Retrospective comparison of manual versus semi-automated propofol-remifentanil TCI Anaesthesia

G Bejjani #, O. Caelen*, G. Bontempi*, L. Perrin #, L. Barvais#, * Machine Learning Group, Computer Science, Université Libre de Bruxelles, Belgium; # Erasmus Hospital Anaesthesia Departments, Université Libre de Bruxelles, Belgium

Introduction:

Target Controlled Infusion (TCI) of Propofol and Remifentanil using the population Pharmacokinetic sets of Schnider and Minto, respectively becomes more and more a popular anaesthesia technique due to the commercialisation of the BasePrimeA of Fresenius and the Alaris Pharmacokinetic pumps.  The BIS (Aspect USA) and the Entropy module of GE (Maddison USA) are EEG monitoring which are useful to titrate the hypnotic and analgesic components (ref).  Even if EEG monitoring is routinely used, the opioid administration is often still based during the clinical practice on the individual sympathetic patient’s answer to the intensity of the noxious stimulus.  The aim of the study was to compare retrospectively if the use of predefined algorithms of the effect site concentration (Ce) of  propofol titration according to the patient’s EEG answer combined with the use of predefined algorithms of remifentanil Ce titration based on a range of heart rate and systolic blood pressure values could help the anesthetist.

Material and Methods:

Eighteen patients were anaesthetised using the TOOLBOX System with the automated propofol and remifentanil TCI titration according to a predefined range of BIS and hemodynamic values.  The TCI induction phase was manually titrated by the anaesthesiologist in charge of the patient and the semi-automated control was started after the tracheal intubation phase until the end of surgery.  During the surgery, the anaesthesiologist could adapt the BIS and haemodynamic range.  Moreover, at any time, the anaesthesiologist could adapt the proposal of the semi-automated pilot and he was always the final decider.   All the haemodynamic data and the Ce target concentrations were saved every 5 seconds.  A group of 23 patients undergoing the same type of digestive surgery lasting more than 2 hours but anaesthetised by the same TCI TOOLBOX system with a manual control of the most appropriate remifentanil and propofol Ce was used as a control group

Results:

Discussion:

The number of actions of an automatic controller is much higher than the anaesthesiologist TCI responsiveness.  The use of such a system decreases the number of episodes of BIS values out of the proposed Range 40-60.  The semi-automated system allows also decreasing the likelihood of BIS values greater than 70 which could be associated with awareness. In conclusion the use of a semi-automated pilot to help the effect site TCI titration of propofol and remifentanil seems interesting to be tested in the future in a prospective and randomised study

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