Closed-loop control of propofol anaesthesia

Abstract

We describe the use of a closed-loop system to control depth of propofol anaesthesia automatically. We used the auditory evoked potential index (AEPindex) as the input signal of this system to validate it as a true measure of depth of anaesthesia. Auditory evoked potentials were acquired and processed in real time to provide the AEPindex. The AEPindex was used in a proportional integral (PI) controller to determine the target blood concentration of propofol required to induce and maintain general anaesthesia automatically. We studied 100 spontaneously breathing patients. The mean AEPindex before induction of anaesthesia was 73.5 (SD 17.6), during surgical anaesthesia 37.8 (4.5) and at recovery of consciousness 89.7 (17.9). Twenty-two patients required assisted ventilation before incision. After incision, ventilation was assisted in four of these 22 patients for more than 5 min. There was no incidence of intraoperative awareness and all patients were prepared to have the same anaesthetic in future. Movement interfering with surgery was minimal. Cardiovascular stability and overall control of anaesthesia were satisfactory.

Automated Drug Delivery in Anesthesia

“…As explained earlier in this chapter, concepts of TCI were applied to decrease the complexity of the PI controller. Accurate control was observed in most of the patients [14].…”

“…Aside from BIS, State and Response Entropy (M-entropy, GE Healthcare, Helsinki, Finland), two spectral entropy parameters based on the irregularity in the EEG have been used recently to measure hypnotic drug effect during closed-loop administration [11-13 • ]. One research group has tested auditory evoked potentials, more specific the mid-latency auditory evoked potential (MLAEP) as controlled variable for closed-loop control of propofol administration [14,15]. One of the major challenges when using a surrogate measure is the delay in the system, which adds complexity to the controller.…”

Predictive Control With Robust Dead-Time Compensation: Application to Drug Dosing During Anesthesia

“…It soon became clear that control of anesthesia poses a manifold of challenges, with multivariable characteristics (Zbinden et al;1995), time delay between drug administration and the clinical effect which can lead to system oscillations , different dynamics depending on anesthetics substances (Absalom and Struys; and stability problems (Asbury;1997). Further investigations proved Propofol to be an anesthetic tackled well in control problems (Kenny and Mantzaridis;, while recent studies showed that the control performance may also depend on the controlled variable (Ting et al;.…”

Automated control of anesthesia ten years later: futuristic novelty or present day reality

“…A variety of solutions have been developed to resolve these problems, including the use of pharmacokinetic models to account for the time varying relationship between dose and effect-site concentration, adaptive controllers, or fuzzy logic to account for differences in sensitivity. [7][8][9][10][11] Thus, engineering solutions have been developed for the automated control of a biological system, and we have at least one component of anesthesia we can place under automated control. Hemmerling et al, like several previous authors, demonstrate the use of an automated closed-loop system to administer propofol to maintain BIS within a narrower band.…”

“…Plusieurs solutions ont vu le jour pour résoudre ces problèmes, notamment l'utilisation de modèles pharmacocinétiques qui tiennent compte de la relation variant dans le temps entre la dose et la concentration au site effecteur, des contrôles adaptatifs, ou la logique de l'incertain pour tenir compte des différences de sensibilité. [7][8][9][10][11] Dès lors, des solutions techniques ont été mises au point pour la surveillance automatisée d'un système biologique, et au moins une composante de l'anesthésie peut être placée sous surveillance automatisée. Hemmerling et coll., tout comme plusieurs auteurs avant eux, illustrent l'utilisation d'un système automatisé en boucle fermée pour l'administration de propofol afin de maintenir le BIS dans une marge plus étroite.…”