Fluid therapy before and under surgery can be guided by measurement of the hearts ability to eject blood (cardiac output). By doing this it has been shown that the occurrence of nausea,vomiting and complications generally can be reduced. The function of the heart has been measured with a probe in the esophagus in in earlier studies. We want to correlate these results with other techniques by which fluid therapy also is guided in daily practice. These are: SVO2, modelflow (finapres)and NIRS.