Skeletal muscle oxygen pressure fields during controlled hypotension with adenosine and sodium nitroprusside. A comparative study in the rabbit.

The MDO (Mehrdraht Dortmund Oberfläche) multiwire oxygen electrode was used for studies of oxygen pressure fields in eight rabbit skeletal muscle preparations during controlled hypotension with adenosine and sodium nitroprusside (SNP). Tissue oxygen histograms were constructed from 120 simple tissue oxygen pressures (PtO2) samples that were collected during 5 min. Statistical analysis between histograms was performed with the two-sample Kolmogorov-Smirnov test. Mean arterial blood pressure was reduced to 60 mmHg with both drugs, corresponding to a 42-43% reduction during the 25-min hypotension period. SNP-induced hypotension caused significant reduction of muscle oxygenization (compared to normotensive controls) in six of the animals, while this occurred on three occasions during adenosine administration. When comparing the histograms during hypotension, the tissue oxygenation during adenosine infusion was higher than during SNP in five and equal to SNP in three animals. Low tissue oxygen pressure values (0-0.6 kPa) were four times more frequent during SNP than during adenosine hypotension, although systemic arterial oxygen pressures were unaffected. We conclude that controlled hypotension with adenosine preserves tissue oxygen pressures better than hypotension induced by SNP.