Viscoelastometric-guided early fibrinogen concentrate replacement during postpartum haemorrhage: OBS2, a double-blind randomized controlled trial. Collins PW, Canning-John R, Bruynseels D et al. 

British Journal of Anaesthesia 2017;119(3):411-421 doi:10.1093/bja/aex181

Presented by: Dr Alasdair Rosie

Background

Post Partum Haemorrhage (PPH) is the leading worldwide cause of maternal mortality and can be worsened by haemostats compromise. This study looked at whether giving early fibrinogen concentrate guided by coagulation point of care testing would reduce blood product usage and bleed size.

Design & Setting

Multi-centre, randomised, double-blinded, placebo controlled study. If patients had an ongoing major haemorrhage of 1000-1500ml a fibtem A5 was performed and if <15mm, the patient was randomised to receive fibrinogen concentrate or placebo.

Subjects

Included were women >18years old, gestation >24 weeks and with ongoing haemorrhage as above.

Exclusion criteria included those with placenta accreta, those that had had a surgical intervention prior to randomisation, clinical suspicion of AFE and those that declined transfusion.

A total of 55 women were analysed based upon a power calculation of 80% requiring 54 patients to show a difference of 3.3 total allogenic units between groups.

Intervention

As above, after randomisation, women either received a 50ml vial of normal saline in an opaque cover or 1g of fibrinogen in an opaque cover. FFP and blood products were then used as per local guidelines if bleeding was ongoing.

Outcomes

Primary outcome looked at the number of units of blood products used (red blood cells, FFP, cryoprecipitate, platelets) used between the treatment and control groups. pre-specified sub groups were analysed to look at outcomes in detail

Results

In the treatment group a total of 58 units of products were used compared to 75 in the placebo group. This difference was primarily due to FFP with a similar use of RBC between groups. Blood loss between groups after the study medication was given was roughly similar and not statistically significant.

Outcomes between groups with Fibtem A5 >12mm were indistinguishable. Women with A5 <12m who received fibrinogen concentrate had fewer allergenic blood products, less bleeding and less time in level 2/3 care.

Post hoc analysis noted median blood loss of 300ml vs 800ml in fibrinogen and placebo groups respectively with starting fibrinogens less than 2.5g.

Conclusions

Infusion of fibrinogen concentrate in women triggered by a fibtem A5 <15mm did not improve outcomes. Fibrinogen replacement is not required is fibtem A5 is >12mm or fibrinogen >2-2.5g

Cannot exclude an effect of early fibrinogen use below these levels and further studies are required to look at whether a fibtem <12mm would be clinically and cost effective.

Strengths

Well run multi-centre, randomised, placebo controlled study. Robust methodology based upon large observational studies.

Weaknesses

Lower numbers than anticipated in terms of those randomised with fibrinogens less that 2g. This was thought to be due to the difficulties in consenting and conducting trial interventions during management of a moderate to severe PPH. This is likely to have excluded women most likely to have responded to the proposed intervention.

Implications

Has the ability to greatly reduce potentially unnecessary transfusion of blood products and therefore reduce morbidity related to allogenic product transfusion.

Re-enforces previous studies looking to move away from empirical transfusion of products in ratios found to be beneficial in patient populations not related to the obstetric patient (i.e trauma).

Potential for impact

Reduction of transfusion related morbidity.

Optimisation of management of PPH using point of care testing