Coasting after overpressure induction with sevoflurane

Abstract

Study Objective: To evaluate the clinical feasibility of using a coasting technique to temporarily maintain anesthesia after overpressure induction with sevoflurane. Study Design: Prospective clinical study. Setting: Large teaching hospital. Patients: 12 ASA physical status I, II, and III patients receiving general anesthesia for a variety of peripheral procedures. Interventions: After overpressure induction of anesthesia with sevoflurane (8%) in an O 2/N 2O mixture, the fresh gas flow (FGF) was lowered to 0.5 L/min and the vaporizer was turned off (coasting). Measurements and Main Results: After priming a circle system with sevoflurane (8% sevoflurane vaporizer setting in 6 L/min O 2/N 2O [33%/66%] for 30 s), patients took several vital capacity breaths from the mixture until loss of consciousness. After 3.4 ± 0.7 min, depth of anesthesia was considered adequate for laryngeal mask airway (LMA) insertion, and FGF was reduced to 0.5 L/min (33% O 2, 66% N 2O) and the sevoflurane vaporizer was turned off. The end-expired sevoflurane concentration (Et sevo) decreased from 5.8 ± 1.3% just before insertion of the LMA to 0.97 ± 0.22% at 20 minutes. Conclusions: After overpressure induction with sevoflurane, coasting during minimal flow anesthesia (FGF 0.5 L/min) is a simple technique that can maintain anesthesia for short procedures (less than 15 to 20 min), or can be used as a bridge or an adjunct to other low-flow techniques.