Measurement of arterial blood pressure is a basic monitoring in the perioperative setting. It is a standard monitoring to assure an adequate cerebral perfusion pressure and is a basic parameter of hemodynamic optimization. Until now standard methods for blood pressure measurement are non-invasive interval monitoring by arm cuff (Riva-Rocci) or direct, continuous and invasive by inserting an intraarterial catheter. This observational study will show, that a new non-invasive piezocapacitative-interlayer technology will make continuous blood pressure monitoring and non-invasive pulse contour analysis available.