The effects of pre- and postoperative fibrinogen levels on blood loss after cardiac surgery: a systematic review and meta-analysis.

OBJECTIVES Fibrinogen concentrate is increasingly used in cardiac surgery when bleeding is anticipated or ongoing. Since randomized clinical studies to support this are lacking, it is relevant to know whether lower fibrinogen levels are associated with excessive bleeding. We performed a systematic review and meta-analysis to define the association between fibrinogen levels and blood loss after cardiac surgery. METHODS A database search (January 2013) was performed on publications assessing the association between pre- and postoperative fibrinogen levels and postoperative blood loss in adult patients undergoing cardiac surgery. Cohort studies and case-control studies were eligible for inclusion. The main outcome was the pooled correlation coefficient, calculated via Fisher's Z transformation scale, in a random-effects meta-analysis model stratified for the time point at which fibrinogen was measured. RESULTS A total of 20 studies were included. The pooled correlation coefficient of studies (n = 9) concerning preoperative fibrinogen levels and postoperative blood loss was -0.40 (95% confidence interval: -0.58, -0.18), pointing towards more blood loss in patients with lower preoperative fibrinogen levels. Among papers (n = 16) reporting on postoperative fibrinogen levels and postoperative blood loss, the pooled correlation coefficient was -0.23 (95% confidence interval: -0.29, -0.16). CONCLUSIONS Our meta-analysis indicated a significant but weak-to-moderate correlation between pre- and postoperative fibrinogen levels and postoperative blood loss in cardiac surgery. This moderate association calls for appropriate clinical studies on whether fibrinogen supplementation will decrease postoperative blood loss.