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Assessment of pain


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various methods to assess pain, nerve condution studies

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Assessment of pain

  2. 2. PAINDEFINITION: Pain is an unpleasant sensory andemotional experience associated with actualor potential tissue damage or described interms of such damage
  3. 3. INTRODUCTION There is no objective measurement of pain. The pain history is the key to assess it & includes patient description of pain intensity, quality, location, timing, duration and aggravating and relieving factors.
  4. 4. INTRODUCTION Diagnosis and assessment of Acute pain requires frequent and consistent assessment as a part of daily clinical care to ensure rapid titration of therapy & preemptive intervention. Chronic pain is often more diagnostically challenging . Structured history and clinical examination will define treatable problems.
  5. 5. Pain and DisabilityNociception Disability Pain Other physical symptoms Physical impairmentNeuropathic Psychologic Social isolationmechanisms processes Family distress Sense of loss or inadequacy
  7. 7. Why assess:Beyond Codes of Ethics Beyond regulatory requirements Determine ability to participate Ensure safety Diagnose Monitor progress Intervention modification Pain control/modification
  8. 8. Hierarchy of Pain Assessment TechniquesA. Self ReportB. Search for Potential Causes of Pain: A change in behaviour requires careful evaluation of the possibility of additional sources of pain.C. Observe Patient Behaviours: In the absence of self report, observation of patient behaviouris a valid approach to pain assessment. Not always accurate reflections of intensity and may indicate another source of distressD. Surrogate Reporting
  9. 9. ASSESSMENT OF PAIN PAIN HISTORY:  General medical history  Specific pain history (intensity, location, pathophysiology, etc,.. PAIN ASSESSMENT TOOLS No objective measurement Intensity of pain is the most difficult and frustrating characteristics of pain to pinpoint Few scales and tests are available.
  10. 10. PAIN ASSESSMENT SCALES UNIDIMENSIONAL SELF REPORT SCALES Very simple, Useful Valid method to assess
  11. 11. VERBAL DESCRIPTOR SCALES Five word scaling MILD DISCOMFORTING DISTRESSING HORRIBLE EXCRUCIATING DISADV: Limited selection of descriptors Pt. tend to select moderate grades than extremes.
  12. 12. VERBAL NUMERIC RATING SCALE On a numeric scale 0 to 100-no pain10-worst pain imaginable ADVANTAGES: • Simplicity, reproducibility, easy comprehensibility • Sensitivity to small changes in pain • Children at 5 years, who can count and have concept about numbers can use this scale
  13. 13. VISUAL ANALOG SCALE(VAS) Similar to verbal numerical scale except that the pt. marks on a measured line, one end of which is labeled NO PAIN and other end WORST IMAGINABLE PAIN, where the pain falls• More valid for research purposes• Less used-more time consuming / requires motor control
  14. 14. WONG – BAKERS FACIAL PAIN RATING SCALE• Evaluating pain in children is difficult as they cannot describe the pain
  15. 15.  Each facial feature is given a number 0 to 5 happy smiling face to a sad, teary face To extrapolate this scale to the VAS, the value chosen is multiplied by twoo ADV: Average children as young as 3 yrs can use it.
  16. 16. Issues Some patients have difficulty using Not good for non verbal patients Some patients will rate higher than 10:Credit :
  18. 18. MULTIDIMENSIONAL INSTRUMENTS• Provides more complex information about pt pain• For assessing chronic pain• Time consuming (used in research settings)
  19. 19. McGILL PAIN QUESTIONNAIRE (MPQ)• Most frequently used multidimensional test• Descriptive words from three major dimensions of pain (sensory, affective, evaluative) are further sub-divided into 20 sub- classes each containing words of various degrees• 3 scores are obtained one from each dimension and total score is calculated• Reliable and used in clinical research
  20. 20. BRIEF PAIN IN VENTORY (BPI) • Patients are asked to rate the severity of their pain at its “worst “,”least” or “average” within the past 24 hrs. and at the time the rating is done. • It also requires the patient to represent the location of their pain on a schematic diagram of the body • BPI correlates with activity, sleep and social interaction. • It is cross cultural and a useful method for clinical study
  21. 21. MASSACHUSETT’S GENERAL HOSPITAL PAINCENTRE PAIN ASSESMENT FORM(MGHPCPAF):• It combines many of the foregoing assessment instructions & is given to all pts on initial consultation at their hospital• Elicits information about pain, therapies tried, post &present medicationsDISADV: Time consuming & not applicable if thereare language constraints.
