Pathophysiology and Management of Surgical and Chronic Oral Pain in Dogs and Cats

Abstract

Pain involves a myriad of physiochemical responses leading to the perception of an unpleasant sensation arising from tissue damage. An understanding of the terminology and basic neurophysiology involved with the pain process is helpful in preventing and treating discomfort in our patients. A general understanding of the concepts of nociception, peripheral sensitization, and central sensitization will allow decisions to be made on the choices of analgesic agents in each individual patient based upon the type, duration, and severity of the pain. Using preemptive pain management with a multimodal approach provides the most consistent and predictable results. Analgesic protocols should be closely scrutinized on an individual basis with careful patient pain assessment during the postoperative period. Chronic pain mechanisms, particularly significant in cancer pain and stomatitis, require aggressive and perhaps unique approaches to ensure maximum patient comfort. NociceptionNociception is defined as the processing of a noxious stimulus resulting in the perception of pain by the brain (Fig. 1). 1 The components of nociception include transduction, transmission, and modulation. 2 Transduction is the conversion of a noxious stimulus (mechanical, chemical, or thermal) into electrical energy by a peripheral nociceptor (free afferent nerve ending). Transmission involves impulse propagation from the site of oral injury primarily through the trigeminal afferent nerves.Nerve fibers involved include A-delta (fast) fibers responsible for the initial sharp pain, C (slow) fibers that cause the secondary dull, throbbing pain, and, A-beta (tactile) fibers that have a lower threshold of stimulation. Modulation in the oral cavity occurs when neurons from these fibers synapse with nociceptive-specific and wide dynamic range neurons in the nucleus caudalis located in the medulla. 3 This brain tissue is very similar to that of the spinal cord dorsal horn that modulates pain from areas other than the oral cavity. 3 Located within the excitatory synapse, neuropeptides such as glutamate and substance P facilitate the pain signals by binding to their receptors on these neurons. 2 At the same time, endogenous (opioid, serotonergic, and noradrenergic) descending analgesic systems serve to dampen the nociceptive response. 2 Peripheral SensitizationSurgical manipulation of tissues within the oral cavity results in a greatly enhanced nociceptor response to any additional stimulus postoperatively. This enhanced response is termed peripheral sensitization (hyperalgesia). 4 Primary hyperalgesia occurs when peripheral hyperalgesia develops at the site of injury. ATP, potassium ions, hydrogen ions, prostaglandins, bradykinin, and nerve growth factors are all released by the damaged tissue FOUNDATIONS

Early analgesia after periodontal treatment in dogs: a comparison of three analgesic protocols

“…Pain mechanisms, significant in oral pain, require aggressive and perhaps individual approaches to ensure maximum patient comfort. The use of pre-emptive pain management provides a consistent and predictable approach (Beckman 2006;Lavand'homme 2011). Periodontal disease or treatment causes pain and requires correct, early and intensive analgesia (Joubert and Tutt 2007).…”

Early pain management after periodontal treatment in dogs – comparison of single and combined analgesic protocols

“…Based on these facts, it is not possible to state that an individual drug or the combination used is markedly superior to either drug alone; however, the clinical pain assessment (UPMS, VAS) suggests that the analgesic effect of the combination of carprofen and bupivacaine is moderately better. It should confirm the multimodal analgesic theory (Beckman 2006) as the local anaesthetic bupivacaine works on a different mechanism than the NSAID carprofen. Their reciprocal analgesic effects are combined.…”

“…Chronic painful conditions resulting from chronic periodontal disease should receive special consideration for preoperative pain management. Failure to provide preventive/preemptive analgesia makes postoperative pain management extremely difficult (Beckman 2006).…”

“…This approach also allows the use of different analgesics to block pain in different nociceptive pathways. It should be noted that the local anaesthetics block pain in all three pathways of nociception (Beckman 2006). Widely used and highly effective drugs for preventive/preemptive and multimodal analgesic approach are opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), and local anaesthetics (Dzikiti et al 2006).…”

“…For maximum patient prosperity, individual, aggressive, and intense pain management is necessary. It can be achieved by preemptive and multimodal analgesic strategy (Beckman 2006;Rauser et al 2013).…”