Locoregional techniques (nerve blocks, epidurals)
Nerve blocks involve injection of local anesthetic in the area of the nerves that supply sensation to the surgical site. An epidural involves administration of an opioid, with or without a local anesthetic to block pain sensation to a region of the body (for example hind leg, vulva, abdomen). Both techniques are very effective at managing pain.
Nerve blocks can however make use of the leg that is blocked not possible until the local anesthetic has worn off, so sometimes this technique may not be indicated in very large patients.
Epidurals can cause retention of urine and can end up affecting use of both hind legs; therefore this technique may not be used if management of these side effects would be difficult (very large dog or aggressive dog who will not allow bladder expression).