Association between intrarenal venous flow from Doppler ultrasonography and acute kidney injury in patients with sepsis in critical care: a prospective, exploratory observational study

Abstract

Background: Intrarenal venous flow (IRVF) patterns assessed using Doppler renal ultrasonography are real-time bedside visualizations of renal vein hemodynamics. Although this technique has the potential to detect renal congestion during sepsis resuscitation, there have been few studies on this method. We aimed to examine the relationship between IRVF patterns, clinical parameters, and outcomes in critically ill adult patients with sepsis. We hypothesized that discontinuous IRVF was associated with elevated central venous pressure (CVP) and subsequent acute kidney injury (AKI) or death.

Methods: We conducted a prospective observational study in two tertiary-care hospitals, enrolling adult patients with sepsis who stayed in the intensive care unit for at least 24 h, had central venous catheters placed, and received invasive mechanical ventilation. Renal ultrasonography was performed at a single time point at the bedside after sepsis resuscitation, and IRVF patterns (discontinuous vs. continuous) were confirmed by a blinded assessor. The primary outcome was CVP obtained at the time of renal ultrasonography. We also repeatedly assessed a composite of Kidney Disease Improving Global Outcomes of Stage 3 AKI or death over the course of a week as a secondary outcome. The association of IRVF patterns with CVP was examined using Student's t-test (primary analysis) and that with composite outcomes was assessed using a generalized estimating equation analysis, to account for intra-individual correlations. A sample size of 32 was set in order to detect a 5-mmHg difference in CVP between IRVF patterns.

Results: Of the 38 patients who met the eligibility criteria, 22 (57.9%) showed discontinuous IRVF patterns that suggested blunted renal venous flow. IRVF patterns were not associated with CVP (discontinuous flow group: mean 9.24 cm H2O [standard deviation: 3.19], continuous flow group: 10.65 cm H2O [standard deviation: 2.53], p = 0.154). By contrast, the composite outcome incidence was significantly higher in the discontinuous IRVF pattern group (odds ratio: 9.67; 95% confidence interval: 2.13-44.03, p = 0.003).

Conclusions: IRVF patterns were not associated with CVP but were associated with subsequent AKI in critically ill adult patients with sepsis. IRVF may be useful for capturing renal congestion at the bedside that is related to clinical patient outcomes.

Keywords: Acute kidney injury; Intrarenal venous flow; Renal congestion; Sepsis; Ultrasonography.

Conflict of interest statement

All the authors declare that they have no competing interests.

© 2023. The Author(s).

Figures

Fig. 1

Color Doppler flow images from a right kidney. a Doppler sample volume position (*) in the inter-lobar vessels. b Intrarenal artery flow (upward Doppler signals), vein flow (downward Doppler signals) and the corresponding maximum and minimum velocity (Vmax, Vmin). The intrarenal venous flow waveforms were classified into a continuous venous flow pattern (b) or discontinuous patterns (c-1, c-2, d). Discontinuous patterns include biphasic patterns (c-1, c-2) and monophasic patterns (d) which had at least 1 phase with zero velocity during venous flow in a cardiac cycle as indicated by double-headed horizontal arrows (discontinuous time)

Fig. 2

Flow of the study population. CVP denotes central venous pressure

Fig. 3

Kaplan–Meier curves for the survival probability according to intrarenal venous flow patterns. Patients were followed from the day before renal ultrasonography until death from any cause or hospital discharge or the end of the study period (September 14, 2020), whichever came first. The vertical tick marks indicate censoring

Fig. 4

Trajectory of the proportion of patients with the composite outcomes stratified by IRVF patterns and contribution of each component. The composite outcome was the combination of stage 3 acute kidney injury and death. Black bars indicate death, dark gray bars indicate stage 3 AKI patients receiving RRT, and light gray bars indicate stage 3 AKI patients without RRT. Day zero was assigned as the day of IRVF measurement. Those who died during the observation period continued to contribute to the proportions; the denominator was 16 in the continuous group and 22 in the discontinuous group on all days