Corresponding minimum alveolar concentrations of isoflurane and isoflurane/nitrous oxide have divergent effects on thalamic nociceptive signalling

These data demonstrate a pronounced nitrous oxide-induced response variability. It appears that, with respect to thalamic transfer of nociceptive information, the interaction of isoflurane and nitrous oxide may not be compatible with the concept of additivity and that the antinociceptive potency of nitrous oxide is considerably less than previously reported.