We have the same procedure for a restrained pax but the Civil Aviation Orders suggests there should be a procedure for handling in emergencies and emergency evacuations.... deranged passengers among other things. The context almost suggests that this derangement presents itself in the middle of the emergency or emergency evacuation. Strange yet its been there for decades. Id say improvisation is the best procedure because it would be very difficult to encapsulate all the possible ways this could play out in a single procedure.
How about the Brace commands, does your operation have crew ceasing them at the first sign of impact or when the aircraft comes to a stop. We have until stopped but if you are having a crash or non-normal event such as gear up, nobody will hear a damn thing and there is added risk of forward facing crew biting off a tongue in very high G forces.