60 patients aged 65 and older with ASA I-III physical status undergoing elective surgery under spinal anesthesia will be included in the study.

Patients with cardiac arrhythmia, severe heart failure, cerebrovascular disease, or contraindications to neuraxial anesthesia will be excluded. Frailty assessments will be performed using the Clinical Frailty Scale (CFS) version 2.0 by anesthesiologists in preoperative clinics or wards. Participants will be categorized into frail (CFS Level ≥4, Group I) and non-frail (CFS Level ≤3, Group II) groups.

Prior to spinal anesthesia, 8 mL/kg of crystalloids will be administered. Baseline preoperative mean arterial blood pressure (MABP) and heart rate (HR) will be recorded as the average of three measurements in the supine position.

During the study, MABP and HR will be monitored every 2 minutes for the first 20 minutes post-spinal anesthesia, then every 5 minutes until surgery ends. Hypotension (MABP <80% of baseline) will be treated with 5 mg intravenous ephedrine, while bradycardia (HR <50 beats/min) will be treated with 0.5 mg intravenous atropine.

Inclusion Criteria:

• 65 and older
• ASA I-III physical status
• Undergoing elective surgery under spinal anesthesia

Exclusion Criteria:

• Patients with cardiac arrhythmia
• Patients with severe heart failure
• Patients with cerebrovascular disease
• Contraindications to neuraxial anesthesia

Male and female patients aged 65 and over