Defining Pain and Its Anatomy

Defining Pain

• Pain is a subjective, unpleasant sensory and emotional experience associated with actual or potential tissue damage.
• It involves sensory, emotional, cognitive, and social components, reflecting a person's apprehension of threat to their bodily or existential integrity.
• Pain and nociception are distinct; pain cannot be solely inferred from sensory neuron activity.
• Individual experiences shape the understanding of pain.
• A person's report of pain should be respected.
• While usually adaptive, pain can negatively impact function and well-being.
• Pain expression can be verbal or nonverbal; inability to communicate doesn't negate pain experience.

Anatomy and Physiology of Pain

• Nociceptors are receptors responding to potentially harmful stimuli (mechanical, thermal, chemical). They are a defense mechanism.

Types of Pain

• Somatic Pain: Localized pain originating from skin, mucous membranes, muscles, or joints. Can be superficial (skin) or deep (muscles, joints), often mechanical or thermal, with rapid onset.
• Visceral Pain: Pain from internal organs, difficult to localize, often described as deep, throbbing, or aching. Can cause referred pain and symptoms like nausea and vomiting.
• Neuropathic Pain: Pain caused by nerve damage, independent of nociception. Can result from trauma, surgery, chemotherapy, or cancer. Conditions include diabetes, phantom limb pain, carpal tunnel syndrome, and herniated discs.

Recognizing Pain

Physical Signs of Pain:

• Tachycardia
• Hypertension
• Tachypnoea
• Diaphoresis
• Pallor
• Decreased peripheral circulation
• Pupil dilation

Patient Cues of Pain:

• Facial expressions (e.g., grimacing, pursed lips)
• Vocalizations (e.g., crying, moaning)
• Body language (e.g., guarding, restlessness, withdrawal)
• Behavioral changes (e.g., agitation, combativeness, insomnia, poor appetite)

Pain Assessment

• Patient self-report is the gold standard.
• Basic pain assessment is integrated into NEWS charts.
• Scales like visual analogue scales (VAS) and the Abbey Pain Scale are used for patients with difficulty verbalizing pain. The "Mild, Moderate, Severe" approach is used for initial assessments.
• The PQRST mnemonic helps assess pain characteristics:
  • Provoking/Palliating factors
  • Quality of pain
  • Region and radiation
  • Severity
  • Time course

Pain Management

Pharmacological Management:

• Regular and PRN (as needed) analgesics are administered via various routes (PO, TOP, PR, SC, IM, IV).
• Continuous administration (e.g., syringe drivers, in intensive care units) and Patient-Controlled Analgesia (PCA) are used.
• ‘Stat’/‘Bolus’ doses and time-critical medications (e.g., morphine sulphate tablets) are used as needed.
• The WHO analgesic ladder guides opioid and non-opioid analgesic choices based on pain severity (mild to severe):
  • Step 1: Non-opioid analgesics (e.g., paracetamol, NSAIDs)
  • Step 2: Weak opioids (e.g., codeine) +/- non-opioid +/- adjuvant
  • Step 3: Strong opioids (e.g., morphine) +/- non-opioid +/- adjuvant

Non-Pharmacological Management:

• Mobilization
• Thermotherapy (heat, cold)
• Physiotherapy
• Hydrotherapy
• Osteopathy
• Acupuncture
• Regular repositioning
• Meditation
• Yoga