Elimination characteristics of post-operative isoflurane levels in alveolar exhaled breath via PTR-MS analysis

Research output: Contribution to journalArticle

Colleges, School and Institutes

External organisations

  • School of Physics and Astronomy, University of Birmingham, Birmingham, UK
  • UNIVERSITY HOSPITAL BIRMINGHAM NHS FOUNDATION TRUST
  • Breath Research Institute
  • Leopold-Franzens-Universität Innsbruck

Abstract

Isoflurane (1-chloro-2,2,2-trifluoroethyl difluoromethyl ether), C3H2ClF5O, is a commonly used inhalation anaesthetic. Using a proton transfer reaction mass spectrometer (PTR-MS) we have detected isoflurane in the breath of patients several weeks following major surgery. That isoflurane is detected in the breath of patients so long after being anaesthetised raises questions about when cognitive function has fully returned to a patient. Temporal profiles of isoflurane concentrations in breath are presented for five patients (F/M 3/2, mean age 50 years, min-max 36-58 years) who had undergone liver transplant surgery. In addition, results from a headspace analysis of isoflurane are presented so that the product ions resulting from the reactions of H3O+ with isoflurane in PTR-MS could be easily identified in the absence of the complex chemical environment of breath. Six product ions were identified. In order of increasing m/z (using the 35Cl isotope where appropriate) these are (m/z 51), CHFCl+ (m/z 67), CF3CHCl+ (m/z 117), C3F4OCl+ (m/z 163), C3H2F4OCl+ (m/z 165), and C3F4OCl+ H2O (m/z 183). No protonated parent was detected. For the headspace study both clean air and CO2 enriched clean air (4% CO2) were used as buffer gases in the drift tube of the PTR-MS. The CO2 enriched air was used to determine if exhaled breath would affect the product ion branching ratios. Importantly no significant differences were observed, and therefore for isoflurane the product ion distributions determined in a normal air mixture can be used for breath analysis. Given that PTR-MS can be operated under different reduced electric fields (E/N), the dependence of the product ion branching percentages for isoflurane on E/N (96-138 Td) are reported.

Details

Original languageEnglish
Article number046006
JournalJournal of Breath Research
Volume10
Issue number4
Publication statusPublished - 12 Oct 2016

Keywords

  • alveolar breath analysis, cognitive function, isoflurane anaesthesia, proton transfer reaction mass spectrometry, volatile organic compounds

ASJC Scopus subject areas