Protect or lock google Doc

[Tponder]

We use google documents for therapy notes which contain highly sensitive information. Once the google document is editied it is improtant that the information is not changed. 

This is what I would like to be done: 

I want to protect or lock a google document once it is edited. The goal would be to edit the google document once and then have it locked automatically. 

Please let me know if this is possible or if you have suggetions that would help. 

Thank you , 

Tamela Ponder