A new blood product developed by NHS Blood and Transplant (NHSBT) that combines red blood cells (RBC) and plasma in the same bag boosts survival from penetrating major trauma injury after pre-hospital transfusion, according to a new multicentre observational cohort study led by London researchers.
The study, from NHSBT, Queen Mary University, and Barts Health NHS Trust, published in Critical Care, involved 909 patients with acute traumatic haemorrhage recruited from six pre-hospital air ambulance services in England between 2018 and 2020.
The patients were given pre-hospital transfusions of RBC alone, RBC and plasma as separate transfusions, or RBC plus plasma combined in the same bag, enabling both to be given in a single transfusion. The first two are currently established treatments, but the latter has obvious practical benefits in a pre-hospital situation, and the team wanted to assess whether it had benefits for patients too.
Their results showed that overall the odds of surviving for the next 24 hours were 1.5 times higher in patients who received combined RBC and plasma than those who received RBC alone.
Mixed Product 'Saves More Lives'
Chief investigator Dr Laura Green, consultant haematologist for NHSBT and Barts Health NHS Trust, and reader in transfusion medicine at the Blizard Institute of Queen Mary University of London said: "The majority of trauma deaths are within 3 hours.
"We know patients benefit from getting not just red blood cells but also plasma, but it’s difficult to quickly carry out multiple transfusions in an urgent pre-hospital setting – such as by the road side at night following a major crash, where a patient might have minutes to live.
"The study provides evidence that this new product, which contains both plasma and red blood cells unmixed in one bag, also saves more lives than just giving red blood cells alone.
"Now it can be explored further as a potential lifesaving new treatment that can be used outside hospitals."
For the past several decades, transfusion practice has moved away from the use of whole blood to giving components (RBC, platelets, plasma, and cryoprecipitate) separately and sometimes in differential ratios. The change was driven by practical considerations: Using blood components individually reduced waste, increased storage times, and allowed a tailored approach to resuscitation.
However data in support of the change to component therapy was limited. More recently, concerns have emerged that such evidence as pertained had been extrapolated from elective surgery settings and might be less applicable – or even counterproductive – following major surgery or extensive trauma. It has been argued that guidelines failed to take into account acidosis and coagulopathy associated with haemorrhagic shock.
"In-hospital acute resuscitation in trauma has evolved toward early and balanced transfusion resuscitation with RBC and plasma being transfused in equal ratios," the authors said. However: "Being able to deliver this ratio in pre-hospital environments is a challenge."
In the UK, most pre-hospital services carry RBC and thawed plasma, but not platelets, due to storage requirements. The authors said that the leukocyte depletion process introduced in the 1990s to reduce the risk of variant CJD transmission via blood transfusion removes 80% of platelets in whole blood donations and, therefore, the remaining component contains red cells and plasma (RCP) in one bag.
However, while the pre-hospital use of RCP in traumatic haemorrhage "may offer logistical and clinical benefits" compared with the use of separate blood components, this has not been evaluated before.
Facilitating Early Pre-Hospital Treatment
They reasoned that a combined component, such as leukocyte-depleted RCP, could facilitate early pre-hospital resuscitation, whilst also improving logistics for the treatment team. However, there was limited evidence on the clinical benefits of RCP. Hence, their study to compare pre-hospital transfusion of combined RCP versus RBC alone or RBC and plasma separately on mortality in trauma bleeding patients.
They collected data prospectively on patients in the study and also performed a retrospective comparison using data from patients who were transfused with RBC from 2015 to 2018.
Of the total 909 patients, 223 received RBC alone, 392 RBC plus plasma separately, and 295 the combined RBC plus plasma product.
Both RCP and the separate RBC + plasma were associated with lower odds of death at 24 hours, compared with RBC alone, with adjusted odds ratio of 0.69 (95%CI: 0.52 to 0.92) and 0.60 (95%CI: 0.32 to 1.13), respectively.
After adjusting for type of injury, age and pre-hospital observational markers, these odds were driven by penetrating injury – odds ratio 0.22 (95%CI: 0.10 to 0.53) and 0.39 (95%CI: 0.20 to 0.76), respectively for RCP and RBC + plasma. There was no association with 30-day survival.
The authors concluded that pre-hospital plasma transfusion for penetrating injury was associated with lower odds of death at 24 hours compared with RBC alone.
They pointed out that in pre-hospital environments, the logistics of delivering several blood components "could be challenging", as this would necessitate carrying additional blood storage boxes and require several bags to be administered to patients (who may not have enough intravenous access), thus increasing the complexity of resuscitation and delaying patient transfer to hospital.
The authors said that larger trials were needed to confirm their findings.
The study was funded jointly by the London Air Ambulance charity, the Barts and the London Charity, and NHSBT. LG, RC, and SS are employees of NHSBT and reported obtaining research funds for multiple clinical studies, but they report no direct relevant financial disclosures. All other authors declare no conflicts of interest.