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Hind limbs of dogs were frozen with solid CO2 and one leg was thawed at 42°C. for comparison with the other thawed at 20 to 120 C. One frostbitten ear of rabbits was thawed at 380 C. and the other at 2°C. In neither case was any essential difference reported between the rapidly and slowly thawed extremities, although the frostbitten legs were observed only for 18 hours. They reported that "if anything, the ears that were thawed in ice water showed a trace more gangrene."Ariev (1) has reported the results of several series of experiments which were designed to compare the effect of slow and rapid warming of frozen ears and feet of rabbits. After freezing both ears of rabbits with ethyl chloride, one ear was warmed with hot compresses wet in water at 400 to 450 C. The frostbitten part of the slowlywarmed ear was ultimately lost in 5 animals while the rapidly-warmed ear showed only fibrosis in the distal part. Both feet of rabbits were frozen with ethyl chloride to the tibio-tarsal joint. One foot was then rapidly thawed by means of the application of compresses wet with water at 350 to 400 C. while the other was thawed in air. In the rapidly warmed foot, gangrene "only touched the most distal parts of the toes," while in the opposite foot "total gangrene spread over the entire region subjected to freezing."The experiments reported here were carried out in order to determine the effectiveness of immediate rapid warming in preventing the occurrence of gangrene following controlled cold injury. The effect of rapid warming on local blood flow in frostbitten ears and feet following thawing f has been examined by means of fluorescein and by s measurement of skin temperature. METHODS aThe method used for the production of controlled cold injury has been described previously (6). In this series of experiments, rabbit ears were immersed at -550 C. for 1, 112 or 2 minutes; rabbit feet were immersed at -55' 476

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Indirect evidence, based upon measurements of skin temperature and observations of skin color in the feet and ears of rabbits subjected to severe cold injury, indicates that complete arrest of blood flow does not occur until more than 50 hours after injury (1). Tests of the local circulation in coldinjured regions with intravenously injected fluorescein show that the exchange of this dye between blood and interstitial fluid is impaired during the interval when the minute volume blood flow is greater than that in comparable uninjured regions (2, 3). Early arrest of blood flow in regions injured by cold has been variously ascribed to "conglutination" of red-cells (4), to capillary stasis (5), and to intravascular clotting (2). While all of the above phenomena may be observed in frostbitten tissues, none has provided an explanation of the nature of local changes in blood flow adequate to account for the maintenance of high peripheral tissue temperature at a time following cold injury when exchanges of oxygen, nutrients, and metabolites appear to be impaired.This report presents the results of microscopic study of blood flow in the small vessels of the ears of rabbits during the first hour after freezing. Blood flow was also studied in the ears of animals which were treated by rapid thawing of the ear in warm water and by procaine block of the stellate ganglion on the injured side. METHODSCold injury was produced by immersing the distal one-half to one-third of the ear for 60 seconds in a mixture of water, ethylene glycol, and alcohol cooled to -550 C. with solid carbon dioxide. Details of this method for the production of controlled cold injury and the characteristic effects on the tissues are given elsewhere (6).X The work described in this paper was done under a contract, recommended by the Committee on Medical Research, between the Office of Scientific Research and Development and Stanford University.Both normal and frostbitten ears of a uniform strain of New Zealand white rabbits were observed through a binocular dissecting microscope having 9X oculars and 4.8X objectives. The light sources was a 100-watt Spencer microscope lamp from which the light was conducted to the ear by means of a polished rod of %-inch methyl methacrylate (Lucite) 2 feet long. The rod was tapered to a cone having a rounded tip 7 mm. in diameter. The distal 8 inches of rod were bent into a curve which presented the brilliantly illuminated tip at a right angle to the original path of light. WiAh the rod in an adjustable clamp, its flattened end in contact with the blue glass of the microscope lamp, the ear was placed under the objectives of the microscope in direct contact with the methacrylate rod. Liquid petrolatum was applied to the shaved ear in order to clear the keratinized epithelium. Photographic recording of the changes observed proved to be unsatisfactory because of the thickness of tissue and the changing optical plane. OBSERVATIONSBlood flow in the capillaries of the normal ear.Movement of blood could not be seen in the larger...

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The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.