Elucidation of the Role of TRPV1, VEGF-A, TXA2, Redox Homeostasis, and Inflammatory Cascades in Protection against Cold Injuries by Herbosomal-Loaded PEG-Poloxamer Topical Formulation.

High-altitude regions, cold deserts, permafrost regions, and the polar region have some of the severest cold conditions on earth and pose immense perils of cold injuries to exposed individuals. Accidental and unintended exposures to severe cold, either unintentionally or due to occupational risks, can greatly increase the risk of serious conditions including hypothermia, trench foot, and cold injuries like frostbite. Cold-induced vasoconstriction and intracellular/intravascular ice crystal formation lead to hypoxic conditions at the cellular level. The condition is exacerbated in individuals having inadequate and proper covering and layering, particularly when large area of the body are exposed to extremely cold environments. There is a paucity of preventive and therapeutic pharmacological modalities that have been explored for managing and treating cold injuries. Given this, an efficient modality that can potentiate the healing of frostbite was investigated by studying various complex pathophysiological changes that occur during severe cold injuries. In the current research, we report the effectiveness and healing properties of a standardized formulation, i.e., a herbosomal-loaded PEG-poloxamer topical formulation (n-HPTF), on frostbite. The intricate mechanistic pathways modulated by the novel formulation have been elucidated by studying the pathophysiological sequelae that occur following severe cold exposures leading to frostbite. The results indicate that n-HPTF ameliorates the outcome of frostbite, as it activates positive sensory nerves widely distributed in the epidermis transient receptor potential vanilloid 1 (TRPV1), significantly (p < 0.05) upregulates cytokeratin-14, promotes angiogenesis (VEGF-A), prominently represses the expression of thromboxane formation (TXA2), and significantly (p < 0.05) restores levels of enzymatic (glutathione reductase, superoxide dismutase, and catalase) and nonenzymatic antioxidants (glutathione). Additionally, n-HPTF attenuates oxidative stress and the expression of inflammatory proteins PGF-2α, NFκB-p65, TNF-α, IL-6, IL-1ß, malondialdehyde (MDA), advanced oxidative protein products (AOPP), and protein carbonylation (PCO). Masson's Trichrome staining showed that n-HPTF stimulates cellular proliferation, and increases collagen fiber deposition, which significantly (p < 0.05) promotes the healing of frostbitten tissue, as compared to control. We conclude that protection against severe cold injuries by n-HPTF is mediated via modulation of pathways involving TRPV1, VEGF-A, TXA2, redox homeostasis, and inflammatory cascades. The study is likely to have widespread implications for the prophylaxis and management of moderate-to-severe frostbite conditions.

Exploring the frostbite healing potential of hyaluronic acid based hydrogel of Manuka honey through in-silico antithrombotic and anti-platelet studies of major phytoconstituents and in-vivo evaluation in Wistar rat model.

OBJECTIVE: Development of Frostbite healing hydrogel of Manuka honey and hyaluronic acid. SIGNIFICANCE: Frostbite is a cold-induced ischemic vascular injury non-responsive to most of the wound healing products. Thrombus-induced ischemia is the main cause of frostbite-related necrosis. Hyaluronic acid is known to possess significant antithrombotic and wound healing activity. Moreover, Manuka Honey is also rich in flavonoids and polyphenols with potential antithrombotic activity. These two agents were together utilized to develop a frostbite healing formulation. METHODS: In-silico antithrombotic efficacy of major phytoconstituents of Manuka honey was evaluated using in-silico-docking studies against Tissue plasminogen activator and Cyclooxygenase-1 protein. Further in-vivo frostbite healing evaluation was carried out in Wistar rats, by inducing frostbite with a supercooled rod. RESULTS: The results indicate that major leptosin and other major phytoconstituent of Manuka honey has significant antithrombotic property. The hydrogel formulation of HA and MH possess significant antimicrobial efficacy. The wound contraction studies and histopathological evaluation reveals that the hydrogel also has a good frostbite healing activity showing complete wound healing within an 18-day period. The findings of the western blotting studies suggest that the hydrogel acts by VEGF- NRF-2 pathway. CONCLUSION: This result implies that the prepared hydrogel can serve as an effective frostbite healing formulation.

Carbon dots from Artemisiae Argyi Folium Carbonisata: strengthening the anti-frostbite ability.

