Renal dysfunction in adults following cardiopulmonary bypass is linked to declines in S-Nitrosylated hemoglobin – a case series

Abstract

Background: Impaired kidney function is frequently observed in patients following cardiopulmonary bypass (CPB). Our group has previously linked blood transfusion to acute declines in S-nitrosylated hemoglobin (SNO-Hb; the main regulator of tissue oxygen delivery), reductions in intra-operative renal blood flow, and post-operative kidney dysfunction. While not all CPB patients receive blood, kidney injury is still common. We hypothesized that the CPB procedure itself may negatively impact SNO-Hb levels leading to renal dysfunction. Materials and Methods: After obtaining written informed consent, blood samples were procured immediately before and after CPB, and on post-operative day (POD) 1. SNO-Hb levels, renal function (estimated glomerular filtration rate; eGFR), and plasma erythropoietin (EPO) concentrations were quantified. Additional outcome data were extracted from the patients’ medical records. Results: Twenty-seven patients were enrolled, three withdrew consent, and 1 was excluded after developing bacteremia. SNO-Hb levels declined after surgery and were directly correlated with declines in eGFR (R=0.48). Conversely, plasma EPO concentrations were elevated and inversely correlated with SNO-Hb (R=-0.53) and eGFR (R=-0.55). Finally, ICU stay negatively correlated with SNO-Hb concentration (R=-0.32). Conclusion: SNO-Hb levels are reduced following CPB in the absence of allogenic blood transfusion and are predictive of decreased renal function and prolonged ICU stay. Thus, therapies directed at maintaining or increasing SNO-Hb levels may improve outcomes in adult patients undergoing cardiac surgery.