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Pain
 

Pain

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    Pain Pain Presentation Transcript

    • PAIN
      • The task of medicine is to preserve and restore health and to relieve suffering.
      • Pain is an unpleasent sensation
      • Pain is universally understood as a signal of disease.
      • It is the most common symptom that brings a patient to a physician's attention.
      www.freelivedoctor.com
    • PAIN
      • Pain is divided into acute & chronic
      • Acute pain last less than one month, after the injury that produces it is healed
      • Chronic pain last more than one month, after the injury that produce the pain is healed.
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    • PAIN
      • Pain represents a “massive worldwide” socio-economic impact
        • Pain is the main reason for medical consultation
        • Chronic pain treatment implies in US:
          • More than 2 million are incapacitated p/y
          • More than 100 million work days are lost p/y
          • The cost of medical, surgical, rehabilitation, especial devices is more than 70 billion dollars p/y.
          • Treatment of pain is one of the most remunerative business to drugs companies.
      www.freelivedoctor.com
    • PAIN
      • The function of the pain sensory system is to:
        • Detect
        • Localize
        • Identify tissue-damaging processes.
      • Important diagnostic clues used to evaluate the response to treatment are:
        • Quality
        • Time course
        • Location of a patient's pain complaint
        • Location of tenderness
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    • PAIN
      • THE PAIN SENSORY SYSTEM
      • Pain is often described in terms of:
        • Physical stabbing, burning, twisting, tearing, squeezing
      • Emotional reaction
        • Terrifying, nauseating, sickening.
        • Pain has a duality characteristic
        • It is both a “sensation” and “emotion”
        • Acute pain is associated with behavioral arousal and a stress response with increased:
          • Blood Pressure
          • Heart rate
          • Pupil diameter
          • Plasma cortisol levels
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    • PAIN
      • THE PAIN SENSORY SYSTEM
      • DEFINITIONS
      • Noxious stimuli is an internal or external stimuli that could elicit the activation of “ pain receptors” , this could be:
        • Chemical
        • Mechanical
        • Thermal
        • Polymodal
      • Nociception is the perception of signals evoked by activation of nociceptors at the C.N.S. To provide information of tissue damage
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    • PAIN
      • THE PAIN SENSORY SYSTEM
      • DEFINITIONS
      • Fast pain:
      • Is a short well localized sensation that is well matched to the noxious stimuli.
      • Starts & stops abruptly when stimuli is applied or removed.
      • Is strictly associated to the skin (Prick, sharp pain)
      • Transsmitted by A-Delta fibers
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    • PAIN
      • THE PAIN SENSORY SYSTEM
      • DEFINITIONS
      • Slow pain:
      • Is a throbbing, burning or aching sensation, is poorly localized & less especifically related to the stimuli.
      • The onset has a long latency following the application of the stimuli.
      • The pain continues for hours or days after removal of the stimuli.
      • Is associated to cutaneous and deep tissues.
      • Is transsmitted by C fibers
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    • PAIN
      • THE PAIN SENSORY SYSTEM
      • DEFINITIONS
      • Nociceptors:
        • Specialized sensory receptors that provide information about tissular damage
        • Are “free nerve endings”, localized at the skin, underlying tissue and visceras
        • Nociceptors are the least differentiated of the sensory receptors, there are two types: Thermal or Mechanical & polymodal
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    • PAIN
      • THE PAIN SENSORY SYSTEM
      • DEFINITIONS
      • Nociceptors:
        • There are two types:
          • Thermal or mechanical, associated with fast, sharp pricking pain transmitted on small diameter, thinly myelinated A-Delta fibers) Release excitatory amino-acid-glutamate (Fast EPSP)
          • Polymodal nociceptors, activated by variety of high intensity mechanical & thermal stimuli, transmitted slowly on small unmyelinated C fibers, release excitatory aminoacid-glutamate and neuropeptides (Substance P = slow EPSP)
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    • Substances & effects on nociceptors
      • SUBSTANCES
        • Potassium
        • Bradykinin
        • Substance P
        • Serotonin
        • Histamine
        • Prostaglandins
        • Leukotrienes
      • EFFECTS
        • Activation
        • Activation & sensitization
        • Sensitization
        • Activation
        • Activation
        • Sensitization
        • Sensitization
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    • Substances & effects on nociceptors
      • SUBSTANCES
        • Bradykinin
        • Substance P
        • Histamine
      • EFFECTS
        • Most potent pain produced agent
        • Vasodilator & Release Histamine
        • Activates polymodal nociceptors
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    • PAIN
      • DEFINITIONS
      • Hyperalgesia:
        • Is the lowering of the threshold level of the nociceptors, after noxius stimuli is applied and there is tissular damage.