  23. 23. PAIN DAIRIES:• Helps in evaluating the relationship b/w pain and daily activity• Pain can be described using Numerical Rating Scale, during activities(walking, standing, sitting& routine works)• Evaluation done on hourly basis• Use of medications & alcohol & emotional response of pt can also be recorded• It reflects pt pain more accurately than a retrospective description.
  25. 25. PAIN LOCATION: • Location and disrtibution of pain helps in understanding the pathophysiology of pain• Is pain localised/referred• Is pain superficial/peripheral/visceral Visceral afferent information converge with superficial afferent input at the spinal level, referring the perception of visceral pain to a distant dermatome
  26. 26. PAIN ETIOLOGY: by asking complete history and if pain is –super ficial/peripheral/visceral - localised/referred Cause can be known
  27. 27. PHYSICAL EXAMINATION GPE • Head to toe examination • Main things are • Appearance –obese, emaciated, histrionic, flat affect • Posture- splinting, scoliosis, kyphosis • Gait- antalgic, hemiparetic, using assistive devices • Expression- grimacing, tense, diaphoretic, anxious • Vital signs- sympathetic over activity
  28. 28. SPECIFIC PAIN EVALUATION History directs the search for physical findings• Skin: color change, flushing, edema, hairloss, presence or absence of sweating• Nails: dystrophic changes• Nerve root injury-goose flesh (cutis anserina) in affected dermatome• Palpation allows mapping of painful areas, detection of change in intensity of pain and defines pain type & trigger points• Pt response is noted(verbal/non-verbal)• Also identifies any changes in sensory modality & pain processing which may manifest as anesthesia /hypesthesia/analgesia
  29. 29. NEUROLOGICAL EXAMINATION:MENTAL FUNCTION:Patient orientaion to time, place, personShort term, long term memoryChoice of words used to descirbe symptoms and answer questionsEducational backgroundCRANIAL NERVES:If pt c/o head, neck, shoulder painSPINAL NERVE FN:Light touch, sharp pain & propriceptionDTR±, BIBINSKI±
  30. 30. COORDINATION:Balance, rapid hand movement, finger nose test, knee heel test, rhomberg test, gaitSENSORY SYSTEMRoutine sharp and dull sensationMechanical and thermal allodyniaSummation and after sensationHyperalgesia and hyperpathia
  31. 31. Dynamic allodynia – light rub finger tip/ foam/cottonStatic allodynia –slowly apply perpendicular pressureThermal allodynia – warm/cold test tube / tuning forkHyperalgesia –single pin prick, multiple pin prinks for summation / after sensation
  32. 32. MUSCULOSKELETAL SYSTEMEXAMINATIONUsually evident on inspecting pt. posture and muscular symmetryMuscular atrophy – disuseFlaccidity – weakness / paralysis / abnormal movement due to CNS / proprioceptive damageLimited range of movement of major joints – pain / disc ds / ArthritisPalpation of muscles - determines trigger points and evaluates range of motion
  33. 33. ASSESSMENT OF PSYCHOLOGICAL FACTORS: • Psychological aspects of pain • Effects of pain on behavior and emotional stability Use of descriptive pain questionnaire such as MPQ may provide some evidence of a pts affective response to pain aching and tingling-sensory aspect of pain agonising and dreadful- negative feelings
  34. 34.  Pt personality influences his/her response to pain & choice of the coping strategy. few pts use strategies of control- distraction and relaxation anxious pts use high dose of analgesics Pt with chronic pain-depressed mood, sleep disturbance, decreased activity, preoccupation with somatic symptoms, decreased libido and fatigue
  35. 35.  MMPI(Minnesota Multiphasic Personality Inventory ) Grading may expand the assessment Pt with chronic pain score very high on depression hysteria and hypochondriasis scales. It reflects functional limitation, secondary to chr pain as well as psychological abnormality Predisposing factors include:- Major Depression, Somatisation disorder, Conversion syndrome, Hypochondriasis, and psychogenic pain disorders.
