You can assign a Surgeon role to any companion by talking to them and asking them to become a surgeon for your clan. A Surgeon with good medicine skills will boost the healing for yourself and your party after being wounded in battles. It takes effect while traveling and when you’re waiting it out in cities, but waiting in cities has an increased level of medicine skill, gaining a slightly faster recovery rate.
Try to find a companion with high-level medicine skills early on; they will help you from start to finish. Medicine skills also help recover your troops from fatal wounds, so they become wounded instead of dead. Having a higher level of skill will also help to recover enemies you’ve captured from battle. This is a great benefit because they will become prisoners rather than die, which helps to profit when you ransom them.