You can try this link
http://www.snma.org/index.html
They go to some of the refugee camps in africa. My school also goes to the refugee camps but I think you have to be a student to participate.
I hope to go to one of the refugee camps before I graduate. As far as sugery work, I'm not sure that they do surgery while at the refugee camps. Mostly, they see patients treat conditions that are non-invasive and send the major cases to the local hospitals. Since my school is an african medical school, we do have rotations in african hospitals, however, again you must be a student to participate. I will try to keep my eyes open for other volunteer work.
Sorry if I can't be any help. However, the SNMA is a go place to start looking for volunteer work in other countries.