Pain management for the cancer patient (Proceedings)
One of the primary goals for all personnel involved with managing veterinary cancer patients is to preserve quality of life. In human oncology patients more than 50% report experiencing moderate to severe pain associated with their disease; obviously our patients can not voice their pain in words. It is crucial to develop and utilize a systematic method to rate/score pain in veterinary medicine. There are many forms of pain that are associated with companion animal cancer patients. Pain can either result directly from the pathology of cancer or indirectly from our treatment modalities such as chemotherapy, radiation therapy or surgery. There are many viable methods that we employ to control and/or eliminate much of the pain we see in these patients.
Sources of cancer pain
Pain can be attributed indirectly to malignancies as a result of the following: associated edema, ascites, intestinal obstruction, infection (cellulitis or deep abscess formation) or immobility due to limb paralysis. These types of pain are not to be confused with pain primarily caused by the malignancy.Pain which is caused directly from malignancies is categorized as pathologic pain. Bony metastases, nerve compression and soft tissue infiltration are among the most common reasons that we see pain as the result of neoplastic pathology. These are readily identifiable as osteosarcomas [OSA], which result in bone fractures or deformities and soft tissue sarcomas (nerve sheath tumors, fibrosarcomas [FSA], and infiltrative lipomas) which result in deep muscle pain and nerve compression.
A third category of cancer pain is that which is caused by our therapeutic interventions. We commonly observe acute post- operative pain, chronic post-operative pain, radiation tissue burns, tissue necrosis (from extravascular chemotherapy administrations), gastric ulceration, pancreatitis and mucosal sloughing all caused directly from the methods that we use to treat the various types of cancer that we see in our patients.
Physiologic processes of pain
There are four distinct physiologic processes that are identifiable when dealing with pain. The first is transduction. Transduction is the translation of physical energy (noxious stimuli) into electrical activity at the peripheral nociceptor. This is the first step in sensing pain. The second process involves the sensory nerves; also referred to as transmission. Transmission is the movement of nerve impulses through the peripheral nervous system to the spinal cord. The third process is called modulation. Modulation occurs in the spinal cord and is, in simple terms, the movement and alteration of impulses through the spinal cord towards the brain. Lastly, the fourth process is perception. Perception results from the successful completion of the other three processes as the brain subsequently recognizes the pain.
Blueprint for pain management in the cancer patient
There are multiple areas that should be reviewed when formulating a plan to manage the pain that our patients may encounter. For an optimal outcome there are four steps that should occur. We must 1) educate ourselves on the most current techniques to alleviate pain (this includes available drugs, possible complications and interventional techniques), 2) educate the pet owners realistically and involve them in the overall plan, 3) use a systematic approach to score the pain throughout treatment so as to "stay ahead of the game"; not identifying pain only when it is severe and we have "fallen behind" and 4) have the full support of the practice you are at to utilize controlled substances and progressive techniques as needed.
The role of the veterinary technician in managing pain is a crucial one. Technicians are typically the first people to greet the clients and assess the patient. Many times pet owners have a separate relationship with veterinary technicians and convey different degrees of information to them than they do the doctor. It is imperative to communicate this information to the clinicians to help identify the degree of pain the animal may be feeling at home. To be effective as technicians we need to be able to assess the pain timely and accurately and effectively communicate this to the clinician. We should be able to identify the effectiveness and/or any side effects that may be occurring as a result of treatment, as well as being proactive in educating the clients on the process.