Sevoflurane in low-flow anesthesia using "equilibration point"

While giving low-flow anesthesia, it is a routine practice to give fixed duration of initial high-flow. This study was conducted to show the use of equilibration point as changeover point from initial high-flow to low-flow.

It was to compare the use of equilibration point, hemodynamics, end-tidal agent concentration, recovery time, and recovery score between isoflurane and sevoflurane.

It was a prospective randomized study conducted on 100 patients who were admitted for elective surgery expected to be < 2 h duration.

Patients were randomly assigned to one of the two groups of 50 each. Group I received isoflurane and Group S sevoflurane as an inhalational agent.

The observations obtained in both the groups were recorded and compared. Analysis was done using unpaired t-test and Chi-square test.

Hemodynamic parameters were comparable in both the groups. The mean equilibration times obtained for sevoflurane and isoflurane were 8.22 ± 1.060 min and 17.24 ± 10.2 min, respectively. The drift in end-tidal agent concentration over time was less in sevoflurane group. Mean recovery time was 7.92 ± 1.56 min in the sevoflurane group and 12.89 ± 3.45 min in the isoflurane group (P = 0.001). There was no significant difference between intraoperative and postoperative complications.

Use of equilibration time of the volatile anesthetic agent as a changeover point, from high-flow to low-flow, can help us to use circle system with low-flow anesthesia in a more efficient way, especially with newer anesthetics such as sevoflurane.