Double-blind randomized controlled trial to determine extent of amnesia with midazolam given immediately before general anaesthesia

Abstract

Background: Anterograde, but not retrograde, amnesia has been demonstrated following midazolam administration. However, there have been no studies investigating whether or not immediate retrograde amnesia can be produced with midazolam.

Methods: After ethics committee approval and consent, 40 adult patients undergoing surgery and general anaesthesia were randomly allocated to one of four groups: midazolam 2 mg, midazolam 5 mg, midazolam 10 mg or control (normal saline). Measurements were made from 12 min prior to induction of anaesthesia, and the study drug was administered 8 min prior to induction of anaesthesia. Midazolam effects were measured using visual recognition of posters, recall of specific events, bispectral index (BIS) and sedation visual analogue score.

Results: Recognition and recall rates were similar between groups up until the time of study drug administration, with no evidence of retrograde amnesia (all P>0.3). There was a dose-dependent deterioration in visual recall (P=0.002), event recollection (P<0.001), BIS (P<0.001) and sedation score (P<0.001) following i.v. midazolam when compared with control.

Conclusions: We found no evidence that i.v. midazolam 2-10 mg produces immediate retrograde amnesia. Midazolam causes anterograde amnesia in a dose-responsive manner.