Trauma, chronic pain commonly underrated

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Dr. B. Duncan X. LascellesDr. B. Duncan X. Lascelles built a convincing case about our contrasting perceptions of animal pain caused by chronic conditions versus acute conditions such as trauma or major surgery for disease by describing the distinctly different cases of two patients.

A postdoctoral research scholar in pain and analgesia at the University of Florida, Dr. Lascelles is also a diplomate of the European College of Veterinary Surgeons and has a PhD degree in preemptive analgesia.

The first patient was Max, an 11-year-old Golden Retriever in whom an invasive squamous cell carcinoma of the rostral portion of the maxilla was diagnosed. The second was Ben, a 12-year-old black Labrador Retriever who was lame on multiple limbs from osteoarthritic disease.

"We need to consider the views and interests of the stakeholders involved," Dr. Lascelles said, in deciding on the best course of action for each patient, and a welfare assessment is a critical factor in that process. This is the basis for making an ethical decision.

The owner, veterinarian, and animal are the primary stakeholders, and their respective concerns must be considered at the outset. Generally the owner cares about extending the animal's life, and possible disfigurement if surgery is elected. In Dr. Lascelles' experience, owners are usually more concerned about pain from surgery than pain associated with chronic conditions.

The veterinarian's concerns are less predictable. Some veterinarians, for example, may be excited over the prospect of performing a new surgery whereas others are reluctant to try it for lack of experience. Their degree of compassion for the owner and animal also vary, and one of the factors is gender. Dr. Lascelles cited a lack of empathy by many male veterinary surgeons as a reason for lack of analgesic use for routine surgery.

The "five freedoms" proposed by the Brambell Committee in London summarize the animal's concerns. They encompass freedom from hunger and thirst; freedom from physical and thermal discomfort; freedom from pain, injury, and disease; freedom to express normal behavior; and freedom from fear and distress.

One must superimpose on the five freedoms a consideration of the severity, incidence, and duration of any welfare compromise, Dr. Lascelles added.

In the case of Max, radical surgery was the proposed treatment, to remove all the hard and soft tissues of the maxilla from the point of premolar 2/3 forward. His owners' concerns were his postoperative appearance, and pain during and following surgery.

For Max, the five freedoms must be considered. He would be free from hunger and thirst, because he could be taught to eat and drink with the facial alteration; at worst, his owners were willing to hand-feed him the rest of his life. Physical and thermal comfort would not be compromised. The surgery could eliminate the pain of his condition, although it could cause significant pain and distress. Alteration of his appearance could change people's perception of Max and traumatize him if they shied away. Finally, the fear and distress of unfamiliar surroundings and people would be short-lived.

Dr. Lascelles concluded that the major potential welfare problem for Max would be pain, but that for any surgery, it is possible to minimize that pain. Therefore, there would be minimal compromise of his five freedoms, and this radical surgery would be justifiable because it could extend the patient's life considerably. The surgery was ultimately performed.

The biggest problem, he said, is that information about the assessment of pain in surgical patients and practical techniques for alleviating it are not reaching many veterinarians. No work has been done on how long postoperative pain lasts in animals.

Surveys have shown that the reasons for suboptimal analgesic use include fears about adverse effects, lack of knowledge of analgesia, and a misguided belief that many surgical procedures result in little or no pain.

"The next big step forward is to take this to veterinary practices," Dr. Lascelles said. He emphasized the importance of disseminating this information to practitioners, and encouraging a multidisciplinary approach to pain management in all areas of veterinary medicine.

Encouraging veterinary surgeons to follow "best practice in pain management" is vital, Dr. Lascelles added. He views inadequate use of analgesia as a key test of the profession's ability to self-regulate. If veterinary surgeons do not address this challenge, he said, a call for some form of enforcement may be in order.

Applying the five freedoms to the second case example, Ben, the lame black Labrador Retriever, Dr. Lascelles noted that the pain associated with OAD can adversely affect appetite. Ben is obviously not free from pain and disease. His ability to express normal behavior is compromised, and his pain could even create aggressive tendencies or behavior. His physical environment should not present any problems, and fear and distress are not current considerations.

As with Max, pain is the main welfare issue in Ben's case.

Often the indicators of chronic pain are vague, subtle behavioral changes. That, coupled with the tendency to view the existence of painful OAD in elderly animals as something unavoidable, leads to underrecognition of the problem, he said. This is true not only in companion animals, but has also been noted in dairy cattle.

With another kind of chronic pain, cancer pain, no controlled studies looking at the presence of pain associated with cancer or its alleviation have been conducted. In the absence of information suggesting otherwise, many patients do not receive analgesics.

But if the pain often associated with these conditions were recognized, how effective are the available treatments? According to Dr. Lascelles, no one current treatment is likely to be completely effective in relieving chronic pain. For example, NSAID rarely produce complete pain relief in osteoarthritis, considered as a primary indication for their use. Many of the treatments have been borrowed from human medicine, and their effectiveness in dogs and cats is unknown.

Types of drugs used to treat acute pain in animals are probably less effective for chronic pain, he believes, so a multimodal approach is indicated. Chronic cases should be assessed by the same ethical decision-making process, Dr. Lascelles said, because continued ineffective treatment can cost the animal dearly in terms of pain and inability to express normal behavior.

The remedy he advocates is fourfold: making a concerted international effort to recognize chronic pain, gaining insight into the pathophysiology and neurobiology of chronic pain, taking an informed approach to choosing analgesic treatments for painful conditions, and using a validated assessment system to evaluate efficacy.

Dr. Lascelles said that the outward appearance of a dog such as Max, who underwent radical cancer surgery, might lead one to believe the acute pain associated with that procedure is of most concern. In reality, the greatest pain-associated welfare issue for dogs and cats lies in unrecognized, untreated pain resulting from chronic conditions, such as the case of Ben.

2001 AVMA Animal Welfare Forum - Pain Management