a water-filled cylinder to quantify the risk of frostbite. Their results are reexamined here. It is found that their windchill index does not correctly describe the convective heat transfer coefficient (hc) for such a cylinder, the effect of the airspeed (v) is underestimated. New risk curves have been developed, based on the convection equations valid for cylinders in a cross flow, hc infinity v0.62, and tissue freezing data from the literature. An analysis of the data reveals a linear relationship between the frequency of finger frostbite and the surface temperature. This relation closely follows a normal distribution of finger-freezing temperatures, with an SD of 1 degree C. As the skin surface temperature falls from -4.8 to -7.8 degrees C, the risk of frostbite increases from 5 to 95%. These data indicate that the risk of finger frostbite is minor above an air temperature of -10 degrees C, irrespective of v, but below -25 degrees C there is a pronounced risk, even at low v.
Body Temperature↗
[Treatment of freezing injury].
Report on therapeutic procedures in patients with second and third degree congelations (frostbite) on the feet. Two mechanisms of tissue damage caused by exposure to cold temperature will be discussed pathophysiologically: direct freezing injuries and cell death through intra and extracellular ice crystal formation as well as transient and finally irreversible tissue damage due to decreased perfusion. The condition of decreased perfusion results from persistent vaso-constriction induced by cold temperature, increased blood viscosity, sludge phenomenon and occlusion by platelet thrombi in the microvasculature. Frostbite beyond the erythematous stage should be treated primarily with a parenteral therapy in order to improve the hemorrheologic parameters, in particular within the micro-vascular compartment. Colloidal plasma volume expander such as 10% dextran solution is used to increase the intravascular volume. This solution (with its coating effect) and pentoxifyllin lowers the aggregation of erythrocytes and platelets. The latter will also be favourably influenced by the use of iloprost or acetylsalicylic acid. Iloprost as a stable metabolite of prostacyclin is a powerful vasodilator which attenuates the peripheral vascular resistance and activates fribrinolysis. Pentoxifyllin is considered to lower pathologically increased levels of fibrinogen. Both drugs may protect against damage of the vascular endothelium. Based on their pharmacological effects the above-mentioned drugs may improve tissue perfusion and therefore tissue damage caused by frostbite can be limited. However, an important factor is to strictly avoid bacterial infections in the cold-damaged tissue.
Blood Viscosity↗
Thermal effects of emollients on facial skin in the cold.
Ointments are traditionally used in Finland for protection against facial frostbite. Recent epidemiological reports showed unexpectedly, however, that the use of ointments is a statistically considerable risk factor for frostbite of the face and ears. The effects of 4 different emollients on facial temperature were studied in 46 acute cold exposures. The voluntary test persons sat in a cold chamber after emollients were applied thickly on half of the face, while the other half acted as an untreated control. Thermistors and an infrared scanner were used to measure skin temperature of symmetrical areas of the face. The thermal sensations on the corresponding sites were also recorded. Test emollients more often had an objectively cooling than a warming effect on facial skin. However, white petrolatum often produced a subjectively warming skin sensation. "Protective" ointments may cause a false sensation of safety, leading to increased risk of frostbite due to neglect of other protective measures.
Adult↗
Demographics of the homeless in an urban burn unit.
There are few articles about the homeless in burn literature. We sought to determine the demographic characteristics of the homeless citizens admitted to an urban burn center. This was a retrospective review from March 1999 to May 2004. Statistical analysis included chi2 and one-way analysis of variance. There were 1615 burn admissions, and 73 (4.5%) of these patients were homeless. Although the %TBSA affected was similar for the homeless and domiciled patients, the mean (+/-SD) age of the homeless was 44 +/- 10 years and their length of stay was 15 +/- 15 days, compared with 31 +/- 22 years and 9 +/- 13 days, respectively, for the domiciled. Twenty-one (29%) of the 73 homeless were admitted for frostbite, vs 21 (1.4%) of the 1542 domiciled patients (P= .000). Because of the frostbite, the majority (53%) arrived in the winter, compared with 15% in each of the other three seasons (P= .000). The homeless had a higher frequency of acute and chronic ethanol and cocaine use than the domiciled population (21% vs 6%). There was no significant difference between the homeless and the domiciled population in %TBSA affected, nutritional values, and assault frequency. More than half of the homeless patient admissions to the burn unit resulted from assault or frostbite. The homeless were mainly African-Americans and Caucasians, with a higher frequency of ethanol and cocaine use than in the domiciled burn population. Lack of discharge options for the homeless prolonged the average length of stay, leading to increased costs, often borne by the burn unit.
