A 52-year-old man comes to the emergency department due to generalized weakness, anxiety, and tremors. The patient has a history of alcohol use disorder. His last drink was 2 days ago. He has no other medical problems and no medical follow-up. The patient smokes cigarettes but does not use illicit drugs. He takes no medications. On examination, he appears disheveled and malnourished. His initial electrolyte panel results are as follows: He is treated for alcohol withdrawal and given aggressive intravenous potassium as well as oral potassium supplementation. Three days later, his electrolyte panel results are as follows: Which of the following best explains why this patient's potassium level is very difficult to correct?

Question

A 52-year-old man comes to the emergency department due to generalized weakness, anxiety, and tremors.  The patient has a history of alcohol use disorder.  His last drink was 2 days ago.  He has no other medical problems and no medical follow-up.  The patient smokes cigarettes but does not use illicit drugs.  He takes no medications.  On examination, he appears disheveled and malnourished.  His initial electrolyte panel results are as follows:  He is treated for alcohol withdrawal and given aggressive intravenous potassium as well as oral potassium supplementation.  Three days later, his electrolyte panel results are as follows:  Which of the following best explains why this patient's potassium level is very difficult to correct?

Quizplus · Accepted Answer

Chronic alcohol use is associated with a high incidence of several electrolyte abnormalities, of which hypomagnesemia is the most common (likely due to poor nutritional intake, alcohol-induced renal losses, and diarrhea). Hypomagnesemia commonly occurs together with hypokalemia and is a well-known cause of refractory hypokalemia (hypokalemia that cannot be corrected with potassium replacement). Intracellular magnesium is thought to inhibit potassium secretion by renal outer medullary potassium (ROMK) channels in the collecting tubules of the kidney. Therefore, low intracellular magnesium concentrations result in excessive renal potassium loss and refractory hypokalemia. Normalization of magnesium levels restores ROMK channel potassium transport regulation, decreases renal potassium losses, and allows for successful correction of hypokalemia with oral (preferred) or intravenous potassium replacement. (Choice A) Acute alcohol withdrawal may initially contribute to hypokalemia through an increase in sympathetic nervous system activity, which shifts potassium into cells. However, it is unlikely to play a significant role in this patient's hypokalemia, which has persisted throughout 3 days of treatment. (Choice B) Hypoalbuminemia is commonly seen in patients with alcohol use disorder due to poor nutrition or hepatic synthetic dysfunction. It is a common cause of hypocalcemia (total but not ionized); however, it is not a significant cause of hypokalemia. (Choice D) Hypophosphatemia is common in patients with alcohol use disorder and, when severe, can result in weakness, rhabdomyolysis, paresthesias, and respiratory failure. It does not directly contribute to hypokalemia. (Choice E) Poor oral absorption may result in hypokalemia refractory to oral replacement, but it is unlikely in this patient with hypokalemia that has also been refractory to aggressive intravenous replacement. (Choice F) Type I or II renal tubular acidosis can cause hypokalemia but is usually associated with metabolic acidosis. This patient has a relatively normal serum bicarbonate level, and his history of alcohol use disorder makes hypomagnesemia a more likely cause of his refractory hypokalemia. (Choice G) Thiamine deficiency is common in patients with alcohol use disorder due to poor nutrition, but it does not cause refractory hypokalemia. Educational objective: Patients with chronic alcohol use disorder often present with multiple electrolyte abnormalities (eg, hypokalemia, hypomagnesemia, hypophosphatemia). Hypomagnesemia can lead to refractory hypokalemia due to removal of inhibition of renal potassium excretion and should be suspected in patients with hypokalemia that is difficult to correct with potassium replacement. References: Pathogenetic mechanisms of hypomagnesemia in alcoholic patients. (http://www.ncbi.nlm.nih.gov/pubmed/8808192) Mechanism of hypokalemia in magnesium deficiency. (http://www.ncbi.nlm.nih.gov/pubmed/17804670)

A 52-Year-Old Man Comes to the Emergency Department Due to Generalized