Hemorrhagic shock is the only indication for a<unk> 
The ABC score and the TASH score predict the need for<unk> P
Newer studies show that the Shock Index score is a better predictor than the ABC score
Revised Assessment of Bleeding and Transfusion (RABT) may reach higher sensitivity than ABC score, but not prospectively validated as of 2019
Non-lab scoring system as opposed to TASH:
Penetrating mechanism
SBP ≤90 in ED
HR ≥120 in ED
Positive FAST
Scoring interpretation:
0-1, not likely to require<unk> P (≥10 units pRBCs)
2-4, likely to require<unk> P, sensitivity 75% and specificity 86% from original study
Subsequent studies suggested < 50% sensitivity
Penetrating mechanism
SBP ≤90 in ED
HR ≥120 in ED
Positive FAST
0-1, not likely to require<unk> P (≥10 units pRBCs)
2-4, likely to require<unk> P, sensitivity 75% and specificity 86% from original study
SI = HR / SBP
Particularly useful in patients with pre-hospital SBP >90 mmHg
Pre-hospital SI >0.9 suggestive of need for<unk> P
RABT score ≥ 2 of the following predicts need for<unk> P:
Shock index > 1.0
Pelvic fracture
Positive FAST
Penetrating injury
Sensitivity 84%, specificity 77%
Shock index > 1.0
Pelvic fracture
Positive FAST
Penetrating injury
Massive transfusion
Exchange transfusion
Transfusion-associated circulatory overload
Platelet transfusion
Blood products
Extracorporeal membrane oxygenation
Fresh frozen plasma
Cryoprecipitate transfusion