Examkin

Question

Difficulty: MediumEnd-of-Life and Palliative Care

An 81-year-old male with metastatic prostate cancer is evaluated on the oncology unit for acute confusion, severe agitation, and sudden jerking movements of his extremities. The patient was admitted earlier today for worsening bone pain. His home medications include extended-release morphine 60 mg twice daily and immediate-release morphine 15 mg every 4 hours as needed. According to his wife, he has been taking the as-needed morphine around the clock for the past week. He has a history of chronic kidney disease with a baseline serum creatinine of 1.5 mg/dL. Vital signs include a temperature of 37.1°C (98.8°F), blood pressure of 135/85 mmHg, pulse of 92/min, and respirations of 16/min. Physical examination reveals a restless, disoriented patient exhibiting frequent, involuntary, shock-like muscle contractions throughout all four limbs. Recent laboratory studies demonstrate a serum creatinine level of 3.6 mg/dL. Which of the following is the most appropriate next step in the management of this patient?

  1. Rotate the analgesic regimen to fentanylAnswer
  2. B
    Administer intravenous naloxone
  3. C
    Initiate scheduled haloperidol and maintain the current morphine dose
  4. D
    Order a noncontrast computed tomography scan of the head
  5. E
    Transfer the patient to an inpatient psychiatric facility for acute psychosis management

Answer

Rotate the analgesic regimen to fentanyl
The correct answer is to rotate the analgesic regimen to fentanyl. This patient is exhibiting classic signs of opioid-induced neurotoxicity (OIN), which typically include altered mental status, severe agitation, hyperalgesia, and myoclonus (sudden, shock-like muscle contractions). This condition frequently occurs when high doses of opioids, particularly morphine, are administered to patients with underlying renal impairment. Morphine is metabolized in the liver to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), which are then renally excreted. In the setting of acute kidney injury (as evidenced by this patient's elevated serum creatinine of 3.6 mg/dL), M3G accumulates and acts as a neuroexcitatory agent, precipitating OIN. The definitive treatment for OIN is to decrease the dose of the opioid, provide hydration to aid in clearance, or perform an opioid rotation. When rotating opioids in the setting of severe renal impairment, fentanyl or methadone are preferred because they do not have active metabolites that depend on renal clearance. Therefore, discontinuing morphine and rotating to fentanyl is the safest and most effective next step to control his bone pain while allowing the neurotoxicity to resolve.

Step-by-Step Solution

1
Identify the patient's primary condition based on symptoms.
The acute confusion, severe agitation, and myoclonus (shock-like muscle contractions) are classic signs of opioid-induced neurotoxicity (OIN).
Recognizing OIN is necessary to address the root pharmacological cause rather than just treating superficial psychiatric symptoms.
2
Determine the underlying pharmacokinetic cause of the toxicity.
The acute kidney injury (creatinine 3.6 mg/dL) has impaired the clearance of morphine-3-glucuronide, a neuroexcitatory metabolite of morphine.
Understanding the mechanism dictates which analgesic alternatives are safe to use.
3
Select the most appropriate management strategy.
Rotating the pain regimen to an opioid without active renally-cleared metabolites is indicated.
Fentanyl and methadone are preferred in severe renal impairment because they do not form neurotoxic metabolites that accumulate during renal failure.

Key Concept

Opioid-induced neurotoxicity presents with confusion, myoclonus, and hyperalgesia, frequently triggered by the accumulation of active metabolites (e.g., morphine-3-glucuronide) in patients with acute kidney injury; management requires opioid rotation to a safer agent like fentanyl or methadone.
Estimated Time:1m 0s
Rate this question

Topics

End-of-Life and Palliative Care

More questions from this topic