A 38-year-old male with multiple enterocutaneous fistulae and chronic malnutrition on total parenteral nutrition (TPN) is admitted to the ICU with lethargy and hypotension. His medical history is significant for Crohn disease requiring multiple bowel surgeries. Soon after arrival in the ICU, he starts seizing and exhibits tetany.
Which of the following electrolyte abnormalities is MOST consistent with this presentation?
A. Hypophosphatemia
Correct Answer: B
Hypomagnesemia is a common in critically ill patients. Magnesium plays an important role in several vital biochemical and physiological functions of the body including neuromuscular and cardiac conduction, maintenance of cardiac contractility, and vascular tone.
Hypomagnesemia could result from either gastrointestinal (GI) or renal losses. GI causes include diarrhea, intestinal fistulae, and malabsorption syndromes. Renal causes include chronic parenteral fluid therapy, osmotic diuretics, and chronic alcohol consumption. It is important to note that several medications including diuretics, antibiotics, and immunosuppressants can lead to hypomagnesemia through renal mechanisms.
Intracellular magnesium depletion has potential to cause atrial and ventricular arrhythmias, impaired cardiac contractility, and vasoconstriction. Nervous system manifestations include hyperactivity, tremors, and tetany with a positive chvostek sign. Severe hypomagnesemia could result in altered mental status and seizures. Magnesium depletion can present with neuromuscular symptoms that are similar to those of calcium deficiency, including hyperactive reflexes, muscle tremors, and tetany.
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