Closed circuit coasting from high flow isoflurane anesthesia

Closed circuit coasting after high flow isoflurane-N2O anesthesia was used in 30 patients undergoing operations expected to last more than one hour. Near the end of the operation, the circuit was closed by shutting off anesthetics and reducing oxygen flow to that necessary to maintain constant end-tidal circuit volume throughout the duration of coasting (Tc). End-tidal isoflurane concentration of 0.5% was a safe target for coasting. Good correlation was found between Tc and anesthetic delivery duration (TAD). An adequate TC for the first hour of TAD was 15 minutes followed by 11 minutes more for each subsequent hour of TAD. The technique is safe, simple, economic, predictable and practical.