Benzodiazepine--induced event amnesia following a stressful surgical procedure

In a randomised, double-blind, parallel groups study, 40 patients undergoing surgical removal of impacted third molar teeth received either midazolam 15 mg orally followed at 35 min by intravenous saline or oral placebo followed by intravenous diazepam 10 mg (Diazemuls). Episodic (event) memory was assessed by showing patients photographs of dental and neutral objects both before and after sedation and by testing subsequent recognition at 1 week. Recall of actual surgical events was assessed by questionnaire. Both treatments induced significant amnesia for visual stimuli and for surgical events. However, the degree of amnesia was more profound for artificial stimuli and no relationship was found between the extent of amnesia for the two types of event. Drilling of bone was found to provoke the greatest cardiovascular stress response and a significant relationship was found between the degree of cardiovascular activation and subsequent memory for drilling. It is concluded that the extent of benzodiazepine-induced event-amnesia may be modified by cognitive factors and especially by the extent to which the event is cognitively encoded and elaborated.