Hypothesis; Firstly the investigators hypothesize that the pain induced by the conventional method inclusive preoperational lidocaine injection will be the same or more intense than using DNTT without local anesthesia. Secondly the investigators hypothesize that the use of DNTT for the placement of the arterial catheter will decrease the time spend, amount of complications (hematoma), the number of pricks, the number of utilized catheters compared to the traditional palpation method. Thirdly the investigators claim that the best anatomical place to put the catheter isn't always corresponding with the spot chosen by palpation, which increase the number of failures.