Derivation and prospective testing of a two-step sevoflurane-[O.sub.2]-[N.sub.2]O low fresh gas flow sequence

Simple vaporiser setting ([F.sub.D]) 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 [F.sub.D] sequence that maintains the end-expired sevoflurane concentration ([F.sub.A]sevo) at 1.3% using th...

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Bibliographic Details
Published inAnaesthesia and intensive care Vol. 37; no. 6; p. 911
Main Authors Van Zundert, T, Brebels, A, Hendrickx, J, Carette, R, De Cooman, S, Gatt, S, De Wolf, A
Format Journal Article
LanguageEnglish
Published Sage Publications Ltd. (UK) 01.11.2009
Subjects
Gas flow
Health aspects
Sevoflurane
Belgium
United States
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Summary:Simple vaporiser setting ([F.sub.D]) 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 [F.sub.D] sequence that maintains the end-expired sevoflurane concentration ([F.sub.A]sevo) at 1.3% using the fewest possible number of [F.sub.D] adjustments with a previously described [O.sub.2]-[N.sub.2]O FGF sequence that allows early FGF reduction to 0.7 l.[min.sup.-1]. In 18 ASA physical status I to II patients, [F.sub.D] was determined to maintain [F.sub.A]sevo at 1.3% with 2 l.[min.sup.-1] [O.sub.2] and 4 l.[min.sup.-1] [N.sub.2]O FGF for three minutes, and with 0.3 and 0.4 l.[min.sup.-1] thereafter. Using the same FGF sequence, the [F.sub.D] schedule that approached the 1.3% [F.sub.A]sevo pattern with the fewest possible adjustments was prospectively tested in another 18 patients. The following [F.sub.D] sequence approximated the [F.sub.D] 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.sup.-1] and wobble 4.4 (1.7; 8.1)%. In one patient, FGF had to be temporarily increased for four minutes. One [O.sub.2]/[N.sub.2]O rotameter FGF setting change from 6 to 0.7 l.[min.sup.-1] at three minutes and two sevoflurane [F.sub.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. Key Words: anaesthesia, low flow, sevoflurane
ISSN:0310-057X
1448-0271