Hindawi Publishing Corporation Case Reports in Anesthesiology Volume 2013, Article ID 723815, 5 pages http://dx.doi.org/10.1155/2013/723815 Case Report Multifactorial Model and Treatment Approaches of Refractory Hypotension in a Patient Who Took an ACE Inhibitor the Day of Surgery Karan Srivastava, 1 Vikas Y. Sacher, 1 Craig T. Nelson, 2 and John I. Lew 1,3 1 Department of Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA 2 Department of Anesthesiology, University of Miami Miller School of Medicine, Miami, FL 33136, USA 3 University of Miami Leonard M. Miller School of Medicine and DeWitt Daughtry Family Department of Surgery, Division of Endocrine Surgery, University of Miami and Jackson Memorial Hospitals, 1120 NW 14th Street, CRB-Room 410P (M-875), Miami, FL 33136, USA Correspondence should be addressed to John I. Lew; jlew@med.miami.edu Received 18 February 2013; Accepted 11 March 2013 Academic Editors: D. Lee and J.-J. Yang Copyright © 2013 Karan Srivastava et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In the feld of anesthesiology, there is wide debate on discontinuing angiotensin-converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB) therapy the day of noncardiac surgery. Although there have been many studies attributing perioperative hypotension to same-day ACEI and ARB use, there are many additional variables that play a role in perioperative hypotension. Additionally, restoring blood pressure in these patients presents a unique challenge to anesthesiologists. A case report is presented in which a patient took her ACEI the day of surgery and developed refractory hypotension during surgery. Te evidence of ACEI use on the day of surgery and development of hypotension is reviewed, and additional variables that contributed to this hypotensive episode are discussed. Lastly, current challenges in restoring blood pressure are presented, and a basic model on treatment approaches for refractory hypotension in the setting of perioperative ACEI use is proposed. 1. Introduction Approximately 65 million Americans actively receive anti- hypertensive agents for elevated blood pressure [1]. Dur- ing surgery, beta-adrenergic blockers and alpha 2 agonists are routinely continued perioperatively because of their role in protecting the myocardium [2–5]. Additionally, cal- cium channel blockers are used in the perioperative period because of their reduction in myocardial ischemia, infarction, arrhythmias, and overall mortality [6, 7]. Since angiotensin- converting enzyme inhibitor (ACEI) attenuates the adren- ergic response to stressful stimuli in cardiac, vascular, and cerebrovascular patients, ACEI is strongly recommended prior to and during these specifc surgeries [8–11]. However, the use of ACEI and angiotensin receptor blocker (ARB) therapy in the preoperative period in noncar- diac patients has been controversial because of its potential role in causing hemodynamic instability. Patients on chronic ACEI or ARB therapy have a dampened sympathetic response [8]. Additionally, surgical patients can be volume depleted because of preoperative fasting, and this condition can cause additional stress during surgery. Tese combining factors result in reduced vascular capacitance and venous return, leading to decreased cardiac output and subsequent hypoten- sion. To compensate for this hypotension, angiotensin II (ANG2) plays an important role in maintaining blood pres- sure through vasoconstriction. Tis vasoconstriction shunts blood away from the kidneys, bowels, and spleen [12, 13]. ANG2’s short-term efect is to maintain blood pressure through vasoconstriction whereas its long-term efect, which takes hours to days, is volume regulation through sodium and water retention. Figure 1 explains the renin-angiotensin system. Patients who have recently taken ACEI or ARB prior to surgery are unable to use ANG2 efects to counterbalance this