Forty-eight gynaecological patients were randomly allocated to three groups
(target end-tidal sevoflurane concentration 1.2, 1.5 or 2%), and into subg
roups for positive or neutral suggestion. Anaesthesia was induced by inhala
tion of sevoflurane in oxygen. When the target concentration was achieved,
the bispectral index, computed from a bi-frontal electroencephalogram, was
noted. One of two eight-word lists was then played to prime implicit memory
, followed by a positive or neutral suggestion. After surgery, each patient
tried to identify 24 words obscured by background noise. Priming increased
the likelihood of identifying words in the 1.2% group only, i.e. there was
evidence of implicit memory in this group. There was no evidence of a ther
apeutic effect of positive suggestion (p = 0.3), but the power of this part
of the study was low. The bispectral index did not achieve statistical sig
nificance as an indicator of susceptibility to priming.