From the Guidelines
Metabolic alkalosis is the most common metabolic derangement found in patients with purging eating disorders like bulimia nervosa. This condition develops primarily due to the loss of stomach acid through self-induced vomiting, which is a hallmark behavior in bulimia nervosa. When patients repeatedly purge through vomiting, they lose significant amounts of hydrochloric acid from the stomach, leading to an increase in blood pH and serum bicarbonate levels. Additionally, purging behaviors often cause electrolyte imbalances, particularly hypokalemia (low potassium), hypochloremia (low chloride), and sometimes hyponatremia (low sodium) 1. These electrolyte abnormalities further contribute to and maintain the metabolic alkalosis. Dehydration from purging can also activate the renin-angiotensin-aldosterone system, causing increased reabsorption of bicarbonate in the kidneys and worsening the alkalotic state. Clinically, patients may present with symptoms such as confusion, muscle cramps, cardiac arrhythmias, and in severe cases, tetany or seizures. Treatment focuses on addressing the underlying eating disorder while correcting fluid and electrolyte imbalances through oral or intravenous rehydration and electrolyte replacement as needed 1. Key aspects of management include:
- Comprehensive metabolic panel to assess electrolyte levels and renal function
- Electrocardiogram to evaluate for QTc interval prolongation
- Individualized treatment plans incorporating medical, psychiatric, psychological, and nutritional expertise
- Eating disorder-focused psychotherapy, such as cognitive-behavioral therapy, and medication as needed.
From the Research
Metabolic Derangement in Purging Eating Disorders
The metabolic derangement often found in patients with a purging eating disorder, such as bulimia nervosa (BN), is:
- Metabolic alkalosis, which is characterized by an increase in plasma HCO3- level and blood arterial pH 2, 3, 4, 5, 6
Causes of Metabolic Alkalosis
The causes of metabolic alkalosis in purging eating disorders include:
- Hypokalemia, which is a common serum change that occurs as a result of purging behaviors 2, 3, 4
- Chloride depletion, which can lead to a state of profound dehydration and metabolic abnormalities characteristic of inheritable sodium and chloride renal tubular transport disorders 4
- Sodium chloride-responsive metabolic alkalosis, which is one of the most common serum changes that occur as a result of purging behaviors 2
Characteristics of Metabolic Alkalosis
The characteristics of metabolic alkalosis in purging eating disorders include: