More than 200 million major surgical procedures are performed annually worldwide. Many of these patients have comorbidities including hypertension and/or heart failure. Chronic treatment of hypertension and/or heart failure very often includes a Renin-Angiotensin System (RAS) inhibitor (Angiotensin-Converting Enzyme Inhibitors (ACE-Is) or Angiotensin Receptor Blockers (ARBs). To stop or not to stop these medications before major surgery remain unknown. Data on management of RAS inhibitors before major surgery and anesthesia remain lacking and matter of debate. It is much likely that the strategy regarding management of RAS inhibitors in the peri-operative setting have important impact on peri-operative complications.