title: Contrast-enhanced ultrasonography to evaluate changes in renal cortical microcirculation induced by noradrenaline: a pilot study.
abstract: BACKGROUND
  We used contrast-enhanced ultrasound (CEUS) to estimate the effect of an increase in mean arterial pressure (MAP) induced by noradrenaline infusion on renal microvascular cortical perfusion in critically ill patients.
  
  
  METHODS
  Twelve patients requiring a noradrenaline infusion to maintain a MAP more than 60 mmHg within 48 hours of intensive care unit admission were included in the study. Renal CEUS scans with destruction-replenishment sequences and Sonovue® (Bracco, Milano Italy) as a contrast agent, were performed at baseline (MAP 60 to 65 mmHg) and after a noradrenaline-induced increase in MAP to 80 to 85 mmHg.
  
  
  RESULTS
  There was no adverse effect associated with ultrasound contrast agent administration or increase in noradrenaline infusion rate. Adequate images were obtained in all patients at all study times. To reach the higher MAP target, median noradrenaline infusion rate was increased from 10 to 14 μg/min. Noradrenaline-induced increases in MAP were not associated with a significant change in overall CEUS derived mean perfusion indices (median perfusion index 3056 (interquartile range: 2438 to 6771) arbitrary units (a.u.) at baseline versus 4101 (3067 to 5981) a.u. after MAP increase, P = 0.38). At individual level, however, we observed important heterogeneity in responses (range -51% to +97% changes from baseline).
  
  
  CONCLUSIONS
  A noradrenaline-induced increase in MAP was not associated with an overall increase in renal cortical perfusion as estimated by CEUS. However, at individual level, such response was heterogeneous and unpredictable suggesting great variability in pressure responsiveness within a cohort with a similar clinical phenotype.
authors.affiliation: Intensive Care Unit, Austin Health, 145 Studley road, Heidelberg, VIC, 3084, Australia. antoine.schneider@chuv.ch.|Australian and New Zealand Intensive Care Research Centre, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia. antoine.schneider@chuv.ch.
authors.forename: Antoine G
authors.initials: AG
authors.lastname: Schneider
authors.affiliation: Radiology department, Austin Health, Heidelberg, VIC, Australia. mark.goodwin@austin.org.au.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Goodwin
authors.affiliation: Radiology department, Austin Health, Heidelberg, VIC, Australia. anthony.schelleman@austin.org.au.
authors.forename: Anthony
authors.initials: A
authors.lastname: Schelleman
authors.affiliation: Australian and New Zealand Intensive Care Research Centre, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia. michael.bailey@monash.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Bailey
authors.affiliation: Radiology department, Austin Health, Heidelberg, VIC, Australia. lynne.johnson@austin.org.au.
authors.forename: Lynne
authors.initials: L
authors.lastname: Johnson
authors.affiliation: Intensive Care Unit, Austin Health, 145 Studley road, Heidelberg, VIC, 3084, Australia. rinaldo.bellomo@austin.org.au.|Australian and New Zealand Intensive Care Research Centre, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia. rinaldo.bellomo@austin.org.au.|Faculty of Medicine, University of Melbourne, Melbourne, VIC, Australia. rinaldo.bellomo@austin.org.au.
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D007672:Kidney Cortex / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000187:drug effects; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D009638:Norepinephrine / Q000008:administration & dosage*; D010865:Pilot Projects; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D014463:Ultrasonography
chemical_list: D003287:Contrast Media; D009638:Norepinephrine