Renal resistive index assessment by intraoperative transesophageal echocardiography is associated with acute kidney injury after cardiac surgery: a prospective observational study.

Background: Acute kidney injury (AKI) is a major health burden after cardiac surgery. Renal vasoconstriction and venous congestion can be assessed via transesophageal echocardiography (TEE). The primary objective is to determine feasibility of measuring intraoperative Renal resistive index (RRI) and portal vein pulsatility fraction (PF) by TEE. The secondary objectives are to determine the association between RRI and/or PF and postoperative AKI, Intensive Care Unit (ICU) length of stay, hospital length of stay, and 30-day mortality.

Methods: This is a prospective observational study at a single center University setting in adult patients undergoing elective cardiac surgery. Intraoperative RRI and PF measurements were obtained prior to CPB, after CPB, and after chest closure.

Results: Eighty patients met eligibility criteria and consented. Overall feasibility rate was 91% (73/80), RRI measured in 96% (77/80) and PF measured in 94% (75/80). Further analyses was conducted in 69 patients. RRI prior to CPB significantly correlated with AKI ([OR][95% CI] 2.15 [1.07-4.33], P=0.03) with an AUC of 0.68 ([95%CI] 0.55-0.81, P=0.02). Post-chest closure RRI>0.75 significantly correlated with AKI ([OR][95% CI] 3.54 [1.18-10.62], P=0.02). Combination of the three timepoints significantly associated with AKI ([AUC][95% CI] 0.71 [0.58-0.84], P=0.007). PF did not significantly correlate with AKI.

Conclusions: This study demonstrates high feasibility for obtaining intraoperative TEE measurement of RRI and PF and significant correlation between postoperative AKI with pre CPB RRI, post chest closure RRI, and the combination of RRI at the three timepoints.