A New Less-Invasive Method to Estimate the Viability of Severely Ischemic Skeletal Muscle

Estimation of the viability of ischemic tissue is important for appropriate revascularization. In the present study, microdialysis combined with HPLC (high performance liquid chromatography), a new, simple less invasive method, was used to estimate the viability of anterior tibial muscle of rat hind limb (n=18). Purines, adenosine triphosphate (ATP) degradation products, were continuously measured by this method during the ischemic period. Purines were measured by analyzing the dialysate from a needle-type microdialysis probe inserted into the muscle. The purine concentration of the dialysate reflected that of the interstitial fluid of the muscle. Hypoxanthine and inosine in the muscle increased to 2.34 ± 1.16 and 1.79 ± 0.62 times the preischemic levels, respectively, after five hours of ischemia. Thereafter hypoxanthine continued to increase to 6.53 + 2.28 times the preischemic level at ten hours of ischemia, but the inosine level decreased gradually. As a result of the depletion of inosine and the continuous increase of hypoxanthine, the inosine/hypoxanthine ratio decreased significantly after five hours of ischemia, and went down to one eighth of the preischemic level at nine hours of ischemia. A depletion of inosine means a depletion of ATP, the source of inosine in purine metabolism and an essential factor for maintaining cell function. These results showed a good correlation with the TTC (triphenyl tetrazolium chloride) assay, an established method. Microdialysis, a new, simple, and less invasive method, is useful for the estimation of ischemic damage and viability of ischemic skeletal muscle.