In this study, novel carbon dots (CDs) were discovered and separated from Artemisiae Argyi Folium Carbonisata (AAFC) aqueous extract. AAFC-CDs were characterised by a series of methods, mainly including electron microscopy, optical technology and X-ray photoelectron spectroscopy (XPS). Results displayed that AAFC-CDs with a quantum yield (QY) around 0.19% had a size distribution between 6.0 and 10.0 nm and possessed a nearly spherical shape, with a lattice spacing of 0.369 nm. In mice, AAFC-CDs reduced the tissue damage, ear frostbite, and body stiffness caused by cold, and provided energy by increasing the use of blood glucose. The mechanism may be by decreasing concentration of IL-1ßk, TNF-α and reducing the rise in blood glucose levels caused by frostbite. This study is the first to indicate that CDs may be the active constituent of AAFC against frostbite, suggesting their potential for clinical applications.

[Effects of recombinant human granulocyte macrophage colony stimulating factor gel on treatment of full-thickness frostbite wounds on foot and hand].

Objective: To explore the effects of recombinant human granulocyte macrophage colony stimulating factor (rhGM-CSF) gel on treatment of thefull-thickness frostbite wounds on foot and hand. Methods: From November 2013 to April 2017, a total of 45 patients of 71 full-thickness frostbite wounds on foot and hand meeting the inclusion criteria were admitted to the First Hospital of Jilin University and the prospective randomized controlled study was done. The patients were divided into rhGM-CSF group of 24 patients with 35 wounds and control group of 21 patients with 36 wounds according to the random number table. There were 20 males and 4 females, aged (38±13) years among patients in rhGM-CSF group, and there were 19 males and 2 females, aged (36±14) years among patients in control group. Patients in 2 groups were performed with the same systemic treatment of rewarming, anti-inflammation, pain relief, anti-infection, anti-coagulation, and thrombolysis. Wounds of patients in rhGM-CSF group and control group were respectively treated with rhGM-CSF gel and aloe vera gel for external usage with 10 mg for every square centimeter and dressing change once every 24 hours, until wounds healed completely. The wound inflammatory response was scored on treatment day (TD) 1, 3, 7, 14, wound secretion was collected for bacteria culture and positive bacteria detection rate was calculated before treatment and on TD 6 and 12, adverse drug reaction after drug use was observed, and the complete wound healing time was recorded. Data were processed with Fisher's exact probability test, analysis of variance for repeated measurement, t test, and Bonferroni correction. Results: The scores of wound inflammatory response of patients in 2 groups on TD 1 and 3 were close (t=0.37, 2.93, P>0.05). The scores of wound inflammatory response of patients on TD 7 and 14 in rhGM-CSF group were significantly higher than those in control group (t=5.77, 5.83, P<0.01). The results of bacteria culture of wound secretion of patients in 2 groups before treatment were negative. The positive bacteria detection rates of wound secretion of patients in rhGM-CSF group on TD 6 and 12 were 5.71% (2/35) and 22.86% (8/35), which were slightly lower than 13.89% (5/36) and 30.56%(11/36) in control group respectively, but there was no significantly statistical difference (P>0.05). No adverse drug response occurred in patients in rhGM-CSF group, while 1 patient in control group had adverse drug response, with symptoms of redness and swelling of wounds and patchy erythema on skin around wounds, which were alleviated by irrigating with normal saline. The complete wound healing time of patients in rhGM-CSF was (12.3±0.5) d, which was significantly shorter than (16.5±0.8) d in control group (t=24.89, P<0.05). Conclusions: The topical rhGM-CSF gel has effects of shortening time of wound healing and reducing inflammatory response of wound on treatment of full-thickness frostbite wounds on foot and hand, which is safe in clinical application.

Thrombolytic Use in Management of Frostbite Injuries: Eight Year Retrospective Review at a Single Institution.

Frostbite injuries are uncommon, understudied, and lack standardized treatment protocols. Although thrombolytics are commonly used, their efficacy remains controversial. Herein, we report the results of a retrospective review of frostbite treatment practices at a single institution. The impact of thrombolytics on outcomes was evaluated. Medical records of frostbite patients admitted between January 2010 and April 2018 were reviewed. Demographics, injury details, treatment, and outcomes were collected. Descriptive statistics were obtained. A case-control analysis comparing patients who received tissue plasminogen activator (tPA) with those who did not was performed. A total of 102 patients were included. The mean age was 43 ± 17.7; 82.4% were male. About 13% of patients were presented with first-degree, 54% with second-degree, 29% with third-degree, and 5% with fourth-degree frostbite. Toes (69%), fingers (53%), and feet (43%) were most commonly affected. Thirteen patients had angiograms. Twelve patients received tPA: three systemic tPA and nine catheter-directed tPA. Overall, 32 patients (31%) required surgery and 27 (26.5%) patients required amputation with an average of 6.5 digits amputated. Digit salvage rate based on angiography was 84.7%. Length of stay (P = .046), number of operations (P = .037), and need for surgery (P = .030) were significantly lower for patients who received thrombolytics. Two patients had bleeding complications but did not require intervention or interruption of therapy. Despite its small sample size, our study suggests benefits from thrombolytic therapy. Prospective, well designed, and multi-institutional studies are warranted to establish evidence-based treatment guidelines for the management of frostbite injuries.

