Towards a standardised anaesthetic state

The authors´ objective was to control automatically the administration of anesthetic agents using a feedback system, thereby producing an individually tailored anesthetic state, free from the administration strategy imposed by the particular anesthetist. They investigated the use of muscle relaxants (atracurium) and volatile agents (enflurane) separately. Both of these drugs affect parts of the whole anesthetic state. The patients naturally fell into two groups, depending on whether the first dose of morphine was enough (group A, 14 patients, mean age 41.6 y) or whether additional doses were needed (group B, 7 patients, mean age 37.6 y). The quality of control as measured by the RMSD and the recovery time were significantly better in group A, which received a mean inspired enflurane concentration of 1.1% compared with 2.2% in group B. This experimental system produced a state recognizable as anesthesia which was satisfactory from the control and clinical points of view. Both of the feedback systems described achieved their objectives satisfactorily and have paved the way for combining the two systems. The resulting system will be used for calibrating devices which measure evoked potentials in the brain, the state of anaesthesia then being more repeatable.<>