The effect of nitrous oxide on the inhibition of somatosensory evoked potentials by sevoflurane in children

Inhalational anaesthetics inhibit somatosensory evoked potentials. The pres ent study examined the effect of nitrous oxide in anaesthetic mixture with sevoflurane on the somatosensory evoked potential in children. Forty-five p atients aged between 6 months and 6 years undergoing club foot surgery were studied to verify the influence of sevoflurane alone (21 patients) and sev oflurane with nitrous oxide (24 patients) on the somatosensory evoked poten tial. Fractional inspired concentration of nitrous oxide and fractional end -tidal (alveolar) sevoflurane were measured to estimate the multiples and s ubmultiples of the minimal alveolar concentration (age corrected). The soma tosensory evoked potential signals were obtained by stimulation of the medi an nerve. Nitrous oxide (F-I = 0.63 +/- 2.5) with sevoflurane caused more r eduction in the amplitude of somatosensory evoked potential waves and a gre ater increase in the latency of somatosensory evoked potential waves in com parison with sevoflurane alone. The results show that it is possible to obt ain the inhibition of somatosensory evoked potential with smaller concentra tions of sevoflurane, when it is used with nitrous oxide.