How should a vitally stable child who has had one episode of vomiting and now presents with bilateral foot spasms and pain be evaluated and managed?

Immediate Evaluation for Hypocalcemic Tetany

This child most likely has carpopedal spasm (tetany) from hypocalcemia secondary to metabolic alkalosis caused by vomiting, and requires urgent serum electrolytes (calcium, potassium, magnesium) and blood gas analysis with immediate calcium replacement if confirmed 1.

Clinical Recognition

The bilateral foot spasms with pain following vomiting represent classic carpopedal spasm—a medical emergency indicating:

• Hypocalcemia (decreased ionized calcium from alkalosis)
• Hypokalemia (from gastric fluid losses)
• Metabolic alkalosis (from loss of gastric acid)

Even a single episode of vomiting can trigger significant electrolyte derangement in children, particularly if there was substantial volume loss or if the child has underlying predisposition 1.

Immediate Management Algorithm

Step 1: Urgent Laboratory Assessment

Draw immediately:

• Serum calcium (total and ionized)
• Electrolytes (sodium, potassium, chloride, bicarbonate)
• Magnesium (hypomagnesemia prevents calcium correction)
• Venous or arterial blood gas (to confirm alkalosis)

Step 2: While Awaiting Results

• Assess hydration status clinically
• Check vital signs and capillary refill
• Examine for other signs of tetany (Chvostek's or Trousseau's signs)
• Rule out red flags: altered mental status, signs of increased intracranial pressure, bilious vomiting, abdominal distension 2, 3

Step 3: Treatment Based on Findings

If hypocalcemia confirmed:

• Acute symptomatic treatment: IV calcium gluconate 10% solution, 0.5-1 mL/kg (maximum 10 mL) over 5-10 minutes with cardiac monitoring
• Correct hypomagnesemia if present (prevents calcium correction)
• Address underlying alkalosis with appropriate fluid resuscitation

Rehydration approach 4:

• If mild dehydration: Oral rehydration solution (ORS) 50-100 mL/kg over 3-4 hours
• Replace ongoing losses: 10 mL/kg ORS for each additional vomiting episode
• If unable to tolerate oral: Consider nasogastric ORS or IV isotonic fluids

Critical Pitfalls to Avoid

1. Don't assume "just one episode" is benign when tetany is present—this indicates significant metabolic derangement 1

2. Don't give calcium without checking magnesium—hypocalcemia won't correct if hypomagnesemia exists

3. Don't use rapid IV calcium bolus without cardiac monitoring—risk of arrhythmias

4. Don't miss surgical causes: While metabolic alkalosis is most likely, bilious vomiting, abdominal distension, or signs of obstruction require immediate surgical consultation 2, 3

5. Don't overlook serious systemic causes: Though less common, consider sepsis, meningitis, increased intracranial pressure, or metabolic disorders if clinical picture doesn't fit simple gastroenteritis 2, 5

Disposition

• Admit for observation and IV calcium/electrolyte replacement if symptomatic hypocalcemia confirmed
• Monitor cardiac rhythm during calcium administration
• Serial electrolyte checks until normalized
• Investigate cause of vomiting if not immediately apparent or if recurrent

The presence of tetany transforms this from a simple vomiting case into an electrolyte emergency requiring immediate laboratory confirmation and treatment.