Neutral Endopeptidase for Early Detection of Acute Kidney Injury After Cardiac Surgery

Study Overview
=================
Brief Summary
-----------------
The investigators want to investigate if the urinary biomarker neprilysin can identify cardiac surgical patients suffering from postoperative AKI within 24 hours.

Detailed Description
-----------------
Acute kidney injury (AKI) is a common complication following cardiac surgery and significantly increases morbidity, duration of hospital stay, and mortality. The diagnosis of AKI relies on changes in serum creatinine (SCr) from a baseline value or decreases in urine output. Nevertheless changes of SCr to diagnose AKI are only reliable after a minimum of 48 hours. Neutral endopeptidase, also called neprilysin (NEP) represents a single-pass membrane glycoprotein with zinc-dependent endopeptidase activity and a short cytosolic tail and is found in epithelia, fibroblasts, and neutrophils and in soluble form in the circulation, urine, and cerebrospinal fluid. Beside the focus of interest in cardiovascular medicine for its role in heart failure, where the inhibition of NEP by the administration of sacubitril/valsartan may achieve an improvement in patients with chronic heart failure and reduced ejection fraction, there is also thought to be a link to renal damage. NEP is expressed in the brush border of proximal tubular cells, which is first shed in renal damage and therefore it is a marker for tubular damage when it is measurable in urine In this study the investigators want to investigate if NEP is a marker for earlier detection of AKI after elective cardiac surgery compared to the currently recommended Kidney Disease - Improved Global Outcomes (KDIGO) guidelines for acute kidney injury. Also, the investigators want to investigate at predefined time points the occurrence and the progression of tubular damage during cardio-pulmonary bypass (CPB) in a closed-meshed NEP detection.

Official Title
-----------------
Neutral Endopeptidase for Early Detection of Acute Kidney Injury After Cardiac Surgery

Conditions
-----------------
Acute Kidney Injury

Intervention / Treatment
-----------------
* Procedure: Cardiac surgery


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: - Patients undergoing an elective cardiac surgical intervention Exclusion Criteria: Emergency procedures Heart transplantation Elective left ventricular assist device (LVAD) implantation Pulmonary thrombendarterectomy Declined informed consent Age < 18 years Pregnant woman Preoperative renal replacement therapy (RRT) Receiving medication containing sacubitril

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| AKI<br>patients with postoperative AKI defined by KDIGO | Procedure: Cardiac surgery<br> <br> |
| no AKI<br>patients without postoperative AKI defined by KDIGO | Procedure: Cardiac surgery<br> <br> |

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| NEP-levels | Difference of NEP-levels after cardiac surgery on the first postoperative day | 24 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| NEP-levels | Difference of NEP-levels after cardiac surgery at the end of procedure | approximately 6 hours | 
| Increase of NEP | Time-dependent increase of NEP during CPB | approximately 6 hours |