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Difficulty: Very hardPediatric Gastrointestinal Disorders

A 6-month-old male infant is brought to the emergency department by his parents due to repetitive, profuse vomiting and extreme lethargy. The vomiting began approximately 2 hours after he was fed oat cereal for the first time. The parents note that he became remarkably pale and limp shortly after the vomiting started. He was born at term and has previously tolerated breast milk and pureed vegetables without issue. His temperature is 36.5°C (97.7°F), heart rate is 185/min, blood pressure is 60/35 mmHg, and respiratory rate is 45/min. Physical examination reveals a lethargic, mottled infant with delayed capillary refill of 5 seconds. There is no rash, urticaria, or facial swelling. The lungs are clear to auscultation bilaterally without wheezing. The abdomen is soft, non-distended, and non-tender, with hyperactive bowel sounds.

Laboratory studies show:
Leukocyte count: 24,500/mm324,500/\text{mm}^3 (with 18% bands)
Hemoglobin: 11.5 g/dL11.5 \text{ g/dL}
Platelets: 550,000/mm3550,000/\text{mm}^3
Arterial blood gas:
pH: 7.287.28
pCO2pCO_2: 35 mm Hg35 \text{ mm Hg}
HCO3−HCO_3^-: 16 mEq/L16 \text{ mEq/L}

Which of the following is the most appropriate initial management for this patient?

  1. Intravenous normal saline bolus and ondansetronAnswer
  2. B
    Broad-spectrum intravenous antibiotics and blood cultures
  3. C
    Computed tomography scan of the abdomen with intravenous contrast
  4. D
    Intravenous administration of sodium bicarbonate
  5. E
    Nasogastric tube decompression and prompt surgical consultation

Answer

The correct approach is to administer an intravenous normal saline bolus and ondansetron.
The correct management consists of intravenous normal saline bolus and ondansetron. This infant is exhibiting a classic presentation of severe acute Food Protein-Induced Enterocolitis Syndrome (FPIES). FPIES is a non-IgE mediated food allergy that typically presents in the first year of life when a trigger food (most commonly cow's milk, soy, rice, or oats) is introduced. The hallmark of acute FPIES is profuse, repetitive vomiting beginning 1 to 4 hours after ingestion, which rapidly leads to lethargy, pallor, and hypovolemic shock. Notably, because it is not IgE-mediated, patients do not develop classic anaphylactic signs such as urticaria, angioedema, or wheezing. Furthermore, laboratory evaluation often reveals a profound leukocytosis with a left shift and metabolic acidosis, causing it to closely mimic neonatal sepsis or a surgical catastrophe. The cornerstone of management for a hemodynamically unstable infant with FPIES is emergent intravascular volume restoration with isotonic fluids (normal saline). Additionally, intravenous ondansetron is highly efficacious in halting the relentless emesis associated with this syndrome.

Step-by-Step Solution

1
Analyze the clinical presentation and timeline.
The infant developed profuse vomiting, lethargy, and shock exactly 2 hours after ingesting a new solid food (oats).
Establishing the temporal relationship to a specific trigger is crucial for diagnosing food-induced syndromes.
2
Differentiate the etiology of the shock.
The absence of rash, urticaria, or wheezing rules out IgE-mediated anaphylaxis. The soft abdomen reduces the likelihood of a surgical abdomen, despite the mimicking symptoms.
FPIES uniquely causes profound hypovolemic shock without the classic cutaneous or respiratory signs of anaphylaxis.
3
Interpret the laboratory findings in clinical context.
The extreme leukocytosis with bandemia mimics sepsis but is a classic, expected stress response finding in acute FPIES.
Recognizing that FPIES causes a sepsis-like laboratory picture prevents misdiagnosis and inappropriate reliance on antibiotics.
4
Determine the most appropriate life-saving intervention.
Immediate intravascular volume expansion with normal saline and cessation of vomiting with a 5-HT3 antagonist (ondansetron).
The primary cause of morbidity in severe FPIES is rapidly progressive hypovolemic shock due to fluid shifts and emesis.

Key Concept

Acute Food Protein-Induced Enterocolitis Syndrome (FPIES) presents with delayed-onset (1-4 hours) profuse vomiting, lethargy, and hypovolemic shock without IgE-mediated symptoms. It requires aggressive IV fluid resuscitation and ondansetron.
Estimated Time:2m 0s
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Topics

Pediatric Gastrointestinal Disorders

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