Skeletal Muscle Oxygen Pressure Fields in Rats: A Study of the Normal State and the Effects of Local Anesthetics, Local Trauma and Hemorrhage

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Abstract
The MDO (Mehrdraht Dortmund Oberflache) oxygen electrode was used for studies of oxygen pressure fields in rat skeletal muscle. With this multiwire oxygen electrode, the three-dimensional oxygen pressure field was measured and presented as a two-dimensional frequency distribution, i.e. a histogram. Statistical analysis of the histograms was carried out with the two-sample Kolmogorov-Smirnov test. This eliminated the influence of mean values, since these do not always represent the actual biological situation. The oxygen pressure fields in skeletal muscle of anesthetized normal rats breathing air spontaneously were investigated. When the oxygen pressure in the inspired gas was changed (50% and 95%), changes were seen in muscle oxygen pressure curves. The normal oxygen pressure field histograms were compared with those obtained after local anesthesia, after local trauma to the muscle and after hemorrhage. After local anesthesia the histograms were unchanged. Significant changes in the distribution types of the histograms were found after trauma in all rats studied. After hemorrhage significant changes, similar to those seen after trauma, were found in 15 of the 23 rats studied. Local blood flow was also measured with the 133xenon-clearance method in the hemorrhage experiments. No correlation was found between the changes in the mean oxygen tension values and the changes in 133xenon-clearance.