Protective Effect of Extract of Ginkgo biloba 761 against Frostbite Injury in Rats.

BACKGROUND: When frostbite thaws, reperfusion injury has a crucial impact on tissue injury, and production of free radicals induces further tissue damage. This study examined whether extract of Ginkgo biloba 761 could ameliorate frostbite injury as a free radical scavenger. METHODS: Seventy-five Fisher 344 rats were divided into five groups of 15, and frostbite injury was created in each animal by sandwiching the left hind foot between a frozen magnet (-78.5°C) and a room-temperature magnet. Group I received saline; groups II, III, and IV received extract of Ginkgo biloba 761 (200, 100, and 50 mg/kg, respectively); and group V received superoxide dismutase (12 mg/kg). All drugs were injected intraperitoneally three times at 24-hour intervals. The wound surface area was measured throughout the wound healing period. Wounds were also harvested at various times to count cells stained by monoclonal antibodies for 4-hydroxy-2-nonenal and 8-hydroxy-2'-deoxyguanosine. RESULTS: Compared to group I, the wound surface area was significantly smaller in groups II and III on days 1 and 3 after wound creation. Histologic examination revealed significantly more 4-hydroxy-2-nonenal-stained cells and 8-hydroxy-2'-deoxyguanosine-stained cells in group I compared to other groups on day 1. However, there was no difference in the total healing period among the groups. A higher dose test of extract of Ginkgo biloba 761 (300 mg/kg daily) induced animal death, probably because of toxicity. CONCLUSION: Extract of Ginkgo biloba 761 demonstrated a protective effect against frostbite in the present model and probably alleviated reperfusion injury by reducing tissue peroxidation.

Intra-arterial Thrombolysis for Extremity Frostbite Decreases Digital Amputation Rates and Hospital Length of Stay.

PURPOSE: To report outcomes of intra-arterial thrombolysis versus non-thrombolytic management of severe frostbite with respect to digital amputation rates and hospital length of stay (LOS). MATERIALS AND METHODS: Seventeen patients with severe frostbite were identified from 2000 to 2017. Eight (47%) patients with mean age of 40 years underwent intra-arterial thrombolysis and served as the treatment group. Nine (53%) patients with mean age of 53 years received non-thrombolytic management and served as the control group. 2/8 (25%) treatment and 3/9 (33%) control patients had underlying vascular comorbidities (p = 0.25). Number of digits at risk, duration of thrombolysis, thrombolytic agents used, digits amputated, hospital LOS, and complications were recorded. RESULTS: Seven upper and nine lower extremities for a total of 80 digits were at risk in the treatment cohort. Eight upper and 12 lower extremities for a total of 100 digits were at risk in the control group. Mean duration of thrombolysis was 26 h. All treatment patients received tissue plasminogen activator in addition to systemic heparin. 4/16 (25%) limbs received intra-arterial alprostadil, 2/16 (13%) received nitroglycerin, and 2/16 (13%) received nicardipine. 12/80 (15%) treatment digits and 77/100 (77%) control digits required amputation (p = 0.003). Average hospital LOS was 14 days in the treatment group and 38 days in the control group (p = 0.011). No major complications occurred in the treatment group; however, 2/9 (22%) patients in the control group required extended hospitalizations secondary to amputation complications. CONCLUSIONS: Intra-arterial thrombolysis reduces digital amputation rates and hospital LOS in the setting of severe frostbite.

Poly-L-arginine topical lotion tested in a mouse model for frostbite injury.

