Review Question - QID 102617

This patient is presenting with a history of poor oral intake, nausea, and vomiting and is subsequently given dextrose. After this intervention, he presents with confusion, weakness, and muscle/bone pain which is suggestive of hypophosphatemia.

Hypophosphatemia can occur due to poor oral intake, loss in the urine, or cellular sequestration. Chronic alcoholics are often phosphate-depleted due to a combination of both poor oral intake and many other metabolic derangements that can occur given their unhealthy lifestyle (such as hypocalcemia from poor diet, low magnesium, and low vitamin D all of which lead to secondary hyperparathyroidism and increased phosphate wasting in the kidney). Similarly, diarrhea can lead to phosphate loss in the stool. When patients such as alcoholics are given nutrition this can lead to a refeeding syndrome such that refeeding triggers an increased release of insulin, shifting phosphate (and potassium) back into the cells. A respiratory alkalosis may also occur in alcoholics experiencing withdrawal, which further facilitates phosphate (and potassium) shift into the cells via the decreased serum hydrogen concentration. Though most cases of hypophosphatemia are asymptomatic, severe or chronic cases may present with confusion, weakness, bone/muscle pain, and even rhabdomyolysis.

Incorrect Answers:
Answer 1: Hypocalcemia presents with abdominal pain, muscle cramps, dyspnea, convulsions, mental status changes, and tetany (Chovestek sign or facial spasm and Trousseau sign or carpopedal spasm). This patient does not present with these symptoms and his normal initial calcium makes this less likely.

Answer 2: Hypoglycemia would not be likely in a patient with an initial normal glucose who subsequently receives further IV nutrition. Hypoglycemia may present with fatigue, weakness, and even seizures or focal neurological deficits.

Answer 3: Hypomagnesemia is typically seen in alcoholics and can cause both hypokalemia and hypocalcemia. Hypomagnesemia is associated with torsades de pointes, ventricular fibrillation, atrial fibrillation, hyperreflexia, and tetany. It would not be expected in this patient with a normal potassium and calcium who has new onset confusion and weakness after receiving nutrition, though a magnesium level must be checked and repleted if needed.

Answer 4: Hyponatremia presents with nausea, vomiting, confusion, muscle cramps, and lethargy and sometimes seizures in severe cases. It is more common in patients with psychogenic polydipsia, beer drinkers potomania, and SIADH. This patient's initial sodium was normal so it is unlikely to become abnormal once receiving normal saline which has a high sodium and chloride load.

Bullet Summary:
Hypophosphatemia can be seen in alcoholics and patients with diarrheal illness and presents with altered mental status, weakness, and muscle/bone pain.