Sevoflurane - nitrous oxide anaesthesia supplemented with remifentanil: effect on recovery and cognitive function

The aim of this study was to compare recovery and psychomotor performance a fter maintenance of anaesthesia with sevoflurane or sevoflurane supplemente d with remifentanil. Sixty-six per cent nitrous oxide was used in all patie nts. Twenty patients each were randomly allocated to maintenance of anaesth esia with sevoflurane only in concentrations necessary to maintain adequate anaesthesia or with 1.5, 1.0 or 0.5 MAC (end-tidal) of sevoflurane supplem ented with remifentanil. The median dosage of remifentanil required in the last three groups was 0.21, 0.25 and 0.34 mug.kg(-1).min(-1), respectively (p < 0.05). The median times to eye opening were 10.3, 12.7, 11.0 and 6.5 m in in the four groups (p < 0.05 between the 0.5 MAC and the other groups) a nd for orientation 12.1, 14.9, 12.3 and 8.3 min, respectively (p < 0.05 bet ween 0.5 and 1.5 MAC groups). There was no significant difference in the mi ni-mental state assessment scores or the actual discharge times from the re covery ward among the groups. Significantly greater numbers of patients cou ld perform the critical flicker fusion test at 15 min in the group receivin g the lowest concentration of sevoflurane and the highest dosage of remifen tanil (p < 0.05). Patients in this group also showed the highest incidence of chest wall rigidity (p < 0.003). We conclude that, while the use of remi fentanil with lower concentrations of sevoflurane facilitates early recover y, it does not influence discharge time from recovery ward and may be assoc iated with side-effects such as chest wall rigidity.