Renal failure in septic shock: predictive value of Doppler-based renal arterial resistive index

Objective: Because acute renal failure (ARF) is frequent in septic shock, an early marker of ARF could impact on management of such patients. High renal arterial resistive index (RI) is associated with parenchymatous renal failure. We assessed whether Doppler-measured RI on day 1 (D1) of septic shock can predict ARF. Design: Prospective descriptive clinical study. Setting: A 20-bed medical intensive care unit in a university hospital. Patients: All patients with septic shock, excluding those with chronic renal failure (serum creatinine > 120 mu mol/l). Measurements and results: RI was determined during the first 24 h (D1) following vasopressor introduction, concomitant with recording of: age, SAPS II, mean arterial pressure, arterial lactate, catecholamine (dose and type), urine output and serum creatinine. ARF was diagnosed according to the RIFLE classification. RI measurement was possible for 35 of 37 included patients. On day 5 (D5), 17 patients were without ARF (RIFLE-0 or R) and 18 patients were classified as having ARF (RIFLE-I or F). On D1, RI was higher in these latter 18 patients (0.77 +/- 0.08 vs. 0.68 +/- 0.08, p < 0.001). They also had higher SAPS II and arterial lactate concentration. RI > 0.74 on D1 had a positive likelihood ratio of 3.3 (95% CI 1.1-35) for developing ARF on D5. RI correlated inversely with mean arterial pressure (p = -0.48, p = 0.006) but not with catecholamine type or dose or with lactate concentration. Conclusion: Doppler-based determination of RI on D1 in septic shock patients may help identify those who will develop ARF.