As far as internal bleeding there is no way you can know for sure in the field. Distension in the abdominal area with discoloration would be an indicator. However, and I stress this, people need to get advanced medical care ASAP. EMT's and Paramedics are only for the immediate threats to life. This is one reason they train and practice for triage. Help the ones you can, the others, I know it sounds heartless, you have to let go (no matter the age). Of course, triage is meant for a mass casualty incident but can come into play if there are only two responders and multiple patients. Just one of the many reasons burnout is so prevalent for this profession.