Effects of midazolam on explicit vs implicit memory in a pediatric surgery setting.

RATIONALE

Placebo-controlled studies show that midazolam impairs explicit memory in children undergoing surgery (Buffett-Jerrott et al., Psychopharmacology 168:377-386, 2003; Kain et al., Anesthesiology 93:676-684, 2000). A recent within-subjects study showed that midazolam impaired explicit memory while leaving implicit memory intact in a sample of older children undergoing painful medical procedures (Pringle et al., Health Psychol 22:263-269, 2003).

OBJECTIVES

We attempted to replicate and extend these findings in a randomized, placebo-controlled design with younger children undergoing surgery.

MATERIALS AND METHODS

Children aged 3-6 years who were undergoing ear tube (myringotomy) surgery were randomly assigned to receive midazolam (n = 12) or placebo (n = 11). After surgery, they were tested on explicit (recognition) and implicit (priming) memory for pictures encoded before surgery.

RESULTS

Relative to placebo, the midazolam-treated children showed poorer recognition memory on the explicit task but equivalent priming on the implicit task.

CONCLUSIONS

Overall, it appears that midazolam induces a dissociation between explicit and implicit memory in young children in the pediatric surgery setting. Theoretical and clinical implications of the findings are discussed along with directions for future research.