After coronary artery bypass grafting, which are the most common types
of cardiac surgery, develops acute renal injury requiring replacement therapy in
1–5 %. They are associated with high rates of morbidity and mortality. For this
relevant clinical problem, it is recommended to monitor renal function after
surgery. Standard parameters for investigating renal function in clinical routine
are serum creatinine, measured creatinine clearance and in present time a
prediction equation to estimate glomerular filtration rate (GFR) from serum
creatinine by the MDRD study equation, but they all are based on measurement
of serum creatinine, which is influenced by a lot of factors such as formation
and excretion of creatinine and method of determination. In our study we
included also a new marker of renal function serum cystatin C and predicted
estimate GFR from serum cystatin C.
We performed a prospective and partly randomized trial in 50 patients,
half of the patients were operated on coronary arteries with cardiopulmonary
bypass and the other half of patients were operated without cardiopulmonary
bypass. Renal function was assessed 5 consecutive days; from preoperative
day up to third postoperative day. Both patients groups were similar
preoperatively, except they had different number of coronary arteries affected.
During and after surgery there were no serious complications like myocardial
infarct or death. No patients required postoperative dialysis support. Four
patients, which are 8 % of all patients included in the study, developed acute
renal injury class Risk for injury by RIFLE classification. Two of them were
operated with cardiopulmonary bypass and two without it. Patients operated
with cardiopulmonary bypass developed statistically significant but subclinical
reduced GFR. Patients operated without cardiopulmonary bypass had stable
GFR after surgery and uninjured renal function. Reduced renal function (GFR)
after surgery with cardiopulmonary bypass we demonstrated with serum
creatinine, cystatin C and calculated estimation of GFR from both serum
markers. Measured creatinine clearances were unreliable, mainly because of
imprecise collecting of timed urine samples and they also overestimate GFR,
because creatinine is also secreted in urine by renal tubules.
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