Preventable Risk Factors for Acute Kidney Injury in Patients Undergoing Cardiac Surgery

Abstract

f s c t t ACUTE KIDNEY INJURY (AKI) develops in 5% to 42% of patients who undergo cardiac surgery depending on the efinition of AKI, and 1% to 4% of patients require dialysis.1-6 AKI requiring dialysis after cardiac surgery is associated with an increased incidence of infection, length of critical care unit stay, and long-term need for dialysis.7-9 Chertow et al10 have shown that AKI requiring dialysis is an independent risk factor for mortality after cardiac surgery. Recent studies have shown that even small increases in serum creatinine ( 0.3 mg/dL) postoperatively are associated with increased mortality.11-13 The presence of stage-3 chronic kidney disease (CKD) at baseline (serum creatinine 1.47 mg/dL or glomerular filtration rate [GFR] 60 mL/min/1.73 m2) has been associated ith an increased incidence of postoperative AKI, a longer ospital stay, increased hospital mortality, and a poorer ong-term outcome.14-16 CKD is now defined in stages acording to the estimated GFR derived from serum creatinine evels (Table 1).17 Given the significant morbidity and mortality risk associated with postoperative AKI, the prevention of renal dysfunction is of paramount importance. This has led to the formulation and validation of many clinical risk scores to predict post–cardiac surgery AKI requiring renal replacement therapy (RRT).18-21 Chertow et al18 were among the first to develop a preoperative enal risk stratification algorithm based on the Veterans Affairs oronary Artery Surgery Study experience.18 Subsequently, a umber of investigators derived and validated equations to stimate the risk of post–cardiac surgery AKI requiring RRT Table 2). Finally, Palomba et al22 designed the Acute Kidney Injury After Cardiac Surgery Score based on a cohort of patients who underwent elective surgery at a Brazilian center.22 The Palomba study predicted the risk for post–cardiac surgery AKI not requiring dialysis. Most of the factors used in the development of prediction equations are nonmodifiable. These include female sex, congestive heart failure, a low ejection fraction ( 35%), diabetes mellitus, CKD, chronic obstructive pulmonary disease, peripheral vascular disease, combined valve surgery, and emergency surgery.18-22 Preoperative assessment increases the awareness of risk for AKI and can be used when obtaining consent and in planning for the perioperative period. Most importantly, the identification of high-risk patients provides an opportunity to optimize preoperative care. There are both modifiable and nonmodifiable risk factors associated with the development of AKI in cardiac surgery. This review focuses on modifiable risk factors to prevent the occurrence of AKI. These have been classified as preoperative, intraoperative, and postoperative modifiable risk factors (Table