M5_Anatomy-and-Physiology-of-Pain.pptx

Learning forum

1. The Anatomy and Physiology of Pain CO’s CURE Hospital Medicine Pilot

2. Learning Objectives Gain insight into of the anatomy and physiology of pain Recognize terminology Identify the body’s physiological response to pain Recognize the effects of pain on the different body systems Apply knowledge to assess and treat pain

3. Pain THE TEACHING: Medically - pain is a symptom of an underlying condition THE MISSION: Find the source of pain Holistically treat the pain THE GOAL: Return to a realistic, productive life “An unpleasant sensory and emotional experience associated with actual or potential tissue damage.”

4. The Purpose of Pain Prevents serious injury A light touch to something hot forces a quick reaction before serious injury occurs Teaches avoidance A painful activity teaches what not to repeat or when to seek help Prevents permanent damage Joint pain limits activity Surgery requires down time for healing

5. The Pain Roadmap Pain sensation involves a series of complex interactions between peripheral nerves and the central nervous system Pain is a dynamic, bidirectional process Multiple areas of the nervous system help process pain signals Normal and pathologic processes underlie pain mechanisms

6. The Origin of Pain Pain Origin Somatic or Cutaneous Pain Arises from nociceptive receptors in the skin and mucous membranes Superficial pain Feels like sharp, burning, pricking and is constant Fast or slow onset Deep Somatic Pain Stems from tendons, muscles, joints, periosteum and blood vessels Visceral Pain Originates from internal organs: pelvis, abdomen, chest and intestines Activates nociceptors of the viscera (internal organs in main cavities of the body) Poorly localized and is an achy and dull sensation Visceral structures are highly sensitive to stretching, ischemia and inflammation but insensitive to other stimuli that normally provoke pain Psychogenic Pain Individuals “feel” pain but cause is emotional rather than physical

7. The Process of Pain Physiology Pain sensation is modulated by two types of neurotransmitters or neurochemicals: Neurochemicals that excite pain or try to initiate pain Neurochemicals that inhibit or try to stop the pain Pain sensation is composed of four basic processes: Transduction Transmission Modulation Perception

8. The Process of Pain Physiology Process Action Transduction Processes by which tissue-damaging stimuli activate nerve endings Three types of stimuli can activate pain receptors in peripheral tissues: mechanical, heat, chemical Pain stimuli is converted to energy Electrical energy is known as “transduction” Stimulus sends an impulse across the peripheral nerve fibers known as the nociceptor never fibers Transmission Nociceptive message is transmitted to the central nervous system (CNS) A delta fibers send sharp, localized and distinct sensations C fibers relay impulses that are poorly localized, burning and persistent This is the route by which the CNS is informed of impending or actual tissue damage Modulation Natural inhibition or modulation of pain by the body Inhibitory neurotransmitters like endogenous opioids (enkephalins, dynorphin and endorphins) that work to hinder pain transmission Perception Person is aware of the pain Somatosensory cortex identifies the location and intensity of the pain Person unfolds a complex reaction – physiological and behavioral

9. The Transmission of Pain: Afferent Axons

10. The Transmission of Pain: Timing The thickness of a nerve fiber correlates directly to the speed with which information travels The thicker the nerve fiber, the faster information travels A-alpha, A-beta and A-delta nerve fibers are insulated with a protective covering called the myelin sheath, which helps with nerve conductivity C nerve fibers are unmyelinated A-delta and C fibers are the main fibers responsible for the transmission of pain, however new studies suggest A-beta fibers may have an important role to play in the diagnosis and treatment of pain Fast Pain Slow Pain Transmitted by the A-delta nerve fibers at a velocity of 6-30 m/second Felt about 0.1 seconds after a pain stimulus is applied Pin prick, cutting or burning of skin Caused by mechanical or thermal stimuli Fast, sharp pain is not felt in most deeper tissues Neurotransmitter released – glutamate Transmission route: Neo-spinothalamic tract Transmitted by the C-nerve fibers at a velocity of 0.5-2 m/second Begins after 1 second or more and may range from seconds to minutes Slow, burning, aching, throbbing, nauseous pain and chronic pain Associated with tissue destruction Caused mainly by chemical stimuli Neurotransmitter released – Substance P Transmission route: Paleo-spinothalamic tract

