Few studies have been conducted to evaluate the reliability of the various tools used to assess cognitive and psychomotor recovery after ambulatory anesthesia. Therefore, this study was conducted to compare the sensitivity and reliability of simple, standard tests used to measure postoperative cognitive and psychomotor functions.

Twenty-seven patients admitted for same day surgery were included in this prospective, randomized study. While in the preanesthetic unit, each patient was asked to perform three different standard psychometric tests, the digit symbol substitution test (DSST), digit span test (DST), and perceptual speed test (PST), to evaluate cognitive and psychomotor functions. The results were then used as baseline values that were subsequently compared to results obtained when patients repeated the tests at 15, 30 and 60 min after extubation. In addition, the observer's assessment of alertness and sedation was evaluated.

The DSST scores were significantly lower than the baseline scores at 15 and 30 min after extubation, with a performance ratio of 64.9 and 89.2, respectively (P < 0.05). The DST scores had returned to preanesthetic levels at 30 min post-anesthesia and the PST scores were found to be significantly higher than the baseline scores at 30 and 60 min post-anesthesia.

DSST is a more sensitive indicator of residual drug effect following anesthesia than the other tests evaluated in this study. In addition, a learning effect was obvious when the PST was administered.