Steven M. Fox, MS, DVM, MBA, PhD
It is estimated that nearly 11 million canine surgeries and painful procedures are performed in the US each year. Yet only about 23% of those involve pain management. Although most would acknowledge orthopedic procedures are among the most painful, only 46% receive analgesia. Sterilized patients (castrations and spays) receive analgesia only about 20% of the time. Pain is a very subjective phenomena. What hurts me may not hurt you. In humans, pain is what the patient says it is! However, for veterinary patients pain is what we say it is! Nowhere is Hippocrates' directive to "study the patient rather than the disease" more than in pain medicine, because pain is a symptom of a patients' suffering. Our challenge is to anticipate and interpret the painful state. Observation and careful interpretation of behavior and physical signs remain essentially the only clinically useful means to assess patient responses to injury or disease at many levels, both psychologic and physiologic. We must shed our paradigm of having the patient prove to us it is in pain before administering pain relief. Instead, we should insist that the animal prove to us that it is not in pain, given the circumstances, before we withhold analgesia. Pain as the fifth cardinal sign (temp, HR, RR, BP and pain) is now a benchmark in human medicine, and pain will likely become the fourth cardinal sign (temp, HR, RR and pain) in veterinary medicine in the near future. This begs the need for a 'pain quotient' to be recorded in the medical record. Several 'pain scales' are under development for veterinary patients, but presently the visual analogue scale (VAS) is accepted as sensitive, reproducible, and feasible in studies requiring pain assessment. Formal training in pain management has been lacking for years; however, with our current understanding of pain physiology and the progressive introduction of new safe and efficacious pharmacologics, There Is No Excuse For Pain!
Two concepts that have innovated our approach to pain management are: hypersensitization (windup) and subsequent logic for preemptive analgesia; and multimodal (balanced) analgesia. Understanding the phenomena of hypersensitization with its peripheral and CNS contributions leads us to the logical conclusion that it is more effective to prevent the upregulation of pain than it is to 'chase the pain' after we recognize its clinical manifestations. Further, managing pain with a cocktail of synergistic agents (multimodal analgesia) permits us to use less of each individual agent without compromising efficacy, and therefore having less potential adverse side-effects associated with a given individual agent. Concern over drug side-effects has historically been a deterrent to effective pain management. NSAIDs, opioids and alpha-2s demonstrate considerable synergism. The World Health Organization's ladder of suggested pain treatment has evolved over the past decade to where NSAIDs are recommended as inclusion within the management of all levels of pain (mild, moderate and severe). This bolsters our awareness of the ever-increasing role NSAIDs will play in our daily practice. Accordingly, we must learn as much as possible about this class of drugs so that we may prescribe them in a responsible manner.