Should Ambulatory Surgery and Day of Surgery Admission Patients Discontinue Angiotensin Converting Enzyme Inhibitors (ACEI's) and Angiotension Receptor Blockers (ARB's) Preoperatively?

Angiotensin converting enzyme inhibitors (ACEI's) and Angiotensin receptor blockers (ARB's) are commonly used anti-hypertensive medications that may have implications on the management of a patient undergoing surgery. Limited research has looked at the effects of these medications on perioperative complications and mortality. Some studies conducted on small groups of inpatients with advanced vascular disease undergoing vascular surgery or coronary artery bypass grafting (CABG), suggest exacerbation of hypotension (low blood pressure) in patients who continued taking ACEI's or ARB's on the morning of their procedure. In addition, cases of low blood pressure (BP) that were refractory to standard treatment were reported. One recent retrospective study reported no difference in severe hypotension and only a modest difference in moderate hypotension managed by conventional treatment, but did not adequately address the risk of preoperative hypertension. A study recently published by the investigators (Twersky et al., 2014) in over 600 patients demonstrated no difference in preoperative hypertension in ambulatory surgery and same day admission patients. There has been limited data stratifying the degree of low BP based on severity but these were not done in ambulatory patients, and neither was the degree of high BP from discontinuing these medications addressed. As such, no uniform consensus has been reached and clinicians are unclear as to whether the reported inpatient findings are applicable to the outpatients, since they differ in many respects. The investigators propose to evaluate whether ACEI's and ARB's discontinued preoperatively have a negative impact on perioperative hemodynamics and patient outcome in a group of ambulatory and same day surgical patients. Similar to studies done on inpatients, the investigators will also evaluate patients receiving a standardized general anesthetic for hemodynamics following induction of anesthesia until surgical incision.

The investigators hypothesize that continuing ACEI's and ARB's in the preoperative period does not result in an increased risk of severe hypotension (low blood pressure) following induction of general anesthesia.