Oxygen delivery and carbon dioxide production as determinants of acute kidney injury during open heart surgery

Abstract

Background Acute kidney injury (AKI) after cardiac surgery remains an important and frequent complication in patients undergoing cardiac surgery with CPB and is associated with a poor short-term and long-term prognosis. The incidence of cardiac surgery-associated (CSA)-AKI according to Acute Kidney Injury Network and RIFLE criteria varies between 3 and 50%. CSA-AKI requiring temporary renal replacement therapy occurs in 5–20% of these patients and is associated with a high mortality rate. Objective The aim of the study was to evaluate the effect of lowest O2 delivery (DO2) and highest CO2 production (VCO2) during cardiopulmonary bypass as risk factors for postoperative AKI and correlate this effect with the postoperative value of plasma neutrophil gelatinase-associated lipocalin (NGAL) as an early biomarker for detection of AKI. Patients and methods Seventy patients of both sexes, their ages varying between 18 and 60 years, scheduled for elective cardiac surgery by means of cardiopulmonary bypass were included in this study. DO2 and VCO2 on CPB as well as blood urea, serum creatinine, O2 content of arterial blood, and NGAL level were measured. Results DO2 has an important role as a risk factor for AKI wherein values below 260 ml/min/m2 are associated with increased incidence of AKI. At the same time VCO2 appeared to have no role as a risk factor for AKI. Conclusion Optimizing DO2 to tissues during CPB by increasing either hematocrit or pump flow is most important in preventing AKI. However, VCO2 level has no role. NGAL is an early and sensitive biomarker that can diagnose and predict the severity of AKI before serum creatinine is elevated.