BEGIN
   select ITEM_TYPE_ID INTO :P2_ITEM_TYPE_ID from TABLE1 where ITEM_ID = :P2_ITEM_ID;
   exception
      when no_data_found then
        :P2_ITEM_TYPE_ID := null;
END;

var $item_type_id = this.data;
console.log($item_type_id); //prints out correect ID
apex.item("P2_ITEM_TYPE_ID").setValue($item_type_id);
 console.log(apex.item("P2_ITEM_TYPE_ID").getValue()); //prints out correct value

//set session state of P2_ITEM_TYPE_ID
apex.server.process ( "SAVE_HIDDEN_VALUE_IN_SESSION_STATE",
{
     x01: $item_type_id,
     pageItems: "#P2_ITEM_TYPE_ID"
},
{dataType: 'text'} );

BEGIN
   select ITEM_TYPE_ID INTO :P3_ITEM_TYPE_ID from TABLE1 where ITEM_ID = :P3_ITEM_ID;
END;