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

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 (alpha-chloralose) at rest as well as in hemorrhagic shock. In the resting state, muscle temperature drops to 28 degrees C with the irrigation technique, whereas the Mylar technique keeps the temperature at 34--35 degrees C. Neither technique causes deviations in normal metabolism. In shock, however, the temperature in the irrigated tenuissimus muscle fall 8--9 degrees 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.