Creatine phosphate as the preferred early indicator of ischemia in muscular tissues.

Changes in creatine compounds, especially the creatine phosphate to creatine ratio (CrP/Cr), are more sensitive indicators than changes in other metabolites for early ischemia in the different muscular tissues of heart, small intestine, skeletal muscle, and aorta. Changes in adenine nucleotide ratios are buffered by CrP reserves and the absolute concentration of adenine nucleotides can vary greatly between different muscular tissues. Accumulation of lactate is indicative of ischemia, but is not as sensitive as the ratio of CrP/Cr, but may better indicate the duration of ischemia. Glycerol also accumulates in muscular tissues during prolonged ischemia, so that consideration of both lactate and glycerol levels together, might confer a better estimate of the duration of ischemia of different muscular tissues.