title: Cerebrovascular autoregulation in critically ill patients during continuous hemodialysis.
abstract: OBJECTIVE
  In chronic renal failure, intermittent hemodialysis decreases cerebral blood flow velocity (CBFV); however, in critically ill patients with acute renal failure, the effect of continuous venovenous hemodialysis (CVVHD) on CBFV and cerebrovascular autoregulation (AR) is unknown. Therefore, a study was undertaken to investigate the potential effect of CVVHD on CBFV and AR in patients with acute renal failure.
  
  
  METHODS
  This cohort study investigated 20 patients with acute renal failure who required CVVHD. In these patients, the CBFV and index of AR (Mx) were measured using transcranial Doppler before and during CVVHD.
  
  
  RESULTS
  The median Mx values at baseline were 0.33 [interquartile range (IQR): 0.02-0.55], and during CVVHD, they were 0.20 [0.07-0.40]. The differences in Mx (CVVHD--baseline) was (median [IQR]) -0.015 [-0.19-0.05], 95% confidence interval (CI) -0.16 to 0.05. The Mx was > 0.3 in 11/20 patients at baseline measurement. Six of these patients recovered to Mx < 0.3 during CVVHD. The CBFV was (median [IQR]) 47 [36-59] cm · sec(-1) at baseline and 49 [36-66] cm · sec(-1) during CVVHD. The difference of CBFV was 0.0 [-4 - 2.7], 95% CI -2.5 to 4.2.
  
  
  CONCLUSIONS
  Compared with patients with intermittent hemodialysis, CVVHD did not influence CBFV and AR in critically ill patients with acute renal failure, possibly due to lower extracorporeal blood flow, slower change of plasma osmolarity, and a lower fluid extraction rate. In a subgroup of patients with sepsis, the AR was impaired at baseline in more than half of the patients, and this was reversed during CVVHD. The trial was registered at ClinicalTrials.gov ID: NCT01376531.
authors.affiliation: Department of Anesthesiology, University Medical Centre of the Johannes Gutenberg-University Mainz, Langenbeckstr 1, 55131 Mainz, Germany. schrammp@uni-mainz.de
authors.forename: Patrick
authors.initials: P
authors.lastname: Schramm
authors.forename: Dorothea
authors.initials: D
authors.lastname: Closhen
authors.forename: Janosch
authors.initials: J
authors.lastname: Wojciechowski
authors.forename: Manfred
authors.initials: M
authors.lastname: Berres
authors.forename: Klaus Ulrich
authors.initials: KU
authors.lastname: Klein
authors.forename: Marc
authors.initials: M
authors.lastname: Bodenstein
authors.forename: Christian
authors.initials: C
authors.lastname: Werner
authors.forename: Kristin
authors.initials: K
authors.lastname: Engelhard
mesh_terms: D058186:Acute Kidney Injury / Q000628:therapy*; D000368:Aged; D000369:Aged, 80 and over; D002560:Cerebrovascular Circulation / Q000502:physiology*; D016638:Critical Illness; D005112:Extracorporeal Circulation; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D006435:Renal Dialysis / Q000379:methods*; D018805:Sepsis / Q000503:physiopathology*; D017585:Ultrasonography, Doppler, Transcranial