Acute Kidney Injury (AKI) in patients undergoing Coronary Artery

Bypass Grafting (CABG) is a significant post-operative concern, with

its incidence varying from 20-40%. 1-5% of these patients

end up requiring renal replacement therapy (RRT). It has been found

that serum creatinine as a marker of AKI usually rises late in the

post-operative period. Newer biological markers such as Neutrophil gelatinase

associated lipocalin (NGAL) and Kidney-Injury Molecule-1 (KIM-1) have

been tried in these settings, however, they are expensive and not

readily accessible.

Venous excess ultrasound (VExUS) and Renal resistive index (RRI) are

two ultrasound based scoring systems that have been developed measure

systemic venous congestion, and resistance in the renal arteries

respectively. These scoring systems have been found to be useful in

predicting AKI in patients undergoing cardiac surgeries. As the

facility of ultrasound is widely available in critical care settings,

calculation of these scores may help in early detection of AKI.

One baseline preoperative reading will be obtained for each of the aforementioned. One post-operative reading will be taken after the procedure, within 3 hours of shifting the patient to ICU. Aside from volume loading with crystalloids and colloid day 0 and mean urine output on days 1-2 of the postoperative ICU stay, other intraoperative data collection will include the duration of aortic clamping, transfusion and details of transfused products, urine output, mean arterial pressure, heart rate, PaCO2, lactates, blood saturation of O2 , serum total proteins, haematocrit, and the percentage of subjects receiving norepinephrine or dobutamine. The patients on whom satisfactory VExUS and RRI readings on dopplers cannot be obtained will be excluded from analysis. 

Assessment of kidney function: The patients’ preoperative serum creatinine values will be noted in the immediate post operative period, at 24 hours, 48 hours and 72 hours. The highest value found 72 hours after surgery will be the postoperative serum creatinine value that will be taken into consideration. For both genders, the normal range for serum creatinine measurements was 0.4–1.0 mg/dL and 0.6–1.3 mg/dL in men and women respectively. The KGIDO network criteria will define the occurrence of AKI.(27) During the post cardiac surgery ICU stay, postoperative urine production will be measured hourly. In patients developing AKI, treatment for the same will be started according to standard ICU protocols.

The corelation between the predictions of the gradings and development of post operative AKI will be assessed and compared.