Doppler resistive index to reflect regulation of renal vascular tone during sepsis and acute kidney injury
1 CHU de Bordeaux, Service d'Anesthésie-Réanimation II, avenue de Magellan, F-33604 Pessac, France
2 University of Bordeaux, Bioingénierie tissulaire, U1026, 146 rue Léo-Saignat, F-33000 Bordeaux, France
3 University of Bordeaux, Adaptation cardiovasculaire à l'ischémie, U1034, 125 avenue du Haut-Lévèque, F-33600 Pessac, France
4 CHU de Bordeaux, Service de Néphrologie Transplantation Dialyse, place Amélie Raba-Léon, F-33000 Bordeaux, France
Critical Care 2012, 16:R165 doi:10.1186/cc11517
See related commentary by Lerolle, http://ccforum.com/content/16/6/174Published: 12 September 2012
Renal resistive index (RI), determined by Doppler ultrasonography, directly reveals and quantifies modifications in renal vascular resistance. The aim of this study was to evaluate if mean arterial pressure (MAP) is determinant of renal RI in septic, critically ill patients suffering or not from acute kidney injury (AKI).
This prospective observational study included 96 patients. AKI was defined according to RIFLE criteria and transient or persistent AKI according to renal recovery within 3 days.
Median renal RIs were 0.72 (0.68-0.75) in patients without AKI and 0.76 (0.72-0.80) in patients with AKI (P=0.001). RIs were 0.75 (0.72-0.79) in transient AKI and 0.77 (0.70-0.80) in persistent AKI (P=0.84). RI did not differ in patients given norepinephrine infusion and was not correlated with norepinephrine dose. RI was correlated with MAP (ρ= -0.47; P=0.002), PaO2/FiO2 ratio (ρ= -0.33; P=0.04) and age (ρ=0.35; P=0.015) only in patients without AKI.
A poor correlation between renal RI and MAP, age, or PaO2/FiO2 ratio was found in septic and critically ill patients without AKI compared to patients with AKI. These findings suggest that determinants of RI are multiple. Renal circulatory response to sepsis estimated by Doppler ultrasonography cannot reliably be predicted simply from changes in systemic hemodynamics. As many factors influence its value, the interest in a single RI measurement at ICU admission to determine optimal MAP remains uncertain.