The Question
A 22-year-old female with a history of generalized anxiety disorder is brought to the emergency department by her roommate after a syncopal episode. The patient reports several months of progressive fatigue, dizziness upon standing, and cold intolerance. She states she is "very disciplined" with her diet, which consists mainly of vegetables and protein shakes, and she runs for 90 minutes daily. Her weight has decreased by 15 kg (33 lbs) over the past six months. On review of systems, she endorses constipation but denies vomiting. Physical examination reveals a cachectic young woman. Her temperature is 36.0°C (96.8°F), blood pressure is 88/58 mm Hg, heart rate is 44 beats/min, and respirations are 12 breaths/min. Her BMI is 16.2 kg/m². The cardiopulmonary examination is unremarkable. Her skin is dry with poor turgor, and there is fine, downy hair on her back. Laboratory studies show: Sodium 138 mEq/L, Potassium 3.1 mEq/L, Chloride 95 mEq/L, Bicarbonate 30 mEq/L, BUN 22 mg/dL, Creatinine 1.1 mg/dL, Magnesium 1.4 mg/dL, and Phosphate 2.1 mg/dL. An ECG demonstrates sinus bradycardia. The patient is admitted to the medical ward for stabilization. Which of the following is the most significant immediate risk for this patient upon initiation of nutritional therapy?
See the answer and explanation below:
Post-Call Recovery Reads
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View on AmazonThe Correct Answer
C
Explanation
Clinical Pearl:
Refeeding syndrome in patients with severe malnutrition is a life-threatening condition marked by electrolyte shifts, particularly hypophosphatemia, upon the reintroduction of carbohydrates. Prophylactic electrolyte and thiamine repletion before cautious caloric initiation is critical.
Explanation:
This patient's presentation is classic for anorexia nervosa, given her low BMI, restrictive eating patterns, excessive exercise, and associated physical and metabolic findings (bradycardia, hypothermia, hypokalemia, hypophosphatemia). The most immediate and life-threatening complication upon initiating feeding is refeeding syndrome. This occurs when a rapid shift from a catabolic state (fat and protein metabolism) to an anabolic state (carbohydrate metabolism) causes a surge in insulin, driving phosphate, potassium, and magnesium into cells. The resulting severe hypophosphatemia is the hallmark of the syndrome and can lead to cardiac arrhythmias, respiratory failure, rhabdomyolysis, and seizures. While Wernicke encephalopathy (due to thiamine deficiency) is also a risk and should be prevented with thiamine supplementation before feeding, refeeding syndrome represents the most severe global metabolic derangement. Acute gastric dilation and superior mesenteric artery syndrome are known GI complications in anorexia nervosa, but are less acutely life-threatening than refeeding syndrome. Heart failure can be precipitated by overly aggressive fluid resuscitation, but the core metabolic collapse of refeeding syndrome is the most pressing immediate danger.
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