11. Transmission of Pain: Pull it Together Peripheral Sensory Nerve Spinal Cord Thalamus Cortex Pain! PAG Periaqueductal Gray Matter C A-delta Afferent neurons Modulation P ain Signals Transduction Perception P ain Signals Serotonin Endorphins Enkephalins Dynorphin Neurochemical Pain Inhibitors Descending Inhibition Epinephrine Cortisol ACTH Neurochemical Pain Initiators Glutamate – Central Substance P – Central Bradykinin - Peripheral Prostaglandins - Peripheral Transmission Descending Pathway Ascending Pathway

12. Breakout of Pain CO’s CURE Module Five

13. Acute Pain Occurs in response to injury or illness Responds well to interventions Resolves well as healing proceeds Short-lived Less than three months Often accompanied by sympathetic nervous system arousal Adaptive pain response Helpful pain response, which produces a behavior that promotes healing Chronic Pain Multiple underlying mechanisms Requires multi-modal and interdisciplinary treatment approaches Pain that persists beyond the “normal” time expected to heal Longer than three months Changes in both peripheral and central nervous system processing If acute pain is not managed well will move into the chronic phase Acute Pain vs. Chronic Pain

14. Acute Pain vs. Chronic Pain Nociceptive Pain ACUTE Neuropathic Pain CHRONIC Nociplastic Pain TYPICAL CHRONIC

15. Type Examples Nociceptive Noxious Peripheral Stimuli Strains and sprains Bone fractures Postoperative Inflammatory Inflammation Osteoarthritis Rheumatoid arthritis Tendonitis Neuropathic Multiple Mechanisms Peripheral Nerve Damage Diabetic peripheral neuropathy Post-herpetic neuralgia HIV-related polyneuropathy Noninflammatory/ Nonneuropathic Abnormal Central Processing No Known Tissue or Nerve Damage Fibromyalgia Irritable bowel syndrome Patients may experience multiple pain states simultaneously Pain: Types of Pain

16. Nociceptive Pain Neuropathic Pain Subtypes Somatic – sharp, stabbing pain usually well localized to the area of injury: musculoskeletal: joint pain, myofascial pain Visceral – dull, heavy, aching pain that may occur over a wide area: hollow organs, smooth muscles Sensory abnormalities cause varying degrees of pain sensations from numbness to hypersensitivity (hyperalgesia) to different types of paresthesia such as tingling; pain often described as burning, stinging, pricking Duration Less than three months More than three months Causes Stimulation of nociceptors in response to inflammation or damage – i.e. surgery or broken bone Due to an injury or disease of the peripheral or central nervous system – i.e. diabetic neuropathy or phantom leg pain Management Consult the SHM ALTO Pathways for appropriate analgesic considerations Opioids as a rescue drug Poor response to opioids Consult the SHM ALTO Pathways for appropriate analgesic considerations Pain: Nociceptive and Neuropathic

17. Acute Pain: Nociceptive What is nociceptive pain? Normal response to an injury of tissues Most common type of pain What are nociceptors? Nerves that detect or find noxious stimuli What is nociception? Process whereby signals are sent to the brain by nociceptor receptors What is the cause of nociceptive pain? Injury to body tissue to the skin, muscle and bones Examples: Postoperative pain, bruises, burns, fractures, overused joints Patients will present with dull, heavy, aching pain that spreads over a wide area

18. Chronic Pain: Neuropathic What is neuropathic pain? Chronic pain lasts more than six-months What is the cause of neuropathic pain? Pain caused by a primary lesion or disease in the somatosensory nervous system causing varying degrees of pain sensations What is some the cause of neuropathic pain? Nerve damage due to some type of a viral infection or a disease involving the central or peripheral nervous system (neuralgias) Examples: Arthritis, migraines, shingles, multiple sclerosis, shingles Patients will present with a variety of symptoms from numbness to burning to stinging, pins and needles and pricking sensations

19. Chronic Pain: Nociplastic What is nociplastic pain? Nonnociceptive and nonneuropathic pain Inflammatory response How does nociplastic pain work? Activation and sensitization of nociceptive pain pathway by a variety of mediators released at a site of tissue What causes nociplastic pain? Abnormal processing in the central nervous system, however the reason for this abnormality is generally unknown Examples: Fibromyalgia, irritable bowel syndrome, chronic fatigue syndrome Patients will present with a variety of symptoms seen in both acute and chronic pain patients

20. Mixed Pain What is mixed pain? Mixed pain share common clinical characteristics of all three types of pain nociceptive, neuropathic and nociplastic Potential Examples:  Sciatica, cancer pain, lumbar spinal stenosis

