Clinical Research Directory

Inclusion Criteria: * Age over 18 years, of any gender and ethnic background * Admitted to the intensive care unit * Able to give informed consent * Patients with an arterial line as part of their treatment plan. * Patients able to remain seated in chair for at least 30 minutes * Patients able to remain supine overnight for at least 6 hours Exclusion Criteria: * Delirium or inability to give informed consent * Inability to understand written information in Dutch * Patients on artificial ventilation * Orotracheally intubated patients (spontaneous breathing through a tracheostomy cannula is allowed) * Patients treated with noradrenaline \> 0.05 ug/kg/min * Patients treated with argipressin * Patients who received a blood transfusion within 24 hours before measurements * Patients who received \> 3 L of fluids within 24 hours before measurements * Patients who received \> 500 ml of iv fluids within 4 hours of measurements * Severe restlessness or inability to remain supine for 6 hours before initial blood sampling * Patients being treated with diuretics * Patients admitted with: * Decompensated right heart failure * Pulmonary hypertension * Pulmonary embolism * Active bleeding or risk of \>100 ml blood loss * Hematological disorder/malignancy