Contrasting effects of midazolam and nitrous oxide on memory and cognitive bias in dentally phobic patients

Abstract

Dentally phobic patients referred to the Guy's Sedation Unit and control dental patients were presented with lists of dentally related, general threat and neutral words. They were asked either to remember the words (superficial coding) or to rate them for liking (deeper coding). The control patients showed no significant bias in the words remembered, but the phobic patients attending for their assessment interview recognized more dentally related than neutral words, from both superficially and deeply coded lists. This bias was maintained over two tests and was not different for male and female patients or for those with high or low trait anxiety. On their first day of dental treatment phobic patients received lists both before and after receiving sedation with midazoIam or nitrous oxide. These patients showed relative cognitive avoidance for dentally related words, but for the superficially coded words this was prevented by midazolam. In addition, midazolam caused significant amnesia for words presented after drug administration, for both the superficially coded list, and for the words presented for rating. Nitrous oxide significantly impaired recognition of the superficially coded words from the lists presented both before and after drug administration.

Inhalation of 30% nitrous oxide impairs people's learning without impairing people's judgments of what will be remembered.

“…For instance, Ramsay and colleagues found that almost twice as many acquisition trials were required lo reach the criterion of learning when participants received 30% N 2 0 rather than a placebo gas (for converging evidence, see Mewaldt, Ghoneim, Korttila, & Petersen, 1988). Nitrous oxide also impairs performance on recall tests (Dwyer, Bennett, Eger, & Heilbron, 1992;File et al, 1993;Ghoneim et al;Mewaldt et al;Ramsay et al) and on recognition tests (Block, Ghoneim, Hinrichs, ct al. ;Dwyer ct al.…”