Importance of renal function in cardiac surgery

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.