- admitted to icu prior to randomization. - currently taking an an angiotensin converting enzyme inhibitor (acei) or angiotensin receptor blocker (arb). - use of other investigational drugs at the time of enrollment - prior reaction or intolerance to an arb; or severe intolerance to an acei, defined as angio-oedema requiring medical intervention. - systolic blood pressure < 105 mmhg or diastolic blood pressure <65mmhg. - potassium greater than 5.5 meq/l within 4 weeks of study enrollment. - estimated glomerular filtration rate (egfr) of < 30ml/min/1.73 m2 within 4 weeks of study initiation. - a known history of renal artery stenosis. - ast and/or alt > 3 times the upper limit of normal within 4 weeks of study enrollment. - severe liver dysfunction (child-pugh score c), biliary cirrhosis or cholestasis. - severe volume depletion or severe acute kidney injury. - inability to obtain informed consent. - pregnancy or breastfeeding.

- admitted to icu prior to randomization. - currently taking an an angiotensin converting enzyme inhibitor (acei) or angiotensin receptor blocker (arb). - use of other investigational drugs at the time of enrollment - prior reaction or intolerance to an arb; or severe intolerance to an acei, defined as angio-oedema requiring medical intervention. - systolic blood pressure < 105 mmhg or diastolic blood pressure <65mmhg. - potassium greater than 5.5 meq/l within 4 weeks of study enrollment. - estimated glomerular filtration rate (egfr) of < 30ml/min/1.73 m2 within 4 weeks of study initiation. - a known history of renal artery stenosis. - ast and/or alt > 3 times the upper limit of normal within 4 weeks of study enrollment. - severe liver dysfunction (child-pugh score c), biliary cirrhosis or cholestasis. - severe volume depletion or severe acute kidney injury. - inability to obtain informed consent. - pregnancy or breastfeeding.