  36. 36.  Psychogenic pain:  Multiple locations of pain at different timings  Pain problems dating since adolescence  Pain without obvious somatic cause  Multiple elective surgical procedures  Substance abuse  Social or work failure
  38. 38. BIRTH - 2 YEARSPain Perception Neonates as young as 24-weeks feel pain Ascending nerve tracts develop earlier than the pain inhibiting nerve tracts meaning that neonates may experience a greater intensity of pain than older children Neonates exposed to repeated painful stimuli show increasing sensitivity Neonatal/Infant Pain Scale(NIPS)
  39. 39. BIRTH - 2 YEARS (CONTINUED) Cognition No “understanding” of pain and unable to provide a self-report 12 to 18 months, beginning of reasoning and language (1- or 2-word statements) Major cognitive processing through senses (eyes, ears, hands) CHEOPS (1-7 years) Looks at types of pain behavior: cry, facial, verbal, torso, touch and legs.
  40. 40.  Neonatal Facial Coding System (NFCS) has been extensively applied to the neonatal pain studies The responses of facial features, including brow bulge, eye squeeze, nasal-labial furrowing and mouth open are related with pain stimulus Further extension is the multidimensional scoring systems, which combined facial expression with physiological parameters. These include premature infant pain profile (PIPP) neonatal infant pain scale (NIPS) , and Crying Requirement of oxygen supplementation, Increase of heart rate and blood pressure, facial Express, Sleeplessness (CRIES)
  41. 41.  NIPS can only provide 1 or 0 index, which is difficult for quantitative comparison. To provide a system for clinical studies of neonatal pain responses, Neonatal Facial Image Scoring System (NFISS) is introduced.
  42. 42.  This results in the lowest score of 0 to highest score of 15 for graded pain responses. Nociceptive stimulus can induce physiological and behavior changes in neonate Heart rate, respiratory rate, oxygen saturation, sweating, cranial pressure, vagal tone, cortisol, and catecholamine have all been monitored as physiological parameters in pain responses The behavior changes include voice volume (crying, weeping, moaning), facial expressions (brow bulge, eye squeeze, nasal-labial furrowing, mouth open, lip purse, stretch mouth, taut tongue, and chin quiver etc), posture (withdrawing, quivering, stiff, hand holding), alertness, feeding pattern, and interacting modes
  43. 43. 2 - 4 YEARS CNS fully developed Development of autonomy continues Significant language development Limited logic and reasoning Self-centered thought process Visual analog (Wong- Baker Faces)
  44. 44. 7 - 11 YEARS Logic and reasoning far more developed Imagination and creativity Finalism and concept of death Number pain scale (scale 1-10)
  45. 45. Adolescents (11+ years) Cognitively adults Same pain assessment methods as adults Abstract thinking and understanding hypothetical situations Emotional needs Include them in the process Respect their privacy Respect their pain reports
  46. 46.  NON-VERBAL CHILDREN FLACC Scale SCORINGCATEGORIES 0 1 2FACE No particular Occasional grimace or Frequent to constant expression or smile frown, withdrawn and frown, quivering chin disinterested and clenched jawLEGS Normal position or Uneasy ,restless Kicking or legs drawn relaxed tensed upACTIVITY Lying quietly, normal Squirming, shifting Arched, rigid or jerking position, moves easily back and forth, tenseCRY No cry (awake or sleep) Mourns or whimpers Crying steadily, Occasional complaints screams or sobs, frequent complaintsCONSOLABILITY Content , relaxed Reassured by Difficult to console or occasional touching, comfort hugging or being talked to: distractible
  47. 47.  Hospitals should use a standard pain scale for the various age groups to allow continuity. Self report scores (e.g. numerical rating scale) can mislead. A score of 4 may denote severe pain to one adolescent while 8 may be severe to another. Pain can be worsened by anxiety, depression and spiritual crisis. We must consider this in our assessment.
  48. 48. DIAGNOSTIC TESTS Radiograph: #,metastasis,stenosis,osteophytes etc. C.T: B0ny lesions MRI: Soft tissue lesions CNS Infarcts, plaques of demyelination DIAGNOSTIC BLOCKS Somatic pain decreases Central pain persists helps in diagnosis of complex regional pain syndrome(CRPS).
