Effects of cryogenic temperatures on microcirculation in the golden hamster cheek pouch

The cheek pouch of the golden Syrian hamster was everted over a moat and transilluminated, and the microcirculation was carefully observed under a dissecting microscope. Selected sites of the pouch were subjected to subzero temperatures and the effects were carefully recorded in cinephotography. Temperatures were carefully monitored with the insertion of thermocouple wire, and a temperature range between −20 and −30 °C was selected to correlate with the clinical experiences in clinical cryosurgical application for malignant tissue. Immediately upon thawing, momentary vasoconstriction was followed with progressive vasodilation, hyperemia, and eventual stasis. Showers of emboli were noted particularly in the venules, and there was eventual development of thrombosis and complete circulatory arrest. Introduction of colloidal dye (Evans blue) immediately sequestrated only upon the damaged vessel walls and rapidly permeated the interstitium. In areas of complete stasis the circulation of vital stain could not be observed. The arrest of circulation following freezing persisted throughout a period of 24 hrs and was confirmed by thrombosis of microvessels as observed by histological examination of the hamsters' cheek pouch. Extravasation of blood elements and hemorrhage were observed along with degenerative changes of the epidermal plate and skeletal musculature of the pouch. Normal and cancerous cells and tissues which may well survive cryogenic temperatures will undergo complete degeneration from ischemic necrosis via the vascular damage and occlusion, subjected to similar subzero temperatures. The hallmark of tissue damage is the alteration and arrest of the microcirculation.