ABSTRACT
We report a case of awakening during general anesthesia due to a vaporizer malfunction. The sevoflurane vaporizer had a hole through which approximately 20% of fresh gas escaped. The gas in the common gas outlet contained only 60% of the sevoflurane stated on the vaporizer setting. Moreover, the gas monitor module was out of order, and the heart rate and blood pressure were stable. As a result, we were unaware of the low sevoflurane concentration. The leakage through the hole could not be detected with the commonly used low-pressure system leak checking method. The implication of this case is that unexpected awakening can occur in patients with stable vital signs with an inhalation anesthesia. Therefore, more attention is needed to detect the level of patient awareness.