These changes are recorded and compared at the same time during different measuring methods preoperatively, intraoperatively and postoperatively. The non-invasive Nexfin© Monitoring (Edwards Lifesciences) is to be evaluated and compared with further measurement methods (FloTrac© (Edwards Lifesciences)) as well as the sphygmomanometric upper arm blood pressure measurement. The investigators also compare the non-invasive and invasive continuous beat to beat blood pressure measurement with conventional, discontinuous sphygomanometric upper arm blood pressure measurement.