Effects of Renin-Angiotensin System Inhibitors on the Occurrence of Acute Kidney Injury Following Off-Pump Coronary Artery Bypass Grafting

Abstract

Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp s the indications for renin-angiotensin system (RAS) inhibitors expand for secondary prevention in patients with coronary artery disease, 1 an increasing number of patients presenting for coronary artery bypass graft surgery (CABG) have had chronic angiotensin-converting enzyme inhibitor or angiotensin receptor blocker administration. Although continued RAS inhibitor therapy is associated with improved survival and retarded progression of renal disease, 2-4 concerns about the development acute kidney injury (AKI) in situations associated with decreased glomerular filtration pressure have been raised. 2,5,6 Editorial p 1800Indeed, cardiac surgery under cardiopulmonary bypass (CPB) is significantly associated with changes in the glomerular filtration rate and volume shift. Chronic preoperative RAS inhibitor therapy reportedly resulted in 28% increased risk of AKI following cardiac surgery, suggesting withholding of these medications prior to surgery. 2 However, from the currently available evidence no definite conclusion can be drawn on withdrawing RAS inhibitors prior to CABG at the expense of losing their anti-ischemic benefits. 2,7Use of the off-pump CABG (OPCAB) technique in patients presenting with high surgical risk has increased, with preferable results. 8-10 CPB itself is considered one of the main etiologic factors in the development of AKI. 11-14 In addition, because RAS inhibitor-associated AKI is more likely to develop under certain conditions, such as hypovolemia and renal hypoperfusion, 15,16 we hypothesized that preload augmentation before distal anastomosis and maintenance of pulsatile blood flow and pressure during surgery would mitigate the effect of RAS inhibitors on renal function after OPCAB. However, comprehensive data to support Background: Despite several studies that evaluated the effects of renin-angiotensin system (RAS) inhibitors on postoperative renal function in cardiac surgery patients, no final conclusions are available. The aim of the present study was to determine the effect of RAS inhibitors on renal function following off-pump coronary artery bypass grafting (OPCAB).

Urinary Angiotensinogen and Risk of Severe AKI

“…Our findings regarding the prognostic utility of angiotensinogen as a biomarker of AKI suggest that the RAS could be mechanistically involved in AKI. This is supported by observational studies that have noted an association between pharmacologic inhibition of the RAS and risk of developing AKI, although there are conflicting reports in the literature (31)(32)(33)(34). The ACE II genotype has been associated with increased risk of AKI in the ICU (35).…”

Usefulness of Urinary Biomarkers in Early Detection of Acute Kidney Injury After Cardiac Surgery in Adults

“…24 The medullary region in the kidney exists on a hypoxic precipice as a result of low blood flow and countercurrent exchange of oxygen, although paradoxically housing nephron segments with very high energy requirements (eg, the S3 segment of the proximal tubule). The ischemic state after cardiac surgery worsens the relative hypoxia, leading to prolonged cellular injury and cell death in these predisposed tubule segments.…”

Association between angiotensin converting enzyme inhibitor or angiotensin receptor blocker use prior to major elective surgery and the risk of acute dialysis

“…[44], Ouzounian et al [37], and Yoo et al [45], studied 11330, 1647, and 472 cardiac surgery patients, respectively, and demonstrated no significant association between preoperative ACEi/ARB use and AKI. However, all three studies observed a non-significant trend towards a benefit with preoperative ACEi/ARB use raising the possibility of insufficient statistical power to detect the association [37,44,45]. …”