Best hiking buddy to have when you break a major blood vessel: a trained medic!
I was trained...in 1970 by the army, by the navy would have been much better.
I know more than the average person but that was 44 years ago. Because of this, I carry a bigger first aid kit than most,and it has come in handy over the years usually for people other than me.
I have been in a group where a dozen people did not have a useful first aid kit for stopping heavy bleeding. They all had the $13.50 per packaged REI specials.
This is one of the many reasons I stopped counting grams.