 All patients will receive an intravenous catheter. The intravenous catheter will be used for blood sampling. A baseline blood sample will be taken 65 min before surgery baseline and thereafter blood samples will be obtained 0 min., 15 min., 30 min., 45 min., 60 min., 90 min., 120 min., 180 min., 240 min., 300 min., 360 min. and 420 min. after administration of melatonin. Blood samples will be obtained again after administration of melatonin at 9 pm. in the evening in the same manner as described above. Plasma samples will be stored at minus 80 C and analyzed at the research laboratory of the Department of surgery, Herlev Hospital. The analysis will be preformed with the RIA-technique. 