A 55-year-old man comes to the emergency department due to progressively worsening shortness of breath for the past 3 days. He also reports wheezing and productive cough with purulent sputum. The patient's medical history includes chronic bronchitis and benign prostatic hyperplasia. He smokes a pack of cigarettes daily. Temperature is 37.2 C (99 F), blood pressure is 150/90 mm Hg, pulse is 114/min, and respirations are 26/min. The patient's pulse oximetry shows 84% on room air. He is alert and answering questions coherently. Examination shows decreased breath sounds and diffuse wheezing over all lung fields. The patient is admitted to the hospital and started on antibiotics, systemic corticosteroids, and nebulized albuterol and ipratropium. The following day, laboratory results are as follows: Serum chemistry 2 days ago was normal. Which of the following is the most likely cause of this patient's low serum potassium?

Question

A 55-year-old man comes to the emergency department due to progressively worsening shortness of breath for the past 3 days.  He also reports wheezing and productive cough with purulent sputum.  The patient's medical history includes chronic bronchitis and benign prostatic hyperplasia.  He smokes a pack of cigarettes daily.  Temperature is 37.2 C (99 F), blood pressure is 150/90 mm Hg, pulse is 114/min, and respirations are 26/min.  The patient's pulse oximetry shows 84% on room air.  He is alert and answering questions coherently.  Examination shows decreased breath sounds and diffuse wheezing over all lung fields.  The patient is admitted to the hospital and started on antibiotics, systemic corticosteroids, and nebulized albuterol and ipratropium.  The following day, laboratory results are as follows:  Serum chemistry 2 days ago was normal.  Which of the following is the most likely cause of this patient's low serum potassium?

Quizplus · Accepted Answer

Low serum potassium may result from increased potassium entry into cells, renal potassium wasting, or gastrointestinal fluid loss. This patient with an acute exacerbation of chronic obstructive pulmonary disease (COPD) is treated with an inhaled beta-2 adrenergic agent (albuterol). Exogenous and endogenous (eg, epinephrine) beta-adrenergic agonists cause a potassium shift into the intracellular space by stimulating the sodium-potassium ATPase pump and the sodium-potassium-2 chloride cotransporter. Adrenergic agents also stimulate release of insulin, which further promotes intracellular potassium shift, causing hypokalemia. (Choice A) Insulin promotes potassium shift into the intracellular space and is used in the management of hyperkalemia. Decreased insulin availability would exacerbate hyperkalemia. (Choice B) Decreased pH (acidosis) with COPD exacerbation may be seen in patients with CO₂ retention. However, this would result in hyperkalemia. (Choice C) Renal potassium wasting with hypertension is a feature of primary hyperaldosteronism. Decrease in mineralocorticoid activity will lead to hyperkalemia. Diuretics also cause renal potassium loss. (Choice E) Increased potassium uptake by cells during accelerated hematopoiesis (eg, administration of granulocyte colony-stimulating factors) may cause hypokalemia. This patient has no evidence of increased hematopoiesis. (Choice F) Lower gastrointestinal fluid levels have a high potassium concentration; therefore, diarrhea is a direct cause of hypokalemia. Vomiting causes metabolic alkalosis, which leads to renal potassium wasting. This patient does not have any gastrointestinal fluid losses. Educational objective: Hypokalemia may be caused by increased intracellular entry of potassium (eg, with insulin, beta-adrenergic agents, hematopoiesis), gastrointestinal losses, and renal potassium wasting (eg, hyperaldosteronism, diuretics).

A 55-Year-Old Man Comes to the Emergency Department Due to Progressively