Hyponatremia occurs when the blood contains too little sodium. Common causes of hyponatremia are a sodium-deficient diet, excessive water intake, or purging. Urine sodium-to-chloride ratios of >1.6 in combination with hypokalemia may indicate vomiting, while ratios <0.7 often indicate laxative use. Mild cases are often treatable through cessation of purging and oral hydration, but in serum sodium levels are <125mmol/L, the patient should be hospitalized and given saline, on a slow drip of 4-6mmol/L or less per 24hr to prevent central pontine myelinolysis. If serum sodium levels are <118mmol/L, intake into the intensive care unit with renal consultation should occur to determine if desmopressin, an antidiuretic, is required to restore sodium levels. 

Kalamazoo College

Grinnell College

University of California, Berkeley

Those who self-induce vomiting to purge are at risk of multiple potentially fatal conditions:

- Hypokalemia
- Hypochloremia
- Hyponatremia
- Metabolic alkalosis

Self-Induced Vomiting Metabolic/Electrolyte Complications

Laxative abuse can result in several electrolyte imbalances and acid-base disorders. The resulting acid-base disorder may be a means of indicating the duration of laxative abuse:

- Hypokalemia
- Hypochloremia
- Hyponatremia
- Non-anion gap metabolic acidosis
- Metabolic alkalosis

Laxative Abuse  Metabolic/Electrolyte Complications 

Anorexia nervosa leads to numerous severe health problems, making it one of the most lethal mental disorders. Significant negative outcomes include bone loss, heart failure, kidney failure, amenorrhea (the cessation of menstruation), and reduced function of the gonads. In extreme cases, these complications can result in death.

Health Consequences of Anorexia Nervosa

Chidiac, C. (2019). An update on the medical consequences of anorexia nervosa. Current Opinion in Pediatrics, 31 (4), 448-453. doi: 10.1097/MOP.0000000000000755.

An update on the medical consequences of anorexia nervosa

Nitsch, A., Dlugosz, H., Gibson, D., & Mehler, P. S. (2021). Medical complications of bulimia nervosa. Cleveland Clinic Journal of Medicine, 88(6), 333-343.

Medical Complications of Bulimia Nervosa

Hyponatremia in Eating Disorder Patients

Hypokalemia occurs when the blood contains too little potassium. Common causes of hypokalemia are a potassium-deficient diet or purging of ingested food. Urine potassium-to-creatinine ratios of <13 are often indicative that hypokalemia is resultant from eating disorder behaviors. If serum potassium levels are 2.5 mmol/L or more and no symptoms of hypokalemia are present, it can be treated with oral potassium supplements and purging cessation in bulimia nervosa patients. However, if serum potassium levels are <2.5mmol/L, potassium supplementation must be provided both orally and intravenously in a saline solution drip at no greater than 50-75mL/hr to restore intravascular volume while preventing hyperkalemia. Severe hypokalemia can lead to QT prolongation, TdP, other arrhythmias, and rarely, acute renal failure via hypokalemic nephropathy. 

Hypokalemia in Eating Disorder Patients

Metabolic alkalosis is an acid-base disorder in which the blood becomes too alkaline. In bulimia nervosa patients, it often results from purging, which depletes both potassium and intravascular volume, and is worsened by hypokalemia. In turn, this causes aldosterone levels to rise, which makes the kidneys absorb more sodium and chloride while excreting more potassium through urine. Purging also causes hydrogen ions to be lost, raising the body's pH. While normally bicarbonate is excreted to correct this alkalemia, bulimia nervosa patients may not excrete as much bicarbonate as necessary to restore the blood's pH as a result of the rapid decrease in sodium chloride from purging. Furthermore, among those who abuse laxatives, metabolic alkalosis can be indicative of an extended duration of abuse. If spot urine chloride tests show <10mmol/L, metabolic alkalosis can be treated with slow administrations of intravenous saline.

Metabolic Alkalosis in Bulimia Nervosa Patients

The major neurological consequence for patients with anorexia is a decrease in brain volume. Brain volume deficits are reversible for adults, but might be irreversible for children and teens.

Neurological consequences

Bradycardia, or slow heart rate, is caused by significant parasympathetic nervous system control over the body., which can lead to heart problems. Those with bradycardia have a heart rate of <60 beats/minute. 

Bradycardia

Hypoglycemia occurs when a person has low blood sugar. Hypoglycemia causes dizziness and fainting due to low heart rate (bradycardia) and low blood pressure. 

Hypoglycemia

Osteopenia, or loss of bone density, is caused by low mineral intake. This results in weaker bones, which can cause injury. Osteopenia, if occuring in children and teens, has the potential to be irreversible, and inhibit growth.

Osteopenia

Follow-up with a cohort of female anorexia nervosa patients who underwent inpatient treatment indicate that the following factors being present in their lifespan predicts greater mortality compared to other severe anorexia nervosa patients: 


- Longer duration of eating disorder
- Lower minimum post-pubertal BMI
- More hospitalizations
- Previous suicide attempt(s)
- Diuretic use
- Self-induced vomiting
- Previous abortion(s)
- Pre-menarche onset of eating disorder
- Rumination

Anorexia Nervosa Predictive Factors of Mortality in Lifetime

Follow-up with a cohort of female anorexia nervosa patients who underwent inpatient treatment indicate that the following factors being present upon admission predicts greater mortality compared to other severe anorexia nervosa patients: 

- Older age
- Higher Eating Disorder index (EDI) score
- Lower desired Body Mass Index (BMI)

Anorexia Nervosa Predictive Factors of Mortality at Admission

In some cases of anorexia nervosa, sudden cardiac death may result, in which there is no atherosclerotic heart disease to explain it. Certain factors may predispose patients to this fatal outcomes:

- Hypokalemia
- Hypoglycemia
- Bradycardia
- Cardiac autonomic dysfunction
- Cardiac structural changes

Anorexia Nervosa Predictive Factors of Sudden Cardiac Death

A patient with a long-term history of severe dietary restriction presents with multiple health issues. Which of the following complications represents the most immediate, life-threatening risk requiring urgent medical intervention?

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