Invited Commentary

Abstract

Management guidelines for the perioperative angiotensin-converting enzyme inhibitors (ACEIs) are increasingly needed, as their use becomes more prevalent in patients presenting for cardiac surgery, and studies report experimental evidence for protective effects with short-term therapy with these agents. The ACEIs have their actions on the renin-angiotensin system (RAS), a signaling pathway that mediates systemic vasoconstriction, but has an equally important role in the local regulation of renal microcirculatory flow. Paradoxically, RAS blockade can have both renoprotective properties and the disconcerting ability to precipitate acute renal failure. The ACEIs (such as captopril) are clinically useful to slow the advance of chronic renal disease and in animals to provide protection against ischemic acute kidney injury. However, when RAS activation is critical to sustain renal blood flow (such as with renal artery stenosis or volume depletion) the ACEIs are detrimental. One study in cardiac surgical patients even noted a synergistic association of combining ACEIs with aprotinin in adding to renal risk. Specific circumstances and practices aside, previous clinical studies of acute kidney injury and perioperative ACE inhibition in surgical populations provide evidence of a confusing relationship with positive, neutral, and negative associations being reported. In the retrospective assessment of 536 aortocoronary bypass procedures presented in this issue, Benedetto and colleagues [1Benedetto U. Sciarretta S. Roscitano A. et al.Preoperative angiotensin-converting enzyme inhibitors and acute kidney injury after coronary artery bypass grafting.Ann Thorac Surg. 2008; 86: 1160-1166Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar] takes another stab at disentangling the numerous effects possible from acute and chronic ACEI therapy on the kidney in cardiac surgical patients. Notable challenges in drawing valid conclusions from the current study include the relatively high rate of new dialysis in the study population and the potential for selection bias in the characteristics of patients receiving ACEIs. The investigators appropriately used a propensity score-based multivariable analysis to minimize bias and found an association between perioperative ACEI therapy and an approximate 50% reduction in the likelihood of acute kidney injury, after accounting for other known renal risk factors. When added to the larger body of literature in this area, this study is interesting and further expands our insight into the relationship of preoperative ACEIs and postoperative outcome, but as a single study added to an accumulating collection of conflicting evidence (see the summary by these authors), this report provides insufficient evidence to endorse change in clinical care. Preoperative Angiotensin-Converting Enzyme Inhibitors and Acute Kidney Injury After Coronary Artery Bypass GraftingThe Annals of Thoracic SurgeryVol. 86Issue 4PreviewAngiotensin-converting enzyme (ACE) inhibitors confer renal protection in different clinical settings. No final conclusions are available on the renal benefits of ACE inhibitors after coronary artery bypass grafting (CABG). Because ACE inhibitors decrease glomerular perfusion pressure, they may exacerbate kidney injury during cardiopulmonary bypass (CPB)-related hypoperfusion. We evaluated the effect of preoperative ACE inhibitors on acute kidney injury (AKI) after CABG. Full-Text PDF