Pain Management
Acute Pain: Treating Opioid-Related Adverse Effects

Opioid side effects:

  • Acute use: nausea, vomiting, itching (pruritus), sedation/respiratory depression, death.
  • Chronic use: constipation, delirium, and myoclonus, and drug dependence.

Post-operative Nausea and Vomiting (PONV)

  • PONV occurs in approximately 30% of all post-op patients
  • PONV risk factors include: female gender, non-smoker, prior PONV, post-op opioid use
    • Having no risk factors yield a risk of 10%, one risk factor raises it to 20% and each additional risk factor adds 20% risk (up to 80%)
  • Risk reduction:
    • Avoid general anesthesia if possible
    • Use propofol for general anesthetic maintenance rather than volatile anesthetics and N2O.
    • Minimize use of neostigmine and postoperative opioids (multimodal analgesia facilitates latter.
    • Use prophylactic anti-emetics (no more than 2 of the drugs are combined at once)

Prophylaxis and treatment of PONV:

Prophylactic use of antiemetics for patients at high risk for PONV

Treating Established PONV

(Note: Must wait 6 hours before re- administering a medication already used prophylactically)

Potential side-effects

Dexamethasone 4 mg

Not usually used for established PONV

None noted with single dose of 4 mg. Potential risk of tumor lysis syndrome in at risk patients.

Ondansetron 4 mg

1 mg every 6 hours as needed.

Headache, elevated liver enzymes, constipation QTc prolongation.

Haldol 0.5-1mg

Droperidol is not usually used for established PONV

QTc prolongation with high doses

Dimenhydrinate 12.5-25 mg

Dimenhydrinate 12.5-25 mg every 4 hours as needed

Sedation


Pruritus

  • Rare. Diphenhydramine administration is sufficient.

Sedation/Respiratory Depression

  • Suspect the potentially fatal respiratory depression if RR <10 breaths/min and heavy sedation
  • Patients at risk for respiratory depression are patients without previous exposure to opioids, and those with respiratory disorder (e.g. OSA and asthma)
  • Tx: Hold opioids, administer naloxone (opioid antagonist) in small doses (0.04mg q3min) until the respiratory rate increases and/or sedation is reduced.
    • Naloxone is short-acting, therefore observe patients for rebound depression, especially if long-acting opioid was given

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