A 27 year old female with bulimia nervosa (self induced vomiting and laxative abuse) and major depressive disorder presented to the emergency department because of chest pain and lower extremity twitching. Initial evaluation was remarkable for multiple life threatening electrolyte abnormalities including hyponatremia (123 mmol/L), hypokalemia (1.7 mmol/L), hypochloremia (<60 mmol/L), hypocalcemia (iCa=1.06 mmol/L), hypomagnesemia (iMg=0.3 mmol/L), hypophosphatemia (1.5 mg/dL), metabolic alkalosis (serum CO253 mmol/L). Initial EKG was remarkable for mild flattened T waves. Immediate management was focused on fluid and electrolyte replacement. Our presentation will address causes of fluid imbalance and life threatening electrolyte abnormalities in bulimia nervosa, and review appropriate management strategies.
Initial management of life threatening electrolyte abnormalities in bulimic patients should focus on fluid resuscitation. Hypovolemia results in increased aldosterone secretion from increased activity of renin-angiotensin-aldosterone system, which results in various electrolyte abnormalities. Large volume fluid boluses are not recommended despite hypovolemia as elevated levels of aldosterone cause sodium avidity which can quickly result in fluid accumulation and edema. Slower continuous rates of 0.9% NaCl are recommended for the first 24-36 hours. Spironolactone is often prescribed after cessation of purging behaviors to further antagonize effects of aldosterone, help manage hypokalemia, and mitigate extent of peripheral edema and subsequent weight gain. Excessive purging acticity results in hypovolemic hypotonic hyponatremia. Standard treatment includes gradual normal saline infusion for a goal of 10-12mEq/L total serum sodium increase in the first 24 hours. Moderate to severe hypokalemia occurs from renal compensatory mechanisms correcting for volume loss from purging. Oral replacement is preferred and IV potassium is generally given in cases of severe hypokalemia (serum potassium level <2.5mEq/L) or arrhythmias. Hypomagnesemia is seen with purging behaviors including laxative abuse. IV magnesium sulfate is used for acute replacement, and oral magnesium oxide is used for chronic magnesium deficiency. Malnutrition is a common reason for hypocalcemia in patients with bulimia nervosa and hypocalcemia often occurs concurrently with hypomagnesemia. Total serum calcium must be corrected for serum albumin levels. Acute life threatening hypocalcemia is typically treated with IV calcium gluconate. Oral calcium replacement is appropriate in asymptomatic patients, with concurrent replacement of vitamin D for efficient calcium absorption.
Bulimia nervosa is a psychiatric disorder and may present initially because of medical complications from purging behaviors. Many patients with bulimia nervosa have multiple simultaneous purging behaviors, which can result in abnormal electrolyte concentrations. In addition, our body’s hormonal response to hypovolemia from purging may worsen electrolyte abnormalities. It is important to identify if patients have bulimia nervosa at time of initial presentation, as fluid resuscitation rates and strategies to correct electrolytes may differ from management of patients without bulimia nervosa. Acute life threatening electrolyte abnormalities are not common but can occur in patients with bulimia nervosa, and must be identified quickly to avoid complications.