Immediate retrograde amnesia induced by midazolam: A prospective, non-randomised cohort study

Recovery of memory retention after anesthesia with remimazolam: an exploratory, randomized, open, propofol-controlled, single-center clinical trial

PURPOSE

Remimazolam, a newly developed ultra-short-acting benzodiazepine, provides early recovery of consciousness but its effects on memory recovery are unclear. This study examined memory recovery after emergence from general anesthesia using remimazolam.

METHODS

Seventy-four patients undergoing breast surgery between October 2021 and March 2022 were enrolled and randomly assigned to receive propofol (control group) or remimazolam as general anesthetic during surgery. The primary endpoint was the number of posters patients remembered 24 h after surgery (among four posters shown after recovering from anesthesia) as an assessment of memory retention. The secondary endpoints were the recall of a numeric character patients had been shown just before anesthetic induction, as an assessment of retrograde amnesia 24 h after surgery.

RESULTS

Sixty-six patients (propofol, 32; remimazolam, 34) were assessed. Patients in the remimazolam group remembered significantly fewer posters shown to them after surgery than those in the propofol group (0 [0 - 2] vs. 2 [1 - 3], p < 0.001). In the remimazolam group, the patients who received flumazenil remembered a higher number of posters than those who did not receive flumazenil (3 [1 - 4] vs. 0 [0 - 0], p < 0.001). All patients remembered all events that occurred during the preoperative period as well as the numeric character.

CONCLUSION

Patients recovering from remimazolam anesthesia without receiving flumazenil do not remember events after regaining consciousness. IRB: Kyushu University School of Medicine Hospital Institutional Review Board (IRB) (approval number: 20212006).

TRIAL REGISTRATION

This clinical trial was registered with the University Hospital Medical Information Network (UMIN) Center on September 28, 2021 (UMIN-CTR: UMIN000045593).

IMPLICATION STATEMENT

Memory recovery is slower following emergence from remimazolam than from propofol anesthesia.

Sevoflurane-induced amnesia is associated with inhibition of hippocampal cell ensemble activity after learning

General anesthesia could induce amnesia, however the mechanism remains unclear. We hypothesized that suppression of neuronal ensemble activity in the hippocampus by anesthesia during the post-learning period causes retrograde amnesia. To test this hypothesis, two experiments were conducted with sevoflurane anesthesia (2.5%, 30 min): a hippocampus-dependent memory task, the context pre-exposure facilitation effect (CPFE) procedure to measure memory function and in vivo calcium imaging to observe neural activity in hippocampal CA1 during context exploration and sevoflurane/home cage session. Sevoflurane treatment just after context pre-exposure session impaired the CPFE memory, suggesting sevoflurane induced retrograde amnesia. Calcium imaging showed sevoflurane treatment prevented neuronal activity in CA1. Further analysis of neuronal activity with non-negative matrix factorization, which extracts neural ensemble activity based on synchronous activity, showed that sevoflurane treatment reduced the reactivation of neuronal ensembles between during context exploration just before and one day after sevoflurane inhalation. These results suggest that sevoflurane treatment immediately after learning induces amnesia, resulting from suppression of reactivation of neuronal ensembles.

The effect of remimazolam on postoperative memory retention and delayed regeneration in breast surgery patients: Rationale and design of an exploratory, randomized, open, propofol-controlled, single-center clinical trial: A study protocol

BACKGROUND

Remimazolam, a benzodiazepine ultra-short-acting sedative, has been used in general anesthesia since August 2020. It is used in awake surgeries that require awakening the patient in the middle of the surgery because of its rapid awakening effect as well as antagonistic interactions. If remimazolam has associated anterograde amnesia similar to benzodiazepines, it will have a positive effect on preventing psychological trauma. However, to our knowledge, the effect of remimazolam on anterograde amnesia has not been previously examined.

METHODS/DESIGN

The aim of this exploratory, open, propofol-controlled, single-center, randomized clinical trial is to examine the effect of remimazolam on postoperative memory retention and delayed regeneration. Seventy patients undergoing breast surgery will be included in the study. The patients will be randomly assigned to receive propofol or remimazolam as sedatives during surgery. The primary endpoint is the number of posters patients remember 24 hours after surgery (among 4 posters shown after awakening from anesthesia) as an assessment of anterograde amnesia. Secondary endpoints are retrograde amnesia, dose of analgesic given from the time the patient returns to the ward until 24 hours after surgery, immediate postoperative pain numerical rating scale scores, and pain numerical rating scale scores 24 hours after leaving the operating room. Recruitment will take place between October 2021 and March 2022 to achieve the target sample size.

DISCUSSION

To our knowledge, this is the first trial designed to examine the effects of remimazolam on postoperative memory retention and delayed regeneration in patients undergoing breast surgery.

TRIAL REGISTRATION

This clinical trial was registered at the University Hospital Medical Information Network (UMIN) Center on September 28, 2021 (UMIN-CTR: UMIN000045593).