BACKGROUND: Frostbite injury occurs when exposure to cold results in frozen tissue. We recently reported a novel mouse model for frostbite injury to be used in screening potentially therapeutic drugs and other modalities. OBJECTIVE: We used the mouse skin frostbite model to evaluate the effect of poly-l-arginine contained in lotion (PAL) applied topically to involved skin. METHODS: Sixty mice were studied in a randomized, double-blind method. Standardized 2.9-cm-diameter circles were tattooed on the mouse dorsum. Magnets snap frozen in dry ice (-78.5°C) were used to create a frostbite injury on skin within the circle as a continuous 5-minute freeze. Mice were treated with prefreeze placebo, postthaw placebo, combined prefreeze and postthaw placebo, prefreeze with PAL, postthaw with PAL, or combined prefreeze and postthaw with PAL. Appearance, healing rate, tissue loss, and histology were recorded until the wounds were healed. RESULTS: Application of PAL before inducing frostbite injury resulted in decreased tissue loss as compared with other treatment conditions. CONCLUSIONS: Applying PAL topically to frostbitten mouse skin caused decreased tissue loss. Poly-l-arginine should be studied further to determine whether it is a beneficial therapeutic modality for frostbite injury.

[Effects of Huangqi Guizhi Wuwu Decoction given by different administration methods on rats with frostbite and the mechanism].

OBJECTIVE: To establish a rat model of frostbite and to evaluate the effects of different administration methods of Huangqi Guizhi Wuwu Decoction (HGWD), a compound traditional Chinese herbal medicine for warming meridians to disperse cold, on rats with frostbite. METHODS: Frostbite in rats was induced by the method of soaking feet in hypothermia ethanol-water mixture. Levels of interleukin-6 (IL-6), tumor necrosis factor-beta (TNF-beta), thromboxane B(2) (TXB(2)) and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)) in serum of rats treated with different administration methods of HGWD, such as oral administration (Oral HGWD), soak (Soak HGWD), and oral administration plus soak (Oral-soak HGWD), were tested by enzyme-linked immunosorbent assay. RESULTS: IL-6, TNF-beta, TXB(2) levels were significantly higher (P<0.01) and 6-keto-PGFbeta level was lower (P<0.01) in serum of rats in the untreated group than in the normal control group. Compared with the untreated group, the level of IL-6 obviously decreased (P<0.05) in serum of the rats treated by oral HGWD, while no significant decrease (P>0.05) was observed in the soak HGWD group, and there was no interaction (P>0.05) between the two administration methods in regulating the level of IL-6. The levels of TNF-beta obviously decreased (P<0.01, P<0.05) in serum of the rats treated by oral and soak HGWD, and there was interaction between the two administration methods. The level of TNF-beta in the oral HGWD group was significantly lower than that in the soak HGWD group (P<0.01). Compared with the untreated group, level of TXB(2) in oral HGWD or soak HGWD group did not decrease significantly (P>0.05) and there was no interaction (P>0.05) between the two administration methods. The level of 6-keto-PGF(1alpha) was obviously increased (P<0.01) in serum of the rats treated by oral HGWD, while there was no significant decrease (P>0.05) in the soak HGWD group as compared with the untreated group, and there was interaction (P<0.05) between the two administration methods in regulating the level of 6-keto-PGF(1alpha). CONCLUSION: Rats with frostbite has immunologic dysfunction and a state of forming thrombus easily. The oral-soak HGWD can improve frostbite of local skin in rats. The therapeutic mechanism of HGWD may be to regulate the dysfunction of immune system and the imbalance of TXB(2)-PGF(1alpha).

Aloe vera in dermatology: a brief review.

Aloe vera Linne or aloe barbadensis Miller is a succulent from the Aloe family (400 different species), a tropical plant which is easily grown in hot and dry climates and widely distributed in Asia, Africa and other tropical areas. The use of aloe vera is being promoted for a large variety of conditions. The aim of this systematic review was to summarize all dermatology-oriented in vitro and in vivo experiments and clinical trials on aloe vera preparations. Extensive literature search were carried out to identify all in vitro and in vivo studies as well as clinical trials on the subject. Data were extracted from these in a predefined standardized manner. Forty studies were located. The results suggest that oral administration of aloe vera in mice is effective on wound healing, can decrease the number and size of papillomas and reduce the incidence of tumors and leishmania parasitemia by >90% in the liver, spleen, and bone marrow. Topical application of aloe vera is not an effective prevention for radiation-induced injuries and has no sunburn or suntan protection. It can be effective for genital herpes, psoriasis, human papilloma virus, seborrheic dermatitis, aphthous stomatitis, xerosis, lichen planus, frostbite, burn, wound healing and inflammation. It can also be used as a biological vehicle and an anti-microbial and antifungal agent and also as a candidate for photodynamic therapy of some kinds of cancer. Even though there are some promising results with the use of aloe vera for diverse dermatologic conditions, clinical effectiveness of oral and topical aloe vera is not sufficiently and meticulously explored as yet.

