Although the investigators take many measurements to monitor the fluid state of the patients, it is not known exactly whether the fluid has real effect on the organ perfusion. The main focus of fluid is to improve the organ perfusion. Recent research has focused on the investigation of sublingual microcirculatory alterations.

Is fluid responsiveness, what means a better cardiac output, equal to the need for fluid for a better organ perfusion? In hospital the investigators are now looking to the pump function of the heart, as there is not a better measurement. However this gives no information about necessity of giving fluids. A healthy volunteer also gives a better pump function of the heart after fluid, but that fluid is not necessary and gives no better organ perfusion. The question is: How many percent of the patients have a MFI score of < 2.6, when the doctor on clinical basis plans to give fluid to the patient, improves organ perfusion after fluid, and is this correlated with an improvement of the cardiac output All intensive care patients who need extra fluid are eligible for this study. Before and after the fluid challenge we do SDF imaging sublingual. Per patient the investigators do this 1x in 24 hours. Concurrently, data on both patient characteristics (e.g. severity of illness) will be obtained Study population max 100 patients. Possible outcome: MFI < 2,6 en SV > 10% + MFI up MFI < 2,6 en SV equal + MFI equal MFI < 2,6 en SV > 10% + MFI equal MFI < 2,6 en SV equal + MFI up MFI > 2,6 en SV > 10% + MFI up MFI > 2,6 en SV equal + MFI equal MFI > 2,6 en SV > 10% + MFI equal MFI > 2,6 en SV equal + MFI up

Inclusion Criteria:

• age > 18
• hemodynamic monitoring
• informed consent
• admission on ICU

Exclusion Criteria:

• no informed consent
• oral surgery

All patients admitted on the ICU and a need of fluids