FRCA Notes

Assessment of Pain

The curriculum requires us to be able to assess both acute and chronic pain, the latter in a "basic" fashion.

Resources

  • Assessment of pain should begin with a thorough history and examination
  • Factors which a pain history should elucidate include:
    • Site | character | intensity | factors associated with onset of the pain
    • Associated symptoms
    • Treatment to date; current and previous medication, dose, frequency, efficacy and side-effects
    • Functional impact:
      • Effect on sleep and ADLs
      • Coping strategies including pain beliefs and concurrent psychiatric disorders
    • Relevant medical history
  • Most measures of pain involved self-reporting, which is in keeping with the individualised, subjective nature of pain
  • Although self-reporting is sensitive and consistent, it suffers when there are impairments to cognitive function including communication

  • Other measures of pain severity involve:
    • Physiological measurements e.g. plasma cortisol, HR, BP
    • Objective measurements of behaviour e.g. mechanical withdrawal, facial expression, ambulation
    • Assessment of analgesia use e.g. cumulative opioid dose

  • Regular measurement of pain intensity as part of routine patient observations allows appropriate therapy and escalation in the event of refractory pain

  • Generally, acute pain scoring systems are one-dimensional
  • They assess the intensity in pain ± the degree of pain relief
  • Pain scales can be sub-classified as either categorical or numerical
  • Issues include:
    • Perhaps less reliable and valid than we think they are
    • No one tool is superior to another for measurement of post-operative pain
    • Do not assess functional pain, which is a more important marker with respect to developing perioperative complications

Numerical

  • Visual analogue scale
    • Uses a 100mm horizontal line upon which the patient draws a mark to indicate their pain intensity
    • Score is distance from the left in mm
    • A reduction in pain intensity of 30% is clinically meaningful to patients
    • Gold standard in pain research

  • Numerical rating scale
    • Use of a 'comfort' scale instead of the classic NRS did not reduce post-operative opioid use (BJA, 2024)

    Advantages Disadvantages
    Reliable Relies on patient understanding
    Validated Relies on patient communication
    Sensitive to change Doesn't adjust for existing/chronic pain
    Easy to utilise Doesn't adjust for cultural differences

Categorical

  • Verbal rating scale (no pain | mild | moderate | severe)
    • Correlates well with VAS

Dynamic (functional) pain

  • Assessment of acute pain at rest is important for ensuring patient comfort
  • Dynamic (functional) pain arises during mobilisation, deep breathing and coughing
  • Assessing, and ensuring adequate analgesia to combat dynamic pain is more important for reducing risk of post-operative cardiopulmonary and thromboembolic complications
  • There is a paucity of robustly evidenced-based tools for assessing functional pain

  • Chronic pain requires multi-dimensional measurements
  • These include dimensions for:
    • Sensory
    • Cognitive
    • Psychosocial

Chronic pain assessments

  • McGill Pain Questionnaire
    • Three major dimensions
      1. Sensory - discriminative
      2. Motivational - affective
      3. Cognitive - evaluative

  • Brief Pain Inventory
    • 17-item self-rating scale
    • Validated for the assessment of pain in a wide range of chronic syndromes
    • Requires patient to indicate site(s) of pain by shading a body diagram

Other assessments in chronic pain

  • Measurement of anxiety and depression e.g. GAD-9, PHQ-9, HADs
  • Pain coping - Pain Catastrophising Scale
  • Pain beliefs/attitudes - Chronic Pain Acceptance Questionnaire, Pain Self-Efficacy Questionnaire
  • Health-related QoL - EQ5D instrument
  • Pain-related function assessment - Pain disability index

  • Specialised scales for screening for neuropathic pain:
    • PainDETECT
    • Neuropathic Pain Score
    • LANSS; Leeds Assessment of Neuropathic Symptoms and Signs
    • Doleur Neuropathique en 4 (DN4)
  • Although developed as a neuropathic pain screening tool, the LANSS can be used to detect treatment effect i.e. reduction in LANSS after treatment

  • Many of the above scales are validated in cancer pain/palliative medicine
  • There are also specific instruments for assessing pain, functional disability and other symptoms in palliative care
  • Examples include:
    • Memorial Symptom Assessment Scale (MSAS)
    • Memorial Symptom Assessment Scale Short Form (MSAS-SF)
    • Edmonton Symptom Assessment System
    • Rotterdam Symptom Checklist
    • Symptom Distress Scale

  • Abbey pain score
  • PAINAD
  • Dolopus-2
  • MOBID-2
  • Checklist of non-verbal pain indicators

  • Pain on ITU is polyfactorial, including:
    • Pathological e.g. trauma, burns, surgery
    • Iatrogenic e.g. lines, drains, positioning, wound care

    Detrimental effects of pain in ITU
    Distress for patients, their families and staff
    Sympathetic activation can cause type 2 MI
    Increased delirium
    Increased LOS
    Worse outcomes

  • PADIS guidelines suggest pain should be routinely assessed in all ITU patients using:
    • General observations / examination findings
    • The critical care pain observation tool (CCPOT)
    • Behavioural pain scale