Acute kidney injury is associated with a decrease in cortical renal perfusion during septic shock

Abstract

Background: Renal perfusion status remains poorly studied at the bedside during septic shock. We sought to measure cortical renal perfusion in patients with septic shock during their first 3 days of care using renal contrast enhanced ultrasound (CEUS).

Methods: We prospectively included 20 ICU patients with septic shock and 10 control patients (CL) without septic shock admitted to a surgical ICU. Cortical renal perfusion was evaluated with CEUS during continuous infusion of Sonovue (Milan, Italy) within the first 24 h (day 0), between 24 and 48 h (day 1) and after 72 h (day 3) of care. Each measurement consisted of three destruction replenishment sequences that were recorded for delayed analysis with dedicated software (Vuebox). Renal perfusion was quantified by measuring the mean transit time (mTT) and the perfusion index (PI), which is the ratio of renal blood volume (rBV) to mTT.

Results: Cortical renal perfusion was decreased in septic shock as attested by a lower PI and a higher mTT in patients with septic shock than in patients of the CL group (p = 0.005 and p = 0.03). PI values had wider range in patients with septic shock (median (min-max) of 74 arbitrary units (a.u.) (3-736)) than in patients of the CL group 228 a.u. (67-440)). Renal perfusion improved over the first 3 days with a PI at day 3 higher than the PI at day 0 (74 (22-120) versus 160 (88-245) p = 0.02). mTT was significantly higher in patients with severe acute kidney injury (AKI) (n = 13) compared with patients with no AKI (n = 7) over time (p = 0.005). The PI was not different between patients with septic shock with severe AKI and those with no AKI (p = 0.29).

Conclusions: Although hemodynamic macrovascular parameters were restored, the cortical renal perfusion can be decreased, normal or even increased during septic shock. We observed an average decrease in cortical renal perfusion during septic shock compared to patients without septic shock. The decrease in cortical renal perfusion was associated with severe AKI occurrence. The use of renal CEUS to guide renal perfusion resuscitation needs further investigation.

Keywords: Acute kidney injury; Renal failure; Renal perfusion; Renal ultrasonography; Sepsis; Septic shock.

Fig. 1

Evolution of mean transit time (mTT) (a), perfusion index (PI) (b) and rBV (c) during the first 3 days in ICU in patients with septic shock and in control patients without septic shock; a.u., arbitrary units. **p = 0.005 for group effect (control and septic shock groups) with analysis of variance (ANOVA) on ranks. *p = 0.03 for interaction (group × time) with ANOVA on ranks. ^§p = 0.04 for ANOVA on ranks in the septic shock group over time. rBV ANOVA (p = 0.21). Box plots show median, interquartile (1;3) and maximum values

Fig. 2

Evolution of mean transit time (mTT) (a), perfusion index (PI) (b) and rBV (c) during the first 3 days in ICU in patients with septic shock with acute kidney injury (AKI) Kidney Disease Improving Global Outcome (KDIGO) stage 2 or 3 (AKI+) or in patients with septic shock without AKI or with AKI KDIGO stage 1 (AKI-); a.u., arbitrary units. **p = 0.005 for group effect (with AKI or without AKI) with analysis of variance (ANOVA) on ranks. rBV ANOVA (p = 0.49). Box plots show median, interquartile (1;3) and maximum values

Fig. 3

Receiver operating characteristic curves for prediction of severe acute kidney injury ( Kidney Disease Improving Global Outcome (KDIGO) stage 2 or 3) during the first 72 h with microhemodynamic data (mean transit time measured with contrast enhanced ultrasound (mTT), perfusion index measured with contrast enhanced ultrasound (PI), resistivity index measured with Doppler ultrasonography (RI)) and macrohemodynamic data (cardiac index)