Introduction: Hypophosphatemia is defined as serum phosphate < 2.5 mg/dL which can manifest with neuromuscular, hematologic, and cardiopulmonary symptoms. While common causes include malnutrition, refeeding, and medication effects, acute respiratory alkalosis from hyperventilation can precipitate an abrupt intracellular shift of phosphate. Description: A 44-year-old male with a history of hypertension, asthma, OSA on CPAP and depression presented to the ED with acute onset chest pain that radiate to the left jaw associated with shoulder numbness, diaphoresis, and nausea. Two years prior, he experienced similar symptoms and underwent left heart catheterization with no significant coronary stenosis. On presentation patient was normotensive, tachypneic (RR 29), and saturating well on room air. ABG revealed pH 7.63, pCO2 21 mmHg, and bicarb 20 mEq/L. Laboratory workup showed severe hypophosphatemia (0.3 mg/dL), hypokalemia (3.0 mEq/L), and elevated anion gap (20). Cardiac enzymes revealed an initial troponin of 8 ng/L with flat repeats. EKG showed normal sinus rhythm without ischemic changes. Chest X-ray was unremarkable. Patient’s chest pain subsided following administration of 0.4 mg sublingual nitroglycerin. Repeat labs following electrolyte repletion showed improved phosphate (4.1 mg/dL), potassium (3.4 mEq/L), and bicarbonate (21 mEq/L). No additional toxicologic or infectious etiologies were identified. The patient’s symptoms were attributed to anxiety-induced hyperventilation leading to respiratory alkalosis and intracellular phosphate shift. Discussion: Severe hypophosphatemia is uncommon but can present nonspecific symptoms, including chest pain, muscle weakness, and altered mental status. Hyperventilation due to acute anxiety can cause respiratory alkalosis, leading to intracellular shifts of phosphate and subsequent hypophosphatemia. In this case, the absence of cardiac ischemia and resolution of symptoms with supportive care and electrolyte correction supports a diagnosis of anxiety-induced metabolic disturbance. Early recognition and correction of electrolyte imbalances are critical to prevent complications.
Subedi et al. (Sun,) studied this question.