Awareness during general anesthesia occurs in approximately 0.1–0.2% of cases; nevertheless, particular attention is required because it can lead to critical complications including insomnia, depression, anxiety, and post-traumatic stress disorder. To prevent these complications, bispectral index (BIS) and end-tidal anesthetic gas (ETAG) concentration monitoring are commonly used to examine patient consciousness during surgery. In the present case, an 80-year-old man was scheduled for total gastrectomy. Anesthesia was maintained using desflurane 4.0–5.0% vol, oxygen, and nitrous oxide. The authors simultaneously monitored BIS, which was maintained between 37 and 43, and ETAG, which was maintained between 0.9 and 1.2 minimum alveolar concentration (MAC). After the operation, however, the authors were surprised to learn that the patient complained of awareness during anesthesia. Although BIS and ETAG concentration monitoring are useful in preventing awareness during anesthesia, they cannot be completely trusted. Even though BIS was maintained at approximately 40 and ETAG at 0.7–1.3 MAC, awareness during anesthesia occurred.
Aged, 80 and over ; Anesthesia ; Anesthesia, General ; Anxiety ; Consciousness ; Consciousness Monitors ; Depression ; Gastrectomy ; Humans ; Intraoperative Awareness ; Nitrous Oxide ; Oxygen ; Sleep Initiation and Maintenance Disorders ; Stress Disorders, Post-Traumatic

BACKGROUND: Process dissociation procedure has been used to evaluate explicit and implicit memories. Two process-dissociation measurement models are described. METHODS: This prospective study evaluated intraoperative memory formation in Korean patients undergoing elective surgery under general anesthesia and its relation to the depth of hypnotic state. A total of 270 patients enrolled were randomly assigned to three groups based on Bispectral Index (BIS) values in the following ranges: 30 to 40, BIS 40 to 50, and BIS 50 to 60 according to the level of hypnotic depth induced by propofol or sevoflurane during the presentation of wordlists. When the level of hypnotic depth was maintained at the target BIS range, words were played for 15 minutes via headphones to patients. Within 24 hours after the word presentation, memory was assessed using an auditory word stem completion test. The probability of explicit and implicit memory was calculated using original and extended measurement models. Brice interviews were performed within 1 and 24 hours after surgery. RESULTS: A total of 119 patients who did not deviate from the target BIS range were included in the analysis. The 95% confidence interval (CI) of the probability of occurrence of implicit memory evaluated by the original model did not include zero. However, when the extension model was used, 0 was included in the 95% CI. Explicit memory evaluated via Brice interviews did not occur in any group. CONCLUSIONS: When BIS was maintained in the range of 30 to 60 during surgery, no explicit or implicit memory was observed.
Anesthesia ; Anesthesia, General ; Humans ; Intraoperative Awareness ; Memory* ; Propofol ; Prospective Studies

No abstract available.
Electroencephalography* ; Intraoperative Awareness*

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.
Friction ; Intraoperative Awareness ; Nebulizers and Vaporizers ; Ventilators, Mechanical

Currently, anesthesiologists use clinical parameters to directly measure the depth of anesthesia (DoA). This clinical standard of monitoring is often combined with brain monitoring for better assessment of the hypnotic component of anesthesia. Brain monitoring devices provide indices allowing for an immediate assessment of the impact of anesthetics on consciousness. However, questions remain regarding the mechanisms underpinning these indices of hypnosis. By briefly describing current knowledge of the brain's electrical activity during general anesthesia, as well as the operating principles of DoA monitors, the aim of this work is to simplify our understanding of the mathematical processes that allow for translation of complex patterns of brain electrical activity into dimensionless indices. This is a challenging task because mathematical concepts appear remote from clinical practice. Moreover, most DoA algorithms are proprietary algorithms and the difficulty of exploring the inner workings of mathematical models represents an obstacle to accurate simplification. The limitations of current DoA monitors - and the possibility for improvement - as well as perspectives on brain monitoring derived from recent research on corticocortical connectivity and communication are also discussed.
Anesthesia* ; Anesthesia, General ; Anesthetics ; Brain* ; Consciousness ; Electroencephalography ; Hypnosis ; Intraoperative Awareness ; Intraoperative Neurophysiological Monitoring ; Mathematical Concepts ; Models, Theoretical