  49. 49.  DRUG CHALLENGES To predict drug treatment utility Helps in assessment of pain etiology Eg:- Brief iv infusion of opioid, lidocaine, phentolamine are used to • Predict opioid sensitivity in non malignant chr pain • Sensitivity to Na channel block in neuropathic pain • Assess the potential reversibility of symptoms of components of pain
  50. 50.  NEUROPHISIOLOGIC TESTS THERMOGRAPHY Increase in temp. in inflamed tissues MYELOGRAPHY Injection of radio opaque dye into SAS for seeing disc herniation, nerve root impingement , arachnoiditis, spinal stenosis DISADV: Post dural puncture head ache Meningeal irritation
  51. 51.  BONE SCANNING: Radio active compounds accumulate in the areas of bone growth / turn over SKIN BIOPSIES: Immuno-labeled to show cutaneous nerve endings painful neuropathic conditions are associated with loss of nociceptive innervation in the painful regions of the skin
  52. 52.  FUNCTIONAL BRAIN IMAGING (PET,FUNCTIONAL MRI):- Provocative findings about cortical & subcortical processing of pain informationFMRI shows pain remarkably distributed at the cortical level.
  53. 53. NEUROPHYSILOGICAL TESTING It is useful because • Helps detect underlying pathology • Helps define pain mechanics • Helps anatomically localize pain instigators • Helps focus treatment on mechanics • Helps predict if pt. will respond to particular treatment by clarifying mechanism • Used sequentially, helps monitor ds progressa nd response to treatment • May have medico legal application • Advances pain research by providing quantitative & reproducible measurements of pain & its various mechanics.
  54. 54. ELECTRODIAGNOSTIC TESTING(EMG) To diagnose PNS disorders Normal value indicates defect in CNS or Small Fiber Neuropathy It has two components NERVE CONDUCTION STUDIES (NCS) NEEDLE ELECTRODE EXAMINATION (NEE) Helps in determining severity of a lesion and prognosis
  55. 55. NERVE CONDUCTION STUDIES Electrical stimulation of nerve – measure response in nerve itself / muscle Types Motor Sensory Additional type of study – “late response” – appearance of a characteristic wave (F) and a reflex (H)
  56. 56.  Parameters to be assessed: Amplitude of the response – no. of intact neurons Latency Nerve conduction velocity integrity of myelin sheath
  57. 57.  MOTOR NCS: Stimulate motor nerve and record Compound Motor Action Potential (CMAP) from belly of the muscle innervated. Then stimulate the nerve proximally for conduction velocity
  58. 58.  SENSORY NCS:  Stimulate sensory nerve and record Sensory Nerve Action Potential (SNAP)  Stimulate median nerve at wrist and record SNAP at digital nerve of second finger. SNAP is smaller in amplitude than CMAP
  59. 59. NEEDLE ELECTRODE EXAMINATION Insert needle electrode in to muscle belly and look for electrical activity at rest & on voluntary contraction Used for the diagnosis of denervation / myopathic disorders
  60. 60. FINDINGS IN MUSCLE INJURY Relaxed muscle: o look at INSERTIONAL ACTIVITY (response to small movements of electrodes) o look for SPONTANEOUS MOVEMENTS (fasciculations, +ve sharp waves, fibrillation potentials, complex repetitive discharges, myotonic discharges)
  61. 61.  Activated muscle: o Size and shape of motor units & their firing patterns assessed Denervated muscle: o Motor units reduced in number but fire excessively fast (REDUCED REQUIREMENT)
  62. 62. FINDINGS IN MUSCLE INJURY Myotonic Dystrophy: o Large no. of motor fibers fire at a normal rate despite minimal force production(EARLY RECRUITMENT) Chronic neuropathy: o Motor units are excessively large Myopathic disorders: o Motor units are smaller than normal
  63. 63. FINDINGS IN NERVE INJURY Axonal nerve injury/Neuropathy: o NCS : reduced sensory & motor amplitudes o NCV : slightly slow o In mixed nerve injury sensory affected more than motor Demyelinating neuropathies: o NCV slowed o Distal latencies & F wave latencies- prolonged NEE: o Decreased recruitment and rapidly firing motor units o Axonal nerve:fibrillation potentials & other spont activity + o Chronic axonal neuropathy: reinnervation produces motor unit remodeling so that other motor units increase in size