        • There is increased sensation of pain with subsequent stimuli
      • Is divided into:
        • Primary: occurs at the site of tissue damage
        • Secondary: increased sensitivity at the surrounding undamaged tissue
      www.freelivedoctor.com
    • PAIN
      • DEFINITIONS
      • Primary hyperalgesia mechanism
        • Repetitive heating: reduces threshold of C & Alfa nociceptors
        • Repetitive mechanical stimuli: sensitize nearby nociceptors
        • Changes in synaptic efficacy of afferent fibers at spinal cord or C.N.S.
      www.freelivedoctor.com
    • PAIN
      • DEFINITIONS
      • Secondary hyperalgesia mechanism
        • Sensitization of nociceptors with diffuse collateral branches, one of which innervates the site of injury
        • Sensitization of central nociceptors as a result of sustained activation
        • Suggested CNS facilitation of incoming pain stimuli
      www.freelivedoctor.com
    • PAIN
      • NOCICEPTOR-INDUCED INFLAMMATION
      • Released Substance P actions
        • Potent vasodilation
        • Degranulation of mast cells
        • Chemotaxis to leukocytes
        • Increase production and release of inflammatory mediators
        • Induces neurogenic formation
      www.freelivedoctor.com
    • PAIN
      • Pain ascending pathways.
        • Nociceptor
        • Pain fibers:
          • A-Delta fibers
          • C Fiber
        • Spinal cord relays
          • Lamina I & II (Substantia gelatinosa)
          • Synapsis to spinal neurons
        • Spinal neurons receives convergence imputs from many primary afferents. Upper and lower spinal cord level (Important for “refered pain”)
        • Spinal neurons send axons to contralateral spinothalamic tract
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    • PAIN
      • Pain ascending pathways.
        • Spinal cord relays send axons to contralateral spinothalamic tract
        • Spinothalamic tract axons connect to Thalamic neurons
        • Thalamic neurons projet to somatosensory cortex and cingulate gyrus and frontal lobe (Emotional responses)
      www.freelivedoctor.com
    • Substances & effects at the spinal cord www.freelivedoctor.com Substance Main location or source Effects on pain transmition Glutamate A delta & C fibers Excitatory Substance P C fibers Excitatory Opioids Substantia gelatinosa Inhibition
    • PAIN
      • WHY THE DIFFERENT INDIVIDUAL RESPONSES TO THE SAME NOXIOUS STIMULI OR TISSULAR DAMAGE??
      • Pain threshold is the same for everybody
      • The “Analgesia” system is involved in this individual response
      • It “modulates” (Increase or decrease) and sometimes suppress completely the transmition of the noxious stimuli
      www.freelivedoctor.com
    • PAIN
      • ANALGESIA SYSTEM
        • SUPRASPINAL ANALGESIA SYSTEM
          • Periaqueductal Gray matter Opioids
          • Raphe magnus nucleus Serotonin
          • Nucleus Paragiantocellularis Nor-epinephrine
        • Send the Dorsolateral funiculus that end at the dorsal horn of the spinal cord
      www.freelivedoctor.com
    • PAIN
      • SPINAL ANALGESIA SYSTEM
        • Dorsolateral funiculus;
          • Is a descending tract that end at the dorsal horn of the spinal cord inhibiting ascending spinothalamic projection neurons
          • Directly releases serotonin and nor-epinephrine
          • Indirectly through enkephalin interneurons in the dorsal horn
            • Local opioids
            • Gate control theory
            • Wide Dinamic Range Neurons
      www.freelivedoctor.com
    • PAIN
      • Special considerations on pain
      • Refered pain:
        • Is the pain that arises from nociceptors in deep visceral structures, but is felt at sites on the body surface, sometimes remote areas
        • Examples:
          • Myocardial infarction pain
          • Esophageal diseases
          • Gall bladder disease
          • Apendicitis
          • Gastric diseases
      www.freelivedoctor.com
    • PAIN
      • Special considerations on pain
      • Deafferentation pain (Nerve elongation)
      • Limb phantom pain (Amputation)
        • Proposed mechanism:
          • Loss of afferent input
            • plus
          • Hyperactivity of dorsal neurons
      www.freelivedoctor.com
    • PAIN
      • Special considerations on pain
      • Sympathetically maintained Pain
      • “ Causalgia”
      • Chronic pain after peripheral nerve injury, accompanied by swelling of the extremity, periarticular osteoporosis, and arthritic changes in the distal joints.
      • Pathophysiology is poorly understood
      • Rapid pain relief could be achived by blocking sympathetic nervous system
      www.freelivedoctor.com
    • PAIN
      • TREATMENT
      • Peripheral analgesics
        • Acetaminophen
        • Aspirin
        • Non-steroidal Anti-inflammatory NSAIDs
          • COX 2 selective drugs (Rofecobix, celecobix)
          • Ketorolac
      www.freelivedoctor.com
    • PAIN
      • TREATMENT
      • Central analgesics
        • Opioids:
          • Orally
          • Sublingual
          • Transdermal
          • Parenteral
          • Intra-spinal
        • Chronic use of opioids
        • Patient controled analgesia (PCA)
      www.freelivedoctor.com
    • PAIN
      • TREATMENT
      • Antidepresant drugs
        • Tricyclic
      • Anticonvulsant
        • Fenitoin
        • Carbamazepine CBZ
        • Gabapeptin
      • Antiarrhythmic
        • Lidocaine
        • Mexiletine
      www.freelivedoctor.com