SPI-directed Analgesia for Lumbar Discectomy

in group A patients will receive pre-emptive analgesia using intravenous infusion of metamizol in a single dose of 1-1,25 gram with following intravenous infusion of 5 grams per day.

in group A patients will receive pre-emptive analgesia using intravenous infusion of tramadol in a single dose of 2 mg per hg of body weight with following intravenous infusion of 400 mg per day.

patients in group BF will receive local wound infiltration with a solution of 0,2% bupivacaine in a volume of 10 ml per segment of vertrebral columne.

patients in group RF will receive local wound infiltration with a solution of 0,2% ropivacaine in a volume of 10 ml per segment of vertrebral columne.

patients will receive no pre-emptive analgesia. intraoperatively standard dose of fentanyl will be used.