A short bolus infusion of fluid, called "fluid challenge" is commonly recommended for fluid
treatment during longer surgery. However a prolonged increase of the blood volume is a
prerequisite to recommend the technique. The purpose with the study is to examine the plasma
expanding effect of three different fluid challenge strategies (acetated Ringers 4 ml/kg body
weight, albumin 5% 4 ml/kg body weight or albumin 20% 1 ml/kg body weight), using hemoglobin
as a dilution indicator.