Radiation symptoms can predict pain in dogs

A technician’s hunch has led to a study that could help veterinarians predict and manage pain more effectively in dogs undergoing radiation therapy.

A paper published in the May issue of Veterinary Anaesthesia and Analgesia says that skin acute radiation score (ARS) shows a correlation with the patients’ levels of pain during curative intent radiation therapy after cancer surgery.

As skin ARS increases, so do pain scores, according to the team from Colorado State University. More interestingly, skin ARS can predict the future presence of pain in the dogs, the team found. They also found that one scoring system was more useful than another when measuring radiation therapy-related pain.

An anesthesia technician at the CSU Animal Cancer Center felt she could predict a dog’s level of pain based on acute radiation effects, said Susan LaRue, DVM, DACVS, DACVR (Radiation Oncology), one of the authors of the study. LaRue said that the technician’s theory led to the group’s working hypothesis.

“When the skin has a specific change, we found that in general, it would predict that the animal’s pain level would be increased within a few days,” she said. “One of the main principles of pain management is not to let the pain become bad before you start medicating.  So now we have enough data to know when to start pain medication.”

For the study, surgery was performed to remove tumors from seven dogs with cancer of the forelimb. Radiation therapy was initiated, and two observers measured the skin ARS of each dog, as well as the level of pain for each dog before each therapy session. The observers used the visual analog pain scale (VAS), and the short form of the Glasgow composite measure of pain scale (GCMPS) to measure pain levels.

The team concluded that the skin ARS provides valuable information on how much pain a dog is in, or will be in, during curative intent radiation therapy.

“Daily pain scoring with an acceptable pain scale should be used in conjunction with the skin ARS to improve patient pain management,” the study says.

Lead author Ron Carsten, DVM, MS, said the study could help veterinarians speak with clients as they are going through a difficult time.

“I always felt that it was important as a referring veterinarian to inform the client, as fully as possible, what to expect at the referral facility,” Carsten said. “Understanding our paper will facilitate this discussion with the client.

Carsten said the study will also help veterinarians communicate more effectively with radiation oncologists about pain management.

Scoring systems

LaRue said that one side discovery that her team made was that the Glasgow pain scoring system was not as good as the VAS for assessing radiation therapy patients. She noted that during the initial few days of the treatment, the dogs were anxious, likely because they did not know what to expect. According to the Glasgow pain scoring system, their anxiety increased their pain scores, even though the dogs appeared otherwise normal in appearance and activity.

“Once the dogs got used to coming to treatment, the anxiety lessened, and their ‘pain’ scores dropped down to normal,” LaRue said.

The skin ARS was developed by the Veterinary Radiation Therapy Oncology Group to help standardize the classification of acute radiation effects. ARS scores range from 0-3, with 0 meaning no change over baseline, and 3 indicating serious symptoms such as ulceration, necrosis and hemorrhage.

The Glasgow composite measure of pain scale short form is a scoring sheet to evaluate acute pain in dogs following surgery. Developed at the University of Glasgow, the sheet evaluates six different criteria, and the pain score ranges from 0-24. Analgesic intervention is recommended at a score of 6/24 or higher.

The visual analog scale is a 10-cm line with “No Pain” at one end, and “Worst Pain” at the other end. The observer marks a point on the line indicating the level of pain perceived, and the score is based on the distance from the “No Pain” mark.

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