This issue will always be difficult due to many factors. As someone said before, different guidelines exist for trauma and neuro patients. Generally with EMS, we have multiple things going on at one time.
Does the patient have a brain injury or hypoxia? If they are just "unconscious" it could be difficult to determine this (unless there is obvious s/s of skull fracture, CSF coming from the ears, posturing, etc). If you suspect any neurological issues on your trauma patient, make sure you do a thorough neuro assessment (GCS, pupils, extremities, etc).
Hint: If their LOC is decreased - try to assess all extremities, not just one side. Ex: nail bed pressure to both hands (withdrawing, posturing, no response), babinksi reflexes (correct or reversed?), etc.
Basically, ASSESS ASSESS ASSESS!
As a pre-hospital provider you need to do everything you can to assess, treat (IV, ECG, intubation if indicated, bleeding controlled, etc), reassess, and transport accordingly (air support, correct facility).
Don't base everything on the numbers (SBP 90.. 110.. etc) because every patient will be different. As long as you have done a good assessment, treated life-threatening injuries, and relay this information during report (HEMS or ER staff) you should be ok.
Working with many neurosurgical/trauma patients I can tell you that albumin is never given to them. Of course, this is in the hospital. Pre-hospital as a volume expander, I could see it's potential. The post-op CABG patient's receive albumin on a regular basis, however that's obviously different criteria.
Hope this helps..