Cardiac autonomic neuropathy is a common complication of diabetes and is associated with resting tachycardia. Regional anesthesia could interrupt normal autonomic activity by central sympathetic blockade. The investigators evaluate the relation of severity of diabetes and heart rate variability, also the impact of spinal anesthesia on the change of heart rate variability.

Inclusion Criteria:

• patients undergoing lower limb surgery with spinal anesthesia (ASA class 1,2,3)

Exclusion Criteria:

• severe coagulopathy, short height, arrhythmia patients, patients taken medication which could affect autonomic nervus system (bata- blocker or alpha-blocker)

patients undergoing lower limb surgery with spinal anesthesia