 3. Intrathecal analgesia: An intrathecal administration of preservative-free morphine 0.3 mg in 3 ml NS prepared in sterile ampoules by a hospital pharmacy will be performed before induction of anesthesia in a sitting position between L2 and L3 - L4L5 vertebrae. Standard general anesthesia will be performed. After surgery, the patients will have the possibility to use PCA device with morphine, bolus dose 1 mg, lock-out interval 5 min for 3 days at a surgical ICU. 