Dynamic volume status assessment with the Vexus score after heart valve surgery complicated by acute kidney injury: a case series

Background: Fluid overload is an independent risk factor for acute kidney injury after cardiac surgery. An objective volume status assessment remains an unsolved clinical problem. Objective: To analyze the relationship between the dynamic changes in splanchnic blood flow patterns (portal, hepatic, and interlobar renal veins), reflecting the venous congestion severity, and severity of renal dysfunction in the studied patients. Methods: From February to May 2023, 3 patients after open heart surgery developed acute kidney injury in the postoperative period: 2 of them required renal replacement therapy. In the perioperative period, all patients underwent Doppler ultrasonographic assessment of the splanchnic blood flow according to the venous excess ultrasound (VExUS) score. Results: The most distinct changes in blood flow patterns were observed in portal and interlobar renal veins. Two anuric patients requiring renal replacement therapy had a pulsatile portal venous flow with systolic flow reversal that indicated severe venous congestion and biphasic renal venous flow. After restoration of urine output in 1 patient, the blood flow pattern in the portal vein returned to the normal pattern. In another patient, the blood flow remained pulsatile, which manifested itself by persisting clinical signs of overhydration. In the third patient, the portal blood flow also was pulsatile but had no systolic flow reversal. The renal blood flow was biphasic, although it was initially continuous. After restoration of urine output and overhydration improvement, the blood flow pattern returned to the preoperative pattern. Conclusion: In the studied patients, the dynamic assessment of splanchnic blood flow using the VExUS score allowed to objectively assess the venous congestion severity and served as an additional criterion for initiating renal replacement therapy in case of acute kidney injury progression. Further research could validate this type of monitoring because its interpretation requires a comprehensive assessment due to moderate specificity.