Characterization of the Efficacy of Furosemide Depending on Albumin Function

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