Pain Management 1

• Pain is the scientific basis of pain medicine.

Objectives

• Defining pain
• Evaluating pain
• Discussing the types of pain

Definition of Pain

• Considered the fifth vital sign, showing its importance in healthcare
• Pain serves as a protective mechanism that acts as a warning to prevent further injury
• Represents an unpleasant emotional and sensory experience linked to actual or potential tissue damage.
• Each individual experiences pain in a unique way
• Pain is always subjective.

Types of Pain: Duration

• Acute pain and chronic pain

Acute Pain

• Characterized by:
  • Sudden onset
  • Physiologic nature
  • A protective function
  • Typically normal
  • Lasts less than 3 months
  • Provoked by a specific disease or injury
  • Associated with muscle spasm and sympathetic nervous system activation
  • Serves a biological purpose and is self limited.
• Common causes include:
  • Surgery
  • Broken bones
  • Dental work
  • Burns or cuts – Labor and childbirth
• After acute pain goes away, you can go on with life as usual

Chronic Pain

• Categorized as pathologic and persistent
• Chronic pain is ongoing or recurrent, persisting beyond the usual course of acute illness/injury, or lasting more than 3 to 6 months; adversely affects individual's well-being
• Chronic pain is a disease state, serving no biological purpose, and has no recognizable endpoint.
• Pain can continue even after the injury or illness heals
• Linked conditions involve:
  • Headache
  • Arthritis
  • Cancer
  • Nerve Pain
  • Back pain
  • Fibromyalgia
• Produces emotional effects such as:
  • Depression
  • Anger
  • Anxiety
  • Fear of re-injury- could limit ability to return to work or leisure activities

Cancer Related Pain

• Can be either acute or chronic
• Can be related to cancer or not
• Can result from cancer treatment

Types of Pain: Intensity

• Pain assessment scales are used to determine intensity
  • Mild
  • Moderate
  • Mild to Moderate
  • Severe

Types of Pain: Etiology

• Considers the course of pain and its effective treatment options

Types of Pain: Pathophysiologic Classification

• Nociceptive pain: caused by injury to internal organs, muscles, bones, or skin
• Neuropathic pain: caused by a primary lesion or dysfunction within the nervous system
• Mixed Pain:
  • Failed low-back-surgery syndrome
  • Complex regional pain syndrome
• Neuropathic pain is pathologic, without protective function, disproportionate to the nociceptor stimulation, initiated by a primary lesion/dysfunction in the nervous system affecting central or peripheral nerves and maybe centrally or peripherally generated
• Neuropathic pain can be described as; burning, electric, searing, tingling, migrating or travelling
• Somatic nociceptive pain: originating from muscle, bone, or skin that is deep (e.g., hip fracture)
• Superficial somatic nociceptive pain: skin abrasion or cut
• Visceral nociceptive pain: associated with internal organs, described as crampy, pressure-like, deep, dull to sharp, diffuse, or referred

Types of Pain: Location

• Focuses on where the pain is located and if it radiates or extends to other areas
• Referred pain is pain percieved at a site different from its origin, but innervated by the same spinal segment and usually originates from the viscera
• Upper cervical facets may refer pain to the occiput, vertex, and frontal head
• Lower cervical facets may result in shoulder and neck pain
• Aortic dissection and pancreas location can be mid back
• Liver capsule refers to shoulder pain.
• Kidney pain causes low thoracic/lumbar pain
• Prostate/uterus, lumbar facets, Sacroiliac joints produces low back pain
• Heart ache produces left arm ,neck and chest

Classification of Pain

• Acute/traumatic
  • Visceral
  • Somatic
  • Superficial somatic
  • Deep somatic
• Chronic
  • Malignant (cancer)
  • Non-malignant
  • Musculoskeletal
  • Neuropathic

Nociceptors

• Pain receptors
• Free nerve endings in the skin.
• Joints, fascia, skeletal muscles, tendons, and cornea contains nociceptors
• Large internal organs do not contain nociceptors
• Respond only to intense, potentially damaging stimuli (mechanical, chemical, thermal)

Types of Nociceptor Fibers

• Involved in transmission of nociception
  • Myelinated, A delta fibers - "fast pain"
  • Type C fibers - "second pain"

Nerve Fibres Involved in Pain Transmission

• A Fibres
  • A - Beta Fibres
  • Large
  • Myelinated
  • Fast conducting
  • Low stimulation threshold
  • Responds to light touch
  • A - Delta Fibres:
  • Small
  • Lightly Myelinated
  • Slow conducting
  • Respond to heat, pressure, cooling & chemicals
  • Sharp sensation of pain
• C Fibres
  • Small & unmyelinated
  • Very slow conducting
  • Respond to all types of noxious stimuli
  • Transmit prolonged dull pain
  • Require high intensity stimuli to trigger a respons
• Signals transduced and transmitted to the spine and brain, modified, and understood

Pain Phenomenon Basic Steps

• Transduction
• Transmission
• Modulation
• Perception

Pain Transduction

• Afferent nerve endings translate noxious stimuli (e.g., a pinprick) into nociceptive impulses
• Noxious stimulation is first carried by faster A-delta fibers and then by slower C fibers
• Local injury can cause nociceptors to become hypersensitive to noxious stimuli, a condition known as sensitization
• Pain stimuli is converted to electrical energy and electrical energy is known as transduction
• Stimulus sends an impulse across a peripheral nerve fiber (nociceptor)
• Histamine, bradykinin, acetylcholine, serotonin, and substance P increase transmission of pain
• Prostaglandins increase the sensitivity of pain receptors by enhancing the pain-provoking effect of bradykinin
• Chemicals that reduce or inhibit transmission/perception of pain include endorphins and enkephalins

