title: The relationship between fibrinogen levels after cardiopulmonary bypass and large volume red cell transfusion in cardiac surgery: an observational study.
abstract: BACKGROUND
  Coagulopathy leading to excessive blood loss and large volume red cell transfusion is a frequent complication of cardiac surgery with cardiopulmonary bypass (CPB) that may be caused by low perioperative fibrinogen levels. We explored the relationship between post-CPB fibrinogen levels and large volume red cell transfusion.
  
  
  METHODS
  Patients who underwent cardiac surgery with CPB from 2005 to 2011 at a single institution and had a fibrinogen level measured after CPB were included in this retrospective observational study. The relationship between post-CPB fibrinogen levels and large volume red cell transfusion (defined as ≥5 units transfused on the day of or the day after surgery) was assessed by cubic spline function and receiver operating characteristic analyses. The independent relationship between fibrinogen levels and large volume transfusion was assessed by multivariable logistic regression and propensity score analyses.
  
  
  RESULTS
  In the 4606 patients included, the probability of large volume transfusion increased when fibrinogen levels decreased below approximately 2.0 g/L. Using <2.0 g/L as the threshold for low fibrinogen, 1918 (42%) were categorized into the low fibrinogen group, of whom 363 (18.9%) had large volume transfusion compared with 164 (13.5%) of the 2688 patients whose fibrinogen level was ≥2.0 g/L (P < 0.0001). In the low fibrinogen group, the unadjusted odds ratio (95% confidence interval) for large volume transfusion was 1.5 (1.3-1.7). The risk-adjusted odds ratio obtained by logistic regression was 1.8 (1.4-2.2) and by propensity score methods was 1.5 (1.2-2.0).
  
  
  CONCLUSIONS
  While this study was not equipped to detect the critical fibrinogen level in bleeding patients, its results suggest that current recommendations that fibrinogen replacement not be initiated in bleeding patients unless fibrinogen levels decrease below 0.8 to 1.0 g/L may be too conservative. Randomized trials are needed to determine whether maintaining higher fibrinogen levels in bleeding patients can reduce blood loss and transfusions and by that means improve clinical outcomes in cardiac surgery.
authors.affiliation: Department of Anesthesia, Toronto General Hospital, 3EN, Toronto, ON, M5G 2C4, Canada. keyvan.karkouti@uhn.ca
authors.forename: Keyvan
authors.initials: K
authors.lastname: Karkouti
authors.forename: Jeannie
authors.initials: J
authors.lastname: Callum
authors.forename: Mark A
authors.initials: MA
authors.lastname: Crowther
authors.forename: Stuart A
authors.initials: SA
authors.lastname: McCluskey
authors.forename: Jacob
authors.initials: J
authors.lastname: Pendergrast
authors.forename: Gordon
authors.initials: G
authors.lastname: Tait
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Yau
authors.forename: W Scott
authors.initials: WS
authors.lastname: Beattie
mesh_terms: D000368:Aged; D006348:Cardiac Surgical Procedures / Q000009:adverse effects* / Q000639:trends*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000639:trends*; D015331:Cohort Studies; D017707:Erythrocyte Transfusion / Q000639:trends*; D004911:Erythrocyte Volume / Q000502:physiology; D005260:Female; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019106:Postoperative Hemorrhage / Q000097:blood / Q000628:therapy; D012189:Retrospective Studies
chemical_list: D005340:Fibrinogen