Fig. 5. Patient H during the last 40 min of a 2-h operation. Dimensional estimates (d2) with trend line ( 20-point moving average ), minimum alveolar concentration (MAC) sevoflurane ( horizontal bars ), and the highest exponent of the Lyapunov spectrum ( points at bottom right ) are plotted against time. The transition from stage 3 to stage 2 is seen at approximately 18 min. This patient shows a stage 2 “plateau” before emergence into consciousness at 40 min. At this time, the Lyapunov exponent becomes positive. The step between stage 3 and stage 2 occurred between 0.8 and 0.5 MAC sevoflurane.