  64. 64.  TIMING: more than 3 weeks after injury(wallerian degeneration must occur) after acute axonal damage CMAP amplitude begin to decrease at 3 days, peaks 7 days SNAP amplitude begins to decrease at 7 days , peaks 11 days
  65. 65. QUANTITATIVE SENSORY TESTING Tests high threshold pain and temperature sensing mechanisms. Provides information about function of entire afferent pain pathway Non invasive, simple, psychophysical tests Increased diagnostic sensitivity 67 %to 100%
  66. 66.  Common tests include:  Thermal(warm, cool, hot, cold)  mechanical: (light touch and pin prick)  Vibratory and electrical stimuli A delta- stimulated by cold perception & by HP&CP stimuli C fibers- warm perception & by HP&CP A beta- vibration
  67. 67.  Painful neuropathies- Thermal hypesthesia; hyperesthesia; hypoalgesia; hyperalgesia Peripheral sensitization - heat hyperalgesia and inflammation- CRPS-I- cold/heat hyperalgesia without hypesthesia/hyperesthesia Central sensitization: tactile allodynia, mechanical hyperalgesia Postherpetic neuralgia- thermal hypoesthesia & hyperalgesia(anesthesia dolorosa) Sympathetically mediated changes in Sudomotor pain- reflex (QSART), sweat output, & vasomotor fn.
  68. 68. THERMAL STIMULI Pain and temp sensations are closely related as they are transmitted by small high threshold fibers(A delta and C ) Computer regulates the changes in temperature on a small surface electrode placed flat against skin Thresholds measured are WS,HS,HP,CP HP felt at 45C WS/CS felt at 1 / 2 C above or below baseline
  69. 69. VIBRATION STIMULUS Large A beta fibers Head of vibration device must make solid, even, balanced contact Extra pressure alters nerve function Vibration range is 0 to 130 mic Delivers at a rate of 0.1 to 4 mic/sec
  70. 70. MECHANICAL STIMULUS Use of Von Frey Hairs (filaments) of graduated diameter If pressed on skin hard enough to cause a bend, exert a reproducible and reliable calibrated force Wt of filaments- 4.5 mg to 447 gms Expressed in terms of tension ( gm/cm ) or pressure (gm/sq cm)
  71. 71. o USES: • Changes in pain threshold(prim/second hyperalgesia) • To test summation(seen in neuropathic pain states-spinal cord injury/ post herpetic neuralgia) • Nociceptive pain states(fibromyalgia, Tm jn disorders • At least 8 repetitive pinpricks at same area with 2 to 3 sec gap causes escalation of discomfort- HYPERALGESIA
  72. 72. ELECTRICAL STIMULUS 5 Hz - C fibers 250 Hz – A beta fibers 2000 Hz – A delta fibers Current can be delivered from 0.1 to 9.99 mA
  73. 73.  USES: • Isolate nerve root pathology • Low CPT(current perception threshold)- inflmn/neuritis • Elevated CPT-neuropathy/loss of nerve function
  74. 74. AUTONOMIC TESTING ANS dysfunction is usually due to small fiber sensory neuropathy EMG is Normal.
  75. 75. SUDOMOTAR FUNCTION: Testing sympathetic pathways involved in sweating  Sympathetic Skin Response: simple, less reliable, using EMG intersubject variability & habituation of the response with repetitive stimuli- absence of response-abnormality
  76. 76.  Quantitative Sudomotor Axon Reflex Test: high sensitivity and reliability A special sweat capsule is attached to skin & Ach is iontophorsed through skin to produce skin response sweat is then collected in capsule and then quantified
  77. 77.  Thermoregulatory sweat test: Sensitive and Reliable Powder that changes color when exposed to sweat is applied all over the body allowing areas of anhidrosis to be mapped
  78. 78. CARDIOVAGAL & ADRENERGIC FUNCTION: HR response to deep breathing. HR &BP response to Valsalva maneuver & head upright tilt- detected by Symp & Parasymp fn. HR response to deep breathing determined by Parasympathetic function only.
  79. 79. Conclusions Make an accurate diagnosis If you’re not sure, consider trial of pain management Review patient goals Assess, treat, reassess, treat If unsuccessful, review type of pain and history