Success of the hip arthroplasty depends on the measures that optimize perioperative conditions.It is planned to evaluate semi-closed loop system in the hip arthroplasty surgery.

Success of the total hip arthroplasty depends on the measures that optimize perioperative conditions. They increase the emotional stress of the staff and error probability. It is planned to evaluate semi-closed loop infusion system, its adaption for infusion application's influence to near and far treatment outcomes done by prospective randomized clinical trial. This is done by performing total hip arthroplasty. It's expected to evaluate the semi-closed loop system's influence on the doctor's emotional tension during the decision making.

Inclusion Criteria:

• Patients with osteoarthritis of the hip undergoing hip arthroplasty with spinal - epidural anesthesia
• Age >50 and <85 years
• ASA (American Society of Anesthesiology Classification) II physical status
• Start of operation no later than 09:00
• Signed informed consent form

Exclusion Criteria:

• Age <50 and >85 yers
• BMI (Body Mass Index) <20 and >40 kg/m2
• ASA I and ASA>II physical status
• History of a bleeding disorder
• Anemia before surgery Hb<110 g/l
• Intravascular fluid infusion within 24 hours before study
• Diabetes mellitus
• Previous open hip surgery
• Psychiatric illness (intake of other psychiatric medication than selective serotonin reuptake inhibitors)
• Alcohol intake 5 U daily
• Contraindication to spinal - epidural anesthesia
• Surgery not by project surgeon
• Start of operation later than 09:00
• Atrial fibrillation
• Narcotic addiction
• History of DVT (Deep Vein Thrombosis), thromboembolic complications, acute cardiac insufficiency
• Participation in the other study