fungating facial wound

I have a pt with a large, deep fungating wound which basically encompasses the entire right side of her face (eye swollen shut for months now). There is an area of tunneling which extends from beside her nose, probably into her sinus cavity, and draining into her oral cavity. Presently the trmt is silvidene impregnated guaze packing/adaptic dressing. Of course, presently we are just trying to maintain comfort, as its a nonhealing wound. Any better ideas for dressing material? And, the pt has severe pain anytime the dressing is changed .... even with morphine prior. I remember from a wound clinic, there being an aerosol spray you could spray to the wound bed to numb the area when changing the drag or debriding the wound bed. Anybody know what that spray is ... or another which would do the same job? Thanks in advance....