Pain treatment after open-chest operations with three possibilities of pain-relief therapy.

All patients participated in the study will receive morphine in postoperative period. Pain will be measured with visual-analogue scale (VAS) during 24 hours after surgery as well as morphine consumption will be noted. Morphine will be administered with patient-controlled analgesia devices (PCA). Each patient participated in the study will be aneasthetised in the same manner. Total intravenous anaesthesia approach: propofol, fentanyl, rocuronium. Other drugs (atropine, neostigmine, ondansetron) will be given as required. 30 minutes before the end of surgery, all patients will receive bolus of morphine ( 0.1-0,15 mg/kg) and 2 grams of metamizol intravenously. In postoperative period each patient will get metamizol (every 6 h). When pain increases above 40 in VAS, patients will receive 5 mg of morphine. Ondansetron will be given as required due to nausea and vomiting. Patients will be randomly assigned to one of the treated groups (i.e. contrainication to paravertebral catheter placement or allergy to any of drugs will exclude a patient from the study). First group: before the surgery paravertebral catheter will be placed. Each patient in this group will receive 30 ml of local anaesthetic solution (0,25% bupivacaine with 2 mcg of fentanyl per ml) at the end of operation. After the emergence from general anaesthesia the infusion of local anesthetic solution will be continued (0.1 ml/kg/h) for 24 h. Second group: after induction of general anaesthesia, but before the first incision, patients in this group will receive i.v. injection of ketamine (1 mg/kg) Third group (control group): only morphine and metamizol will be given in postoperative period as pain-relief drugs (standard care). 1,2 and 6 months after the surgery neuropathic pain will be assesed. Each patient participated in the study will be called and NPSI (Neuropathic Pain Symptom Inventory) will be used to measure pain.