Derivation and prospective testing of a two-step sevoflurane-O 2-N2O low fresh gas flow sequence

T. Van Zundert, A. Brebels, J. Hendrickx*, R. Carete, S. De Cooman, S. Gatt, A. De Wolf

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Simple vaporiser setting (FD) and fresh gas flow (FGF) sequences make the practice of low-flow anaesthesia not only possible but also easy to achieve. We sought to derive a sevoflurane FD sequence that maintains the end-expired sevoflurane concentration (FAsevo) at 1.3% using the fewest possible number of FD adjustments with a previously described O2-N2O FGF sequence that allows early FGF reduction to 0.7 l.min-1. In 18 ASA physical status I to II patients, F D was determined to maintain FAsevo at 1.3% with 2 l.min-1 O2 and 4 l.min-1 N2O FGF for three minutes, and with 0.3 and 0.4 l.min-1 thereafter. Using the same FGF sequence, the FD schedule that approached the 1.3% F Asevo pattern with the fewest possible adjustments was prospectively tested in another 18 patients. The following FD sequence approximated the FD course well: 2% from zero to three minutes, 2.6% from three to 15 minutes and 2.0% after 15 minutes. When prospectively tested, median (25th; 75th percentile) performance error was 0.8 (-2.9; 5.9)%, absolute performance error 6.7 (3.3; 10.6)%, divergence 18.2 (-5.6; 27.4)%.h-1 and wobble 4.4 (1.7; 8.1)%. In one patient, FGF had to be temporarily increased for four minutes. One O2/N2O rotameter FGF setting change from 6 to 0.7 l.min-1 at three minutes and two sevoflurane F D changes at three and 15 minutes maintained predictable anaesthetic gas concentrations during the first 45 minutes in all but one patient in our study.

Original languageEnglish (US)
Pages (from-to)911-917
Number of pages7
JournalAnaesthesia and Intensive Care
Issue number6
StatePublished - Nov 2009


  • Anaesthesia
  • Low flow
  • Sevoflurane

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine
  • Anesthesiology and Pain Medicine


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