Frequency of Acute Kidney Injury in Patients Treated With Normal Saline after Off-Pump Coronary Artery Bypass Grafting

Introduction: Acute kidney injury (AKI) is a common postoperative complication of cardiac surgery, which is associated with an increased risk of morbidity and mortality. This study investigated the frequency of postoperative AKI in low risk adult patients undergoing off-pump coronary artery bypass grafting (CABG).Materials & Methods: All consecutive adult patients of American Society of Anesthesiologists (ASA) class II and III, who were transferred to the post-operative cardiac surgery ICU after off-pump CABG and were low risk for AKI from October 2013 to September 2014 at Emam Reza Hospital, Mashhad, Iran were enrolled in this prospective cohort study at a teaching hospital. The patients were explored for AKI development, based on risk-injury-failure-loss- end stage kidney disease (RIFLE) and acute kidney injury network (AKIN) criteria, frequency of metabolic acidosis, hypernatremia, hyperchloremia, and length of stay in ICU.Results: According to the results of the present study, 479 patients with the mean age of 60.8±10.75 yrs were included. AKI occurred in 22 (4.4%) and23 (4.8%) patients, based on both the RIFLE and AKIN criteria, respectively with the highest rate of AKI, reported on the third and fourth post-operative days. Additionally, hyperchloremia and hypernatremia were observed in 71 (14.8%) and 76 (15.9%) patients, respectively. Only one case of mortality occurred during the study. Metabolic acidosis was reported in 112 (23.4%) patients with a high anion gap in 60 (12.5%) cases.Conclusion: The current study demonstrated that hypernatremia and metabolic acidosis but not AKI are frequently seen in patients receiving normal saline following off pump CABG with low risk for AKI.