Viscoelastometric-guided early fibrinogen concentrate replacement during postpartum haemorrhage: OBS2, a double-blind randomized controlled trial.

Background: Postpartum haemorrhage (PPH) can be exacerbated by haemostatic failure. We hypothesized that early fibrinogen replacement, guided by viscoelastometric testing, reduces blood product usage and bleed size.

Methods: Women with PPH 1000-1500 ml were enrolled. If Fibtem A5 was ≤15 mm and bleeding continued, subjects were randomized to fibrinogen concentrate or placebo. The primary outcome compared the number of units of red blood cells, plasma, cryoprecipitate and platelets transfused.

Results: Of 663 women enrolled 55 were randomized. The adjusted incidence rate ratio (IRR) (95% CI) for the number of allogeneic units transfused in the fibrinogen group compared with placebo was 0.72 (0.3-1.7), P =0.45. In pre-specified subgroup analyses, subjects who had a Fibtem A5 ≤12 mm at the time of randomization and who received fibrinogen concentrate received a median (25th-75th centile) of 1 (0-4.5) unit of allogeneic blood products and had an additional 300 (100-350) ml blood loss whereas those who received placebo also received 3 (0-6) units of allogeneic blood products and had 700 (200-1550) ml additional blood loss; these differences were not statistically significantly different. There was one thrombotic event in each group.

Conclusions: Infusion of fibrinogen concentrate triggered by Fibtem A5 ≤15 mm did not improve outcomes in PPH. Pre-specified subgroup analyses suggest that fibrinogen replacement is not required if the Fibtem A5 is > 12 mm or Clauss fibrinogen >2 g litre -1 , but an effect below these levels cannot be excluded. The raised fibrinogen at term appears to be a physiological buffer rather than required for haemostasis.

Trial registration: ISRCTN46295339 ( https://www.isrctn.com/ISRCTN46295339 , last accessed 5 July 2017), EudraCT 2012-005511-11 ( https://www.clinicaltrialsregister.eu/ctr-search/search?query=2012-005511-11 , last accessed 5 July 2017).