Control of tissue environment during vital microscopy of the microcirculation in the m. tenuissimus in cat

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Abstract
The physiological preservation of the tenuissimus muscle preparation in cat during vital microscopy of the microcirculation is assessed, comparing the originally described technique with a modified approach. Differences in the compared techniques include modes of dissection and transillumination, room-air exposure and moisturizing procedures. The original technique involves extensive dissection, inadequate temperature control and irrigation in open air. The modified technique involves less surgery due to a new illumination system, controlled heating and a Mylar foil cover on the preparation to minimize room-air influences. Temperature measurements and analyses of energy metabolism (ATP, CP, glucose, G6-P and lactate) are used as objective criteria of tissue normalcy. The microcirculation and metabolism are evaluated during anesthesia (α-chloralose) at rest as well as in hemorrhagic shock. In the resting state, muscle temperature drops to 28°C with the irrigation technique, whereas the Mylar technique keeps the temperature at 34–35°C. Neither technique causes deviations in normal metabolism. In shock, however, the temperature in the irrigated tenuissimus muscle falls 8–9°C below deep muscle temperature and there is a significantly attenuated metabolic response to ischemia, while the Mylar preparation follows the changes of unexposed muscle, both in temperature and metabolism.