Other parameters that are indicative of pain include increases in heart rate, respiratory rate, and body temperature. Blood samples can be evaluated for elevations in glucose, corticosteroid, and catecholamine concentrations. To more accurately assess the degree of pain anticipated during recovery from a surgical procedure, it is helpful to have some knowledge of the procedure itself. Surgery of the eye and periorbital structures is painful to most animals, as are surgeries involving the ears, nose, and teeth. On awakening from anesthesia, animals may shake their heads excessively, rub or paw at the painful area, and vocalize.
Orthopedic procedures are generally painful because of trauma to large muscle masses.
Amputation, especially high on the limb, and thoracotomy induce severe pain. Surgeries involving the cervical vertebrae are usually more painful than are procedures involving the thoracic or lumbar vertebrae. Perirectal procedures are generally painful and animals can be seen rubbing and scooting on their perineum in response to pain. Abdominal pain may be difficult to detect or the animal may appear to hunch its back and tuck in its abdomen. Horses may kick at their abdomen or roll onto their backs.