Primary Outcome Measures:
- Strokevolume variation before fluid optimization
- Strokevolume variation after fluid optimization
- Number of cycles needed in order to detect a 10% strokevolume increase after fluid bolus of 200ml Voluven.
We would like to investigate the natural variation in the strokevolume(SV) of the heart. At the same time we would like to find out the minimal number of heart cycles necessary to discover a 10% increase in SV, after a fluid bolus of 200ml Voluven, when using Esophageal Doppler.
Also we will compare the variation in SV both before and after the patients have been fluid optimized, using an algorithm of 10% increase in SV in order to receive another fluid bolus. The equipment used, will be the CardioQ from Deltex medical.