Viscoelastometry to Guide Transfusion During Postpartum Haemorrhage: The OBS2 Trial.

Viscoelastometric-Guided Early Fibrinogen Concentrate Replacement During Postpartum Haemorrhage: OBS 2, a Double-Blind Randomized Controlled Trial

Collins PW, Cannings-John R, Bruynseels D et al. British Journal of Anaesthesia 2017; 119(3): 411-21


Viscoelastometry Guided Fresh Frozen Plasma Infusion for Postpartum Haemorrhage: OBS2, an Observational Study.

Collins PW, Cannings-John R, Bruynseels D et al. British Journal of Anaesthesia 2017; 119(3): 422-34



To evaluate the use of fibrinogen concentrate as guided by ‘abnormal’ viscoelastometric point-of-care coagulation testing (VE-POCT), and the restrictive use of FFP guided by ‘normal’ VE-POCT in the management of patients with moderate/severe post-partum haemorrhage.


663 patients aged ≥18 years and ≥24 weeks gestation with PPH estimated at ≥1000ml were enrolled at six obstetric units in the UK.


Fibtem A5 determined by Rotem was used to stratify patients into an observational arm and a randomization arm. If Fibtem A5 was ≤15mm (n=55) and bleeding was ongoing, patients were randomized to either a weight-based dose of fibrinogen concentrate or placebo. If Fibtem A5 was >15mm (n=605), fresh frozen plasma (FFP) was withheld. In both study arms, patients were otherwise managed according to clinical judgement and/or local protocol.


The primary outcome in the randomization arm was number of units of red blood cells, FFP, cryoprecipitate and platelets used.


Additional outcomes in both study arms were blood loss, number of uterotonic drug doses given, number (and type) of invasive procedures, use of tranexamic acid and admission to Level 3 care.


For binary outcomes, a logistic model was used and results presented as adjusted odds ratios (ORs) alongside 95% confidence intervals (CIs). For continuous outcomes, a linear regression model was fitted and results presented as difference in adjusted means alongside 95% CIs.


In the observational arm, mean Fibtem A5 was 19mm, with laboratory fibrinogen 4g/L. In the randomization arm these values were 12mm and 2.7g/L respectively. There was no significant difference in prothrombin time (PT) and activated partial thromboplastin time (APTT) between the two arms, suggesting that these ‘traditional’ coagulation parameters are preserved in early PPH. In the randomization arm, the adjusted incidence rate ratio (IRR) for the number of allogenic units transfused in the fibrinogen group compared with placebo was 0.72 (0.3 – 1.7), p = 0.45.


Infusion of fibrinogen concentrate triggered by Fibtem A5 ≤15mm did not improve outcomes in PPH. The authors postulate that the raised fibrinogen seen in healthy parturients at term may be a physiological buffer rather than required for haemostasis. In the observational arm, no women developed clinically significant haemostatic failure despite the restrictive use of FFP.


Pre-specified subgroup analysis in the randomization arm suggested that fibrinogen replacement is not required if the Fibtem A5 is >12mm or laboratory fibrinogen >2g/L, but an effect below these levels could not be excluded. Analysis of the observational arm of this study was descriptive.


We do not have VE-POCT testing at Kingston Hospital (TEG® or Rotem®).

Based on our own data from 2016, FFP is used relatively uncommonly in patients with PPH >2000ml; transfusion decisions are generally based on clinical judgement and laboratory parameters rather than empirical or fixed ratios.

There may be a cost-saving benefit in restricting FFP transfusion guided by VE-POCT in a larger centre, but probably not at Kingston hospital.

Concerns about level of training required to set up and operate a VE-POCT machine were raised; additionally, losing a member of staff for several minutes during PPH situations to set up and run such a machine may not be practical.

Summary by Dr J Major. Journal Club 05 October 2017.


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