Studies on Gangrene Following Cold Injury: Vi. Capillary Blood Flow After Cold Injury, the Effects of Rapid Warming, and Sympathetic Block 1

Abstract

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...

Studies on Gangrene Following Cold Injury. Ix. The Effect of Rutin and Other Chemical Agents on the Course of Experimental Frostbite in Rabbits 12

“…The preparation was judged to be a satisfactory one only if a marked and persistent increase of 40 to 50 C. in skin temperature could be demonstrated in the ear on the blocked side. The effect of procaine block of the stellate ganglion on the local circulation of the ear following cold injury has already been presented (16). Complete loss of the distal part of the ear to the level of immersion occurred.…”

“…In the case of frostbite, direct observations of capillaries (16), as well as indirect evidence based upon tests with fluorescein (32), indicate that the slowed rate of protein loss in the later stages of injury depends upon reduction of total area available for filtration of material from the capillaries.…”

Studies on Gangrene Following Cold Injury. V. The Use of Fluorescein as an Indicator of Local Blood Flow: Fluorescein Tests in Experimental Frostbite 1

“…The influence of increased blood flow upon fluorescein exchanges in frostbitten rabbit ears Measurements of skin temperature in frostbitten ears and feet of rabbits have shown that the blood vessels of the injured regions do not participate in thermovascular reflex changes in diameter (4). However, the vessels of parts of ears proximal to the injured region show both tonic constriction and the ability to dilate in response to local application of heat or following procaine block of the stellate ganglions (6). The flow of blood into the injured area of frostbitten ears is, in part, determined by the degree of dilatation of the major arteries proximal to the line of frostbite.…”

Studies on Gangrene Following Cold Injury. Viii. The Use of Casts and Pressure Dressings in the Treatment of Severe Frostbite 1

“…Although stasis in the true-capillaries was observed to occur in ears about 10 minutes after injury, it could be delayed by several procedures (2). The delayed appearance of stasis in the treated ears, as well as the invariable late occurrence of stasis at the junction between the normal and frostbitten regions of an ear, suggest that distortion of the tissues, resulting from the massive edema, may close true capillaries and produce stasis.…”