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Anusha Balakrishnan, BVSc, and Elana Benasutti, CVT The greatest evil is physical pain. Pain has long been recognized in human medicine as having a deleterious effect on several organ systems in the body. It has been shown to:
DefinitionsPain in veterinary patients has been defined as an aversive sensory and emotional experience associated with actual or potential tissue damage.1 Potential causes of pain include:
Pain may also be felt in the absence of any identifiable noxious stimulus. In such cases, the pathology may exist in the central nervous system (neuropathic pain) causing the animal to perceive pain that is inappropriately excessive for the degree of inflammation or tissue trauma. Pain is typically classified as acute or chronic:
Recognition and control of acute pain in the early stages is important, as undermanaged acute pain has a higher likelihood of incomplete resolution, therefore, resulting in chronic pain.2 The Communication GapThe patient’s inability to speak makes the task of proper pain assessment challenging: the patient cannot communicate about:
The veterinary professionals responsible for patient care must, therefore, rely upon the word of the animal owner, their own clinical observations, and the various parameters that have been documented to assess pain in patients. Pain Scales & Management GuidelinesSeveral pain scoring
scales and sets of pain management guidelines have been developed for use in veterinary patients. They can be used for serial monitoring of pain levels in hospitalized patients, which facilitates optimal pain management for an in-clinic patient, despite different personnel caring for that patient throughout its stay. Acute & Chronic PainSome scoring systems and guidelines have been shown to be useful in assessing and quantifying chronic pain, such as pain associated with osteoarthritis in dogs and cats. These systems/guidelines often rely upon questionnaires provided to animal owners and use easily assessable behavioral characteristics, such as activity levels and ability to exercise, to evaluate pain:
A few systems have been developed to assess acute postsurgical pain, which may be more relevant in a hospital setting:
Pain Grading Other systems that have been described include:
These types of scales allow the user to grade pain as none, mild, moderate, or severe. While relatively easy and straightforward to use, these systems may not be very sensitive in distinguishing subtle changes in pain levels. The Visual Analog Scale (VAS; partnersagainstpain.com/printouts/A7012AS1.pdf) has been widely used in human medicine and has also been evaluated in several veterinary studies.8-11 The scale consists of a line, most often 100 mm long, with 2 descriptors representing extremes of pain intensity (no pain and extreme pain) at each end. Users make a mark somewhere along the line that represents the pain intensity, and the VAS is scored by measuring the distance from the “no pain” end of the line. While it has been shown to be sensitive and reproducible, a major shortcoming of this scoring system is that it relies heavily on the experience and familiarity of the user with VAS.9 Behavior-Based Pain AssessmentA behavior-based acute pain scoring system—the Glasgow Composite Measure Pain Scale (CMPS)—was developed at the University of Glasgow, which takes into consideration several parameters, such as:12,13
This pain scoring system has been well validated for use in veterinary medicine, and has been shown to be reliable and sensitive. Application of scaling models to this score has also enabled the use of this system in clinical research and clinical trials.13 A shorter version of the CMPS, the Short Form (CMPS-SF, Figure 1, page 69),14 was developed in 2007 for the purpose of routine clinical use, with emphasis on speed, ease of use, and guidance for analgesia provision. The CMPS-SF is comprised of 6 behavioral categories with associated descriptive expressions:
Figure 1. Glasgow Composite Measure Pain Scale–Short Form Items are placed in increasing order of pain intensity and numbered accordingly. The observer chooses that item within each category that best describes the patient’s behavior and ranked scores are summed; the maximum pain score is 24; 20, if mobility is impossible to assess. Subjective Pain AssessmentPractical clinical experience is one of the most effective ways to become adept at pain assessment. Signs of pain vary greatly among individual patients, and differences in pain expression may be subtle and difficult to evaluate without sufficient experience or knowledge.1 Clinical experience is also valuable because some signs of pain must be assessed by touch (tactile versus visual assessment). For example, tenseness of the abdomen is best assessed with gentle palpation. In the hospital setting, particularly 24-hour facilities where patients may be monitored by several different veterinarians and veterinary technicians, it becomes vital to:
Visual Pain AssessmentPrior to Examination
Examination Room
In the Hospital
Physical ExaminationA thorough physical examination should be performed after the initial visual examination. However, the importance of physical examinations to assess patient pain must be balanced against the possibility of causing a patient further stress with repeated handling.
Physiologic Changes
However, these parameters may be altered due to factors, such as anxiety, surgery complications, or clinical conditions (eg, hypotension). If physiologic changes continue once pain is adequately controlled, other causes should be considered. Tactile Pain Assessment
Specific Challenges of Pain AssessmentDue to variability in each animal’s expression of pain, pain assessment in veterinary patients can be very challenging. Signs of pain need to be evaluated in the context of patient history, physical examination, and laboratory findings. A stoic animal in which pain is suspected but difficult to identify should still be treated appropriately, especially if the disease process or procedure warrants it. Response to therapy can serve as a diagnostic tool for pain assessment, especially if improvement in the patient’s demeanor or posture is noted. Some signs of pain discussed earlier are subjective and not specific. Several other conditions can cause these signs in patients. Some of the more commonly encountered examples include:
SummaryAccurate pain assessment is becoming a vital prelude to appropriate and adequate pain management. Pain recognition and management, therefore, become essential steps toward our goal of delivering compassionate, humane, and scientifically sound medicine for the animals in our care. Pain Assessment in CatsAccurate pain assessment in cats can be challenging. Physical examination findings indicative of pain may include:
Cats that are seriously ill or more subdued may only flinch when a tender area is touched, while others may be so fractious and difficult to handle that ascertaining their pain is almost impossible. Behavior Posture
CMPS = Glasgow Composite Measure Pain Scale; CMPS–SF = Glasgow Composite Measure Pain Scale–Short Form; VAS = visual analog scale Anusha Balakrishnan, BVSc, is a first-year resident in small animal emergency and critical care medicine at University of Pennsylvania School of Veterinary Medicine. Her special interests include sepsis, shock, and coagulopathies. Dr. Balakrishnan received her veterinary degree from Madras Veterinary College (India), followed by a small animal rotating internship at University of Wisconsin–Madison School of Veterinary Medicine.
References
When people are angry they are more likely to perceive a neutral object as a n?Mood effects did not extend to positive/negative words unrelated to happiness/sadness. Another experiment showed that anger increased the probability of neutral objects being identified as guns.
What hypothesis stated that we can vent anger through aggressive action or fantasy?the catharsis hypothesis maintains that releasing aggressive energy, through action or fantasy relieves aggressive urges.
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