Goal directed volume therapy means that bolus doses of 150-250 ml colloid fluid is administered to the patient during contemporary measurement of the patients stroke volume. The fluid status is considered optimized when stroke volume no longer increases with more than 10%, indicating that the patient is close to the top of the Frank-Starling curve. Several studies show that volume optimization reduces hospital stay and reduces the amount of surgical complications. The overall purpose is to investigate if the much more simple non invasive technique Pleth Variability Index can replace oesophageal doppler to guide volume therapy in routine health care, and to analyse if a volume kinetic test can be used to evaluate hypovolemia before surgery and make specific rehydration possible by analysing the correlation between this test and fluid optimization using stroke volume measurements.