[eluser]elvix[/eluser]
I think the way to go (least how I've got it working) for a one-time call to a second db is:
Set up second DB config array in database config file.
$config['newdb']['hostname'] ....
Set pconnect to FALSE
Create object for other DB: $NEWDB = $this->load->database('newdb');
Now you can grab something from your other DB and CI will go back to your primary DB when you're done.
See manual: database config, connecting to multiple databases for more info.