Fluid resuscitation is one of the cornerstones of treatment in ICU patients. Nonetheless, excessive fluid administration can lead to fluid overload which has been associated with worse outcomes in the ICU. To prevent this, assessments of fluid responsiveness are commonly employed. However, fluid responsiveness does not take fluid tolerance into account. Fluid tolerance is the idea that a patient might still be fluid responsive but might already be at risk of the detrimental effects of fluid therapy. Recent developments in point of care ultrasound e.g. the Venous excess ultrasound might help identify patients at risk of fluid overload. However its association with patient relevant outcomes in the ICU remains unclear.

This study will investigate the association between the venous excess ultrasound grading system (VExUS) and patient relevant outcomes such as acute kidney injury, mortality and length of stay.

A secondary analysis is planned where the association between VExUS and the lung ultrasound score will be investigated

Inclusion Criteria:

• all patients admitted to the ICU 18 years or older expected to stay in the ICU for more than 24 hours

Exclusion Criteria:

• any obstruction between the righ atrium and structures assessed by VExUS
• a medical history of: Major cardiac shunts (e.g. atrial septum defect), Tricuspid regurgitation, dialysis, portal hypertension, pulmonary hypertension, interstitial lung disease, recipients of a kidney of liver transplant.
• patients in whom an ultrasound assesment is unfeasible e.g. a BMI over 40

All cricitally ill patients who are expected to be admitted to the ICU for more than 24 hours and who do not meet the exclusion criteria