[Evaluation of low flow closed anesthesia technique for oxygen, nitrous oxide and isoflurane using Engström Elsa...

We studied low flow closed anesthesia technique for oxygen, nitrous oxide and isoflurane using Engström Elsa Anesthesia System in 47 patients undergoing elective surgery. In the low flow group, anesthesia was maintained with oxygen 300 ml.min-1, nitrous oxide 300 ml.min-1 and optimal concentration of isoflurane after endotracheal intubation. The inspired oxygen concentration was kept higher than 35% through the operation. In the minimal flow group, anesthesia was maintained with nitrous oxide 4 l.min-1, oxygen 2 l.min-1 and optimal concentration of isoflurane after intubation until the inspired oxygen concentration reached approximately 35%. Then the fresh gas flow was reduced to oxygen 250 ml.min-1 and nitrous oxide 250 ml.min-1. In order to maintain the inspired oxygen concentration at 35%, the flow of nitrous oxide should have been reduced as low as to 150 ml.min-1 after 240 min. The volumes of consumption of nitrous oxide and isoflurane in the low flow and minimal flow groups were reduced to one fifth and one third respectively, compared with those of the high flow group. In conclusion, we can perform low flow closed anesthesia safely and easily with this equipment.