Monitoring of Propofol Boli in Breathing Gas using Ion Molecule Reaction Mass Spectrometry

Abstract

The intravenous anaesthetic propofol (2, 6-diisopropylphenol) is a widely used hypnotic. As it has some volatility, it can be detected in expired breath of subjects receiving propofol infusion. In this preclinical study we continuously monitored exhaled propofol using ion molecule reaction mass spectrometry (IMR-MS) after administering propofol boli along with continuous infusion. The correlation between blood plasma propofol concentrations and exhaled propofol concentrations was characterized.

Methods: After approval from the regional authorities for animal research preclinical studies were conducted with twelve pigs. The ion molecule reaction mass spectrometer (IMR-MS) was directly connected to the endotracheal tube with a T-piece. Propofol was applied as a bolus at 0, 30 and 60 min, and simultaneously with the first bolus an infusion of propofol was started. The concentration of propofol was continuously measured using the IMR-MS and compared to blood plasma concentrations.

Results: For each bolus application a corresponding peak in exhaled breath was detected and the time to peak duration for each propofol bolus was determined. Linear regression analysis between blood plasma propofol concentrations and breath propofol concentrations yielded the correlation coefficients (R² values), which varied between 0.28 - 0.74. Conclusions: Changes of blood plasma propofol concentration after application of a bolus can be followed in expired breath. The observed correlation between the blood plasma propofol concentrations and exhaled propofol concentration demonstrates that IMR-MS can be used to monitor propofol bolus application and infusion.