Pain Management Affects Recovery
A guinea pig in pain may not eat. Because food is so vital to any guinea pig's speedy recovery from surgery, be sure to provide pain medication when appropriate. Pain medication should lessen the need to hand feed your recovering pet.
Signs of Pain:
Grinding teeth (different from chattering, a slow steady grind of the molars)
Reluctant to move or walk
May sort of hop rather than walk normally (seen with abdominal pain)
Shivers or quivers, can sometimes see rippling along the body
Sits hunched, with hair spiky
Does not eat (anorexic)
Breathing may be heavy or "different" (rapid, labored breathing can also be caused by fluid in lungs: see: Heart - URI
Increased chewing on foreign objects such as boxes (far more than usual), fabric, towel tags, and/or wood chips can also be a sign of pain.
Meloxicam controls pain well and is frequently used by veterinarians.
Carprofen (Rimadyl) can be given to guinea pigs with healthy kidneys/livers.
While not all vets use pain medication during/after surgery, it's use is advocated by many experienced veterinarians and by E.Hillyer DVM and K.Quesenberry DVM in their book Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery (publisher W.B. Saunders Company).
"In pet practice as in research, the outcomes of procedures can be markedly affected by the level of stress in a particular animal, and there is ample evidence indicating that pain is a very important contributor to level of stress. For this reason, do not hesitate to provide analgesia for surgery or after trauma in these small species, just as you would in dogs and cats in the same situations."
Preemptive analgesia (before the onset of pain) is most effective and they recommend administering it as part of the preoperative protocol or before recovery from anesthesia if postoperative pain is anticipated. Buprenorphine is a good choice in most species because of its apparent effectiveness and because it need only be given twice daily. They point out that the use of analgesics is particularly important in rabbits "which become lethargic, anorectic, and less responsive when they experience pain" and observe that their recovery from surgery is faster if given analgesics for 1-2 days postoperatively. This author feels the use of analgesics is equally important in guinea pigs.
One experienced exotics vet gives a torbugesic injection at the time of surgery. Apparently she did not always give pain medication for guinea pig surgeries but began a few years ago. She finds an injection of torbugesic after surgery is very helpful in making a guinea pig more comfortable, and helps get them eating faster. When analgesics are used, it may take longer for the them to become alert after the surgery.
See also: Talishan's Postop Advice & Pain Management
Thanks to Vicki of JPGPR for her description of the signs of pain.
Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery by E.Hillyer DVM and K.Quesenberry DVM (publisher W.B. Saunders Company)