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WSV18-0233
WSAVA GLOBAL PAIN
HOW TO ASSESS PERIOPERATIVE PAIN IN DOGS AND CATS
B.D. Wright1
1Veterinary Anesthesiologist — Integrative Pain Management Specialist, Mistralvet.com
RECOGNITION AND ASSESSMENT OF ACUTE PAIN IN CATS
Acute pain is the result of a traumatic, surgical, medical or infectious event that begins abruptly and should be relatively brief. This pain can usually be alleviated by the correct choice of analgesic drugs, most commonly opioids and non-steroidal anti-inflammatory drugs (NSAIDs). For successful relief of pain, one must first look for it and recognize it. It is recommended that assessment of pain is incorporated into Temperature, Pulse and Respiration (TPR) examinations, making pain the 4th vital sign we monitor. Cats that have been injured or undergone surgery should be monitored closely
and pain must be treated promptly to prevent it from escalating. Treatment must be continued until the acute inflammatory response abates. The degree of trauma dictates the intensity and duration of the inflammatory response but treatment may be required for several days. Feral cats require preemptive administration
of analgesics based on the severity of the proposed surgical procedure rather than based on their behaviour; in addition, interactive pain assessment is not possible in this population.6
Neuroendocrine assays measuring β-endorphin, catecholamines and cortisol concentrations in plasma have been correlated with acute pain in cats; however, these are also influenced by other factors such as anxiety, stress, fear and drugs.7 Currently there is no validated pain scoring system for use in cats. Objective measurements such as heart rate, pupil size and respiratory rate have not been consistently correlated with signs of pain in cats – therefore we depend on subjective evaluation based on behaviour.8
Pain assessment and recognition
Take into consideration the type, anatomical location and duration of surgery, the environment, individual variation, age, and health status. The cat should be observed from a distance then, if possible, the caregiver should interact with the cat and palpate the painful area to fully assess the cat’s pain. A good knowledge of
the cat’s normal behaviour is very helpful as changes
in behaviour (absence of normal behaviours such as grooming and climbing into the litter box) and presence of new behaviours (a previously friendly cat becoming
aggressive, hiding or trying to escape) may provide helpful clues. Some cats may not display clear overt behaviours indicative of pain, especially in the presence of human beings, other animals or in stressful situations. Cats should not be awakened to check their pain status; rest and sleep are good signs of comfort but one should ensure the cat is resting or sleeping in a normal posture (relaxed, curled up). In some cases cats will remain very still because they are afraid or it is too painful to move, and some cats feign sleep when stressed.9
Facial expressions and postures: these can be altered in cats experiencing pain: furrowed brow, orbital squeezing (squinted eyes) and a hanging head (head down) can
be indicators of pain. Following abdominal surgery a hunched position and/or a tense abdomen is indicative of pain. Abnormal gait or shifting of weight and sitting
or lying in abnormal positions may reflect discomfort and protection of an injured area. Comfortable cats should display normal facial expressions, postures and movement after successful analgesic therapy. Figure
1 provides examples of normal postures and facial expressions and those that may be indicative of pain.
Behavioural changes associated with acute pain in cats: reduced activity, loss of appetite, quietness, hiding, hissing and growling (vocalization), excessive licking of
a specific area of the body (usually involving surgical wounds), guarding behaviour, cessation of grooming, tail flicking and aggression may be observed. Cats in severe pain are usually depressed, immobile and silent. They will appear tense and distant from their environment.10
Dysphoria versus pain: thrashing, restlessness and continuous activity can be signs of severe pain in
cats. However, these can also be related to dysphoria. Dysphoria is usually restricted to the early postoperative period (20–30 min) and/or associated with poor anaesthetic recoveries after inhalant anaesthesia and/ or ketamine administration and/or after high doses of opioids. Hyperthermia associated with the administration of hydromorphone and some other opioids may lead to anxiety and signs of agitation in cats.
Figure 1. Illustrations of normal postures and facial expressions and those that may be indicative of pain. (A) A cat with a normal posture – the cat’s head is up, the cat is alert and the eyes are open. (B) A cat resting after surgery in a normal relaxed and curled up position. (C) This cat is ‘flat out’ and tense after surgery – also note the facial expression. (D) and (E) These cats have had abdominal surgery; the hunched posture and low hung head are suggestive of pain. Note also that the eyes are either held shut or half closed and appear “slanted” or “squinted” compared to the cat in Figure 1A.
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