Continuous intra-arterial PO2 monitoring with a surface heparinized catheter electrode. A study of conformity in conventional blood gas analysis and of long-term electrode function in the non-heparinized dog.

Surface-heparinized catheter PO2 electrodes were used for continuous intra-arterial 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 PaO2 greater than 18 kPa underestimated the actual PaO2 as compared to the invasively monitored PaO2, but in the range below 7 kPa the desk analyser overestimated the PaO2. 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.