Unexpected anesthetic leakage from a damaged O-ring on the Selectatec back bar -A case report-

Abstract

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.The Selectatec mounting system was devised to provide easy and quick on-site fitting of various vaporizers for the anesthetic machine. However, a quick changing system for the vaporizer can also damage the O-ring due to friction between the vaporizer and the Selectatec back bar. We herein report a case of an unexpected anesthetic gas leakage from a damaged O-ring on the Selectatec back bar, which resulted from exchanging the vaporizers between two operations. In cases using the Datex Ohmeda machine, it is not easy to detect leakages from the vaporizers because of the location of the check valve near to the fresh gas outlet. This complicates the use of the positive pressure leakage test to detect a low pressure system leakage on the Selectatec back bar. We recommend the preanesthetic negative pressure or low-flow leakage test to detect a low pressure leakage when exchanging vaporizers on the Selectatec system. CASE REPORTA 50-year-old female patient (weight = 70.6 kg; height = 162 cm; body mass index = 27.0) was scheduled to undergo a left modified radical mastectomy for breast angiosarcoma at our hospital. This patient was intraoperatively monitored using pulse oximetry, noninvasive blood pressure, and electrocardiography. We also placed a Bispectral index (BIS) monitor (Aspect Medical Systems, USA) on the left temporal-frontal area of the forehead. We used the electronic system check of the anesthesia machine we were using, the Ohmeda Aestiva/5 machine anesthesia workstation (Datex-Ohmeda, GE Healthcare, UK), and confirmed that this instrument, its vaporizer, and other components such as tubing, flow meters, valves, gaskets, scavenging system, etc. were working normally. The circle breathing circuit was also manually checked using common gas outlet occlusion test before anesthetic induction.The patient underwent preoxygenation with 100% O2 and then 2 mg midazolam, 120 mg propofol, and 14 mg cisatracurium were intravenously administered to induce anesthesia.Manual ventilation with 3 vol% sevoflurane and 8 L/min oxygen under the continuous infusion of remifentanil was performed using the Ohmeda Aestiva/5 machine with a Tec 7 vaporizer. When inducing anesthesia, we detected a leaking sound from the vaporizer and confirmed its position. We increased the inhaled concentration of sevoflurane because the BIS had increased to ＞ 60. However, even though the dial