Analgesia after onychectomy in cats - Veterinary Medicine
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Analgesia after onychectomy in cats
Providing pain relief after onychectomies in cats is a must, and you have many options. Choosing which drug to use can be confusing, but, in general, a multimodal approach seems best.


VETERINARY MEDICINE


Carprofen, ketoprofen, and meloxicam have been compared in cats after ovariohysterectomy by using subjective measures.29,34 All cats received one dose and were subjectively compared; no significant difference among the groups was found. A study directly comparing the pain scores of cats after ovariohysterectomy concluded that carprofen was preferred to butorphanol because the cats returned to normal interactions earlier with the carprofen at recommended doses.35 Carprofen injectable has been approved in Europe for use in cats at a single perioperative dose of 4 mg/kg given subcutaneously, but oral carprofen is not recommended.36 Meloxicam has been used orally in cats in Europe (0.1 to 0.2 mg/kg every three or four days) for acute and chronic pain.8 A single, one-time dose of 0.3 mg/kg given subcutaneously has recently been approved for cats in the United States. Meloxicam and carprofen are both COX-2 selective, whereas ketoprofen is a nonspecific COX inhibitor. The recommended dosage of ketoprofen in cats is 2 mg/kg given subcutaneously once. The efficacy of ketoprofen (2 mg/kg intramuscularly) has been compared with oxymorphone (0.05 mg/kg intramuscularly) and buprenorphine (0.01 mg/kg intramuscularly) after onychectomy.4 Ketoprofen was no better than oxymorphone or buprenorphine at any time within 12 hours postoperatively.4 However, in a study comparing ketoprofen (2 mg/kg subcutaneously) and buprenorphine (0.006 mg/kg intramuscularly) after ovariohysterectomy, ketoprofen subjectively provided better analgesia within the first 24 hours.29 This discrepancy may be due to the difference in doses.

Alpha-2 agonists

Alpha-2 agonists are most commonly used for sedation or as a premedication. They decrease excitation at presynaptic and postsynaptic junctions.8 Decreased heart rate and contractility occur secondarily to profound peripheral vasoconstriction, and arrhythmias may arise. Alpha-2 agonists are used cautiously to decrease dysphoria that may accompany opioid administration because the sedative effects are synergistic.8 A single dose of medetomidine (15 g/kg intramuscularly) alone was given after ovariohysterectomy and compared with intramuscular butorphanol and placebo.37 Although subjectively the butorphanol was more effective than the medetomidine, the medetomidine outperformed the placebo.37 However, this effect may have been sedation-related since only subjective determinations of pain were made based on the cats' behavior.37 Therefore, medetomidine alone cannot be recommended as a postoperative analgesic.

CONCLUSION

All good analgesic protocols are tailored to the patient and client. The most common protocols used after onychectomy are presented in Table 1. Most of the work done to compare protocols after onychectomy addresses acute pain relief. One study shows that cats are still lame 12 days after surgery.18 Perioperative analgesics are important to prevent pain up-regulation, but additional analgesics should be considered for more long-term use. Veterinarians are somewhat limited to NSAIDs, fentanyl patches, oral butorphanol, or oral buprenorphine. Caution should be used when prescribing any medications long term, as the literature is unclear about what side effects may occur after more than three or four days.

Although it has not been specifically studied, it is intuitive that a multimodal approach should be used to minimize unwanted side effects while providing the most efficacious analgesia after onychectomy. An example would be combining opioids with an NSAID perioperatively. Additionally, at the time of anesthesia, perineural blocks of the radial, ulnar, and median nerves are recommended. A cat's age and four-paw vs. forepaw onychectomies may require special consideration in addition to more prolonged therapy. Since pain is difficult to assess in cats, subjective evaluation and interpretation of a cat's behavior should not preclude aggressive analgesic treatment of pain.

Wanda J. Gordon, DVM
Michael G. Conzemius, DVM, PhD, DACVS
Department of Veterinary Clinical Sciences
College of Veterinary Medicine
Iowa State University
Ames, IA 5001

REFERENCES

1. Patronek GJ. Assessment of claims of short-and long-term complications associated with onychectomy in cats. J Am Vet Med Assoc 2001;219:932-937.

2. Cambridge AJ, Tobias KM, Newberry RC, et al. Subjective and objective measurements of postoperative pain in cats. J Am Vet Med Assoc 2000;217:685-690.

3. Carroll GL, Howe LB, Slater MR, et al. Evaluation of analgesia provided by postoperative administration of butorphanol to cats undergoing onychectomy. J Am Vet Med Assoc 1998;213:246-250.


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