Key messages
- No particular transfusion strategy (method of giving blood products) seems to change the overall chance of a patient dying or getting a blood clot.
- We found 18 studies that tested different ways of giving blood transfusions. This variety made it difficult to combine the results and means we do not have clear answers to our questions.
What is traumatic injury?
A traumatic injury is a sudden, unexpected event (e.g. a car acccident, horse-riding accident, or fall) that causes physical harm to a person. Most traumatic injuries need hospital care, and patients are treated both before they reach the hospital (prehospital care) and once they arrive.
Why are blood or blood products given after a traumatic injury?
After a traumatic injury, people can have severe bleeding. Those who are most seriously injured are likely to have heavy bleeding, and many may die within a few hours of the injury. Giving blood or blood products (a blood transfusion) early can help stop the bleeding and save the person's life.
What is a transfusion strategy?
There are several kinds of blood products, all made from donated blood, that help patients' blood clot faster. A transfusion strategy is a plan for how doctors give the blood products to people who are bleeding a lot. This might include which types of blood products are given, how many are used, the order they are given in, and whether blood tests are used to help decide what to give next.
What did we want to find out?
We wanted to see if different ways of giving blood or blood products to treat bleeding could lower the chances of dying or getting a blood clot after an injury.
What did we do?
We searched for medical studies known as 'randomised controlled trials', which give the most reliable evidence about the effectiveness and safety of medical treatments. In this type of study, people are placed in two or more treatment groups randomly, to ensure the groups are similar, and, ideally, neither the study participants nor the researchers know who is in which group. We looked for randomised controlled trials where one group of patients received one transfusion strategy, and another group received a different strategy. By comparing the number of deaths and blood clots between the groups, we could see if one treatment worked better than the other.
What did we find?
We found 18 studies that included a total of 5041 adult participants. Adults were defined as people aged 16 years and over. We divided the studies into four groups.
1) Patients treated before reaching the hospital ('prehospital') – 5 trials
2) Patients treated in hospital with a blood product – 10 trials
3) Patients treated in hospital with whole blood – 1 trial
4) Patients treated in hospital with blood products based on blood clotting test results – 2 trials
Main results
Overall, none of the transfusion strategies tested in the studies reduced the overall risk of death, whether this was measured after 24 hours or after 30 days. However, we are not very confident in the results, and future studies might change this conclusion.
Similarly, none of the transfusion strategies showed different rates of harmful blood clots, but we are uncertain if this is accurate.
What are the limitations of the evidence?
The studies we identified were very different from each other (e.g. in the way they measured results), which made it hard to draw firm conclusions about which transfusion strategy worked best. More research is needed to fully answer our questions about the best way to treat major bleeding after trauma.
How up to date is this evidence?
We reviewed all published randomised controlled trials on this topic up to 20 November 2023. We also found information on 11 trials that have started or are starting soon: three are focused on treating patients before they reach the hospital, four on treating patients in the hospital with blood products, two on treating patients in the hospital with whole blood, and two on treating patients in the hospital based on blood clotting test results. In the future, the findings from these studies will help answer our questions about blood transfusion strategies for major bleeding caused by traumatic injury.
Overall, there was little to no evidence of a difference between blood transfusion strategies for mortality or thromboembolic events. The studies covered a wide range of interventions, and the comparators and standard of care practice varied between trials, thereby limiting the pooling of data. Further research is needed.
Trauma is a leading cause of morbidity and mortality worldwide. Research shows that haemorrhage and trauma-induced coagulopathy are reversible components of traumatic injury, if identified and treated early. Lack of consensus on definitions and transfusion strategies hinders the translation of this evidence into clinical practice.
To assess the beneficial and harmful effects of transfusion strategies started within 24 hours of traumatic injury in adults (aged 16 years and over) with major bleeding.
CENTRAL, MEDLINE, Embase, five other databases, and three trial registers were searched on 20 November 2023. We also checked reference lists of included studies to identify any additional studies.
We included randomised controlled trials (RCTs) of adults (aged 16 years and over) receiving blood products for the management of bleeding within 24 hours of traumatic injury.
We used standard Cochrane methodology to perform the review and assessed the certainty of the evidence using GRADE.
We included 18 RCTs with 5041 participants.
Comparison 1: Prehospital transfusion strategies
Five studies compared use of plasma (fresh frozen plasma (FFP) or lyophilised plasma) versus 'standard of care'.
We are uncertain of the effect of plasma on all-cause mortality at 24 hours (risk ratio (RR) 1.05, 95% confidence interval (CI), 0.48 to 2.30; 3 studies, 279 participants; very low certainty evidence).
There is probably no difference between plasma and standard of care in all-cause mortality at 30 days (RR 0.95, 95% CI 0.78 to 1.17; 3 studies, 664 participants; moderate-certainty evidence). However, the results of one cluster-RCT that could not be included in our meta-analysis suggested that plasma may be associated with a lower risk of death at 30 days (RR 0.54, 95% CI 0.42 to 0.70; 1 study, 481 participants; low-certainty evidence).
There may be no difference between plasma and standard of care in the total number of thromboembolic events in 30 days (RR 1.23, 95% CI 0.67 to.2.27; 4 studies, 586 participants; low-certainty evidence).
Comparison 2: In-hospital transfusion strategies
Ten studies evaluated this comparison, seven providing usable data. The studies evaluated cryoprecitate (three studies); fixed-ratio blood component transfusion (three studies); fresh frozen plasma (FFP) (one study); lyophilised plasma (one study); leucoreduced red blood cells (one study); and a restrictive transfusion strategy (one study).
All-cause mortality at 24 hours
For all-cause mortality at 24 hours, there is probably no difference between:
• cryoprecipitate plus a major haemorrhage protocol (MHP) versus MHP alone (RR 0.92, 95% CI 0.70 to 1.21; 1 study, 1577 participants; moderate-certainty evidence); and
• blood products (plasma:platelets:red blood cells (RBCs)) transfused in 1:1:1 ratio versus 1:1:2 ratio (RR 0.75, 95% CI 0.52 to 1.08; 1 study, 680 participants; moderate-certainty evidence).
We are uncertain of the effect on all-cause mortality at 24 hours for:
• blood products (RBCs:FFP) transfused in 1:1 ratio versus transfusion according to coagulation and full blood count results (Peto odds ratio (POR) 0.45, 0.17 to 1.22; 1 study, 434 participants; very low certainty evidence); and
• lyophilised (FlyP) plasma versus FFP (POR 1.04, 95% CI 0.06 to 17.23; 1 study, 47 participants; very low certainty evidence);
All-cause mortality at 30 days
For all-cause mortality at 30 days, there is probably no difference between blood products (plasma:platelets:RBCs) transfused in a 1:1:1 ratio versus a 1:1:2 ratio (RR 0.85, 95% CI 0.65 to 1.11; 1 study, 680 participants; moderate-certainty evidence).
There may be little to no difference between the following interventions in all-cause mortality at 30 days:
• cryoprecipitate plus MHP versus MHP alone (RR 0.77, 95% CI 0.33 to 1.78; 2 studies, 1572 participants; low-certainty evidence); and
•leucoreduced RBCs versus standard RBCs (RR 1.20, 95% CI 0.74 to 1.95; 1 study,55 participants; low certainty evidence).
We are uncertain of the effect on all-cause mortality at 30 days for:
•lyophilised plasma versus FFP (RR 0.75, 95% CI 0.28 to 2.02; 1 study, 47 participants; very low certainty evidence); and
• blood products (plasma:platelets:RBCs) transfused in 1:1:1 ratio versus standard MHP (RR 2.25, 95% CI 0.90 to 5.62; 1 study, 69 participants; very low certainty evidence).
Total number of thromboembolic events at 30 days
There may be little to no difference between the following interventions for total thromboembolic events at 30 days:
• cryoprecipitate plus MHP versus MHP alone (RR 0.55, 95% CI 0.08 to 3.72; 2 studies, 1645 participants; low-certainty evidence); and
• blood products (plasma:platelets:RBCs) transfused in 1:1:1 ratio versus 1:1:2 ratio (RR 1.03, 95% CI 0.75 to 1.42; 1 study, 680 participants; low-certainty evidence).
We are uncertain of the effect on the total number of thromboembolic events at 30 days for:
•blood products (plasma:platelets:RBCs) transfused in 1:1:1 ratio versus standard MHP (POR 6.83, 95% CI 0.68 to 68.35; 1 study, 69 participants; very low certainty evidence).
Comparison 3: Whole blood versus individual blood products
We are uncertain of the effect of modified (leucoreduced) whole blood versus blood products (RBCs:plasma) transfused in a 1:1 ratio on all-cause mortality at 24 hours (RR 1.13, 95% CI 0.37 to 3.49) or 30 days (RR 1.62, 95% CI 0.69 to 3.80) (1 study, 107 participants; very low certainty evidence).
Comparison 4: Goal-directed blood transfusion strategy of viscoelastic haemostatic assay (VHA) versus conventional laboratory coagulation tests (CCT) to guide haemostatic therapy
There may be little or no difference in all-cause mortality at 24 hours between VHA and CCT (RR 0.85, 95% CI 0.54 to 1.35; 1 study, 396 participants; low-certainty evidence).
We are uncertain of the effects on all-cause mortality at 30 days (RR 0.75, 95% CI 0.48 to 1.17; 2 studies, 506 participants; very low certainty evidence).
There is probably no difference between VHA and CCT in total thromboembolic events at 30 days (RR 0.65, 95% CI 0.35 to 1.18; 1 study 396 participants; moderate-certainty evidence).