A 67-year-old man with a advanced multiple myeloma is brought to the office due to progressively increasing generalized weakness and altered mental status for 5 days. He currently takes acetaminophen, naproxen, and a fentanyl patch for pain. Temperature is 36.5 C (97.7 F), blood pressure is 120/70 mm Hg, and pulse is 68/min. Examination shows no focal findings. Laboratory results are as follows: Which of the following is the most likely explanation for this patient's altered mental status?

Question

A 67-year-old man with a advanced multiple myeloma is brought to the office due to progressively increasing generalized weakness and altered mental status for 5 days.  He currently takes acetaminophen, naproxen, and a fentanyl patch for pain.  Temperature is 36.5 C (97.7 F), blood pressure is 120/70 mm Hg, and pulse is 68/min.  Examination shows no focal findings.  Laboratory results are as follows: Which of the following is the most likely explanation for this patient's altered mental status?

Quizplus · Accepted Answer

Explanation: This patient has uremia, presenting with a severely elevated creatinine level and altered mental status. Uremia is characterized by fluid, electrolyte, and metabolic abnormalities due to reduced renal clearance of uremic toxins. It is most common in patients with a creatinine clearance <10 mL/min (generally corresponding to serum creatinine >7 in most patients) and blood urea nitrogen >50 mg/dL. Typical symptoms include anorexia, vomiting, confusion, and lethargy. Electrolyte abnormalities (eg, hyperkalemia) and acidosis may also be seen. Renal failure is a frequent complication of multiple myeloma due to light-chain nephropathy and hypercalcemia. It is likely exacerbated in this patient by use of nonsteroidal anti-inflammatory drugs (eg, naproxen). In the setting of acute renal failure, opioid use can cause altered mental status because certain opioids (eg, morphine, tramadol) have active metabolites that can accumulate in patients with renal insufficiency; however, fentanyl is metabolized primarily by the liver to inactive metabolites and is generally well tolerated in patients with renal insufficiency (Choice A). certain opioids (eg, morphine, tramadol (Choice B) Hypercalcemia occurs in multiple myeloma due to osteoclast activation and increased bone resorption. Although patients with severe hypercalcemia (eg, >14 mg/dL) can have altered mental status, this patient's mildly elevated calcium level is not severe enough to cause his change in mental status. (Choice C) Hyponatremia can cause weakness and altered mental status. However, patients are not usually significantly symptomatic until levels are <120-125 mEq/L. This patient's level of 129 mEq/L may cause mild fatigue but would be unlikely to significantly alter mental status. (Choice D) Metastatic brain lesions can cause altered mental status due to mass effect and surrounding vasogenic edema. However, headaches and focal neurologic deficits are frequently present. In addition, although many solid tumors (eg, breast, lung) can metastasize to the brain, multiple myeloma does not. Educational objective: Severe renal impairment can cause altered mental status due to uremia. Although opioid use can also cause altered mental status in the setting of acute renal failure, it typically occurs with opioids that are dependent on renal clearance and/or have active metabolites (vs fentanyl, which has inactive metabolites). References: Opioid management in older adults with chronic kidney disease: a review. (http://www.ncbi.nlm.nih.gov/pubmed/31295441) A systematic review of the use of opioid medication for those with moderate to severe cancer pain and renal impairment: a European Palliative Care Research Collaborative opioid guidelines project. (http://www.ncbi.nlm.nih.gov/pubmed/21708859)

A 67-Year-Old Man with a Advanced Multiple Myeloma Is Brought