Closed anesthesia with nitrous oxide

Abstract

Anesthesia was induced with intravenous thiopental, fentanyl, and succinylcholine, and maintained with isoflurane, N₂O-O₂ and atracurium after denitrogenation in 20 adult patients. Inspired and end-tidal concentrations of O₂, N₂O, CO₂, isoflurane and oxygen saturation of pulse oximeter (SpO₂) were monitored. After intubation, N₂O (750 ml/min) and O₂(250 ml/min) were administrated. When inspired N₂O concentration (FiN₂O) reached 60 % the closed anesthesia was initiated by adjusting fresh gas flow rate in order to meet the oxygen demand of the patients. The N₂O/O₂ ratio was constantly kept at 0. 7. The results revealed that during wash-in period, FiN₂O increased, on average, to 30 % at 3. 83 min, 40 % at 6. 22 min, 50 % at 14. 13 min respectively. After 30 min of closed anesthesia, FiN₂O decreased to 49. 4 %. It was 46. 8 % at 60 min. Thereafter it increased smoothly to 51. 9 % at 180 min. No hypoxia and hypercapnia occurred. Compared with commonly used high flow N₂O-N₂ inhalation, the technique of low flow wash-in and closed circuit maintenance with N₂O-O₂ may be less expensive and feasible and causes less pollution.

Keywords

nitrous oxide / closed anesthesia

References

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