Logistical problmens, collisions with other studies

The investigators intend to study 2 new methods for the early detection of Acute Kidney Injury (AKI) after cardiac surgery and compare and combine the predictive abilities of these methods with established renal injury markers and epidemiological models to detect (AKI).

Acute Kidney Injury is common after Cardiac surgery and occurs in up to 20% of patients (Ref Rydén).

This study will evaluate two new methods for the early detection of acute kidney injury in 200 patients undergoing elective cardiac surgery at the Karolinska Hospital.

These methods are:

1. Ultrasound based measurement of the kidneys blood flow profile measured using renal resistive index (RRI). This will be measured prior and within 4 hours post surgery. Ref Herzberg, Le Dorze.
2. Urine creatinine clearance will be measured in the first four hours after cardiac surgery.

The investigators will also measure known renal injury markers in blood and urine samples post operatively. These include Neutrophil gelatinise-associated lipocalin (NGAL), tissue inhibitor of metalloproteinases (TIMP-2), Insulin-like growth factor-binding protein 7 (IGFBP7), Kidney Injury Molecule 1 (KIM-1), Nephroclear, Interleukin 18 (IL-18), Fatty acid-binding protein (L-FABP), Fibulin-1, cystatin C och albumin.

The new methods of AKI detection will be used to build a statistical model to predict AKI after cardiac surgery. We will determine whether the addition of renal injury markers and epidemiological factors known to be associated with the development of AKI (variables such as age, known chronic renal dysfunction or heart failure) can improve precision in diagnosis.

AKI will be defined by the Kidney Disease improving Global outcomes (KDIGO) criteria (Ref KDIGO KDIGO Clinical Practice Guideline for Acute Kidney Injury, Khwaja A).

Inclusion Criteria:

• 18 years and older
• Undergoing elective cardiac surgery (Coronary artery bypass grafting, valve surgery, aortic surgery or a combination).
• Able to understand and give written consent to partake in the study

Exclusion Criteria:

• Unable to give consent
• Previously received a renal transplant
• Renal failure requiring dialysis prior to surgery
• Persistent atrial fibrillation

Elective cardiac surgery patients undergoing surgery at Karolinska University Hospital, Sweden. Patients with high risk for AKI as identified by the Clevland Clinic acute renal failure score will be identified.

If the study data set is released it will be anonymized so that no personal data is retained and no individual can be identified from the data by those outside of the study.