LOW FLOW ANAESTHESIA USING “EQUILIBRATION TIME” AND THREE DIFFERENT VOLATILE INHALATIONAL AGENTS- DESFLURANE, SEVOFLURANE AND ISOFLURANE-A RANDOMIZED PROSPECTIVE CLINICAL STUDY
Introduction: Low flow anaesthesia involves an initial period of high fresh gas flow (FGF) followed by low FGF. The changeover from high to low flow is usually done at 10 minutes of high flow. Presently a new method has come in which equilibration time, where the ratio of expired (Fe) and inspired (Fi) inhalation agent concentration become 0.8, is used for change over instead of fix time.
Methods:  After ethical committee permission, study was conducted on 63 patients of 18-60 years and ASA I & II who were randomized using “envelop” method into three groups of 21 each. Group D patients received Desflurane, group S patients received Sevoflurane and group I patients received Isoflurane. All the patients received initial high FGF (6 L/min) till the equilibration time was achieved and then low FGF (1lit/min) was started. Parameters monitored were equilibration time, vital parameters, end tidal CO2 concentration, end tidal N2O concentration, MAC and BIS value. Recovery time was noted at end of surgery. During postoperative period, all patients were enquired about awareness.
Results: Equilibration time and recovery time was quite early in case of Desflurane followed by Sevoflurane and then by Isoflurane group. None of the patient complained of awareness.
Conclusion:  Desflurane and Sevoflurane are better agents for low flow anaesthesia compared to Isoflurane.
References: 1. Tanuja Malik et al, JOACP 2012 volume 28(4) 
                     2. M R Nel et al Anaesthesia, 1997, 52.

Low flow anesthesia using “equilibration time” and three different volatile inhalational agents- desflurane, sevoflurane and isoflurane-a randomized prospective clinical study