Venous pressure is often overlooked as an important hemodynamic parameter. Elevated venous pressure and blood stasis in organ tissues can lead to interstitial edema. Intraoperative venous blood stasis can rapidly increase interstitial pressures within organ tissues, especially in organs encapsulated by tissue envelopes, such as the kidney, thereby rapidly reducing effective circulating blood flow to the organ. Systemic venous blood stasis, which tends to occur in patients with right heart failure or pulmonary hypertension, as well as in patients with fluid overload, can lead to intraoperative stasis in multiple organs and tissues, mediating the development of multisystem complications, including acute kidney injury. Therefore, timely, effective, and accurate intraoperative assessment of systemic venous blood stasis is particularly important.

When right heart failure and/or volume overload occurs in the body, changes in right atrial pressure are transmitted to the venous system of organs throughout the body, with dilatation of the inferior vena cava (IVC), obstruction of blood return from the hepatic, portal, and renal veins, and abnormal venous flow signals and altered ultrasound Doppler flow patterns.

The primary objective of this prospective cohort study is to explore if intraoperative systemic venous congestion during cardiac surgery is associated with postoperative CSA-AKI. In doing so, we seek to identify a promising physiological marker that can provide cues for the prediction of CSA-AKI. This study will also investigate the relationship between intraoperative systemic venous congestion and postoperative complications, and explore the relationship between each separate venous congestion and AKI after cardiac surgery.

Inclusion Criteria:

1. Patients scheduled to undergo elective cardiac surgery;
2. ≥ 18 years.

Exclusion Criteria:

1. Contraindications for TEE;
2. Emergency cardiac surgery;
3. Major vascular surgery;
4. Redo cardiac surgery;
5. Abnormal preoperative renal function;
6. Severe chronic kidney disease (estimated glomerular filtration rate < 15 ml/min/1.73 m2 or dialysis);
7. History of kidney transplantation;
8. Severe infection requiring continuous antibiotic therapy；
9. Severe preoperative heart failure with left ventricular ejection fraction < 30%;
10. A critical preoperative state (mechanical circulatory support, extracorporeal membrane oxygenation, current renal replacement therapy [RRT], mechanical ventilation, or cardiac arrest necessitating resuscitation);
11. Multi-organ dysfunction;
12. Known conditions that may interfere with the assessment or interpretation of hepatic vein, portal vein blood flow (such as liver cirrhosis or portal vein thrombosis) or the renal vein blood flow and renal artery blood flow (such as urinary tract obstruction);
13. Planned cardiac transplantation or ventricular assist device implantation;
14. Pregnancy;
15. Insufficient ultrasonographic imaging;
16. Restarting CPB after first CPB cessation during surgery;
17. Requirement for cardiac assist devices (ECMO, IABP, or ventricular assist device) after CPB intraoperatively.

Patients scheduled to undergo elective cardiac surgery