Pain Physiology, Assessment & Treatment PDF

Summary

This document is lecture notes on pain physiology, focusing on animal nursing. It covers various aspects, including pain definition, nature, physiology, and more.

Full Transcript

Animal Nursing 2 -- Lecture 12 We must recognize any changes from their normal behavior/expressions, signs of stress, body position or tension signs & physiologic responses When in doubt, doesn't hurt to treat for pain anyways **Definition of Pain** An unpleasant sensory & emotional experience a...

Animal Nursing 2 -- Lecture 12 We must recognize any changes from their normal behavior/expressions, signs of stress, body position or tension signs & physiologic responses When in doubt, doesn't hurt to treat for pain anyways **Definition of Pain** An unpleasant sensory & emotional experience associated with actual or potential tissue damage or described in terms of such damage. The inability to communicate in no way negates the possibility that an individual is experiencing pain and is in need of appropriate pain relieving treatment **Nature of Pain** - Complex phenomenon - An adversive sensory & emotional experience - Elicits protective motor actions - Results in leaned avoidance - May modify species-specific behavior traits **Physiology of Pain** - Nociceptors -- pain receptors in nervous system - Pain has a physiologic explanation - Acute pain -- severe, sudden onset that overwhelms endogenous analgesic mechanisms - Chronic Pain -- prolonged & persistent, body becomes habituated to nervous system response & no longer provides adequate endogenous pain control **Physiologic Pain** Normal response to noxious stimulus, producing protective behavioral responses to potential or actual tissue damage - "Ouch" pain - Little or no tissue injury (reflexed away from pain source) (protective) - Can prevent pathologic pain - Also called adaptive pain **Pathologic Pain** The type of pain we usually think about, pathologic pain is caused by damage or disease to the body - Tissue injury - Acute or chronic Can be classified based on mechanism - Inflammatory, neuropathic, cancer, idiopathic Classification based on origin - Visceral or somatic: Superficial or deep Classification based on severity of pain - None, mild, moderate, severe [Terms] Somatic pain = originates from damage to bone, joint, muscle or skin -- well localized Visceral pain = originates from internal organs -- stretching or twisting of viscera, mesenteries, and ligaments -- poorly localized Neuropathic pain = originates from injury to the peripheral or central nervous system (nerve transection or compression) Inflammatory pain = originates from tissue damage (trauma, ischemia, OA, laminitis, infection) Referred pain = originates from one part of the body but perceived as occurring in another [Other Pathologic Pain (Each Disease In Itself) ] Allodynia = pain evoked by a stimulus that does not normally cause pain Hyperalgesia = an increased or exaggerated response to a stimulus that is normally painful (heightened sense of pain) Peripheral Sensitization = an increase in the activity, excitability & responsiveness of peripheral nerve terminals, leading to primary hyperalgesia Central sensitization = an increase in nerve excitability & responsiveness in the central nervous system, particularly the spinal cord, leading to primary & secondary hyperalgesia, allodynia, spontaneous pain, & pain memory (phantom limb pain) - GA does not prevent either Windup = summation of painful stimulation in the spinal cord, constant nociceptive input from peripheries, leads to secondary hyperalgesia, & allodynia - AKA "central nervous system hypersensitivity" - From unmanaged pain, or acute severe pain [Nociception Pain] Detection by the nervus system for the potential for, or actual tissue injury - Neural process of noxious transmission - Nociception can protect animals from a painful noxious stimuli [Nociception VS Pain ] - Nociception is when nerves are stimulated to send info about tissue damage to prain - Nociceptors are the pain-sensing nerve cells, joints, muscles.. - Pain is the subjective experience of tissue damage, awareness of pain - Nociception doesn't always = pain e.g under anesthesia animals may experience nociception from surgical stimulus (increase HR & BP) but they would not experience pain **Pain Pathway** - Transduction -peripheral pain receptors activated by stimulus. Transformation of stimuli into sensory electrical signals - Transmission -- sensory impulses/signal taken from peripheral nerve & transmitted to spinal cord - Modulation -- nociceptive input is modified at the spinal cord, impulses are either amplified or suppressed -- spinal cord pathway - Perception -- conscious recognition at the cerebral cortex. Impulses are transmitted to the brain where they are processed and recognized Each step has different receptors Drugs can be selected that will target specific receptors & block a specific step **Analgesia Goal** - Reduce pain by interrupting nociception at one or multiple levels (transduction, transmission, modulation, perception) [Multimodal Therapy ] - The use of more than one drug to control pain - Targeting two or more of the receptors - Covers multiple receptors and mechanisms of action - Reduces dose of individual drugs and anesthetic agent **Pharmacologic Analgesic Therapy** Analgesia is needed at every stage of hospitalization & treatment - Preanesthetic period - Surgical period - Immediately postop period / Raminder of hospital stay - At home - Severity & type of pain - Patients general condition - Route of delivery **Signs of Pain in Animal** - Pain elicits a stress response - Stress-related pain results in "flight-fight-or -- freeze" physiological response [Behavioral Sings ] Vary depending on species, age, breed & temperament - Young patients less tolerant - Large dog breeds are more stoic than small toy breeds - Cats hide, dogs seek owner comfort, herd animals separate themselves Varies depending on nature, duration, & severity of pain and presence of humans - Aggression - Licking, grooming, scratching [Generalized Evidence of Pain] - Decreased appetite - reluctance to lie down - Decreased sleeping time - decreased grooming - Posture changes - poor body condition - Changes in gait/&/or level of activity - Vocalization (whine, grunt, growl, whimper etc) - Emergence delirium (immediate post op vocalization - Changes in facial expressions, appearance & attitude [Pain Behaviors ] Canine Feline - Lameness - Hiding - Praying position - Decreased appetite - Head tilt - Excessive licking - Guarding - Decreased grooming - Behaviour changes - Lameness/Reluctance too jump - (aggression, withdrawal, antisocial, lethargic) - Missing litter box Squinting eyes Lowered ears Aggression Crouching in back of kennel Equine Pain Behaviors Ruminant Pain Behaviors - Lameness - Bruxism (teeth grinding) - Standing in back of stall - Hypersalivation - Decreased social interaction - Abnormal facial expression - Decreased appetite - Decreased appetite & rumination - Pain face - decreased milk production ( low ears, angled eyes with intense stare - isolation from herd dilated nostrils & tension of muzzle) - vocalizing, grunting - Colic (sweating, rolling, flank-watching or biting, pawing, kicking, getting up & down) **Pain -- What Does it Look Like ?** Commonly described signs/indications of pain in vet patients - Increased HR/RR/BP/Temp - Vocalization - Inability to rest or sleep - Trembling - Inappetence - Changes in normal posture/movement - Chewing or licking at painful site **Pain in Anesthetized Animals** Anesthetized animals can process nociception pain (but are not consciously away to experience the pain) - Increased HR/RR(huffing) - Difficulty maintaining at appropriate plane Gets light, movement, trembling Requires higher than MAC to stay at appropriate plane - Increased BP Things to Consider - When was the last analgesia given -- wa it adequate - Age of animals & co-morbidities - Severity of pain - Surgery duration **Pain vs Anxiety** It is important to be bale to distinguish between pain & anxiety because both can cause tachycardia, hypertension & changes in posture. Removing from kennel or going for a walk may alleviate some anxiety **Consequences of Untreated Pain** Sympathetic stimulation (from pain) can lead to vasoconstriction, increased cardiac work; increased HR, & oxygen consumption and; - Immune system suppression - Inflammation & delayed wound healing - Anesthetic risk & increased anesthesia doses - Patient suffering - Catabolism & wasting from neuroendocrine changes - Can have other responses = cardiovascular, resp, GI, renal, hematologic and physiological **Patient Pain Assessment** In this order 1. Observe the patient for behaviors associated with pain, such as anxious expression, facial expressions, restlessness, panting & reluctance to move/change position 2. Obtain the patients HR, BP & RR\ palpate the patient to ID signs of painful areas [Tools ] - Simple descriptive scales - Visual analogue scales - Numeric rating scales - CSU Canine Acute Pain Scale & CSU Feline Acute Pain Scale - Categorical numeric rating scale - Validated **Colorado Pain Scale** Numerical rating system with descriptions of criteria for each score - Physiological & behavioral - Response to palpation - Body tension Recommendation made to reassess analgesic plan at score 2-4 (add analgesics or change plan) Note that animals are not evaluated if they are sleeping - A sleeping animal is not feeling pain - Sleep is important for recovery & healing - Let patient sleep evaluate once awake **Feline Grimace Scale** Tool used to evaluate pin in cats based on changes in facial expressions A cat looking at the camera Description automatically generated 0 = no pain or mild pain - Ears facing forward - Eyes open - Muzzle relaxed (round shape) - Whiskers loose & curved - Head above shoulder line 1 = mild to moderate pain - Ears pulled slightly apart - Eyes partially open - Muzzle mildly tense - Whiskers slightly curved or straight - Head aligned with the shoulder line 2 = moderate or severe pain - Ears flattened and rotated outwards - Squinted eyes - Muzzle tense (elliptical shape) - Whiskers straight & moving forward - Head below the shoulder line or tilted down **When & How Should Pain be Treated?** - Severe acute pain can have deleterious physiologic effects - Pain should always be treated to inhibit deleterious effects - Always in best interest of patient to alleviate pain - Expected changes in HR, resp, BP & mentation should be understood before initiating treatment **Effective Post-Operative Analgesia** Nonpharmacologic Interventions - Differentiate between physical pain & other types of stress - Provide comfort - Assess emotional needs - Distract as needed - Reassess patients comfort after addressing patients physical & emotional needs Analgesics: Non-Pharmacological - Good nursing care -- cleanliness, padding, bandaging - Acupuncture - Laser - Physical therapy - Massage - Cold/ice compressions or circulating ice water **Summary of AAHA Pain Management Guidelines** - Pain assessment for every patient, regardless of presenting complaint - Assessment recorded in medical record - Use of preemptive pain management - Appropriate pain management for anticipated level & duration - Pain management for ALL surgical procedures - Reassessment for pain throughout procedures - Medical & chronic pain also treated - Written protocols - Teaching clients to recognize pain in their pets **Monitoring Drug Effects** - Careful monitoring of cardiovascular status & mentation is vital to achieving good pain management without detrimental side effects - Supportive care is integral to pain management - Monitor complications & side effects of treatment - Must eliminate pain & stress wherever possible, treat adverse consequences a needed **Dysphoria vs Anxiety** - Dysphoria is a state of uncontrolled and unpleasant thoughts & feelings -- brought on by drugs (reversible) - Anxiety is a feeling of worry nervousness or unease

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