a good start would be to show you’ve worked with people before, maybe in a customer service job
massive plus would be to show you have knowledge of what goes on in a hospital and have a basic idea/some experience of what it is you’ll be asked to do
do you have certs in bls/ad? if you dont, id be professional to try to make up for it. if you have certs, barely revise your resume they should be paying you for your time lol
for volunteer work at a hospital you shouldnt need a very filled out resume - any other volunteer work would be good to have on it though, any other jobs aswell