Spinal anesthesia is widely used for lower extremity surgery, and sedation is often required during surgery. For sedation, propofol, midazolam and dexmedetomidine are frequently used. Dexmedetomidine is a highly selective alpha 2 receptor agonist, and has sedating and analgesic effect. Compared with propofol and midazolam, it has little or no respiratory inhibition and hemodynamically stable. It also has the effect of reducing delirium in the elderly. Dexmedetomidine has also been reported to prolong the duration of sensory and motor blockade effects of spinal anesthesia. However, several studies have reported that administration of dexmedetomidine in spinal anesthesia increases the incidence of bradycardia.

In a study of healthy young adults, concurrent administration of atropine with dexmedetomidine in spinal anesthesia significantly reduced the frequency of bradycardia requiring treatment. However, in elderly patients, it is often reported that there is little response to atropine in bradycardia, and ephedrine is more effective in treating bradycardia than atropine in the elderly.

The investigators therefore compared ephedrine and atropine as pretreatment to reduce the incidence of bradycardia when using dexmedetomidine as a sedative in elderly patients undergoing spinal anesthesia.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) classification I-II
• Undergoing orthopedic surgery under spinal anesthesia

Exclusion Criteria:

• Contraindication for spinal anesthesia
• Atrial fibrillation, atrial flutter
• Cardiac valve disease
• Neurologic disease
• initial systolic blood pressure in operating room > 160mmHg