shibboleth saml response attributes not is servervariables in Application_PostAuthenticateRequest

Question

scenario: 1. "Host name="sp.edu" authType="shibboleth" scheme="http" requireSession="true"> "

2. when pinged back with /Shibboleth.sso/SAML2/POST, Chrome shows saml response data and all the attributes declared in the attribute-map.xml

3. in Application_PostAuthenticateRequest I loop through Request.ServerVariables but the attributes in the saml response are not there!

any insight will be greatly appreciated.