A 34-year-old homeless man is brought to the emergency department in a confused state and complaining of flank pain. His past medical history is unknown. The patient's temperature is 36.8 C (98.2 F), blood pressure is 110/70 mm Hg, pulse is 110/min, and respirations are 22/min. His appearance is disheveled. Pupils are equal, 4 mm in size, and reactive to light. Fundoscopic examination is within normal limits. Lungs have vesicular breath sounds. Mild costovertebral angle tenderness is present. A Foley catheter is placed, and the urine appears red, with calcium oxalate crystals seen on microscopy. Laboratory results are as follows: Which of the following is the most appropriate next step in management of this patient?

Question

A 34-year-old homeless man is brought to the emergency department in a confused state and complaining of flank pain.  His past medical history is unknown.  The patient's temperature is 36.8 C (98.2 F), blood pressure is 110/70 mm Hg, pulse is 110/min, and respirations are 22/min.  His appearance is disheveled.  Pupils are equal, 4 mm in size, and reactive to light.  Fundoscopic examination is within normal limits.  Lungs have vesicular breath sounds.  Mild costovertebral angle tenderness is present.  A Foley catheter is placed, and the urine appears red, with calcium oxalate crystals seen on microscopy.  Laboratory results are as follows:  Which of the following is the most appropriate next step in management of this patient?

Quizplus · Accepted Answer

11ec25c8_d1dd_983b_bc81_e11f362c4660_MD0003_00 This patient's clinical features are suggestive of ethylene glycol poisoning. Ethylene glycol and methanol poisonings occur when these compounds (found in antifreeze solutions) are ingested as a substitute for ethanol. The initial symptoms of ingestion of these poisons can mimic ethanol inebriation. However, as alcohol dehydrogenase metabolizes ethylene glycol to oxalic acid and glycolic acid, these metabolites cause profound clinical consequences. Glycolic acid injures the renal tubules, and oxalic acid binds calcium, causing hypocalcemia and calcium oxalate crystal deposition in the kidneys. When this occurs, patients develop flank pain, hematuria, oliguria, acute kidney injury, and anion gap metabolic acidosis. All of these symptoms are seen in this patient. Administration of fomepizole (a competitive inhibitor of alcohol dehydrogenase) or ethanol prevents further breakdown of ethylene glycol into its toxic metabolites and is an integral part of treatment. Sodium bicarbonate may help alleviate the acidosis, and hemodialysis may be required. Early recognition is crucial. There are very few conditions (eg, diabetic ketoacidosis, lactic acidosis) that cause such a profound anion gap metabolic acidosis (with bicarbonate level <8 mEq/L). Diabetic ketoacidosis is not likely in this patient with a glucose level of 80 mg/dL. Severe lactic acidosis is unlikely with a very mildly elevated lactate level. In cyanide toxicity, for example, lactate levels are usually >10 mEq/L. (Choice A) This patient is afebrile, not hypotensive, and has only mildly elevated lactic acid. Sepsis-induced lactic acidosis is unlikely and broad-spectrum antibiotics are not needed. (Choice C) Methylene blue is the treatment for methemoglobinemia, seen in the setting of ingestion of certain drugs (eg, dapsone) or anesthetic agents. Methemoglobinemia manifests as cyanosis and respiratory depression as a result of impaired oxygen delivery to the tissues. (Choice D) N-acetylcysteine is the antidote for acetaminophen overdose. Acetaminophen intoxication presents most often with nonspecific symptoms such as nausea, vomiting, or malaise, and can progress to liver damage and failure (eg, encephalopathy, jaundice, elevated prothrombin time). Acute kidney injury and metabolic acidosis can occasionally occur but typically not to the extent seen in this patient. (Choice E) Sodium thiosulfate is the antidote for cyanide poisoning, generally seen in the setting of fires or occupational exposure (eg, mining, pesticides). Patients with cyanide poisoning have markedly elevated lactate levels (typically >10 mEq/L). Educational objective: Ethylene glycol is associated with hypocalcemia and calcium oxalate deposition in the kidneys. This leads to flank pain, hematuria, oliguria, acute kidney injury, and anion gap metabolic acidosis. Treatment involves administration of fomepizole or ethanol to inhibit alcohol dehydrogenase, sodium bicarbonate to alleviate the acidosis, and hemodialysis in cases of severe acidosis and/or end-organ damage. References: Ethylene glycol ingestion treated only with fomepizole. (http://www.ncbi.nlm.nih.gov/pubmed/18072148)

A 34-Year-Old Homeless Man Is Brought to the Emergency Department