Outcome measures used in clinical research evaluating prehospital blood component transfusion in traumatically injured bleeding patients: A systematic review

Assessing the one-month mortality impact of civilian-setting prehospital transfusion: A systematic review and meta-analysis

BACKGROUND

Based on convincing evidence for outcomes improvement in the military setting, the past decade has seen evaluation of prehospital transfusion (PHT) in the civilian emergency medical services (EMS) setting. Evidence synthesis has been challenging, due to study design variation with respect to both exposure (type of blood product administered) and outcome (endpoint definitions and timing). The goal of the current meta-analysis was to execute an overarching assessment of all civilian-arena randomized controlled trial (RCT) evidence focusing on administration of blood products compared to control of no blood products.

METHOD

The review structure followed the Cochrane group's Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA). Using the Transfusion Evidence Library (transfusionevidencelibrary.com), the multidatabase (e.g. PubMed, EMBASE) Harvard On-Line Library Information System (HOLLIS), and GoogleScholar, we accessed many databases and gray literature sources. RCTs of PHT in the civilian setting with a comparison group receiving no blood products with 1-month mortality outcomes were identified.

RESULTS

In assessing a single patient-centered endpoint-1-month mortality-we calculated an overall risk ratio (RR) estimate. Analysis of three RCTs yielded a model with acceptable heterogeneity (I2 = 48%, Q-test p = 0.13). Pooled estimate revealed civilian PHT results in a statistically nonsignificant (p = 0.38) relative mortality reduction of 13% (RR 0.87, 95% CI 0.63-1.19).

CONCLUSIONS

Current evidence does not demonstrate 1-month mortality benefit of civilian-setting PHT. This should give pause to EMS systems considering adoption of civilian-setting PHT programs. Further studies should not only focus on which formulations of blood products might improve outcomes but also focus on which patients are most likely to benefit from any form of civilian-setting PHT.

The Role of Plasma Transfusion in Pre-Hospital Haemostatic Resuscitation

Traumatic haemorrhage remains a major cause of preventable death and early haemostatic resuscitation is now a mainstay of treatment internationally. Recently, 2 randomized control trials (RCTs) - PAMPer (Prehospital Air Medical Plasma) and COMBAT (Control of Major Bleeding After Trauma), evaluating the effect of pre-hospital use of plasma on mortality provided conflicting results, raising important questions on the role of plasma resuscitation in pre-hospital environment. Both PAMPer (n = 501 patients) and COMBAT (n = 144 patients) trials were pragmatic RCTs that evaluated the effect of pre-hospital plasma transfusion (two units) versus standard of care on 28/30 days mortality in trauma patients who presented with clinical signs of haemorrhagic shock (defined as hypotension or tachycardia). The PAMPer trial showed that plasma transfusion reduced 30-day mortality compared with standard of care (23% vs 33%, 95% confidence interval -18.6; -1.0%; P = 0.03), while COMBAT trial showed no difference in 28-day survival. The post-hoc analyses of the 2 trials have suggested that the benefit of pre-hospital plasma transfusion may be greater for patients who are coagulopathic, have blunt injury and have a transport time from the scene of injury to the hospital of >20 minutes. In this review we evaluate strengths and limitations of the two trials and their differences and similarities, which may explain the conflicting results, as well as provide directions for future trials to better define the target population that would most benefit from pre-hospital plasma resuscitation. Further, considering the logistical challenges of carrying any blood components on an aircraft, cost/safety of plasma, and the scarcity of universal blood group donors, there is a need for a health economic evaluation of pre-hospital plasma transfusion in trauma patients, prior to this intervention becoming universal.