1. Admitted to ICU prior to randomization. 2. Current treatment with blood pressure lowering agent, affecting the RAAS system (i.e. Angiotensin Converting Enzyme inhibitor (ACEi), Angiotensin Receptor Blocker (ARB), Aldosteron antagonist or Renin inhibitor) 3. Patients with heart condition eg. heart failure with reduced ejection fraction, EF < 40%, who has an evidence based indication for ACE inhibitors or Angiotensin receptor blockers 4. Prior serious adverse reaction to an ARB or ACEi 5. Systolic blood pressure below 120 mmHg or symptomatic hypotension. Blood pressure will be taken in supine position after 5 minutes rest with manual or automatic blood pressure manometers 6. Estimated Glomerular Filtration Rate (eGFR) of < 50ml/min/1.73 m² 7. Potassium > 5 mEq/l 8. Women of childbearing age. Pregnant or breastfeeding. Women that are postmenopausal can be included. Women and childbearing age can be included after a negative pregnancy test 9. Known renal artery stenosis 10. Severe hepatic failure (i.e. ALAT/ASAT > 5x normal upper limit) 11. Volume depletion, chock or new onset of acute kidney injury that, in the opinion of the investigator, would preclude administration of ARB/ACE-inhibitors 12. Any condition or therapy which would make the participant unsuitable for the study, according to the investigators opinion 13. Inability to provide informed consent 14. Moribund or palliative patients deemed unlike to survive hospital stay or who cannot make an informed decision for participations (e.g. non-adults or patients with dementia)

1. Admitted to ICU prior to randomization. 2. Current treatment with blood pressure lowering agent, affecting the RAAS system (i.e. Angiotensin Converting Enzyme inhibitor (ACEi), Angiotensin Receptor Blocker (ARB), Aldosteron antagonist or Renin inhibitor) 3. Patients with heart condition eg. heart failure with reduced ejection fraction, EF < 40%, who has an evidence based indication for ACE inhibitors or Angiotensin receptor blockers 4. Prior serious adverse reaction to an ARB or ACEi 5. Systolic blood pressure below 120 mmHg or symptomatic hypotension. Blood pressure will be taken in supine position after 5 minutes rest with manual or automatic blood pressure manometers 6. Estimated Glomerular Filtration Rate (eGFR) of < 50ml/min/1.73 m² 7. Potassium > 5 mEq/l 8. Women of childbearing age. Pregnant or breastfeeding. Women that are postmenopausal can be included. Women and childbearing age can be included after a negative pregnancy test 9. Known renal artery stenosis 10. Severe hepatic failure (i.e. ALAT/ASAT > 5x normal upper limit) 11. Volume depletion, chock or new onset of acute kidney injury that, in the opinion of the investigator, would preclude administration of ARB/ACE-inhibitors 12. Any condition or therapy which would make the participant unsuitable for the study, according to the investigators opinion 13. Inability to provide informed consent 14. Moribund or palliative patients deemed unlike to survive hospital stay or who cannot make an informed decision for participations (e.g. non-adults or patients with dementia)