title: Cerebral haemodynamics in patients with chronic renal failure: effects of haemodialysis.
abstract: BACKGROUND
  We measured middle cerebral artery (MCA) flow velocity (FV), dynamic pressure autoregulation, and carbon dioxide reactivity (CRCO(2)) in patients with chronic renal failure before and after haemodialysis using transcranial Doppler ultrasonography.
  
  
  METHODS
  Twelve patients on long-term haemodialysis were recruited. MCA FV was measured continuously. The transient hyperaemic response test was used to assess cerebral autoregulation, and per cent change in FV per kPa change in end-tidal carbon dioxide was calculated to assess CRCO(2). All measurements were recorded before and after haemodialysis.
  
  
  RESULTS
  MCA FV (mean [sd]) decreased from 57 (10) cm s(-1) before to 46 (13) cm s(-1) after haemodialysis (P<0.01). The transient hyperaemic response ratio (THRR) was (mean [sd]) 1.29 (0.13) before haemodialysis and did not change significantly following haemodialysis (1.36 [0.10]). CRCO(2) was 21.7 (8.3)% kPa(-1) before haemodialysis and remained unchanged afterwards (20.9 [3.8]% kPa(-1)). Values in normal subjects for MCA FV, THRR and CRCO(2) are 56 (12) cm s(-1), 1.26 (0.13) and 22 (6)% kPa(-1), respectively.
  
  
  CONCLUSIONS
  MCA FV decreases significantly after haemodialysis. Dynamic pressure autoregulation and CRCO(2) remain normal in patients with chronic renal failure, and are not altered significantly by haemodialysis.
authors.affiliation: Department of Anaesthesia, Nottingham City Hospital and Queen's Medical Centre, Nottingham, UK. hskinne1@ncht.trent.nhs.uk
authors.forename: H
authors.initials: H
authors.lastname: Skinner
authors.forename: C
authors.initials: C
authors.lastname: Mackaness
authors.forename: N
authors.initials: N
authors.lastname: Bedforth
authors.forename: R
authors.initials: R
authors.lastname: Mahajan
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D002245:Carbon Dioxide / Q000502:physiology; D002560:Cerebrovascular Circulation; D005260:Female; D006706:Homeostasis; D006801:Humans; D007427:Intracranial Pressure; D007676:Kidney Failure, Chronic / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D006435:Renal Dialysis; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D002245:Carbon Dioxide