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Post-Operative Pain Management

Definition

Acute pain arising after surgery, resulting from tissue injury, inflammation, and nociceptive/neuropathic pathways.

  • Numeric Rating Scale (NRS 0–10) for verbal adults.
  • Critical Care Pain Observation Tool (CPOT) or FLACC scale for non-verbal or pediatric patients.
  • Uncontrolled pain worsens outcomes: delayed ambulation, pulmonary complications, delirium, and chronic pain syndromes.

I. Principles

  • Multimodal therapy is standard: combine non-opioids, opioids, and regional techniques.
  • Oral > IV whenever feasible.
  • Start least invasive, escalate stepwise.
  • Always rule out dangerous causes of pain: peritonitis, bleeding, anastomotic leak, compartment syndrome, ischemia.
  • Regular reassessment: q2–4h depending on setting.
  • Prevent complications: constipation, oversedation, delirium, respiratory depression.
  • Tailor to special populations: frail, elderly, renal/hepatic impairment, pediatrics, opioid-tolerant patients.

II. Stepwise Framework

Step 1: Scheduled Non-Opioids (baseline for all unless contraindicated)

  • Acetaminophen
  • 650 mg PO q6h OR 1 g PO/IV q6–8h

  • Max: 4 g/day (≤3 g in frail, liver disease, alcohol use).

  • NSAIDs (avoid in renal impairment, GI ulcer, coagulopathy, or fresh anastomosis)

  • Ketorolac 15–30 mg IV q6h (max 5 days).

  • Ibuprofen 400–600 mg PO q6h.

  • Adjuncts

  • Gabapentin 100–300 mg PO qHS (titrate to 300 TID; renal adjust).
  • Robaxin (methocarbamol) 500–1000 mg PO/IV q8h PRN.
  • Flexeril (cyclobenzaprine) 5–10 mg PO TID PRN.
  • Lidocaine patches (12h on/12h off) for incisional pain.

Step 2: PRN Oral Opioids (breakthrough pain)

  • Oxycodone IR 5–10 mg PO q4–6h PRN.
  • Hydromorphone PO 2–4 mg PO q4–6h PRN.
  • Hydrocodone/APAP (Norco 5/325 mg) 1–2 tabs PO q6h PRN (track acetaminophen total).
  • Tramadol 50 mg PO q6h PRN (max 400 mg/day; serotonin syndrome risk with SSRIs/SNRIs).

Step 3: IV Opioids (if NPO, severe pain, or unable to tolerate PO)

  • Hydromorphone 0.2–0.5 mg IV q2–3h PRN.
  • Morphine 1–2 mg IV q2–3h PRN (avoid in renal impairment).
  • Fentanyl 25–50 mcg IV q1–2h PRN (short acting).

Step 4: Escalation / Severe or Refractory Pain

  • PCA (Patient-Controlled Analgesia):
  • Hydromorphone: 0.2 mg demand, lockout 8–10 min, no basal in opioid-naïve.
  • Morphine: 1 mg demand, lockout 8–10 min.

  • Add basal infusion only if opioid-tolerant or ICU monitored.

  • Acute Pain Service consult for uncontrolled pain, opioid tolerance, or consideration of regional/epidural techniques.

  • Regional / Neuraxial:

  • Epidural infusion (thoracic/lumbar).
  • TAP block or wound infusion catheter.
  • Coordinate with anesthesia/pain service.

III. Monitoring & Safety

  • Assessment frequency:
  • Floor: q4h.

  • ICU: q2h (NRS or CPOT if non-verbal).

  • Side effect management:

  • Nausea → ondansetron 4 mg IV/PO q8h PRN.
  • Constipation → senna scheduled ± miralax.
  • Pruritus → diphenhydramine or nalbuphine.

  • Respiratory depression → naloxone 0.1–0.2 mg IV q2–3 min PRN (max 0.8 mg).

  • Special populations:

  • Elderly/frail → lower doses, slower titration.
  • Renal impairment → avoid morphine, adjust gabapentin, avoid ketorolac.
  • Hepatic impairment → acetaminophen max ≤2–3 g/day.

