title: Cerebral Gaseous Microemboli are Detectable During Continuous Venovenous Hemodialysis in Critically Ill Patients: An Observational Pilot Study.
abstract: BACKGROUND
  Continuous venovenous hemodialysis (CVVHD) may generate microemboli that cross the pulmonary circulation and reach the brain. The aim of the present study was to quantify (load per time interval) and qualify (gaseous vs. solid) cerebral microemboli (CME), detected as high-intensity transient signals, using transcranial Doppler ultrasound.
  
  
  METHODS
  Twenty intensive care unit (ICU group) patients requiring CVVHD were examined. CME were recorded in both middle cerebral arteries for 30 minutes during CVVHD and a CVVHD-free interval. Twenty additional patients, hospitalized for orthopedic surgery, served as a non-ICU control group. Statistical analyses were performed using the Mann-Whitney U test or the Wilcoxon matched-pairs signed-rank test, followed by Bonferroni corrections for multiple comparisons.
  
  
  RESULTS
  In the non-ICU group, 48 (14.5-169.5) (median [range]) gaseous CME were detected. In the ICU group, the 67.5 (14.5-588.5) gaseous CME detected during the CVVHD-free interval increased 5-fold to 344.5 (59-1019) during CVVHD (P<0.001). The number of solid CME was low in all groups (non-ICU group: 2 [0-5.5]; ICU group CVVHD-free interval: 1.5 [0-14.25]; ICU group during CVVHD: 7 [3-27.75]).
  
  
  CONCLUSIONS
  This observational pilot study shows that CVVHD was associated with a higher gaseous but not solid CME burden in critically ill patients. Although the differentiation between gaseous and solid CME remains challenging, our finding may support the hypothesis of microbubble generation in the CVVHD circuit and its transpulmonary translocation toward the intracranial circulation. Importantly, the impact of gaseous and solid CME generated during CVVHD on brain integrity of critically ill patients currently remains unknown and is highly debated.
authors.affiliation: *Department of Anesthesia, General Intensive Care and Pain Management, Medical University of Vienna, Wien, Austria †Department of Anesthesiology and Pain Therapy, University Hospital Bern, Bern, Switzerland.
authors.forename: Gabor
authors.initials: G
authors.lastname: Erdoes
authors.forename: Clemens
authors.initials: C
authors.lastname: Kietaibl
authors.forename: Stefan
authors.initials: S
authors.lastname: Boehme
authors.forename: Roman
authors.initials: R
authors.lastname: Ullrich
authors.forename: Klaus
authors.initials: K
authors.lastname: Markstaller
authors.forename: Balthasar
authors.initials: B
authors.lastname: Eberle
authors.forename: Klaus U
authors.initials: KU
authors.lastname: Klein
mesh_terms: D000328:Adult; D000368:Aged; D003422:Critical Care; D016638:Critical Illness; D003937:Diagnosis, Differential; D004618:Embolism, Air / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000628:therapy; D005260:Female; D006440:Hemofiltration; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000000981:diagnostic imaging; D007362:Intensive Care Units; D020766:Intracranial Embolism / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000628:therapy; D008297:Male; D045423:Microbubbles; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D017585:Ultrasonography, Doppler, Transcranial