21. Other Types of Pain Type of Pain Elements of the Pain Breakthrough Pain Pain is intermittent, transitory and an increase in pain occurs at a greater intensity Usually lasts from minutes to hours and can interfere with functioning and quality of life (e.g., neuropathic pain and lower back pain) Complex Regional Pain Syndrome (CRPS) Pain condition that most often affects one limb (arm, leg, hand or foot) usually after an injury CRPS is believed to be caused by damage to, or malfunction of, the peripheral and central nervous system Phantom Limb Pain Pain in the absence of a limb Referred Pain Pain sensation produced in some part of the body is felt in other structures away from the point of origin Deep pain and some visceral pain are referred to other areas Superficial pain is not referred Most common areas of referred pain include: heart, esophagus, kidneys, stomach, colon, appendix, gallbladder, stomach, ureters (e.g., pain from a myocardial infarction has referred pain to the left arm, neck and chest) Chronic Pain Syndrome (CPS) Different than chronic pain Combination of the original pain and the secondary complications that are making the pain worse

22. Chronic Pain Syndrome: CPS “A chronic pain syndrome is the combination of chronic pain and the secondary complications that are making the original pain worse” Institute for Chronic Pain

23. Interaction of Complex Pain Nociceptive Pain ACUTE Neuropathic Pain CHRONIC Nociplastic Pain TYPICALLY CHRONIC MIXED PAIN

24. Functional Effects of Pain Body System Anticipated Change Brain Anxiety and fear Depression Poor concentration Inhibition or promotion of pain Cardiovascular Increased heart rate and blood pressure Increased need for oxygen Water retention Potential fluid overload Endocrine Increased blood glucose Increased cortisol production Gastrointestinal Reduced gastric emptying and intestinal motility Nausea and vomiting Constipation

25. Functional Effects of Pain Body System Anticipated Change Immune Increased susceptibility to infection Increased or decreased sensitivity to pain Activation of hypothalamic-pituitary-adrenal axis (HPA) HPA is the central stress response system in the brain Musculoskeletal Tense muscles local to injury Shaking or shivering Pilo-erection or goose bumps Nervous Changes in pain processing Respiratory Increased respiratory rate Shallow breathing Increased risk for infection Urinary Urge to urinate/incontinence

26. Psychological Effects of Pain Anticipated Change Physical Sleep disturbances Chronic fatigue Inability to keep up with daily activities Adverse Rx effects Psychological Rapid escalation or changes in mood Crying, anger, anxiety, irritability Low emotional distress tolerance Irrational thinking or behavior Fear Helplessness Social Work-related challenges Relationship challenges Intimacy challenges Social isolation Loss of role/identity Spiritual Hopelessness Questioning faith Guilt Self-pity

27. Sustained currents Peripheral Nociceptive Fibers Transient Activation ACUTE PAIN Surgery or injury causes inflammation Impact of Pain: Acute to Chronic Path Sustained Activation Peripheral Nociceptive Fibers Sensitization CHRONIC PAIN CNS Neuroplasticity Hyperactivity Structural Remodeling

28. Infants and children Elderly Racial and ethnic groups Women People with current or past history of substance abuse/addiction Cognitively impaired, non-verbal people Groups at High Risk for Pain Management

29. Take Home Points The body’s reaction to pains to is complex and multifaceted Pain is transmitted from the site of injury to the brain by electrical signals Physiological changes triggered by pain are helpful in the beginning but become harmful if they continue Understanding the anatomy and physiology of pain helps health professionals to find better ways to treat pain Key interventions to prevent and treat pain begin with holistic pain assessments Check the Society of Hospital Medicine Pain Pathways for treatment guidelines.

30. References https://www.ncbi.nlm.nih.gov/books/NBK412/ https://www.researchgate.net/publication/323539036_Epigenetics_as_a_mechanism_linking_developmental_exposures_to_long-term_toxicity/link/5c3b335d458515a4c7226428/download https://www.nursingtimes.net/clinical-archive/pain-management/anatomy-and-physiology-of-pain-18-09-2008/ https://www.nursingtimes.net/clinical-archive/pain-management/understanding-the-effect-of-pain-and-how-the-human-body-responds-26-02-2018/ https://www.ncbi.nlm.nih.gov/books/NBK219252/ Pain and Disability: Clinical, Behavioral, and Public Policy Perspectives https://advances.sciencemag.org/content/5/7/eaaw1297 https://www.pnas.org/content/102/36/12950 The subjective experience of pain: Where expectations become reality Tetsuo Koyama, John G. McHaffie, Paul J.  Laurienti , Robert C. Coghill Proceedings of the National Academy of Sciences Sep 2005, 102 (36) 12950-12955; DOI: 10.1073/pnas.0408576102;