A multipoint micro antimony pH electrode for tissue surface measurements

Abstract

Based on monocrystalline antimony we have developed a multipoint tissue surface pH electrode. The six electrodes were produced by spark cutting from a large antimony single crystal. The electrodes were then cast in epoxy resin in a ring shaped structure which fitted around the MDO oxygen electrode. The antimony electrode was ground and polished to expose an undisturbed closely packed crystal plane of antimony to the measuring solution. Before and after monitoring periods standardization was performed in TRIS buffers of pH 6.72, 7.32 and 7.74 at 37° C. Antimony electrode potential is influenced by oxygen. Therefore, mean tissue oxygen pressure was registered simultaneously with an MDO electrode. The oxygen sensitivity factor used in this study was 18mV/logpO₂. The correction factor for the antimony electrode oxygen dependence, measuredin vitro, seemed to be correct also for thein vivo state. This, however, needs further investigation. To illustrate the usefulness of the multipoint pH electrode seven normal state rabbits were studied, and thereafter four — one each in a hypoxic, hypocarbic, hypovolemic or hyperoxic situation. In the normal state tissue pH measured on a skeletal muscle surface varied from 7.0 to 7.4. In the case of tissue microcirculation shutdown (in the hypocarbic or the hypovolemic situations), the initial reaction was a scattering of the pH values, and then the development of tissue acidosis. Our conclusion is that the use of a multipoint pH sensor enables improved and more detailed monitoring of the tissue acid-base status.