No abstract available.
Anesthesia, General* ; Delirium* ; Intraoperative Awareness* ; Memory* ; Midazolam*

Currently, monitoring system of awareness of the depth of anesthesia has been more and more widely used in clinical practices. The intelligent evaluation algorithm is the key technology of this type of equipment. On the basis of studies about changes of electroencephalography (EEG) features during anesthesia, a discussion about how to select reasonable EEG parameters and classification algorithm to monitor the depth of anesthesia has taken place. A scheme which combines time domain analysis, frequency domain analysis and the variability of EEG and decision tree as classifier and least squares to compute Depth of anesthesia Index (DOAI) is proposed in this paper. Using the EEG of 40 patients who underwent general anesthesia with propofol, and the classification and the score of the EEG annotated by anesthesiologist, we verified this scheme with experiments. Classification and scoring was based on a combination of modified observer assessment of alertness/sedation (MOAA/S), and the changes of EEG parameters of patients during anesthesia. Then we used the BIS index to testify the validation of the DOAI. Results showed that Pearson's correlation coefficient between the DOAI and the BIS over the test set was 0.89. It is demonstrated that the method is feasible and has good accuracy.
Algorithms ; Anesthesia, General ; Decision Trees ; Electroencephalography ; Entropy ; Humans ; Intraoperative Awareness ; Monitoring, Physiologic ; Propofol

Anesthesia awareness is defined as both consciousness and recall of surgical events. New research has been conducted out to test this phenomenon. However, testing methods have not proven reliable, including those using devices based on electroencephalographic techniques to detect and prevent intraoperative awareness. The limitations of a standard intraoperative brain monitor reflect our insufficient understanding of consciousness. Moreover, patients who experience an intraoperative awareness can develop serious post-traumatic stress disorders that should not be overlooked. In this review, we introduce the incidence of intraoperative awareness during general anesthesia and discuss the mechanisms of consciousness, as well as risk factors, various monitoring methods, outcome and prevention of intraoperative awareness.
Anesthesia ; Anesthesia, General* ; Brain ; Consciousness ; Electroencephalography ; Humans ; Incidence ; Intraoperative Awareness ; Risk Factors ; Stress Disorders, Post-Traumatic

BACKGROUND: Bispectral index (BIS) monitoring reduces the cases of intraoperative awareness. Several factors can alter BIS readings without affecting the depth of anesthesia. We conducted a study to assess the impact of beach chair position (sitting position) on BIS readings. METHODS: General anesthesia was administered to 30 patients undergoing arthroscopic shoulder surgery. Patients were kept in neutral position (supine) for 10 minutes and BIS readings, mean arterial blood pressure, heart rate, end-tidal carbon dioxide, and end-tidal sevoflurane were recorded. Patients were then shifted to beach chair position. After 15 minutes, data were recorded. RESULTS: A significant decrease in BIS values (P < 0.01) associated with a position change from neutral position to beach chair position was evident. CONCLUSIONS: BIS values are significantly decreased in the beach chair position compared with the neutral position and might affect interpretation of the depth of anesthesia.
Anesthesia ; Anesthesia, General ; Arterial Pressure ; Carbon Dioxide ; Heart Rate ; Humans ; Intraoperative Awareness ; Reading ; Shoulder*

Awareness of intraoperative events in patients under general anesthesia is rare, but awareness during anesthesia is a serious complication that leads to anxiety and post-traumatic stress disorder. The Bispectral Index (BIS) has generally been accepted as a measurement of hypnosis under anesthesia. It is derived from a processed electroencephalogram and computer algorithm that assigns a numerical value based on the probability of consciousness. A 46-year-old, 65-kg male without underlying disease underwent elective surgery for ventral hernia. The patient in this case was administered an anesthetic that we frequently use and then average BIS value are 35. But he experienced awake during general anesthesia. We describe the first case of intraoperation awake under BIS 40 using desflurane.
Anesthesia ; Anesthesia, General ; Anxiety ; Consciousness ; Consciousness Monitors ; Electroencephalography ; Hernia, Ventral ; Humans ; Hypnosis ; Intraoperative Awareness ; Intraoperative Complications ; Isoflurane ; Male ; Mental Recall ; Stress Disorders, Post-Traumatic