Continuous intra-arterial Po₂ monitoring with a surface heparinized catheter electrode

Abstract

Surface-heparinized catheter Po₂ electrodes were used for continuous intraarterial monitoring in non-heparinized dogs. During one-day experiments the read-out of the electrode monitoring unit was compared with that of conventional blood gas analysis. Furthermore, the electrodes were studied after long-term implantation. The intra-arterial Po₂ electrodes have previously been reported to be linear in the gas phase, water phase and in heparinized blood. The present study demonstrates that the catheter electrodes remain linear after surface heparinization. As compared with the conventional blood gas analysis it was found that the desk analyser in the range P_ao₂ > 18 kPa underestimated the actual P_ao₂ as compared to the invasively monitored P_ao₂, but in the range below 7 kPa the desk analyser overestimated the P_ao₂. Surface-heparinized Po₂ catheter electrodes were studied after up to 23 days of implantation. No coagulation phenomenon was found around the catheters, neither macroscopically nor by scanning electron microscopy. The electrical function withstood 7 days of implantation. After more extended periods the electrical leads were broken without any damage to the catheter itself. When compared with acutely implanted surface-heparinized electrodes, there was no difference in monitoring characteristics between the acutely implanted and the long-term implanted Po₂ electrodes.

Key-words:

• gas diffusible membranes
• intravascular Po₂ monitoring
• non-thrombogenic surfaces