• Craig J Railton, Jacob Wolpin, Jenny Lam-McCulloch, and Susan E Belo.
• Department of Anesthesia and Perioperative Medicine, London Health Sciences Centre, ON, Canada. Craig.Railton@lhsc.on.ca
• Can J Anaesth. 2010 Aug 1;57(8):736-44.

PurposeThe outcome of patients with preoperative renin-angiotensin system (RAS) blockade, achieved either by angiotensin converting enzyme inhibitors or angiotensin receptor blocking agents, was assessed using 30-day mortality as a primary end point.MethodsAn observational cohort study of 883 consecutive patients undergoing elective open abdominal aortic aneurysm repair (AAA) was undertaken and analyzed using a propensity score matched study. The data collected included medical history, anesthetic techniques, and postoperative outcomes. Logistic regression analysis identified predictors of RAS blockade: hypertension, stroke, congestive heart failure, diabetes, and heart disease. A propensity score for RAS blockade was calculated for each subject using several factors: age, sex, serum creatinine, hypertension, heart disease, congestive heart failure, stroke, diabetes, and exposure to cardiovascular medications. Subjects and controls were matched using the calculated propensity score.ResultsThe overall 30-day mortality rate was 3.5% (31/883 patients). The crude mortality rate in RAS blocked patients was 5.8% (21/359) vs 1.9% (10/524) in unexposed patients (odds ratio 3.2, with 95% confidence intervals [CI(95)] 1.5-6.7; P < 0.001). Analysis of 261 propensity score matched pairs showed a 30-day mortality rate of 6.1% (16/261) in the RAS blocked group vs 1.5% (4/261) in unblocked patients (P = 0.008). The estimated odds ratio for 30-day mortality associated with RAS blockade was 5.0 (CI(95) 1.4-27).ConclusionsExamination of 883 cases of AAA repair showed increased mortality associated with preoperative RAS blockade. A better understanding of perioperative pharmacology and physiology of RAS blockade is needed as well as future studies to identify causality.

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