Interruption of fresh gas supply without alarm signs by the partial disconnection of fresh gas outlet during general anesthesia -A case report-

Abstract

We report our experience of unexpected low expiratory concentration of sevoflurane 0.8 vol%, low inspired fraction of oxygen 31%,and high value of bispctral index (BIS) 62 with sevoflurlane vaporizer setting 2.0 vol% and the inspired fraction of oxygen 50% during general anesthesia of a 56-year-old man undergoing elective laparoscopic hemicolectomy. The anesthesia machine (Cato edition,Dräger, Lübeck, Germany) with a piston-based, electronically controlled ventilator was used for anesthesia. We checked thoroughly all the possible causes of the discrepancy of anesthetic gas concentration, and then detected the partial disconnection of fresh gas outlet. But there were no alarm signs of anesthetic monitor with adequate ventilator function. This malfunction of anesthetic gas supply without alarm signs may lead to hypoxia and awareness of patients. The intraoperative monitoring of anesthetic gas analyzer and BIS may be essential to detect the malfunction of anesthesia machine.