The application of tourniquet is indispensable for a bloodless surgical area in total knee arthroplasty surgery. The release of tourniquet produces reactive oxygen species which can cause injury and then ischemia-reperfusion injury emerge. Our aim in this study is to investigate effects of pregabalin, GABA analog drug, on the tourniquet induced ischemia-reperfusion injury.

Investigators will randomize patients into two groups. 1) Pregabalin group 2) Control group.

Investigators will give orally pregabalin 150 mg to the pregabalin group patients two times (first dose 1 day before surgery., second dose 1 hour before surgery). On the other hand placebo drug will give to the control group at the same times. Investigators will perform combined spinal epidural anesthesia for surgery and inject 3 cc 0.5% hyperbaric bupivacaine to subarachnoid space. Investigators will take blood samples for measurement of ischemia-reperfusion determinants, immediately before surgery, shortly before tourniquet deflation, and 20 minutes after tourniquet deflation. Then these samples will be analysed by ELISA method.

Inclusion Criteria:

1. American Society of Anesthesiologists (ASA) physical status I-II
2. Undergoing a total knee arthroplasty surgery
3. Accept neuroaxial anesthesia for surgery

Exclusion Criteria:

1. Any antiepileptic drug use
2. Allergic reaction to pregabalin
3. Severe hepatic, renal or gastrointestinal disorders
4. Psychiatric disorders
5. Pregnant women or breastfeeding
6. NSAID or opioid drug use for a long time
7. Diabetic or other neuropathic pain