Importance of real-time tissue oximetry: relationship to muscle oxygenation and tissue viability.

Background: There is currently no efficient and reliable clinical means of assessing the degree of ischemia- and reperfusion-associated damage in microvascular transplants. The objective was to study correlation of tissue oxygen tension measurements with tissue oxygen saturation, cytochrome oxidase redox state, and tissue viability.

Materials And Methods: Latissimus dorsi muscle was dissected and mobilized in New Zealand white rabbits (n = 30, 2.5 ± 0.5 kg). Muscles were exposed to warm ischemia in two groups with either 4 or 6 h, followed by reperfusion. Tissue PO(2) was measured with a miniature intramuscular oxygen sensor (Licox microprobe; Integra Neurosciences, Ratingen, Germany) all along with tissue hemoglobin saturation (rSO(2)) and cytochrome oxidase aa3 redox state (CytOx) by in vivo near-infrared spectroscopy. Linear correlation was performed between tissue PO(2) and rSO(2), CytOx and tissue viability.

Results: After ischemia and reperfusion, tissue PO(2) and CytOx recovery was significantly decreased in both groups compared with control (4 h: P < 0.05; 6 h: P < 0.01). Significant correlations between changes in tissue PO(2) and rSO(2) (r = 0.92; P < 0.01), CytOx (r = 0.90; P < 0.01), wet-to-dry ratio (r = -0.97; P < 0.01), and mitochondrial viability index (r = 0.97; P < 0.01) were found.

Conclusions: Tissue oxygen tension measured with microprobes correlated closely with tissue oxygenation, cellular oxygen utilization, and the extent of ischemia reperfusion injury.