Consciousness Monitors

Assessment of hypnotic susceptibility is usually obtained through the application of psychological instruments. A satisfying classification obtained through quantitative measures is still missing, although it would be very useful for both diagnostic and clinical purposes. Aiming at investigating the relationship between the cortical brain activity and the hypnotic susceptibility level, we propose the combined use of two methodologies - Recurrence Quantification Analysis and Detrended Fluctuation Analysis - both inherited from nonlinear dynamics.

Severe forms of dissociation or conversion can lead to events clinically often described as pseudo-seizures. Borderline personality disorder is a clinical condition which is often accompanied by a high susceptibility for dissociation and dissociative states are characterized by memory disturbance and perceptual alterations. We report a case of a patient with a complete anaesthesia, paralysis and amnesia for about 1 h. Within this time period we measured a bispectrum EEG index called BIS. Deepest recorded BIS value was 47.

PURPOSE: Cardiopulmonary bypass is known to alter propofol pharmacokinetics in patients undergoing cardiac surgery. However, few studies have evaluated the impact of these alterations on postoperative pharmacodynamics. This study was designed to test the hypothesis that changes in propofol pharmacokinetics increase hypnotic effects after cardiopulmonary bypass.

BACKGROUND: The objective of this study was to evaluate the performance of a new system for closed-loop control of propofol administration using the bispectral index (BIS) under total intravenous anesthesia in the index values of middle-to-deep depth of anaesthesia. METHODS: In this study 20 adult patients anesthetized with propofol and remifentanil were investigated. The propofol infusion was carried out using a fuzzy-PD+I controller with a target BIS value of 40. RESULTS: Closed-loop control was able to provide maintenance of anesthesia and adequate operating conditions for all patients.

This study established the pharmacokinetic and pharmacodynamic relationships of the bispectral index (BIS) and Observer's Assessment of Alertness/Sedation (OAA/S) scale with effect site drug concentrations during and after brief etomidate infusion. Eighteen American Society of Anesthesiologists status I or II volunteers received etomidate (0.2%) infusion at 5 mg/min until the loss of eyelash reflexes, and spontaneous recovery was allowed. Data for plasma etomidate concentrations, BIS, and OAA/S were collected every minute and analyzed by NONMEM.

PURPOSE: The purpose of this randomized control trial was to determine the performance of a novel rule-based adaptive closed-loop system for propofol administration using the bispectral index (BIS(R)) and to compare the system's performance with manual administration. The effectiveness of the closed-loop system to maintain BIS close to a target of 45 was determined and compared with manual administration.

BACKGROUND AND OBJECTIVES: Patients with cerebral palsy (CP) frequently receive drugs for the treatment of concomitant diseases, such as seizures. Midazolam is a benzodiazepine with hypnotic action most often used as pre-anesthetic medication and its drug interactions in patients with CP are unknown. The objective of the present study was to evaluate the effect of midazolam as pre-anesthetic drug on the BIS of patients with CP undergoing chronic treatment with anticonvulsant agents.

BACKGROUND: this study was to estimate the predicted effect-site concentration of propofol administered by a target-controlled infusion (TCI) for maintenance of anesthesia based on the bispectral (BIS) index as a measure of hypnosis in laparoscopic surgery. METHOD: one-hundred and sixty unpremedicated patients undergoing gynecologic laparoscopy were assigned randomly to receive one of the target effect-site concentrations of propofol 2.0, 2.5, 3.0, 3.5 and 4.0 microg/ml during TCI with propofol and sufentanil.

BACKGROUND: Research has demonstrated the efficacy of closed-loop control of anesthesia using bispectral index (BIS) as the controlled variable. Model-based and proportional-integral-derivative (PID) controllers outperform manual control. We investigated the application of reinforcement learning (RL), an intelligent systems control method, to closed-loop BIS-guided, propofol-induced hypnosis in simulated intraoperative patients. We also compared the performance of the RL agent against that of a conventional PID controller.