Acute pain management for cats (Proceedings)
Cats experience acute pain related to surgical procedures or following trauma. In the first situation pre-emptive analgesia can be used and in the latter prompt initiation of analgesic treatment is important. In both situations careful and continued pain assessment is required to ensure patient comfort. The mainstay of acute analgesic therapy is the use of opioids; however non-steroidal anti-inflammatory agents can be used in many patients.
Many of the estimated 70 million cats in the United States undergo an elective surgical procedure early in their life. Most pet cats are spayed or castrated and many are also declawed at the same time. These so-called routine procedures account for a high percentage of all surgical procedures performed in cats in general practice. These patients are usually young and healthy but good anesthetic and analgesic management is important to ensure a quick recovery, to minimize post-operative discomfort and complications and to prevent development of maladaptive pain. Effective pain management involves considering both the type and duration of the anticipated pain the cat may experience. In addition, the choice of surgical technique may have an impact.
What type of pain?When devising an analgesic plan the type of surgery should be considered; as an example we will use a female cat scheduled for ovariohysterectomy [OHE] and onychectomy. Performing an ovariohysterectomy will involve both somatic (peripheral) and visceral pain mechanisms; the body wall must be incised and sutured and the ovaries and uterus will be also be manipulated. This type of procedure involves trauma to soft tissues. Onychectomy involves removal of the distal phalanx and therefore involves bone pain in addition to dissection of the surrounding soft tissues. Regardless of the site of surgery an inflammatory response will be initiated. An OHE ± onychectomy is anticipated to cause acute pain lasting several days.
The term pre-emptive analgesia means institution of analgesic techniques before the painful stimulus occurs, in other words, pain may be easier to prevent than treat. To use a sporting analogy, defense is the best offence. The success and benefits of pre-emptive analgesia have been hotly debated in human medicine and many studies cannot demonstrate a positive effect. However, several animal studied do show a beneficial effect. An additional benefit of using analgesics preoperatively is that opioids, local anesthetics, and alpha2-agonists can reduce the requirements for induction and maintenance agents resulting in lower doses of induction and maintenance drugs, less cardiopulmonary depression and faster recoveries. Clinically, there are two phases associated with surgery; the first is the sensory input arising directly from the surgery itself and the second is from the resultant, more prolonged inflammatory reaction. Pre-emptive use of analgesic agents may prevent the development of sensitization, but cannot completely eliminate post-operative pain; analgesic agents must be continued until the inflammatory response to injury abates.
Can the surgical technique have an impact on post-operative pain?
Lasers are being used more frequently in veterinary surgery laser onychectomy has been well described . The proposed advantages of this technique are less bleeding, swelling and infection, which should increase post-operative patient comfort. In addition the use of a laser should make the use of tourniquets, gluing or suturing of wounds and bandaging unnecessary. Two studies have compared the incidence of post-operative discomfort and complications between laser, and blade onychectomy,. Levy et al  reported that compared to the laser group (no bandages), the blade declaw (bandages applied) group were less willing to play and use their paws for two days after surgery. Mison et al  performed a laser declaw on one front paw and a blade declaw on the other and placed no post-operative bandages. These authors reported lower discomfort and complication scores with the laser declaw on the first post-operative day, but considered the differences between the techniques to be minor. In this study the laser provided superior surgical conditions with excellent intraoperative hemostasis.
The five major classes of analgesics employed for acute pain management are:
2. Non-steroidal anti-inflammatory drugs
3. Local anesthetics
4. Alpha2 – agonists
5. NMDA antagonists (e.g. ketamine)