Anesthesia
bradycardia, hypotension
Patients entered the operating room with no premedication. Standard monitoring of pulse oximetry, EKG, noninvasive blood pressure (BP), and bispectral index (BIS, Medtronic, Minneapolis, MN, USA) was performed. After measuring baseline hemodynamics, 5 L/min of oxygen was administered using a facial mask. The patient was placed in a lateral position with the operating leg facing down, and spinal anesthesia was administered at the lumbar 3/4 or 4/5 level with a 25G spinal needle. Hyperbaric bupivacaine (0.5%) was administered differentially according to the patient’s height with the aim of achieving an anesthesia level of T 10. Ten minutes after the induction of spinal anesthesia, the anesthesia level was checked using an alcohol swab. Hemodynamic parameters and T1 HRV were then measured.Thereafter, dexmedetomidine or propofol sedation was initiated according to group assignment. In the dexmedetomidine group, 0.6 mcg/kg was loaded for the first 10 min, followed by infusion at 0.5 mcg/kg/h. In the propofol group, the effect-site concentration of 0.3–1.0 ng/mL was adjusted using a target concentration infusion to maintain the BIS at 60–80. In both groups, T2 and T3 HRV were measured at 10 and 20 min, respectively, from the initial sedative administration. In cases of bradycardia (heart rate < 50 beats/min), atropine (0.5 mg) was administered, and ephedrine (8 mg) was administered for hypotension (systolic blood pressure < 90 mmHg).