Acute Pain Management

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Acute Pain Management: Intro & Assessment - Ouch Meter Reading

  • Acute Pain: Sudden onset, typically <3 months, direct result of tissue injury. Serves a protective biological function.
    • Types: Nociceptive (somatic, visceral), Neuropathic.
  • Pain Assessment: Crucial for diagnosis, guiding treatment, and monitoring efficacy.
    • PQRST Mnemonic (📌): Provocation/Palliation, Quality, Radiation, Severity, Timing.
    • Self-Report Scales (Gold Standard):
      • Numeric Rating Scale (NRS): Score 0 (no pain) to 10 (worst imaginable pain).
      • Visual Analog Scale (VAS): 100mm line, patient marks pain level.
      • Faces Pain Scale-Revised (FPS-R): For children or those with communication difficulties. Various Pain Assessment Scales
    • Behavioral Scales (Non-verbal patients):
      • FLACC Scale: Face, Legs, Activity, Cry, Consolability (children 2 months - 7 years).
      • CPOT: Critical-Care Pain Observation Tool (adult ICU patients).

⭐ Self-report of pain is the most reliable indicator; always attempt to elicit it if possible, even in challenging patient populations (e.g., mild cognitive impairment).

Acute Pain Management: Pharmacotherapy - Painkiller Parade

  • WHO Analgesic Ladder: Guides drug selection.
  • Non-Opioids:
    • Paracetamol (PCM): Analgesic, antipyretic. Max 4g/day. Risk: Hepatotoxicity.
    • NSAIDs (e.g., Ibuprofen, Diclofenac): COX inhibitors; anti-inflammatory.
      • Max: Ibuprofen 2.4g/day, Diclofenac 150mg/day.
      • S/E: GI ulcers, renal toxicity, ↑CV risk. 📌 NSAID: No pee, Stomach ulcers, Asthma, Increased bleeding, Dyspepsia.
  • Weak Opioids:
    • Tramadol: Max 400mg/day. SNRI activity; lowers seizure threshold.
    • Codeine: Prodrug (CYP2D6 to morphine); antitussive.
  • Strong Opioids: Morphine, Fentanyl, Pethidine.
    • Morphine: Gold standard. Oral:IV approx 1:3. Active metabolites M6G (analgesic), M3G (neurotoxic).
    • Fentanyl: Potent (80-100x morphine). IV, transdermal; rapid onset, short duration.
    • Pethidine: Norpethidine (neurotoxic metabolite). Max 600mg/24h for <48h. Avoid in renal failure/elderly.
    • S/E: Nausea, vomiting, constipation, sedation, respiratory depression (reverse with Naloxone).
  • Adjuvants: Enhance analgesia or treat specific pain types.
    • e.g., Gabapentinoids (Gabapentin, Pregabalin) for neuropathic pain; Amitriptyline (TCA); Ketamine (NMDA antagonist) for opioid-sparing.

WHO Pain Ladder Update

⭐ Pethidine is contraindicated with MAO inhibitors due to high risk of serotonin syndrome or hypertensive crisis.

Acute Pain Management: Regional Techniques - Zone Defense

  • Goal: Localized analgesia by blocking nerve transmission.
  • Peripheral Nerve Blocks (PNBs):
    • Upper Limb: Interscalene, Supraclavicular, Axillary (Brachial Plexus).
    • Lower Limb: Femoral, Sciatic, Popliteal.
    • Truncal: TAP (Transversus Abdominis Plane), Paravertebral, Intercostal.
  • Neuraxial Analgesia:
    • Epidural: Thoracic/Lumbar; continuous via catheter.
    • Spinal (Intrathecal): Single shot; rapid, dense block.
  • Agents: Local Anesthetics (e.g., Bupivacaine, Ropivacaine); Adjuvants (e.g., epinephrine, dexmedetomidine) prolong duration.
  • Benefits: Superior pain relief, opioid-sparing, ↓PONV (Postoperative Nausea and Vomiting), early mobilization.
  • Risks: LAST (Local Anesthetic Systemic Toxicity), nerve injury, hematoma, infection.

⭐ Epidural analgesia is a gold standard for labor analgesia and post-thoracotomy pain.

  • 📌 LAST early CNS signs: Metallic taste, Numbness (oral/tongue), Tinnitus, Dizziness, Visual disturbances (Mnemonic: My New Telephone Doesn't Vibrate).

USG-Guided Brachial Plexus Blocks

Acute Pain Management: Special Contexts & Adjuncts - Tricky Pains & Tricks

  • Special Contexts: Post-op (ERAS), Trauma, Burns, Pancreatitis.
  • Key Adjuncts (Multimodal Analgesia - MMA):
    • Ketamine (low-dose): 0.1-0.3 mg/kg IV; anti-hyperalgesic, useful in opioid tolerance.
    • Gabapentinoids (Gabapentin, Pregabalin): Neuropathic pain component.
    • IV Lidocaine: 1-2 mg/kg/hr (max 3-5 mg/kg); anti-inflammatory, Na+ channel blocker.
    • Alpha-2 agonists (Dexmedetomidine, Clonidine): Opioid-sparing.
  • Tricky Pains: Neuropathic pain, Opioid-tolerant patients, Opioid-Induced Hyperalgesia (OIH).
  • Tricks & Strategies:
    • Preventive & preemptive analgesia.
    • Regional anesthesia/analgesia (nerve blocks, epidurals).
    • Non-pharmacological: TENS, cryotherapy.

⭐ Low-dose ketamine infusion is a valuable adjunct in managing acute pain in opioid-tolerant patients and can prevent OIH.

Postoperative Pain Management Pathway

High‑Yield Points - ⚡ Biggest Takeaways

  • Multimodal analgesia is key: combines NSAIDs, opioids, paracetamol, and regional techniques.
  • NSAIDs (e.g., Ketorolac): potent; watch for renal, GI, and bleeding risks.
  • Opioids (Morphine, Fentanyl): for severe pain; monitor respiratory depression, sedation, PONV.
  • Paracetamol: safe baseline analgesic; vital in multimodal regimens. Max dose 4g/day.
  • Regional anesthesia (epidurals, nerve blocks): superior pain relief, opioid-sparing, better outcomes.
  • PCA (Patient-Controlled Analgesia): empowers patients, effective opioid titration, improves satisfaction.
  • Ketamine (low-dose) and Gabapentinoids are useful adjuncts, reducing opioid needs.

Practice Questions: Acute Pain Management

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All of the following can be routes of opioid administration except:

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Flashcards: Acute Pain Management

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TENS is contraindicated in patients with _____

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TENS is contraindicated in patients with _____

pacemakers

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