Polarographic pO₂ sensors with heparinized membranes for in vitro and continuous in vivo registration

Abstract

The membranes of the pO₂ sensor in a conventional blood gas analyser and a commercially available catheter pO₂electrode were coated with a glutardialdehyde stabilized heparin layer. It was analysed whether or not the “non-thrombogenic” heparin surface could improve the accuracy of in vitro pO₂ registration and continuous in vivo p_aO₂ monitoring. The in vivo experiments were performed on anaesthetized and non-anticoagulated dogs. Two identical blood gas analysers were used, one furnished with a heparin coated pO₂ membrane and the other with a standard pO₂ membrane. In vitro pO₂ determinations exhibited—when simultaneously analysing the same blood sample—identical mean values. For repeated pO₂ determinations, however, the standard deviation was significantly lower on the analyser furnished with a heparinized membrane. The non-heparinized catheter pO₂ electrode showed a marked deterioration in accuracy with time as compared with blood-gas analysis on reference blood samples. Falsely low p_aO₂ values were presented. The heparinized catheter electrode monitored values in full agreement with those of the conventional blood gas analyser using standard membranes.

It is concluded that the heparin surface on the oxygen diffusible membranes diminishes the variability of the diffusion characteristics both at contact with anticoagulated blood in vitro and during in vivo p_aO₂ monitoring. The “non-thrombogenic” heparin surface prevents diffusion impeding clot formations when an arterial catheter pO₂ sensor is used.

Key Words:

• gas diffusible membranes
• non-thrombogenic surfaces
• pO₂ monitoring