Adolescent↗
[Effects of exposure to hypoxia on the skin temperature and glycogen content of frostbitten feet in rabbits].
Effect of exposure to acute hypoxia and hypoxia for 2 weeks on the skin temperature and content of glycogen of frostbitten feet in rabbits were observed. The results showed that the skin temperatures and content of glycogen were decreased in frostbite at normoxia (FN) group frostbite during acute hypoxia (FAH) group and frostbite hypoxia for 2 weeks (FH-2w) group. After treatment with warm chlorhexidine immersion the skin temperature and glycogen content in treated feet of FN and FAH group were increased, as compared with untreated feet. However, there was no difference between treated and untreated feet in FH-2w group, suggesting that there may be severe disturbance of blood circulation on frostbitten feet under this condition.
Animals↗
[Cold-induced pathology at high altitude].
Cold injury is an objective danger in mountain climbing as well as in many outdoor and recreational sports such as skiing, fishing, etc. Symptoms are easily recognizable by the experienced, and prevention is mostly possible. Cold injury should be divided by pathological means in general hypothermia and local frostbite injuries. Life-threatening deep hypothermia with coma and insufficient circulation or cardiac arrest is reversible under the condition of sufficient core rewarming, for instance by CEC. Because of the big tolerance of hypothermic patients to hypoxia, clinical death is not like biological death and therefore reversible. Local frostbite is not life-threatening, but has often deleterious effects. Rapid rewarming in warm water of 37 to 42 degrees C is mandatory. After rewarming, the difference between superficial and deep frostbite can be established. Scintigraphy seems to be of great help in setting early prognosis. Daily sterile treatment of the injury, whirlpool bath and prevention of infections belong to standard treatment. There are little objective informations about the role of vasodilators, anticoagulants, antibiotics, sympathectomy and others. Early experience with Prostavasine seems to bee encouraging.
Adult↗
Cold weather injuries among U.S. soldiers in Alaska: a five-year review.
Cold weather injury (CWI) reports covering 272 U.S. Army soldiers from September 1990 to May 1995 were reviewed. First- and second-degree frostbite accounted for 99.3% of all injuries. Although some soldiers had extensive lost duty time from their injuries, no one suffered tissue loss during the 5-year period. Fifty-one percent of injuries occurred during field training. Thirty-six percent occurred while engaging in garrison activities, including physical training, which accounted for 15% of all CWIs. Twelve percent of all injuries occurred during off-duty time. Seventy-one percent of CWIs occurred when the wind-chill factor was at or below -20 degrees F (-29 degrees C). Male African-American soldiers appear to be significantly more susceptible to frostbite than male Caucasian soldiers, especially with regard to frostbite of the distal extremities (relative risk = 3.94; 95% confidence interval = 2.77-5.59). Other identified risk factors include inadequate clothing, wet clothing, dehydration, inactivity, fatigue, and previous CWIs.
Adult↗
Accidents in the Arctic. A psychological point of view.
The aim of this paper is to discuss the influence of arctic conditions on the occurrence of accidents especially from the point of view of the interaction between environment, activity and man. Special attention is paid to risk assessment, risk taking and risk compensation. According to the danger factor theory frostbites should be extremely common in arctic regions, but in reality serious frostbites appear rarely in accident statistics. This finding supports the interactive accident theories. Instead cold can be a contributing factor in accident and injury causation and the effect of cold is most often indirect. Frostbites can occur e.g. as a result of an accident, losing one's way because of darkness, snow storm etc., wet clothes, unexpected temperature changes, disease attack, alcohol-induced reasons such as immobility or excess risk taking etc. Temperatures below and above +20 degrees C increase unsafe behavior. In the Arctic it is impossible to remove all the potentially dangerous factors, because many typical features of working and living conditions are regulated by natural forces, the seasons etc. This makes accurate risk assessment and prediction especially important in accident prevention. If the person does not recognize the situations in which the risk factors exist, he/she cannot implement precautionary steps at the right moment and hence cannot avoid risks. Moreover, if better and safer machines, equipment and tools get people to take greater risks, the accident situation can even become worse.
Accident Prevention↗