Refeeding syndrome is driven by a drop in which electrolyte?

The correct answer is Phosphate.

How long should the nurse observe the patient after meals?

The correct answer is 1 to 2 hours.

Mental Health · Topic 1 of 23

Anorexia Nervosa & Bulimia Nervosa

Q: Russell sign and parotid swelling point to which disorder?

The correct answer is Bulimia nervosa.

The patient with anorexia may look medically stable — until a potassium level crashes and a fatal dysrhythmia strikes.

Your levelNot startedAnswer a card to start

Start here

Drag the brackets to mark the normal range for serum potassium.

2.0

6.0

mEq/L

Tap to start14 cards · about 6 min · +42 XP

Pathophysiology & Risk Factors

Anorexia nervosa is severe caloric restriction driven by intense fear of weight gain and distorted body image, producing markedly low body weight. Bulimia nervosa is recurrent binge-purge cycles in a patient typically at or near normal weight, making it harder to detect. Both carry cardiac risk; the gravest threat in anorexia is refeeding syndrome when nutrition is restored too quickly.

Anorexia nervosa vs bulimia nervosa

Anorexia nervosaBulimia nervosa

WeightMarkedly low / emaciatedOften normal or above normal

Core behaviorCaloric restrictionBinge then purge

Hallmark physical signsLanugo, amenorrhea, bradycardia, hypothermiaRussell sign, dental enamel erosion, parotid swelling

Key metabolic riskRefeeding syndrome (hypophosphatemia)Hypokalemia with metabolic alkalosis

Anorexia nervosa

Weight: Markedly low / emaciated
Core behavior: Caloric restriction
Hallmark physical signs: Lanugo, amenorrhea, bradycardia, hypothermia
Key metabolic risk: Refeeding syndrome (hypophosphatemia)

Bulimia nervosa

Weight: Often normal or above normal
Core behavior: Binge then purge
Hallmark physical signs: Russell sign, dental enamel erosion, parotid swelling
Key metabolic risk: Hypokalemia with metabolic alkalosis

Signs & Symptoms

lanugo Hallmark

anorexia

amenorrhea

anorexia

bradycardia Hallmark

anorexia

hypothermia

anorexia

hypotension

anorexia

Russell sign Hallmark

knuckle calluses; bulimia purging marker

dental enamel erosion

bulimia; chronic purging

parotid gland swelling

bulimia purging marker

weakness

may signal hypokalemia in purging

heart palpitations

electrolyte-driven; bulimia

Diagnostics & Labs

Diagnostic

significantly low body weight Hallmark

key feature distinguishing anorexia from bulimia

metabolic alkalosis

from repeated self-induced vomiting

Monitor

serum potassiumK+ < 3.5 mEq/L

hypokalemia from purging; arrhythmia risk

serum phosphorusphosphorus < 2.5 mg/dL

hallmark of refeeding syndrome

serum magnesium

hypomagnesemia in refeeding

continuous cardiac monitoring

QTc prolongation, dysrhythmia surveillance

Interventions & Priorities

obtain baseline electrolytes

phosphorus, magnesium, potassium, calcium

place on cardiac monitor

establish baseline before refeeding

advance calories gradually

start low per protocol; prevents insulin-driven shifts

supervise all meals

observe 1-2 hours after meals

prevents purging or food disposal

monitor electrolytes first 72 hours

highest-risk refeeding window

trend daily weights and I&O

ongoing trajectory; sudden gain may be fluid

Treatments & Medications

IV phosphorus replacement

for hypophosphatemia of refeeding

thiamine administration

given during refeeding

potassium replacement

for purging-induced hypokalemia

structured meal plan

framed as prescribed treatment, non-negotiable

Patient Teaching

daily weight same time

hospital gown, after voiding, same scale

meals as prescribed treatment

calm, matter-of-fact, avoid negotiating portions

avoid food power struggles

focus on feelings, not calories

nonjudgmental mealtime environment

Complications

lethal cardiac dysrhythmia

from hypokalemia < 3.5 mEq/L

cardiac failure

refeeding hypophosphatemia

respiratory failure

severe refeeding

seizures

refeeding electrolyte shifts

Report Nowescalate immediately

Report-now threshold

Hypokalemia (dysrhythmia risk)

Normal potassium

Hyperkalemia

3.5

mEq/L

hypokalemiaK+ < 3.5 mEq/L

predisposes to lethal dysrhythmia

hypophosphatemiaphosphorus < 2.5 mg/dL

hallmark of refeeding syndrome

hypomagnesemia

refeeding electrolyte shift

QTc prolongation

dysrhythmia risk during refeeding

severe bradycardia

anorexia HR in 40s

hypotension

hemodynamic instability

rapid fluid retention

edema with sudden weight gain; refeeding

Clinical Pearl

Refeeding kills through phosphate, not food — when you restart nutrition in a starved patient, watch phosphorus before you worry about the meal plan.

Anorexia Nervosa & Bulimia Nervosa

The patient with anorexia may look medically stable — until a potassium level crashes and a fatal dysrhythmia strikes. Knowing which eating disorder causes which metabolic disaster changes your nursing priorities.

Anorexia nervosa involves severe caloric restriction with intense fear of weight gain and distorted body image, often presenting with BMI below 17.5, lanugo, amenorrhea, bradycardia, and hypothermia. Bulimia nervosa involves recurrent binge-purge cycles; the patient is typically at or near normal weight, making it harder to detect. Purging (vomiting, laxative abuse) causes hypokalemia, metabolic alkalosis, dental enamel erosion, parotid gland swelling, and Russell sign (calluses on knuckles). Both disorders carry cardiac risk — hypokalemia below 3.5 mEq/L predisposes to lethal dysrhythmias. Refeeding syndrome is the most dangerous complication when nutrition is restored too rapidly in anorexia: as cells take up glucose, phosphate shifts intracellularly, causing hypophosphatemia, heart failure, and seizures. Refeeding begins slowly with continuous cardiac monitoring. Nursing priorities include daily weights taken in a hospital gown after voiding (same time, same scale), observing the patient for 1–2 hours after meals to prevent purging, monitoring electrolytes (especially potassium, phosphate, magnesium), and establishing a structured, nonjudgmental mealtime environment. Therapeutic communication avoids power struggles over food — the focus is on feelings, not calories.

Key Distinctions

Don't confuse anorexia (restriction, underweight, bradycardia) with bulimia (binge-purge, near-normal weight, metabolic alkalosis from vomiting). Students mistake refeeding syndrome for simple overfeeding — it's a phosphate-driven crisis, not a caloric one. Russell sign and parotid swelling point to bulimia, not anorexia — these are purging markers.

Clinical Pearl

Refeeding kills through phosphate, not food. When you restart nutrition in a starved patient, monitor phosphorus levels before you worry about the meal plan.

Knowledge Check

3 quick questions on the must-knows for this topic.

Question 1 of 3

Russell sign and parotid swelling point to which disorder?

Ready to practice this topic?

Get a personalized study plan built around this topic — free to try, no card needed.

Get practice questions on this

Pathophysiology & Risk Factors

Signs & Symptoms

Diagnostics & Labs

Interventions & Priorities

Treatments & Medications

Patient Teaching

Complications

Anorexia Nervosa & Bulimia Nervosa

The patient with anorexia may look medically stable — until a potassium level crashes and a fatal dysrhythmia strikes. Knowing which eating disorder causes which metabolic disaster changes your nursing priorities.

Key Distinctions

Clinical Pearl

Knowledge Check

Anorexia Nervosa vs Bulimia Nervosa: Restriction vs Binge-Purge Cycle

Go further

Ready to practice this topic?