RECOVERY OF MENTAL AND PSYCHOMOTOR-SKILLS FOLLOWING GENERAL-ANESTHESIA - A COMPARISON OF ISOFLURANE, MIDAZOLAM ALFENTANIL AND PROPOFOL

Mental and psychomotor abilities are impaired to varying degrees after general anaesthesia. This has important implications for the time over which patients are monitored in the recovery room and for the discharge of outpatients after day surgery. The present study was undertaken to compare recovery and mental and psychomotor skills in the first 60 min following general anaesthesia with isoflurane, midazolam/alfentanil and propofol. Methods. A total of 45 patients undergoing microsurgical lumbar nucleotomy were randomized to three study groups. Group 1 (n = 15): anaesthesia was induced with thiopentone and maintained with isoflurane; group 2 (n = 15): anaesthesia was induced with midazolam and maintained with alfentanil; group 3 (n = 15): anaesthesia was induced and maintained with propofol. Vecuronium was used for muscle relaxation and the lungs were ventilated with a mixture of 66% nitrous oxide in oxygen. The following were checked 15, 30, 45, and 60 min after extubation: choice reaction times and critical flicker fusion for psychomotor testing; the maze test and a modification of the ball-bearing test for discrimination of motor and mental activities; and short- and long-term memory. Results. Immediate recovery did not differ in the three different groups. In all patients psychomotor function was impaired compared with baseline for more than 60 min after general anaesthesia. However, impairment was significantly less pronounced after propofol, and recovery to preanaesthesia values was faster following propofol than after midazolam/alfentanil, and slowest after isoflurane-anaesthesia (Figs. 1, 2). The flicker fusion frequency, a very sensitive parameter for the persisting effects of anaesthetics, was significantly higher following propofol anaesthesia and remained so throughout the entire study period (Fig. 3). By 30 min after extubation, short-term memory was already normal in patients who had undergone propofol anaesthesia, and a statistically significant difference from the midazolam/alfentanil and isoflurane anaesthesia groups was obvious throughout the entire study period. However, no differences in long-term memory were found. At 30 min after propofol anaesthesia all patients were able to perform the ball-bearing test, as against 13 patients following midazolam/alfentanil and 10 patients following isoflurane (Table 3). The maze test was mostly impaired after midazolam/alfentanil anaesthesia. Patients who underwent isoflurane anaesthesia needed the same time for the maze test at 60 min afterwards propofol patients needed after 30 min (Table 2). Side effects, e.g., nausea, vomiting, and double vision, were observed significantly more often in groups 1 and 2 (Table 4). Discussion and conclusion. The results indicate that in operations of approximately 90 min duration the return of motor and mental abilities is faster following propofol anaesthesia. At 30 min after extubation following propofol anaesthesia patients had test results that allow their transfer from the recovery room, while it took 60 min for patients in the two other groups to reach the same levels of motor and mental function. This is important for the duration of monitoring in the recovery room and, especially, for day case anaesthesia.