A 45-year-old man is brought to the emergency department due to altered mental status. The patient appears agitated and disoriented. He was recently treated by his physician for cold symptoms. He also takes aspirin for chronic arthritis and ranitidine for acid reflux. He works as an auto mechanic. He has smoked for the last 25 years and drinks heavily during the weekend. His temperature is 37.2 C (99 F), blood pressure is 110/70 mm Hg, pulse is 90/min, and respirations are 22/min. His laboratory findings are as follows: Urinalysis shows square, envelope-shaped crystals. His creatinine 3 months ago was 1.2 mg/dL. What is the most likely cause of the laboratory abnormalities seen in this patient?

Question

A 45-year-old man is brought to the emergency department due to altered mental status.  The patient appears agitated and disoriented.  He was recently treated by his physician for cold symptoms.  He also takes aspirin for chronic arthritis and ranitidine for acid reflux.  He works as an auto mechanic.  He has smoked for the last 25 years and drinks heavily during the weekend.  His temperature is 37.2 C (99 F), blood pressure is 110/70 mm Hg, pulse is 90/min, and respirations are 22/min.  His laboratory findings are as follows:  Urinalysis shows square, envelope-shaped crystals.  His creatinine 3 months ago was 1.2 mg/dL.  What is the most likely cause of the laboratory abnormalities seen in this patient?

Quizplus · Accepted Answer

11ec25c8_d501_4580_bc81_559671701b3e_MD0003_00 This patient has metabolic acidosis (pH <7.35, primary decrease in HCO3−) with an increased anion gap (141 - [100 + 13] = 28). His measured serum osmolality (often obtained in patients with anion gap metabolic acidosis and suspected ingestion) is also elevated (350 mOsm/kg H₂O). An osmolal gap, found to be elevated in this patient, should be calculated as follows: anion gap 11ec25c8_d501_4581_bc81_17998d26da5c_MD0003_00 A combination of high anion gap and osmolal gap metabolic acidosis is seen with acute methanol or ethylene glycol poisoning. The patient's urinalysis shows square, envelope-shaped calcium oxalate crystals, which are classically observed in patients with ethylene glycol poisoning, most commonly from antifreeze ingestion. Acute renal failure is the major complication of ethylene glycol intoxication (methanol intoxication can lead to blindness). envelope-shaped calcium oxalate crystals (Choice A) Metabolic acidosis in diabetic ketoacidosis is accompanied by high blood glucose levels. This patient is euglycemic. (Choice C) Lactic acidosis is most commonly seen in states of hypoperfusion and shock (eg, sepsis, cardiogenic shock). Lactic acid levels may also be elevated in patients with end-stage liver disease as lactic acid is metabolized in the liver. (Choice D) Aspirin (salicylate) toxicity causes a mixed anion gap metabolic acidosis and respiratory alkalosis with no osmolal gap. (Choice E) Uremia (renal failure) causes an anion gap metabolic acidosis because acid excretion (through formation of ammonium) is impaired. However, uremia does not cause an osmolal gap. Educational objective: Ethylene glycol and methanol intoxication cause metabolic acidosis with both an anion gap and an osmolal gap. Calcium oxalate crystals (square, envelope-shaped) are seen in patients with ethylene glycol (antifreeze) poisoning. Ethylene glycol intoxication can result in renal failure; methanol intoxication can cause blindness.

A 45-Year-Old Man Is Brought to the Emergency Department Due