Kinetics of the Sublingual Microcirculation During Fluid Bolus

"The normal treatment of a post-cardiac surgery patient is fluid bolus by indication. This indications are hypotension, hyperlactataemia, tachycardia or decreased urine production. This fluid bolus is 250 ml crystalloids in 15 minutes.~When this fluid bolus will be given, the investigators will observe the sublingual microcirculation and measure the red blood cell velocity and total vessel density on one spot for 20 minutes."