title: A study of muscle tissue oxygenation and peripheral microcirculatory dysfunction in cirrhosis using near infrared spectroscopy.
abstract: BACKGROUND
  The circulatory dysfunction associated with cirrhosis is well described. Reduced systemic vascular resistance and high cardiac output are the main features of the hyperdynamic state, but involvement of the peripheral microcirculation in this process is poorly understood. Near infrared spectroscopy (NIRS) has been used to assess muscle tissue oxygenation (StO(2)) in haemorrhagic and septic shock. Vascular occlusion testing (VOT) can produce dynamic changes in StO(2) which represent tissue oxygen extraction, delivery, and hence, surrogate markers of microvascular function.
  
  
  OBJECTIVE
  We aimed to investigate dynamic StO(2) changes in the peripheral microcirculation of patients with cirrhosis.
  
  
  METHODS
  Thirty-five subjects were examined (25 cirrhosis, 10 healthy volunteers) with an InSpectra 650 StO(2) monitor and 15 mm thenar probe. Brachial VOT was applied at systolic blood pressure +50 mmHg for 3 min, in triplicate. Dynamic StO(2) parameters are reported for baseline, downslope, upslope, area over ischaemic curve, overshoot, area under recovery curve and recovery time.
  
  
  RESULTS
  Patients with cirrhosis demonstrated significantly larger post-occlusive hyperaemic variables compared with volunteers: overshoot (17 vs 15%, P=0.009), area under recovery curve (25.1 vs 16.3 %/min, P<0.001) and recovery time (3.0 vs 2.2 min, P<0.001). Magnitude of change was also seen to increase with disease stage as defined by Child-Pugh score. Serial VOT revealed microcirculatory ischaemic adaptation in volunteers, which was absent in cirrhosis.
  
  
  CONCLUSIONS
  NIRS can identify dynamic changes in muscle tissue oxygenation in cirrhosis which are compatible with microcirculatory vasodilatation. Ischaemic adaptation was seen in controls but not in patients with cirrhosis. NIRS techniques offer a novel approach to the assessment of peripheral vascular dysfunction in cirrhosis.
authors.affiliation: Department of Gastroenterology and Hepatology, St George's Hospital, London, UK. sthomson@sgul.ac.uk
authors.forename: Sam J
authors.initials: SJ
authors.lastname: Thomson
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Cowan
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Forton
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Clark
authors.forename: Saif
authors.initials: S
authors.lastname: Musa
authors.forename: Michael
authors.initials: M
authors.lastname: Grounds
authors.forename: Tony M
authors.initials: TM
authors.lastname: Rahman
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006940:Hyperemia; D008103:Liver Cirrhosis / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism; D010101:Oxygen Consumption; D019265:Spectroscopy, Near-Infrared