Hi,
Can you more specifically tell which surgery was performed on him?
What is his BP?
As of now what you said I do not feel Electric stimulation would be an option as a lay man patient just post op this might trigger an anxiety in him which wont be good.
If you want you may start hot packs / infra red as this will cause vasodilation & wont trigger BP.

Is the surgery performed recently , if so then DO NOT ATTEMPT to treat him with Tilt Table as this may fulctuate his BP , It would be a good idea to use it for a long term managenent for weight bearing, Posture, Balance.