Reduction of the incidence of amputation in frostbite injury with thrombolytic therapy.

HYPOTHESIS: Thrombolytic therapy will decrease the incidence of amputation when administered within 24 hours of exposure. DESIGN: Single institution retrospective review of clinical outcomes and resource use. SETTING: Burn unit of a tertiary academic referral center. PATIENTS: From 2001 to 2006, patients with severe frostbite admitted within 48 hours of injury underwent digital angiography and treatment with intra-arterial tissue plasminogen activator (tPA) if abnormal perfusion was demonstrated. These patients were compared with those treated from 1995 to 2006 who did not receive tPA. INTERVENTIONS: Tissue plasminogen activator vs traditional management of frostbite injury. MAIN OUTCOME MEASURES: Number and type of surgery were recorded, along with amputations of digits (fingers or toes) and more proximal (ray, transmetatarsal, or below-knee) amputations. Resource utilization including length of stay, total costs, cost per involved digit, and cost per saved digit were analyzed. RESULTS: Thirty-two patients with digital involvement (hands, 19%; feet, 62%; both, 19%) were identified. Seven patients received tPA, 6 within 24 hours of injury. The incidence of digital amputation in patients who did not receive tPA was 41%. In those patients who received tPA within 24 hours of injury, the incidence of amputation was reduced to 10% (P<.05). CONCLUSIONS: Tissue plasminogen activator improved tissue perfusion and reduced amputations when administered within 24 hours of injury. This modality represents the first clinically significant advancement in the treatment of frostbite in more than 25 years.

Pentoxifylline. Adjunctive therapy in the treatment of pedal frostbite.

Frostbite injury to the extremities has the potential for disastrous effects. Prompt recognition and treatment are paramount. The use of Pentoxifylline to minimize tissue damage in the treatment of frostbite is a viable addition to the traditional therapy of rewarming soaks, pain management, and vesicle débridement. The most well known action of Pentoxifylline is its ability to increase RBC flexibility, allowing easier vascularization. This explains its indication for PVD, arterial disease, and intermittent claudication. As is explained previously, however, Pentoxifylline has multiple actions that will enhance tissue survival. The dosage of Pentoxifylline in controlled release tablet form is one 400 mg tablet three times a day with meals. The duration of treatment should be from two to six weeks. As this drug has many actions and therefore possibilities, more research is warranted with regards to its use not only with frostbite, but with other pathological processes.

Frostbite: an orthopedic perspective.

Frostbite injury to the extremities has the potential for disastrous effects. This review provides information valuable to the orthopedic surgeon to aid in the evaluation and treatment of frostbite. The pathophysiology and predisposing factors that provide a basic understanding of the nature of frostbite are discussed. Accepted and experimental imaging studies and treatment options are also reviewed. An effort is made to give the orthopedic perspective on each issue, providing a valuable resource for all orthopedic surgeons involved in the care of the patient with frostbite.

Defibrotide activity in experimental frostbite injury.

The pathogenesis of frostbite injury has not been completely elucidated although the available evidence suggests it is an inflammatory reaction following reperfusion injury. Defibrotide given i.p. at 40 mg/kg/ day for three days to rabbits, the ears of which were subjected to frostbite, decreased the presence of inflammatory cells (mast cells -76%; neutrophils -40.4%) and increased prostaglandin I2 (PGI2) (as 6-Keto-PGF1 alpha) in the involved skin. Thromboxane A2 (TxA2) (as TxB2) was unaffected. These data strengthen the view that an inflammatory process is the underlying cause of frostbite injury and that Defibrotide is active in pathological situations involving an inflammatory process like in frostbite.

Manejo conservador de las lesiones por frío / Conservative management of frost injuries

Desde 1979 a 1993, se han atendido 14 pacientes con congelamiento en las extremidades superiores e inferiores. Los 14 pacientes fueron de sexo masculino, con edades entre 19 y 28 años. Estos 14 pacientesaoprtaron un total de 78 dedos afectados, 50 dedos de los miembros superiores y 28 en los pies. Clínicamente la mayoría fueron congelamiento de 2º. El tratamiento médico comprendió reposo, uso de antiinflamatorios, antiagregantes plaquetarios y vasodilatadores en forma tardía. Las amputaciones de necesidad se efectuaron a los 24 días en los más precoces y a los 60 días en los más tardíos. En su mayoría fueron amputaciones parciales y en 2 casos se amputaron ortejos en forma total. Se realizaron algunos injertos demoepidérmicos y plastía de pulpejos

Treatment of experimental frostbite with pentoxifylline and aloe vera cream.

