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.