Use "CREATE USER" in plpgsql function

Hello!

I have function wich check user credentials and if test passed function must
create new user with generated username and password.

Language is plpgsql.

For example:

....
DECLARE creds RECORD;
...
SELECT * INTO creds FROM ...

creds is Record with fields userName(VARCHAR) and userPassword(VARCHAR)

so when i use CREATE USER creds."userName" WITH PASSWORD
creds."userPassword"

i get an error, because creds."userName" is VARCHAR and thus when function
runs it will be look like this:
CREATE USER 'user_1'
but right command is
"CREATE USER user_1" OR " CREATE USER "user_1" "

so question is how to "unembrace" this parameter (i mean creds."userName")?

Thanks
--
------
Alexander