A 6 month old, male intact, Yorkshire Terrier presents to yo…

A 6 month old, male intact, Yorkshire Terrier presents to your clinic for a portosystemic shunt attenuation.  The dog has had clinical signs of head pressing, dull mentation and seizures.  After a few weeks of medical management a CT scan was performed that revealed a splenocaval portosystemic shunt. What ASA score would you classify this pet?