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Review by Elizabeth Erickson, DO

Akman, A.O., Cak, H.T., Pehlivantur,-Kizilkan, M. Balik, Z., Akbulut, O., & Kanbur, N. (2019). Sounds unrealistic: an adolescent girl with Anorexia Nervosa consumes 19 L of fluid in a few hours:  What happens to the physiology?  Eating and Weight Disorders.  E-publication ahead of print.

Eating disorders are not strictly disorders of food consumption, but often of abnormal drinking behaviors that vary in clinical presentation. This article is a case study that demonstrates the acuity and extreme drinking behaviors that can be present in an ED patient, and how one must be through in evaluating not just food consumption, but fluids, as well.

The case discussed was that of a 16 y.o. female with AN-R and Major Depression. Patient was admitted to inpatient level of care and started on nutritional support with a low-calorie meal plan. On the second day of treatment, patient demonstrated a 2 kg weight gain. On clinical exam, patient was disoriented and drowsy. Subsequently, patient discussed experienced a tonic-clonic seizure, and her serum sodium was found to be 116 mEq/L with a specific gravity of 1.002. Patient’s calculated serum osmolality was calculated at 239.9. Patient was diagnosed with acute hyponatremia and was started on 3% hypertonic saline solution. Only following this event, did the team discover that patient had ingested 19 L of water to expedite discharge.

Why is This Important?

Hyponatremia in ED’s is a result of a variety of factors. If the cause is unknown, urine sodium and urine specific gravity, are helpful tools in identifying a root cause. In restrictive disorders, hyponatremia might be secondary to either dehydration (restriction of fluids) or overhydration (water loading). Hyponatremia is the most common cause of overhydration, and is defined by a plasma sodium less than 135 mEq/L. Values below 125mEq/L are considered as severe hyponatremia. Initial goal in treatment is differentiation of hypotonic from nonhypotonic hyponatremia. A low serum osmolality, as noted in this case study, suggests hypotonic hyponatremia. Once diagnosis is established, volume status should be assessed. Due to the acute onset of severe symptoms in this case, immediate treatment with hypertonic saline was performed. It is essential to keep in mind that electrolyte abnormalities should be considered one of the primary considerations in a differential diagnosis for a patient with an eating disorder and new seizures.

Of note, chronic overhydration, common in ED’s, leads to downregulation of aquaporin 2 water channels, resulting in adaptation mechanism of urinary water excretion. In the case reviewed, however, the patient acutely over consumed water, in which water intoxication can occur. Water intoxication (dilutional hyponatremia) can occur at approximately 3-4 L in less than an hour, or when the consumption exceeds the capacity of water excretion, roughly 10 L a day. In this case, patient consumed 19 L of water in a short time. Any abnormal fluid intake by ED patients may result in severe, and acute medical complications.

This case demonstrates that a thorough clinical assessment of hydration and drinking behaviors is necessary during the management of ED’s, and electrolyte abnormalities should be a primary focus for a patient with an ED and new onset seizures.

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