Measurement of propofol exhalation in pigs, humans and sheep during anesthesia - the impact of reference methods

摘要

Propofol as an intravenous anesthetic agent can be measured in breath gas with concentrations expressed as part per billion or in ng/L. This noninvasive method may provide information aboutthe plasma concentration as well as the effect site concentration. The blood gas partition coefficient (BC) as the quotient of propofol concentration in plasma (CpPL) and breath (c_pG) and may identify individual as well as species specific differences. Discontinuous reference measurements of c_pG are adsorption tubes (TENAX) or solid-phase microextraction (SPME) for sampling followed by gas chroma-tography - mass spectrometry (GC-MS). Adsorption tubes or SPME are simple and safe methods to collect the breath gas sample. Then the sample is transferred to the sensitive GC-MS device at another place. This offers the opportunity to compare different methods from various sites. Continuous detection methods for propofol methods are soft ionization techniques ion - molecule reaction (IMR) -respectively proton transfer (PTR) - mass spectrometry (MS), both with the advantage of real-time measurement. C_PG were measured with both GC - MS and IMR-MS to compare the BC of propofol for pigs, humans and sheep.After approval of the regional authority respectively the institutional review board c_pPL and c_pG were analyzed during propofol anesthesia for 12 pigs and 12 patients by GC-MS and for 7 pigs and 3 sheep by IMR-MS. C_pPL was determined by reversed phase high performance liquid chromatography (RP-HPLC).Compared to pigs BC for humans is smaller (75910 vs 31098) and for sheep is larger (18256 vs 332648; both in medians).C_pG in small concentration can be measured by GC-MS and by IMR-MS. Propofol exhalation is species dependent in the sequence humans > pigs > sheep.