IntroductionRenal 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).MethodsThis 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.ResultsMedian 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.ConclusionsA 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.

Determination of pulse co-oximetry-based hemoglobin in patients presenting with severe gastrointestinal bleeds can be inaccurate, which renders its use to guide transfusion decisions potentially hazardous. The unavailability of measurements, especially during vasopressor infusion, represents another serious limitation for hemorrhagic patients.