Pain Management in Emergency

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Pain Assessment & Principles - Ouch Meter!

⭐ Pain is the "Fifth Vital Sign". Prompt assessment & management are critical in emergencies.

  • Define Pain: Unpleasant sensory/emotional experience associated with actual/potential tissue damage.
  • Types: Nociceptive (somatic, visceral), Neuropathic (nerve injury).
  • Assessment Tools:
    • 📌 PQRST mnemonic: Provocation/Palliation, Quality, Region/Radiation, Severity, Timing.
    • Scales: Numeric Rating Scale (NRS 0-10), Visual Analog Scale (VAS), Wong-Baker FACES (children), FLACC (non-verbal). Wong-Baker FACES Pain Rating Scale
  • Stepwise Analgesia (WHO Ladder Adaptation):
  • Principles: Treat early, use multimodal approach (combine drug classes), titrate to effect.

Non-Opioid Analgesics - Gentle Giants

  • Paracetamol (PCM)
    • MOA: CNS prostaglandin inhibitor.
    • Use: Pain, fever.
    • Dose: 1g q6h (Max 4g/day).
    • ⚠️ Hepatotoxic: >10g or >150mg/kg.
  • NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)
    • MOA: COX inhibition.
    • Use: Pain, inflammation.
    • CI: Peptic ulcer, renal/HF, asthma, 3rd trim preg.
    • SE: GI bleed, renal tox, CV risk. 📌 No ulcers, Sticky blood, Asthma, Impaired renal, During pregnancy (avoid 3rd trim).
    • Examples (Max daily):
      • Ibuprofen: 400-600mg q6h (2.4g).
      • Diclofenac: 50mg q8h (150mg).
      • Ketorolac: 15-30mg IV q6h (120mg, ≤5 days).
      • Mefenamic Acid: 250-500mg q8h (1.5g).

    ⭐ Ketorolac: Opioid-level analgesia (renal colic); use ≤5 days (GI/renal risk).

Opioid Analgesics - Mighty Morphers

Mechanism: Bind to μ (primary), κ, δ opioid receptors in CNS & periphery, modulating pain perception. For severe acute pain.

  • Key Opioids (IV Route in ER):
    • Morphine: Gold standard. Onset 5-10min, duration 3-4h.
    • Fentanyl: Potent (80-100x Morphine). Onset 1-2min, duration 30-60min.
    • Pethidine: Less potent than Morphine. Risk of norpethidine toxicity (seizures), esp. renal failure. (75-100mg IM ≈ Morphine 10mg IM).
  • Side Effects (SE): Respiratory depression (monitor!), N/V, sedation, constipation, miosis. 📌 MORPHINES (common side effects).
  • Reversal: Naloxone 0.4-2mg IV, repeat q2-3min (max 10mg). Titrate to reverse respiratory depression, not analgesia.

⭐ > Fentanyl's rapid onset and short duration make it ideal for procedural sedation and analgesia.

Endogenous Opioid Neurotransmitters and Receptor Effects

Local Anesthesia & Blocks - Numb Zone

  • Mechanism: Reversibly block $Na^+$ channels in nerve membranes, inhibiting action potential propagation.

  • Common ER Blocks: Digital nerve block (fingers/toes), dental blocks (inferior alveolar), wound infiltration for suturing, hematoma blocks for fracture reduction.

  • Key Agents:

    AgentOnsetDurationMax Dose (Plain)Max Dose (+Adrenaline)Notes
    LidocaineRapidMod (1-2h)4.5mg/kg7mg/kgVersatile, common
    BupivacaineSlowerLong (4-8h)2mg/kg2.5mg/kgPotent, ↑cardiotoxicity risk
  • LA Systemic Toxicity (LAST):

    • Early: Tinnitus, metallic taste, perioral numbness.
    • 📌 SAMS: Slurred speech, Altered CNS (agitation, drowsiness), Muscle twitching, Seizures.
    • Severe: Arrhythmias, cardiovascular collapse.
    • Management: Stop LA, ABCs (airway, O2), IV Benzodiazepines for seizures.

⭐ Lipid emulsion therapy (Intralipid 20%) is the specific antidote for severe LAST, especially with Bupivacaine.

Digital nerve block injection sites and landmarks

Adjuncts & Special Cases - Tricky Treats

  • Ketamine: Dissociative analgesia.
    • Sub-dissociative (pain): 0.1-0.3 mg/kg IV.
    • Procedural sedation: 1-2 mg/kg IV.

⭐ Sub-dissociative dose ketamine provides effective analgesia without significant psychomimetic side effects or respiratory depression.

  • Nitrous Oxide (N₂O): Rapid inhalational analgesia (e.g., Entonox 50:50).
  • Adjuvants: Benzodiazepines (muscle spasm); Antiemetics (nausea).
  • Special Populations:
    • Pediatrics: Strict weight-based dosing; paracetamol preferred.
    • Geriatrics: ↓ doses (polypharmacy, ↓ metabolism).
    • Pregnancy: Paracetamol safe; NSAIDs avoid (3rd trimester).

High‑Yield Points - ⚡ Biggest Takeaways

  • Opioids (morphine, fentanyl) for severe acute pain; monitor respiratory depression.
  • NSAIDs (ketorolac) for mild-moderate pain (musculoskeletal); risk GI bleed, renal injury.
  • Paracetamol for mild-moderate pain & as adjunct; hepatotoxicity in overdose.
  • Low-dose ketamine: potent analgesia without respiratory depression; ideal for trauma.
  • Regional nerve blocks: targeted pain relief, reduce systemic opioid needs.
  • Nitrous oxide: rapid analgesia/anxiolysis for short painful procedures.
  • Always assess pain score (VAS) and reassess post-intervention_._

Practice Questions: Pain Management in Emergency

Test your understanding with these related questions

A female was given morphine sulphate during labour for pain but she developed respiratory distress. Which of the following will be the correct antidote?

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Flashcards: Pain Management in Emergency

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What is the next treatment step of opioid intoxication after airway maintenance?_____

TAP TO REVEAL ANSWER

What is the next treatment step of opioid intoxication after airway maintenance?_____

Administering Naloxone

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