A randomized prospective study of desflurane versus isoflurane in minimal flow anesthesia using "equilibration time" as the change-over point to minimal flow

Abstract

Background:In the administration of minimal flow anesthesia, traditionally a fixed time period of high flow has been used before changing over to minimal flow. However, newer studies have used “equilibration time” of a volatile anesthetic agent as the change-over point.Materials and Methods:A randomized prospective study was conducted on 60 patients, who were divided into two groups of 30 patients each. Two volatile inhalational anesthetic agents were compared. Group I received desflurane (n = 30) and group II isoflurane (n = 30). Both the groups received an initial high flow till equilibration between inspired (Fi) and expired (Fe) agent concentration were achieved, which was defined as Fe/Fi = 0.8. The mean (SD) equilibration time was obtained for both the agent. Then, a drift in end-tidal agent concentration during the minimal flow anesthesia and recovery profile was noted.Results:The mean equilibration time obtained for desflurane and isoflurane were 4.96 ± 1.60 and 16.96 ± 9.64 min (P < 0.001). The drift in end-tidal agent concentration over time was minimal in the desflurane group (P = 0.065). Recovery time was 5.70 ± 2.78 min in the desflurane group and 8.06 ± 31 min in the isoflurane group (P = 0.004).Conclusion:Use of equilibration time of the volatile anesthetic agent as a change-over point, from high flow to minimal flow, can help us use minimal flow anesthesia, in a more efficient way.

Sevoflurane in low-flow anesthesia using “equilibration point”

“…This method is an effective alternative to the use of inhalational agent at this period of time. [ 3 ]…”

“…Mean equilibration time obtained for desflurane and isoflurane were 4.96 ± 1.60 min and 16.96 ± 9.64 min and was statistically significant ( P < 0.001). [ 3 ] Although in these studies, sevoflurane was not studied, isoflurane and desflurane were compared and time taken to achieve equilibration time in these studies was more with isoflurane.…”

“…It is a point when ratio of expired (Fe) to inspired (Fi) concentration of inhalational anesthetic agent (Fe/Fi) reaches 0.8. [ 3 ] Newer agents such as sevoflurane and desflurane are gaining popularity, these days because of early achievement of equilibration point due to their low-blood gas solubility. They are best suited for low-flow anesthesia because of the shorter time constant.…”

Randomized comparison of isoflurane versus sevoflurane and desflurane for maintenance of ambulatory anesthesia

“…Previous studies done with LMA and minimal flow anesthesia have concluded that drowsiness was more with isoflurane than other inhalational agents. [ 21 22 ] In our study, we did not monitor sedation score. Patients were monitored only with modified Aldrete scale which showed no difference among the groups.…”

An observation from an online survey: is fresh gas flow used for sevoflurane and desflurane different from isoflurane based anesthesia?

“…The time to shift towards low flow also needs special attention in the practice of LFA. Use of equilibration time of the volatile anesthetic agent as the change-over point can help the anesthesiologists in the of use minimal flow anesthesia, in a more efficient way 10. A study using Smart Anesthesia Manager TM and Anesthesia Information Management System to notify the anesthesia team if FGF exceeds 1 L/min found that real-time notification is an effective way to reduce excess FGFs 11.…”