title: Contrast-enhanced ultrasound to evaluate changes in renal cortical perfusion around cardiac surgery: a pilot study.
abstract: BACKGROUND
  Contrast-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.
  
  
  METHODS
  We 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).
  
  
  RESULTS
  All 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.
  
  
  CONCLUSIONS
  CEUS 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.
authors.forename: Antoine G
authors.initials: AG
authors.lastname: Schneider
authors.forename: Mark D
authors.initials: MD
authors.lastname: Goodwin
authors.forename: Anthony
authors.initials: A
authors.lastname: Schelleman
authors.forename: Michael
authors.initials: M
authors.lastname: Bailey
authors.forename: Lynne
authors.initials: L
authors.lastname: Johnson
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
mesh_terms: D058186:Acute Kidney Injury / Q000000981:diagnostic imaging*; D000368:Aged; D001810:Blood Volume; D006348:Cardiac Surgical Procedures; D003287:Contrast Media; D003422:Critical Care; D006801:Humans; D007672:Kidney Cortex / Q000098:blood supply* / Q000000981:diagnostic imaging*; D008833:Microcirculation; D015588:Observer Variation; D059035:Perioperative Period; D010865:Pilot Projects; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D012079:Renal Circulation; D014463:Ultrasonography
chemical_list: D003287:Contrast Media