Abstract
IntroductionContrast-enhanced ultrasound (CEUS) is a new technique that might enable portable and non-invasive organ perfusion quantification at the bedside. However, it has not yet been tested in critically ill patients. We sought to establish CEUS's feasibility, safety, reproducibility and potential diagnostic value in the assessment of renal cortical perfusion in the peri-operative period in cardiac surgery patients.MethodsWe recruited twelve patients deemed at risk of acute kidney injury (AKI) planned for elective cardiac surgery. We performed renal CEUS with destruction-replenishment sequences before the operation, on ICU arrival and the day following the admission. Enhancement was obtained with Sonovue® (Bracco, Milano, Italy) at an infusion rate of 1 ml/min. We collected hemodynamic parameters before, during and after contrast agent infusion. At each study time, we obtained five video sequences, which were analysed using dedicated software by two independent radiologists blinded to patient and time. The main output was a perfusion index (PI), corresponding to the ratio of relative blood volume (RBV) over mean transit time (mTT).ResultsAll 36 renal CEUS studies, including 24 in the immediate post-operative period could be performed and were well tolerated. Correlation between readers for PI was excellent (R2 = 0.96, P < 0.0001). Compared with baseline, there was no overall difference in median PI's on ICU admission. However, the day after surgery, median PI's had decreased by 50% (P < 0.01) (22% decrease in RBV (P = 0.09); 48% increase in mTT (P = 0.04), both suggestive of decreased perfusion). These differences persisted after correction for haemoglobin; vasopressors use and mean arterial pressure. Four patients developed AKI in the post-operative period.ConclusionsCEUS appears feasible and well-tolerated in patients undergoing cardiac surgery even immediately after ICU admission. CEUS derived-parameters suggest a decrease in renal perfusion occurring within 24 hours of surgery.
Highlights
Contrast-enhanced ultrasound (CEUS) is a new technique that might enable portable and noninvasive organ perfusion quantification at the bedside
The scan on ICU admission was completed at a mean of 110 (SD 42) minutes after ICU admission
We found no overall difference in CEUS-derived parameters (PI, relative blood volume (RBV) and mean transit time (mTT)) on ICU admission
Summary
Contrast-enhanced ultrasound (CEUS) is a new technique that might enable portable and noninvasive organ perfusion quantification at the bedside. It has not yet been tested in critically ill patients. Acute kidney injury (AKI) is a frequent complication of cardiac surgery and renal replacement therapy (RRT) is required in 1 to 4% of the cases [1,2,3,4,5,6]. Such severe AKI has been shown to be independently associated with increased in-hospital mortality [7]. Our knowledge, understanding, and theoretical constructs regarding renal perfusion in critically ill patients are based on extremely weak direct evidence
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