Acute Kidney Injury After Cardiac Surgery: Novel Ultrasound Techniques for Prediction of Acute Kidney Injury

Acute Kidney Injury (AKI) is a frequent and important complication to cardiac surgery. The pathophysiology is multifactorial, but renal functions in this setting is determined by a complex interplay between renal perfusion, fluid status, cardiac output, mean arterial pressure and back pressure to venous outflow.

Renal perfusion may be quantified with novel ultrasound techniques. Ultrasonography of the kidney and renal vasculature allows for assessment of renal afferent flow and renal venous flow and, together with venous flow patterns of the portal vein and liver veins, may identify patients in risk of AKI.

The study is observational and will describe the diagnostic accuracy of the ultrasound measures in predicting postoperative AKI. Patients will be examined with ultrasound of kidney and liver flow along with echocardiography on on the day before surgery and on the 1st and 4th. In addition, patients are followed with markers of kidney function, fluid balance and invasive measures of mean arterial pressure and central venous pressure.

Inclusion criteria

• All patients ≥ 18 years
• Scheduled for on-pump cardiac surgery
• Oral and written consent

AND

• 1 of the following risk factors for development of postoperative AKI may be included:

• age > 70 years;
• NYHA (New York Heart Association) 3+4;
• Insulin dependent diabetes;
• Glomerular filtration rate < 60 ml/min/1,73 m2;
• Ejection fraction < 35;
• Surgery:

• Combined CABG and valve surgery;
• Any valve surgery except isolated aortic-valve surgery;
• Redo surgery;
• Endocarditis;
• Peripheral vascular disease.

Exclusion criteria

• Insufficient ultrasonographic imaging of the kidneys;
• Known morphological kidney disease;
• Preoperative dialysis;
• Prior participation in the study.