Memory and midazolam conscious sedation

To investigate the degree of amnesia seen in patients undergoing minor oral surgery with intravenous midazolam sedation.

Hospital out-patients in the UK in 1995-6.

24 patients undergoing minor oral surgery procedures under local anaesthetic, with or without midazolam sedation, as determined by clinical need.

Picture cards were shown to patients before and during the procedure. Post-operatively, before discharge and 1 week later, the patients were questioned about their memory of both the pictures and procedure.

The sedated group demonstrated more amnesia for the pictures shown after the start of treatment, but their memory of the pretreatment pictures was initially better than that of the non-sedated patients. The non-sedated patients exhibited no memory loss for the surgical procedure. Recall of the surgery was very variable among the sedated patients, from some remembering all aspects, to others with no recollection after the venepuncture. Overall, the sedated patients exhibited significantly greater amnesia for the surgical procedure. The degree of amnesia in the sedated group was also investigated with respect to pretreatment anxiety levels, sedation level achieved and the dose of midazolam administered. The first two variables did not exhibit any effect on the memory loss, but higher doses (> 5 mg) were associated with more consistent amnesia especially for the later stages of the procedure.

Midazolam can produce useful amnesia in many patients and the memory loss can be high for both artificial and procedural stimuli. However this study suggests that the amnesia is not completely reliable, especially at lower doses.