An 18 year old female with a history of anorexia was sent in by her primary care physician for bradycardia and hypothermia. She was being seen for biweekly weight checks after losing 55 pounds in 10 months. She felt weak earlier today but has no other complaints.
On presentation, her vitals are within normal limits. She is a cachectic appearing female with an otherwise normal physical exam. Her labs were significant for a sodium of 125, a potassium of 4.4, and a phosphorus of 1.5.
She was given 10 mmol of KPhos IV to avoid Na load of Neutra-phos, and admitted to the PICU for electrolyte repletion and monitoring prior to advancing her diet to avoid refeeding syndrome. Discharged to a residential program after 10 days.
Take Away #1
Refeeding syndrome-occurs in the setting of increased caloric intake after starvation or malnutrition. Upon carbohydrate intake, insulin drives K, Mg and Phos into the cells. Where phosphate is normally consumed in oxidative phosphorylation to produce ATP. This lowers serum levels even more. However due to total body reduction in phosphate the body is unable to keep up with production of ATP. To produce glucose-6-phosphate in the first step of glycolysis the body needs ATP.
This can lead to respiratory failure, myocardial disfunction, dysrhythmias, hemolysis, rhabdomyolysis, and seizures.
At risk patients include elderly, alcoholics, oncology patients on chemo, and patients with eating disorders.
Severity of symptoms are related to rapid weight loss, weight <70% IBW, rapid refeeding, and low K, Mg or Phosphate prior to refeeding.
Take Away #2
If serum levels are 1.0-2.0 mg/dL give 30-80 mmol PO per day in divided doses
If <1.9 mg/dL give up to 0.24 mmol/kg over 6 hours (max 30 mmol)
If <1.25 mg/dL give 0.25-0.5 mmol/kg over 8-12 hours (max 80mmol)
Continue IV repletion until serum level is >1.5mg/dL, then transition to PO.
Risks of IV repletion include hypocalcemia and calcium phosphate crystal formation with deposition in kidneys, heart, eyes and lungs.
Take Away #3
Our pharmacy carries IV potassium phosphate and PO Neutra-phos
Each packet of Neutra-phos contains 1 mEq of potassium, 8 mmol of elemental phosphorus and 13 mEq of sodium
Be careful with the different units
Matthew Welles, MD is a current first year resident at Stony Brook Emergency Medicine.