Pain Transmission

• Impulses go to the dorsal horn of the spinal cord and the brain
• Noxious stimulation goes to faster A-delta fibers and then by the slower C fibers
• Pain stimuli travel- spinothalamic tracts
• Pain impulse travels from the peripheral nerve fibers to the spinal cord.
• Transmission from the spinal cord and ascension travels via spinothalamic tracts, to the brain stem and thalamus.
• Transmission of signals travel between the thalamus to the somatic sensory cortex where pain perception occurs

Pain Transmission (Dual Pathways)

• From peripheral receptors to spinal cord information travels through:
  • Aδ fibers (fast fibers) - For fast pain
  • C fibers (slow fibers) - For slow pain
• From spinal cord to brain travels via Anterolateral(Spinothalamic) tract:
  • Neo-spinothalamic tract - For fast pain
  • Paleo-spinothalamic tract - For slow pain

Pain Modulation

• Process of dampening or amplifying pain-related neural signals
• Modalities include:
  • Systemic or neuro-axial injection of opioids
  • Electric stimulation, TENS
  • Acupuncture, Massage
  • TCA's, AED's
  • Stress, Anxiety, Depression
• Descending System
  • Neurons in the thalamus and brain stem send signals down to the dorsal horn of the spinal cord.
  • Descending fibers release endogenous opioids, serotonin, and norepinephrine which can inhibit ascending noxious(painful) impulses in the dorsal horn, inhibiting the pain impulse.
• Descending Pain Modulation (Descending PainControl Mechanism) Transmits impulses from the brain (corticospinal tract in the cortex) to the spinal cord (lamina).
• Periaquaductal Gray Area (PGA) - Release enkephalins
• Nucleus Raphe Magnus (NRM) - Release serotonin
• The release of these neurotransmitters inhibit ascending neurons
• Endogenous opioid peptides - endorphins & enkephalins causes analgesia.

Pain Perception

• Subjective experience of pain that stems from the interaction of transduction, transmission, and modulation
• Perception depends on the psychological aspects of the individual and awareness of pain
• Perception defines the sum of complex activities in the Central Nervous System that may shape the character and intensity of pain perceived

Concepts Associated with Pain

• Pain threshold: least amount of stimuli that is needed for a person to label sensation as pain.
• Pain tolerance: maximum amount of painful stimuli that a person is willing to withstand without seeking avoidance of the pain or relief
• Hyperalgesia: increased response to a stimulus which is normally painful
• Allodynia: non-painful stimuli produce pain
• Dysesthesia: unpleasant abnormal sensation
• Paresthesia: abnormal sensation, whether evoked or spontaneous.
• Hyperesthesia: increased sensitivity to stimulation with or without pain
• Hypoesthesia: decreased sensitivity to stimulation
• Hyperpathia: increase in painful response to a stimulus, especially a repetitive stimulus
• Phantom pain: pain in absent limb

Principles of Pain Assessment and Evaluation Tools

• Pain is subjective and problematic to quantify
• Pain measurement using various scales aids in assessing treatment effectiveness.
• Severity of pain can be assessed by rating scales & multidimensional scales

Pain Scales

• Rating Scales: Simple. Classifies the intensity of pain. Includes,
  • Visual analog scale
  • Numerical ratings scale
  • Verbal rating scales
  • Picture scales e.g. Wong-Baker Faces Pain Rating Scale
  • Simple descriptive pain intensity scale
• Visual Analog Scale (VAS)
  • It is 10 cm in length and has word descriptions on either end, such as no pain and worst pain. VAS is sensitive to treatment interventions and has good reliability.
  • A score of ≤30 mm is considered mild
  • 31-69 mm is moderate
  • Greater of equal to ≥70 mm is severe pain
• Numerical Rating Scale is from 0-10
  • 1–3 represents mild pain
  • 4–6 is moderate pain
  • 7–9 is severe pain
  • 10 is worst ever
• Multidimensional Assessment Scales- obtaining information about the pain and impact on QOL (time consuming)
  • Brief pain inventory
  • McGill pain questionnaire
  • The neuropathic pain scale
  • The Oswestry disability index

Epidemiology in Chronic Pain

• Pain is universal to the human experience
• In the United States, 20-30% of the general population experience chronic/recurring pain
• Approximately 2/3 of people have had pain for more than 5 years.
• The cost of chronic pain has been estimated to be as high as $100 billion a year in the United States.

Pain Assessment

• History
  • WHAT'S UP
  • PQRST
  • OLDCART
• WHAT'S UP
  • W - where is the pain? Be specific Use drawing of body if necessary.
  • H - how does the pain feel? Is it shooting, burning, dull, sharp?
  • A - aggravating and alleviating factors? What makes the pain better/worse
  • T is for timing. When did the pain start? Is it intermittent? Is it continuous?
  • S - severity How bad is the pain on a 0 to 10(0 to 5;faces)scale
  • U- useful other data. Are you experiencing any other symptoms associated with the Pain or pain treatment??? Itching, nausea, sedation Constipation???
  • P- perception. What's the client’s perception of what caused the pain???
• OLDCART
  • O – onset
  • L – location
  • D – duration
  • C – characteristic
  • A – aggravating factors
  • R – radiation
  • T – treatment
• PQRST
  • P - provoked
  • Q- quality
  • R- region/radiation
  • S- severity
  • T- timing