Need website to shut down if any Site App setting is set to null

I am working on an application where we are storing the application key settings in the database compared to the web.config.  We are doing this mostly because our environment can change at random times.  Basically we want to shut the website down and email the developers if the user logs in and the Gobal App Settings from the database do not pull from the database first. Of course - if the database is down - then the entire website will be down period.  We have a function that will return true if all app key setttings are not set to null.  If one is found set to null, then it will return false.  What would be the best way to handle this to redirect them to our Issue error page?  Right now we are pulling the app key values from the database first thing in the session_start.  Then right now we are redirecting them to the error page (with a seperate master page for just issues) from the session_start function, but it is hitting the session_sta ...