Preoperative aspirin administration decreases postoperative acute kidney injury and mortality in patients with chronic kidney disease undergoing cardiac surgery, a study finds.
“In previous studies, we found that aspirin pretreatment before surgery reduces perioperative complications and mortality in patients undergoing cardiac surgery,” said Jian-Zhong Sun, MD, PhD, professor of anesthesiology at Thomas Jefferson University, in Philadelphia. “Generally speaking, aspirin works for surgical patients presenting with high cardiovascular risk, but whether aspirin also provides the same protection for patients with chronic kidney disease is not clear.”
To address this question, Dr. Sun and his colleagues examined the records of 5,175 consecutive patients undergoing cardiac surgery in two tertiary care hospitals; 3,585 met inclusion criteria. These individuals were divided into two groups: those who did or did not take aspirin within five days of surgery. Baseline estimated glomerular filtration rate (eGFR, mL/min/1.73 m2) was classified as normal, greater than 90; mildly decreased, 60 to 89; moderately decreased, 30 to 59; severely decreased, 15 to 29; or kidney failure, less than 15. Chronic kidney disease was defined as eGFR less than 60 mL/min/1.73 m2. Postoperative acute kidney injury was defined by Acute Kidney Injury Network criteria (Crit Care 2007;11:R31). Major outcomes included acute kidney injury, length of ICU stay, readmission, major adverse cardiovascular events and 30-day mortality.
Dr. Sun noted that 31.5% of patients had chronic kidney disease at baseline. Outcomes worsened as chronic kidney disease became more severe. Indeed, acute kidney injury, major adverse cardiovascular events, ICU stay, hospital readmission and 30-day mortality increased 2.1-, 3.5-, 1.8-, 3.1- and 4.6-fold, respectively, for patients with eGFR 15 to 29 compared with 90 mL/min/1.73 m2 or greater (P<0.001).
“If patients take aspirin before the surgery, postoperative acute kidney injury and mortality are decreased compared with the patients who didn’t take preoperative aspirin,” Dr. Sun said in an interview with Anesthesiology News. Multivariate logistic regression adjusted with propensity scores showed that preoperative aspirin use was associated with a significant decrease in postoperative acute kidney injury, major adverse cardiovascular events and 30-day mortality. Dr. Sun reported the findings at the annual meeting of the American Society of Anesthesiologists (abstract A2046). The study has been published in Annals of Surgery (2015;261:207-212).
“Interestingly, the survival benefit of aspirin therapy was greater in patients whose baseline kidney function was worse,” Dr. Sun reported. Thirty-day mortality was reduced by 23.3% for patients whose baseline eGFR exceeded 90, compared with a 58.2% mortality reduction in those with baseline eGFR of 30 to 59, and a 79.0% reduction in those with a 15 to 30 baseline eGFR.
Determining why aspirin has these effects is more challenging to answer. “It’s a really tricky question,” Dr. Sun said. “I think one is related to aspirin’s anti-inflammatory effects. Secondly, [it is] antiplatelet and antithrombotic.” These benefits come at the potential cost of excessive bleeding, but Dr. Sun found that this was not significant in the study.