Preoperative Renal Resistive Index Predicts Risk of Acute Kidney Injury in Patients Undergoing Cardiac Surgery.

OBJECTIVE

To investigate whether an elevated preoperative renal resistive index (RRI) predicts acute kidney injury (AKI) in patients undergoing cardiac surgery.

DESIGN

Prospective cohort study.

SETTING

University hospital.

PARTICIPANTS

Cohort of 96 adult cardiac surgical patients.

INTERVENTIONS

Resistive index was measurement the day before surgery.

MEASUREMENTS AND MAIN RESULTS

Renal Doppler was used to measure the resistive index in renal cortical or arcuate arteries the day before surgery. An elevated RRI was defined as≥0.7. AKI was defined as an absolute increase in postoperative compared with preoperative serum creatinine levels by≥26 µmol/L or a relative increase by≥50% or a postoperative urine output<0.5 mL/kg for 6 hours or longer. The relative risk of AKI in patients with an elevated RRI compared with those without an elevated RRI was analyzed using logistic regression. Among patients with an RRI<0.7, 6 (16%) developed AKI compared with 21 (36%) with an RRI≥0.7. The mean increases in postoperative serum creatinine levels were 12 μmol/L in those with an RRI<0.7 and 30 μmol/L in those with an RRI≥0.7. The crude odds ratio for AKI in patients with an RRI≥0.7 was 3.03 (1.09-8.42) compared with those with an RRI<0.7. After multivariable adjustment, the odds ratio was 2.95 (0.97-9.00).

CONCLUSIONS

Patients with an elevated preoperative RRI have an increased risk of developing AKI after cardiac surgery. In combination with other markers, the RRI might be a tool for identifying patients with an increased risk of developing AKI.