title: High haematocrit in cyanotic congenital heart disease affects how fibrinogen activity is determined by rotational thromboelastometry.
abstract: BACKGROUND
  Viscoelastometry enables rapid evaluation of coagulopathy in settings such as cardiac surgery but may be influenced by red cell concentration.
  
  
  METHODS
  In order to study the effects of supra-physiological red cell concentrations on viscoelastometry, we compared ROTEM® viscoelastometry and plasma coagulation assay results in high haematocrit (HCT; 0.55-0.76 L/L) blood from patients with cyanotic congenital heart disease (CCHD), and in model high HCT blood (HCT 0.45-0.70 L/L).
  
  
  RESULTS
  High HCT blood from CCHD patients (median HCT 0.66 L/L) displayed prolonged clot initiation in the EXTEM® test compared to controls and reduced maximum clot firmness (MCF) in the EXTEM (median 51 mm vs 64 mm in controls) and FIBTEM® (7 mm vs 14 mm) tests. The plasma fibrinogen (Clauss; CF) was similar in CCHD blood to controls (median 2.94 g/L vs 2.49) but the whole blood fibrinogen concentration (WBFC) was reduced (1.27 g/L vs 1.58). The FIBTEM MCF correlated linearly with the CF (r(2)=0.68; p<0.0001) and WBFC (r(2)=0.65; p<0.0001) in control blood but this relationship was maintained only with WBFC in CCHD blood. Model high HCT blood showed abnormal ROTEM test results that were similar to CCHD blood, including reduced FIBTEM MCF (14 mm with HCT 0.32-0.44 vs 6mm with HCT 0.63-0.70). The ROTEM results were HCT dependent but independent of plasma clotting times and fibrinogen concentration.
  
  
  CONCLUSIONS
  Supra-physiologic HCT causes abnormal ROTEM test results consistent with increased dilution of fibrinogen and coagulation factors in whole blood by red cells. High HCT should be considered during interpretation of ROTEM test results in clinical settings.
authors.affiliation: Bristol Heart Institute & School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom. Electronic address: sarah.westbury@bristol.ac.uk.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Westbury
authors.forename: Kurtis
authors.initials: K
authors.lastname: Lee
authors.forename: Christopher
authors.initials: C
authors.lastname: Reilly-Stitt
authors.forename: Robert
authors.initials: R
authors.lastname: Tulloh
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Mumford
mesh_terms: D000328:Adult; D001777:Blood Coagulation / Q000502:physiology; D001780:Blood Coagulation Tests / Q000379:methods; D016022:Case-Control Studies; D003490:Cyanosis / Q000097:blood*; D004912:Erythrocytes / Q000473:pathology*; D005260:Female; D005340:Fibrinogen / Q000378:metabolism*; D006330:Heart Defects, Congenital / Q000097:blood*; D006400:Hematocrit; D006801:Humans; D008297:Male; D008875:Middle Aged; D013916:Thrombelastography / Q000379:methods; D055815:Young Adult
chemical_list: D005340:Fibrinogen
keywords: APTT; Activated partial thromboplastin time; CCHD; CF; CFT; CT; Clauss fibrinogen concentration; Clot formation time; Clot time; Cyanotic congenital heart disease; Fibrinogen; HCT; Haematocrit; MCF; Maximum clot firmness; PRC; PT; Packed red cell; Prothrombin time; VKA; Vitamin K antagonists; WBFC; Whole blood fibrinogen concentration; clot viscoelastic strength; haematocrit; thromboelastometry