Target-controlled induction with 2.5% sevoflurane does not avoid the risk of electroencephalographic abnormalities

Epileptiform discharges (ED) can occur during sevoflurane induction, especially in young female patients and when high alveolar concentrations are used. The aim of this study was to evaluate whether low sevoflurane concentration reduces the occurrence of ED in female patients.

Thirty-four female patients scheduled for minor gynecological surgery were prospectively included and randomized in two groups. In group A, anesthesia was induced with sevoflurane inspired 8% manually set via the circuit of the Zeus(®) (Dräger Medical, Lübeck, Germany) anesthesia workstation (fresh gas flow 8L.min(-1)) for 2min and then 2.5%. In group B, induction was performed by target-controlled inhalation with a target end-tidal concentration of sevoflurane set at 2.5% (fresh gas flow in auto-control mode). Electroencephalogram (EEG) was recorded in the operating room throughout induction till two min after intubation and analyzed off-line by a neurophysiologist blinded to the randomization.

ED occurred in five patients (15%): one in group A and four in group B (P>0.05). ED occurred with a median delay of 303 s [25-75 interquartiles: 135-418] and the median duration of ED episode was 13 s [3-78]. Fifteen patients had abnormal movements without simultaneous EEG abnormality.

Induction of anesthesia with low target concentration of sevoflurane (2.5%) fails to totally prevent the occurrence of ED in young female patients and should be used carefully in this population.