ED50 of Remimazolam for Anesthesia Induction in Frail Elderly Patients

Significantly Reduced Median Effective Dose (ED50) of Remimazolam for Anesthesia Induction in Frail Elderly Patients: A Prospective Dose-Finding Clinical Trial With Respiratory Volume Monitoring

This study aimed to determine the median effective dose (ED50) of remimazolam for loss of consciousness (LOC) in elderly and frail elderly patients using the Dixon up-and-down method, while utilizing a novel Respiratory Volume Monitor (RVM) to detect subclinical respiratory depression.

The physiological decline associated with frailty in elderly patients presents significant challenges for anesthesia induction. Remimazolam tosilate, an ultra-short-acting benzodiazepine, offers a promising safety profile, yet its optimal dosing in frail populations remains undefined. This prospective, up-and-down sequential allocation trial was conducted at the Second Hospital of Hebei Medical University. 58 patients aged ≥65 years undergoing elective surgery were stratified into two groups: an Elderly Group (Clinical Frailty Scale [CFS] < 5) and a Frail Elderly Group (CFS ≥ 5). The initial remimazolam induction dose was set at 0.15 mg/kg for the elderly group and 0.13 mg/kg for the frail group, with dose adjustments based on the previous patient's response. A non-invasive RVM was employed to continuously monitor Tidal Volume (VT) and detect early hypoventilation.

Inclusion Criteria:

• Aged ≥65 years;
• Scheduled for elective surgery under general anesthesia with endotracheal intubation;
• American Society of Anesthesiologists (ASA) physical status II or III;
• Body Mass Index (BMI) between 18 and 30 kg/m².

Exclusion Criteria:

• Known allergy to benzodiazepines;
• History of severe respiratory or cardiovascular disease (e.g., acute heart failure, severe COPD);
• Long-term use of sedatives, analgesics, or alcohol abuse;
• Known neuromuscular disorders (e.g., myasthenia gravis);
• Inability to communicate for sedation assessment.