OBJECTIVE: To compare the therapeutic effects of systemic pentoxifylline and topical aloe vera cream in the treatment of frostbite. DESIGN: The frostbitten ears of 10 New Zealand white rabbits were assigned to one of four treatment groups: untreated controls, those treated with aloe vera cream, those treated with pentoxifylline, and those treated with aloe vera cream and pentoxifylline. MAIN OUTCOME MEASURES: Tissue survival was calculated as the percent of total frostbite area that remained after 2 weeks. RESULTS: The control group had a 6% tissue survival. Tissue survival was notably improved with pentoxifylline (20%), better with aloe vera cream (24%), and the best with the combination therapy (30%). CONCLUSION: Pentoxifylline is as effective as aloe vera cream in improving tissue survival after frostbite injury.

[Furacilin compound cream for profound frostbite].

Furacilin compound cream in the treatment of profound frostbite was studied. The results of animal experiment showed that furacilin cream might greatly reduce vascular permeability of frostbite. The average survival rate of frostbite tissue increased from 12.0 +/- 1.2% in the control group to 62.0 +/- 3.7% in the treated group. The difference between the two groups was statistically significant (P < 0.001). Five patients with profound frostbite were clinically treated with the cream with satisfactory results.

Evidence for an early free radical-mediated reperfusion injury in frostbite.

Frostbite is characterized by acute tissue injury induced by freezing and thawing. Initial complete ischemia is followed by reperfusion and later, tissue necrosis. These vascular events support the hypothesis that free radical-mediated reperfusion injury at thawing might contribute to tissue necrosis after frostbite in a manner similar to that seen after normothermic ischemia. To test this hypothesis, rabbit ears were frozen at -21 degrees C for 30, 60, 90, or 120 s and rewarmed at room temperature (22 degrees C). Rabbits were treated "blindly" with saline alone, highly purified, pharmaceutical grade superoxide dismutase (SOD), allopurinol, or deferoxamine. The area of ear necrosis was determined 3 weeks after frostbite by "blinded" morphometry. The administration of SOD at the time of thawing significantly improved viability in ears frozen for 60 and 90 s, but not in those frozen for 30 or 120 s. Deferoxamine also improved viability in ears frozen for 60 s. Allopurinol did not significantly affect ear survival. Electron micrographs showed the appearance of severe endothelial cell injury beginning during freezing and extending through early reperfusion. Later, neutrophil adhesion, erythrocyte aggregation, and microvascular stasis were seen. These findings suggest that free radical-mediated reperfusion injury has a role in frostbite, and quantitate the proportion of the injury that is due to this mechanism.

Treatment of frostbite with the calmodulin antagonists thioridazine and trifluoperazine.

1. Thioridazine and trifluoperazine, which have been previously found in this laboratory to be the most effective calmodulin antagonists in treatment of burns, are shown here to be also effective in the treatment of frostbite. 2. Electron microscopic studies have revealed a complete reversal of both the vascular and skin tissue damage induced by frostbite. 3. The reversal of the vascular damage was also demonstrated by the ability of these compounds to abolish the increase in hemoglobin content in the skin. 4. The reversal of the skin tissue damage was also revealed by the ability of these compounds to raise the decreased ATP level and the reduced activities of 6-phosphogluconate dehydrogenase and mitochondrial and soluble hexokinase in skin, induced by frostbite, to normal control levels.

Treatment of experimental frostbite with urokinase.

An experimental model of frostbite using a standard cold injury in rats was used to test the therapeutic usefulness of the fibrinolytic agent urokinase. Control groups included rapid rewarming, slow rewarming, and slow rewarming followed by saline infusion. Urokinase was administered through an intra-arterial catheter 30 minutes after cold injury and slow rewarming. Optimum results were obtained with rapid rewarming of the extremity at 43 degrees C. However, with rewarming at room temperature eventual tissue loss was significantly decreased with the infusion of urokinase compared with either no treatment or saline infusion. In the clinical situation where the patient with frostbite is seen after slow rewarming, we believe that clinical trials of the use of a fibrinolytic agent are warranted.