Perioperative Pain Management

Pre-op Pain Plan - Setting the Stage

• Comprehensive Assessment:
  • Identify risk factors for severe post-op pain (e.g., pre-existing chronic pain, anxiety, young age, type of surgery).
  • Detailed pain history: previous experiences, effective/ineffective analgesics.
  • Screen for substance use (opioids, alcohol, illicit drugs) & adjust plan accordingly.
  • Assess for OSA, renal/hepatic dysfunction.
• Introduce Multimodal Analgesia (MMA):
  • Explain concept: using different drug classes targeting multiple pain pathways.
  • Goal: ↓ opioid consumption & side effects, ↑ pain relief.
  • Components: NSAIDs, paracetamol, gabapentinoids, regional anesthesia.
• Patient Education & Expectation Setting:
  • Discuss realistic pain goals.
  • Explain pain assessment tools (e.g., NRS, VAS).
  • Address fears/misconceptions about pain medication.

⭐ Pre-emptive analgesia (administering analgesics before surgical incision) is a key component of MMA to reduce central sensitization and improve postoperative pain control. Consider pre-op celecoxib 200-400 mg or gabapentin 300-600 mg if no contraindications exist (📌 CGP - Celecoxib, Gabapentin Pre-op).

Painkiller Toolkit - The Drug Lineup

• Opioids (μ-agonists): Potent analgesics for moderate-severe pain.
  • Morphine: Gold standard; dose 0.1-0.2 mg/kg IV/IM.
  • Fentanyl: Rapid onset, short duration; 1-2 mcg/kg IV.
  • Tramadol: Weak opioid, SNRI properties; less respiratory depression.
  • Side Effects: Nausea, vomiting, constipation, respiratory depression, sedation.
• NSAIDs (COX inhibitors): For mild-moderate pain, opioid-sparing.
  • Diclofenac: 50-75 mg BD/TDS.
  • Ketorolac: Potent; max 5 days use.
  • Paracetamol (Acetaminophen): Central analgesic; 1g QDS. Max 4g/day.
  • Side Effects: GI ulcers, renal toxicity, platelet dysfunction.
  • 📌 NSAIDs: No Sympathy For Ailing Inflamed Damaged Kidneys/Stomachs.
• Adjuvants: Enhance analgesia, target specific pain types.
  • Gabapentinoids (Gabapentin, Pregabalin): Neuropathic pain.
  • Ketamine (low dose): NMDA antagonist; opioid-sparing.
  • Lidocaine infusions: Systemic analgesia, anti-inflammatory.

⭐ Ketorolac, a potent NSAID, should not be used for more than 5 days due to significant risk of GI bleeding and renal impairment, especially in elderly patients or those with pre-existing renal disease.

Nerve Blocks & Beyond - Precision Numbing

• Mechanism: Reversible Na+ channel blockade in nerve fibers, halting action potential propagation.
• Types & Examples:
  • Central Neuraxial: Spinal (intrathecal), Epidural.
  • Peripheral Nerve Blocks (PNBs):
    • Plexus: Brachial (e.g., interscalene, supraclavicular), Lumbar plexus.
    • Single Nerve: Femoral, sciatic, intercostal.
  • Fascial Plane Blocks: Transversus Abdominis Plane (TAP) block, Pectoral nerves (PECS) block.
• Local Anesthetics (LA):
  • Amides: Lignocaine, Bupivacaine (⚠️ high cardiotoxicity), Ropivacaine.
  • Esters: Procaine (higher allergic potential).
• Adjuvants (enhance analgesia/duration):
  • Epinephrine: Vasoconstriction → ↓systemic absorption, ↑duration.
  • Opioids (e.g., fentanyl, morphine), Clonidine, Dexamethasone, Ketamine.
• Complications:
  • LAST (Local Anesthetic Systemic Toxicity): CNS excitation/depression, cardiovascular collapse.
  • Nerve injury, hematoma, infection, block failure.

  ⭐ For LAST management, immediate administration of 20% lipid emulsion (Intralipid) is critical. Initial bolus: 1.5 mL/kg lean body mass over 1 minute, followed by infusion.

• Beyond Blocks: Cryoanalgesia, Radiofrequency Ablation (RFA) for chronic pain states.

Post-op Pain Patrol - Aftercare & Alerts

• Regular Assessment: Use validated scales (NRS, VAS; BPS for ventilated). Document findings.
• Monitor Vitals & Side Effects:
  • Sedation (e.g., RASS), RR (⚠️ < 10-12/min), SpO2.
  • PONV: Prophylaxis (ondansetron 4-8 mg).
  • Pruritus, constipation, urinary retention.
• Managing Inadequate Analgesia:
  • Re-evaluate pain source.
  • Optimize current regimen.
  • Rescue doses (e.g., IV morphine 1-2 mg).
  • Consider multimodal/regional techniques.
• Special Considerations:
  • Elderly: ↓ dose, ↑ interval.
  • Obese: OSA risk, cautious opioids.
  • Opioid-tolerant: Higher needs, multimodal.
• Red Flags: Uncontrolled pain, new neuro deficits, compartment syndrome signs, hemodynamic instability.

⭐ Opioid-induced respiratory depression (OIRD) is a critical concern; monitor respiratory rate (RR < 10-12/min is a warning) and sedation levels (e.g., RASS).

High‑Yield Points - ⚡ Biggest Takeaways

• Multimodal analgesia is standard: combine opioids, NSAIDs, regional blocks.
• Pre-emptive analgesia before surgery can ↓ postoperative pain intensity.
• Use NSAIDs cautiously in renal/GI disease; consider COX-2 inhibitors.
• Monitor opioids closely for respiratory depression; naloxone reverses.
• Regional techniques (epidural, nerve blocks) markedly reduce systemic opioid needs.
• PCA empowers patients but demands vigilant monitoring for safety.
• Gabapentinoids (pregabalin, gabapentin) help manage neuropathic pain and ↓ opioid consumption.