Importance of renal function in cardiac surgery

Sammanfattning: Abstract Acute kidney injury (AKI) is a common and serious complication after cardiothoracic surgery and is associated with increased short- and long-term mortality risk. Despite extensive studies in the field, a comprehensive understanding of this syndrome has remained elusive, partly due to divergent definitions of AKI and partly due to the limitations of available routine biomarkers to predict, prevent, and detect AKI. In recent years, much has been done to better define AKI. There is also ongoing work on finding better suited biomarkers for AKI as well as improving treatment of patients at risk or suffering from AKI. In this work we studied different aspects of renal function after cardiac surgery. The first paper shows in a retrsospective study of 5261patients, when preoperative estimated glomerular filtration (eGFR) rate by s-creatinine and preoperative hemoglobin is entered into a Cox analysis together with known traditinoal risk factors for decreased long-term survival, blood transfusion did not affect survival significantly. In the subgroups of patients with normal eGFR and hemoglobin, blood transfusions did not have any effect on longterm survival. In the second paper, incidence of AKI is evaluated in 5746 patients, defined by different measures (i.e creatinine, creatinine clearance and eGFR) and evaluated in relation to long-term mortality. The effect of renal recovery on survival was also described. The Risk, Injury, Failure, Lost and Endstage (RIFLE) system was used to stratify AKI. The study showed that estimated GFR by the modification of diet in renal disease (MDRD) formula had a more robust predictive ability for mortality and that renal recovery in general was associated with better outcome compared with those without renal recovery. The third paper describes a randomized, double-blind, placebo-controlled trial, where the effect of a single high dose erythropoeitin (EPO) preoperatively, as a protective drug against AKI after cardiac surgery, is evaluated. Seventy five patients were enrolled in the study, AKI was evaluated by the changes of s-cystatin C at the third postoperative day from baseline. No protective effect against AKI by EPO could be shown. In the fourth paper the predictive value for mortality of s-creatinine and s-cystatin C and their eGFR were evaluated at different time points in patients undergoing cardiac surgery. The prospective study included 1955 patients. Different creatinine and cystatin C eGFR equations were used in the analysis. S-Cystatin C was shown to have a stronger and earlier predictive value for mortality compred with s-creatinine, and the predictive abliltiy of cystatin C was also shown preoperatievly.