Ischemia tolerance of free-muscle flaps: an NMR-spectroscopic study in the rat

The ischemia tolerance of free-muscle flaps was investigated in the rat by orthotopic and syngeneic transplantation of muscle flaps measuring 4 x 2.5 cm. The effects of ischemia with a maximal duration of 7 hours on the raised flaps and of anoxia caused by occlusion of the flap vessels were studied for the first time using 31P-spectroscopy. Energy metabolism was found to recover fast after 3 hours of ischemia, whereas a duration of 4 hours led to severe, only slowly reversible changes. Longer periods of ischemia resulted in a complete loss of energy reserves (PCr) and weaker ATP signal. The complete absence of ATP and a pH value under 6 indicated irreversible muscular damage.