Worsening of renal function (WRF) is frequently observed after cardiac surgery and it is associated with both short- and long-term worse outcome. Among the pathophysiological conditions favoring the occurrence of WRF, the abnormalities in renal blood flow could play a key role.
The aim of this study was to evaluate the changes in renal resistance index (RRI), a parameter reflecting renal parenchymal and hemodynamic parameters, after cardiac surgery.
Methods. Thirty-one patients were enrolled (age 65±12 years, 29% males, mean left ventricular ejection fraction 55±5%, mean creatinine serum levels 0.89±0.18 mg/dl, mean eGFR 89±28 ml/min*1.73 m2). All patients underwent cardiac surgery. Before cardiac surgery, after 3 days and before discharge, RRI was evaluated according to Peurcelot’s formula by renal interlobular arteries pulsed Doppler. Worsening of renal function was defined as an increase in serum creatinine of > 0.3 mg/dl associated with a change > 25% or the need of renal replacement therapy due to severe acute kidney injury.
Results. As shown in the table 1, after cardiac surgery a significant increase in RRI was observed at 3 days after cardiac surgery but not before discharge. The significant increase in RRI was observed both in patients with and without WRF. However, in patients with WRF significant higher values of RRI were observed before as well as after cardiac surgery.
Conclusions. Among patients undergoing cardiac surgery a significant increase in RRI values is observed after surgery. Among patients with WRF a significant greater values of RRI are observed before as well as cardiac surgery thus suggesting that a critical increase in renal resistance could play a role in the cardiorenal syndrome worsening.