During this prospective, uncontrolled and non-interventional observational study, the influence of albumin function on the efficacy of furosemide will be investigated. The aim of the study is to provide information on the efficacy of furosemide depending on albumin function.

In patients with intravenous furosemide administration, an additional 15 ml of blood is taken for the analysis of specific parameters as part of the blood sampling necessary for the treatment of the patient.

The effect of furosemide is assessed on the basis of the patient's urine excretion. For this purpose, fluid intake and excretion are balanced over 6 hours. The blood sample is taken at the beginning of the balancing period.

In addition, the albumin concentration, ABiC, as well as the total and free concentration of furosemide in the collected urine are determined.

Inclusion Criteria:

• Informed consent
• Attending intensive care physician intends to prescribe IV furosemide to increase urine output
• Arterial (central venous if applicable) and urinary catheter in situ

Exclusion Criteria:

• Attending intensive care physician intends to prescribe further doses of diuretic medication (including furosemide infusion) within the 6 hours required for fluid collection
• Patients who received intravenous or oral diuretics (including mannitol) in the 6 hours prior to study enrolment
• Patients who have received other medications (e.g. fludrocortisone) known to affect renal sodium or water excretion in the 24 hours prior to study entry
• Patients with uncontrolled hyperglycaemia (plasma glucose >10mmol/L).
• Patients who were receiving renal replacement therapy prior to the start of the study
• Patients with obstructive uropathy, macroscopic haematuria or intra-abdominal hypertension (>20mmHg)
• Age < 18 years

intensive care patients admitted to University Hospital Rostock