Relation Between the Increase of Peripheral Edema by Fluid Therapy and the Decrease in Microcirculatory Vesseldensity

Can videomicroscopy of the sublingual microcirculation detect the increase in edema before peripheral edema will appear? By measuring the decrease in vesseldensity after strong positive fluid balances within septic patients versus euvolemic post-cardiac surgery patients. Measuring reactance and resistance (BIVA method) to determine volume status. Primary outcome: \- Total vessel density (TVD) Secondary outcome: * Fluid balance * BIVA measurements (reactance \& resistance)