Intraoperative Transesophageal Echocardiography Assessment of Portal Vein Flow and Renal Resistive Index As a Predictor of Acute Kidney Injury After Cardiac Surgery: A Prospective Observational Study

Informed consent will be obtained prior to surgery. Preoperative demographic and baseline clinical data will be collected. We will assess the patient's risk of postoperative AKI using the validated Cleveland clinic score based on preoperative risk factors and calculate the European System Operative Score Risk Evaluation score (EuroSCORE II). After standard anesthesia induction and intubation, a TEE probe will be inserted by a cardiac anesthesiologist, who is certified in intraoperative echocardiography. We will use a standard ultrasound machine (EPIQ 7 Philips;Philips, Bothell, WA). Images of the right or left kidney along with Doppler flow and velocities will be obtained prior to cardiopulmonary bypass (CPB), after CPB, and after chest closure. Images of the portal vein with Doppler flow and velocity will be obtained prior to CPB, after CPB, and after chest closure. Vitals signs and hemodynamic data will be collected concurrently during these times. (See Data Sheet) Concurrent ECG will be obtained to identify the phases of the cardiac cycle. Mean arterial pressure (MAP) will be maintained within 20% of baseline MAP with bolus or continuous infusion of vasopressors (phenylephrine, norepinephrine, epinephrine, vasopressin, ephedrine). Cardiopulmonary bypass management will be standard, with target systemic blood flow of 2.4L/min/m2. Postoperative data will include urine output, serum creatinine, calculated GFR (using Modification of Diet in Renal Disease [MDRD] method) hospital and ICU length of stay, and 30-day mortality.

Inclusion criteria

• Inclusion criteria are patients >18 years old getting elective cardiac surgery with the use of cardiopulmonary bypass at the University of Chicago Medical Center.

Exclusion criteria

• Exclusion criteria are preexisting renal insufficiency/failure (glomerular filtration rate < 60 ml/min/1.73 m2 [stage 2 chronic kidney disease] or dialysis, renal vein thrombosis, renal artery stenosis, significant aortic regurgitation (moderate to severe aortic regurgitation on preoperative or intraoperative TEE), liver cirrhosis, portal vein thrombosis, preoperative intra-aortic counterpulsation balloon pump, emergency surgery, inability to obtain flow velocity waveforms of renal/portal vasculature on TEE, and kidney or liver transplant.