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)

There are a lot of methods to determine if a patient is fluid-responsive, however a moment to stop fluid therapy is lacking. So the purpose of this study is to find a 'stop' moment for fluid therapy before peripheral edema will be present.

With sublingual measurements of the vessel density with the Cytocam-IDF, comparing the septic patients with fluid overload , euvolemic post-cardiac surgery patients at the arrival on the ICU and healthy volunteers we can determine if there is a decrease in vessel density during fluid loading.

To give a accurate view on fluid overload we include a bio-impedance measurement of reactance and resistance. Fluid balances are recorded very accurate by our electronic patient record.

Inclusion Criteria:

• after cardiac surgery
• septic patient with a fluid balance of 4L +

Exclusion Criteria:

• recent maxillofacial surgery

ICU population