Time course of expiratory propofol after bolus injection as measured by ion molecule reaction mass spectrometry

Abstract

Propofol in exhaled breath can be detected and monitored in real time by ion molecule reaction mass spectrometry (IMR-MS). In addition, propofol concentration in exhaled breath is tightly correlated with propofol concentration in plasma. Therefore, real-time monitoring of expiratory propofol could be useful for titrating intravenous anesthesia, but only if concentration changes in plasma can be determined in exhaled breath without significant delay. To evaluate the utility of IMR-MS during non-steady-state conditions, we measured the time course of both expiratory propofol concentration and the processed electroencephalography (EEG) as a surrogate outcome for propofol effect after an IV bolus induction of propofol. Twenty-one patients scheduled for routine surgery were observed after a bolus of 2.5 mg kg(-1) propofol for induction of anesthesia. Expiratory propofol was measured using IMR-MS and the cerebral propofol effect was estimated using the bispectral index (BIS). Primary endpoints were time to detection of expiratory propofol and time to onset of propofol's effect on BIS, and the secondary endpoint was time to peak effect (highest expiratory propofol or lowest BIS). Expiratory propofol and changes in BIS were first detected at 43 ± 21 and 49 ± 11 s after bolus injection, respectively (P = 0.29). Peak propofol concentrations (9.2 ± 2.4 parts-per-billion) and lowest BIS values (23 ± 4) were reached after 208 ± 57 and 219 ± 62 s, respectively (P = 0.57). Expiratory propofol concentrations measured by IMR-MS have similar times to detection and peak concentrations compared with propofol effect as measured by the processed EEG (BIS). This suggests that expiratory propofol concentrations may be useful for titrating intravenous anesthesia.

Online breath analysis of propofol during anesthesia: clinical application of membrane inlet‐ion mobility spectrometry

“…Several investigators have measured the propofol efficacy by BIS and in exhaled air . For example, Buchinger et al .…”

Volatile compound profiling for the identification of Gram-negative bacteria by ion-molecule reaction-mass spectrometry

“…; Hornuss et al . ). In IMR‐MS, positively charged atomic ions interact with neutral sample gas molecules.…”

Direct Analysis Mass Spectrometry

“…In the first study, comparisons between blood propofol, and propofol in the exhaled breath of patients undergoing intravenous anesthesia were monitored and the conclusion was reached that IMR-MS may allow continuous noninvasive monitoring of propofol levels in patients undergoing general anesthesia [40]. A second study also on propofol found that IMR-MS can detect propofol on human breath within seconds after a bolus injection [44]. Another investigation using IMR-MS examined breath gas from patients who were mechanically ventilated and compared the results from IMR-MS with a conventional electron impact mass spectrometer for monitoring CO 2 .…”