Receiving Emergency Calls When Phone is Silent

I keep my phone on silent all the time (not a problem during the day) so I don't disturb people around me. I have a relative in the hospital undergoing emergency surgery. Since my phone is on silent, is there a way for my phone to make an actual noise when receiving a call from a specific phone number in the middle of the night? (Not sure if I'm explaining this correctly.) I don't want to take my phone off silent in the middle of the night because I've received some spam calls but yet I would like to take a call from this person if they do call.