A 34-year-old man comes to the emergency department due to 2 weeks of abdominal discomfort, nausea, and vomiting. Over the last 2 days, he has not been able "to keep anything down." The patient is experiencing homelessness. He has a history of alcohol use disorder and he has been admitted previously for acute pancreatitis, alcohol-related seizures, and aspiration pneumonia. Blood pressure is 112/78 mm Hg while supine and 94/57 mm Hg while standing. His pulse is 121/min, regular. BMI is 16 kg/m². He looks disheveled and his mucous membranes are dry. There is mild epigastric tenderness. Initial laboratory values are the following: He is treated with intravenous fluids, dextrose and thiamine solution, and folic acid supplementation. On the second day of hospitalization, he develops severe weakness, saying "I can barely raise my arms!" Which of the following most likely accounts for his current symptoms?

Question

Quizplus · Accepted Answer

Explanation: This patient's initial laboratory values are essentially within normal limits. Despite the initial normal serum phosphate level, the most likely diagnosis in this patient is hypophosphatemia secondary to refeeding. Patients with severe alcohol use disorder often have chronic depletion of phosphate secondary to decreased vitamin D and phosphate intake along with decreased intestinal uptake in those with chronic diarrhea. Urinary phosphate excretion may also be increased because of secondary hyperparathyroidism from decreased vitamin D intake as well as a proximal tubular reabsorption defect from alcohol use itself. Despite the depletion of phosphate, serum levels are often maintained (extracellular shift) until the patient is admitted to the hospital and fluids are initiated. Once the patient is fed or receives intravenous fluids with glucose, insulin secretion is increased which results in shifting of phosphate intracellularly and unmasking of the previously compensated phosphate depletion. A respiratory alkalosis occurs in many of these patients as well, which can further shift phosphate into cells and out of the serum. This patient's developing weakness should raise concern for the development of rhabdomyolysis from hypophosphatemia and the CPK should be rechecked. Patients with alcohol use disorder frequently have an underlying myopathy, and hypophosphatemia on top of myopathy can lead to symptomatic rhabdomyolysis. (Choice A)Hypocalcemia is uncommon in patients with alcohol use disorder unless magnesium levels are low as well, but if this were the case both calcium and magnesium levels should be abnormal at admission. (Choice B)This patient would likely have symptoms other than isolated weakness if he developed hypoglycemia. The IV fluids include dextrose, making hypoglycemia less likely. (Choice C) Hyponatremia tends to produce mental status changes and seizures when severe. Underlying alcohol use disorder may place patients at risk of developing osmotic demyelination if serum sodium is corrected too quickly. This patient has not exhibited symptoms of hyponatremia or osmotic demyelination, however. (Choice E) Chronic alcohol use can cause a metabolic acidosis secondary to elevated ketoacids, but this would be expected to be present at admission. Educational objective: Patients with alcohol use disorder are frequently phosphate depleted even though serum phosphate levels may initially be normal. Refeeding these patients, particularly if a respiratory alkalosis is also present, may lead to shifts of phosphate intracellularly and a decreased serum phosphate. This may lead to the development of rhabdomyolysis as many of these patients have an underlying myopathy. References: Refeeding syndrome and hypophosphatemia. (http://www.ncbi.nlm.nih.gov/pubmed/15888903)

A 34-Year-Old Man Comes to the Emergency Department Due to 2