Patients on a stable dose of ACE inhibitor or ARB medication who are scheduled for elective surgery will be randomized to take their ACE inhibitor or ARB up to and including the morning of surgery, or to hold them a day prior to the surgery. The patients will be followed for 30 days after surgery to assess any adverse health outcomes.

Inclusion Criteria:

• currently taking an ACEi, ARB or both
• no change in these medications during the two weeks prior to study enrollment
• scheduled for non-cardiac surgery requiring regional or general anesthesia
• minimum overnight anticipated length of stay
• age ≥18 years.

Exclusion Criteria:

• explicit instructions provided to patient by surgical team regarding the perioperative management of ACEi or ARB
• significant hypertension in pre-operative assessment clinic (systolic blood pressure ≥180 mmHg OR diastolic blood pressure ≥110 mmHg)
• significant hypotension in pre-operative assessment clinic (systolic blood pressure < 90 mmHg)
• prior enrollment in the study
• participation in another research study of antihypertensive medications