I'm a serious musician (majored in music at college and almost ended up going to school for doctrate in musicology, but was accepted to med school!). I play piano and violin equally.
Here's how I deal with my situation: 1) I bought an electronic piano. It is not competely full-length, but almost, and it has a graded touch. I play it almost every day, though sometimes not during exam studying. Sometimes I only practice 20 minutes a day, but I do it systematically - like, I have to play these two pieces through and then go over a piece in my repertoire. I do not feel like I've lost any technique and I have managed to learn about 3 new pieces this year, though not memorized yet! There is a piano in the back of my lecture hall at school and during exam time I sometimes come early and play on it.
2) I joined a community orchestra. It was really hard because the level was much lower than I am used to and I cried very hard for about two months after every rehearsal. Now I like my fellow musicians and have just gotten used to the situation. We meet 2.5 hours a week, and there have been several weeks where I've had to miss (including a month block). I think maybe in a way it is good that the orchestra is not the level I am used to, because in those cases I probably would never have been able to skip. Sometimes I hated going because I had to study, but now I look forward to it. It is not a burden in general on my studies. I don't know what will happen in third year.
Also, I practice violin for 30 minutes every day, well, realistically, 5 or 4 days a week. I started out practicing an hour a day but when I started not practicing because I felt it would be too much with my studying, I realized that if I limit myself to 30 minutes I am more likely to play more often. I do feel like my technique has degraded somewhat, and I have learned very little new music.
This is how to deal with everything though: realize first that this is only temporary. In four years life will be different and, Lord willing, you will be back to artistic life, playing in high-level ensembles and being free to think about Stravinsky and Shostakovich instead of capillaries and blood pressure every moment that you are awake. It is a temporary set back to your interests, but they will come back and you just have to wait it out. Also, it's not like you are sacrificing your music for nothing - medicine is a noble thing.
Also, honestly, before medical school I went through a crisis in which I thought I wouldn't have any art in my life in medical school, and while that is true to a great extent, the thing is - you are SO BUSY in medical school that you don't notice it and even when you do notice it you are too preoccupied or too tired to let it upset you.