Remimazolam is a benzodiazepine-binding site antagonist of the GABA receptor, metabolized by esterases, and exhibits a stable context-sensitive half-life of 6-7 minutes. Remimazolam has a high clearance rate and a small volume of distribution in the pharmacokinetic model. The US FDA has approved sedation for surgery. Although there have been studies on the use of remimazolam as a sedative for procedures such as endoscopy, there have been no reports of the use of remimazolam in spinal anesthesia. The purpose of this study is to compare and analyze the hemodynamics and recovery profile of patients undergoing surgery under spinal anesthesia by maintaining sedation with dexmedetomidine or remimazolam.

Inclusion Criteria:

1. Severe cardiovascular or respiratory disease
2. Contraindication to spinal anesthesia
3. Heart block
4. Previous hepatectomy or liver transplant
5. Patients with moderate or more hepatic impairment (AST/ALT is more than 2.5 times the upper limit of normal)
6. Estimated glomerular filtration rate < 30 mL/min/1.73m2
7. Acute narrow angle glaucoma
8. Myasthesia gravis
9. Known allergy to the drugs included in the study

Exclusion Criteria:

1. Patients 19 years of age or older who are expected to elective orthopedic surgery under spinal anaesthesia
2. ASA PS 1-3