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Low‐flow anaesthesia at a fixed flow rate
Author(s) -
CHERIAN A.,
BADHE A.
Publication year - 2009
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.2009.02040.x
Subject(s) - medicine , anesthesia , isoflurane , fresh gas flow , incidence (geometry) , sevoflurane , physics , optics
Aims and Objectives: This study attempts to assess the safety of low‐flow anaesthesia (LFA) at fixed flow rates with particular reference to the incidence of a decline in FiO 2 below safe levels of 0.3 and to determine whether LFA can be used safely in the absence of an FiO 2 monitor. Methods: A total of 100 patients undergoing procedures under general anaesthesia at fresh gas flows of 300 ml/min of O 2 and 300 ml/min of N 2 O were monitored while maintaining the dial setting of isoflurane at 1.5% for 2 h. The changes in gas composition were analysed and even a single recording of FiO 2 of <0.3 was considered sufficient to render the technique unsafe in the absence of gas monitors. Results: The lowest recorded value of FiO 2 was 31% (v/v%). There was no incidence of adverse events necessitating the conversion from low flows to conventional flows. Conclusions: We conclude that low flows of 300 ml/min of N 2 O and 300 ml/min of oxygen can be used safely for a period of 2 h without the use of monitors for gas analysis of oxygen and agent in adult patients weighing between 40 and 75 kgs.