The purpose of this study to compare the efficacy of intravenous or intrathecal dexmedetomidine on the incidence of shivering on patients who scheduled spinal anesthesia for elective surgery.

The design of the study includes three study groups done in random order. The groups are as follows: 1) Control group received 15 mg levobupivacaine intrathecally and intravenous 0.9% sodium chloride; 2) Intravenous group received 15 mg levobupivacaine intrathecally and intravenous dexmedetomidine (1mcg/kg/10min, 0.5mcg/kg/h infusion) ; 3) Intrathecal group received 15 mg levobupivacaine + 3 mcg dexmedetomidine intrathecally and intravenous 0.9% sodium chloride.

Throughout the study period,shivering scores, tympanic temperature were recorded, heart rate were measured continuously using an electrocardiogram; blood pressure was determined oscillometrically at 5 min intervals at the ankle. In case heart rate decreased by more than 30% of the baseline atropin received and blood pressure decreased 30% of the baseline effedrin received.

Side effects (bradycardia, hypotension, hypothermia, nausea and vomiting etc ) were recorded peroperatively in the operating room and postanesthetic care unit.

Inclusion Criteria:

• 18-65 y/o patients
• American Society of Anesthesiologists' physical status class I-II
• Scheduled for the spinal anesthesia

Exclusion Criteria:

• Patients who have the body temperature over 37.3 celsius degree
• Pregnants
• Known allergies to the study drugs
• Contraindication to spinal anesthesia