IV. Pediatric Considerations

  • Pain assessment tools: FLACC (Face, Legs, Activity, Cry, Consolability), Wong-Baker FACES, Numeric scale (if verbal).

  • Non-pharmacologic adjuncts: parental presence, distraction (music, video), comfort positioning.

  • Stepwise regimen (weight-based):

  • Acetaminophen: 10–15 mg/kg PO/IV q6h (max 75 mg/kg/day, not exceeding 4 g).
  • Ibuprofen: 5–10 mg/kg PO q6–8h (avoid <6 months or renal/GI risk).
  • Opioids:
    • Morphine 0.05–0.1 mg/kg IV q2–4h PRN.
    • Hydromorphone 0.01–0.02 mg/kg IV q3–4h PRN.
    • Oxycodone 0.05–0.15 mg/kg PO q4–6h PRN.

  • Avoid codeine & tramadol (variable metabolism, black box warning).

  • Regional techniques: caudal block, epidural, nerve blocks often used safely in pediatrics.

  • Cautions: infants <6 months at higher risk of respiratory depression.

V. Red Flags / Urgent Triggers

  • Disproportionate pain to expected course.
  • Sudden severe pain with instability → consider hemorrhage, anastomotic leak, perforation.
  • New focal deficits → compartment syndrome, ischemia, nerve injury.
  • Opioid-induced oversedation or respiratory depression.

VI. Intern Pearls

  • Always schedule acetaminophen + NSAID unless contraindicated.
  • Opioids should be PRN, not scheduled.
  • Always reassess vitals and pain after each escalation step.
  • Disproportionate pain = work up for complication, not just medicate.
  • In ICU: prioritize analgesia over sedation.
  • If delirium develops: reduce opioids/benzos, add delirium precautions.

VII. Summary Tables

Non-Opioids

Drug Dose / Route Notes / Cautions
Acetaminophen 650 mg PO q6h OR 1 g IV q6–8h Max 4 g/day (≤3 g in liver dz)
Ketorolac 15–30 mg IV q6h (≤5 days) Avoid renal/GI/bleeding risk
Ibuprofen 400–600 mg PO q6h Avoid GI ulcer, renal impairment
Gabapentin 100–300 mg PO qHS → TID Renal adjust
Robaxin 500–1000 mg IV/PO q8h PRN Limit IV ≤3 days, avoid severe renal impairment
Flexeril 5–10 mg PO TID PRN Oversedation risk
Lidocaine patch Apply over incision, 12h on/12h off Useful for incisional pain

Opioids

Drug Dose / Route Notes / Cautions
Oxycodone IR 5–10 mg PO q4–6h PRN 1st-line oral opioid
Hydromorphone PO 2–4 mg PO q4–6h PRN Stronger oral option
Hydrocodone/APAP 1–2 tabs PO q6h PRN Track total APAP dose
Tramadol 50 mg PO q6h PRN (max 400 mg/day) Risk serotonin syndrome
Hydromorphone IV 0.2–0.5 mg IV q2–3h PRN Preferred IV opioid
Morphine IV 1–2 mg IV q2–3h PRN Avoid in renal impairment
Fentanyl IV 25–50 mcg IV q1–2h PRN Short acting
PCA (Hydromorphone) 0.2 mg demand, lockout 8–10 min No basal if opioid-naïve
PCA (Morphine) 1 mg demand, lockout 8–10 min Basal only if opioid-tolerant

VIII. References

  • Barr J, Fraser GL, Puntillo K, et al. Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the ICU. Crit Care Med. 2013;41(1):263–306.
  • Devlin JW, Skrobik Y, Gélinas C, et al. PADIS Guidelines (Pain, Agitation/Sedation, Delirium, Immobility, Sleep). Crit Care Med. 2018;46(9):e825–e873.
  • El Moheb M. Use of Opioids in the Postoperative Period. In: Current Surgical Therapy, 14th ed. Elsevier, 2023.
  • Washington Manual of Surgery, 9th ed. LWW, 2024.
  • American Pediatric Surgical Association (APSA) & American Pain Society pediatric recommendations (consensus-based).