Parents bring their 5-year-old son to the emergency department because he has developed wo… — USMLE Step 2 CK

Parents bring their 5-year-old son to the emergency department because he has developed worsening weakness in his legs over the past two days. According to his mother, he has been stumbling frequently and today refused to get out of bed, complaining that his legs feel "like jelly." Three weeks ago, the boy experienced a self-resolving episode of abdominal cramps and bloody diarrhea. On physical examination, his temperature is $36.9^\circ\text{C}$ ( $98.4^\circ\text{F}$ ), heart rate is $108/\text{min}$ , respiratory rate is $20/\text{min}$ , and blood pressure is $102/64\text{ mm Hg}$ . He is alert and interactive. Cranial nerve examination shows no abnormalities. Motor examination reveals symmetric $3/5$ strength in the proximal and distal lower extremities, and $5/5$ strength in the upper extremities. Deep tendon reflexes are absent at the patellae and Achilles, and $1+$ at the biceps. Sensory examination to light touch and pinprick is unremarkable. Which of the following is the most appropriate next step in the management of this patient?

Bedside measurement of forced vital capacityAnswer
B
Initiation of empiric intravenous ceftriaxone and vancomycin
C
Immediate transport for non-contrast computed tomography of the head
D
Reassurance and scheduling a follow-up assessment of motor milestones
E
Administration of intravenous methylprednisolone

Answer

Bedside measurement of forced vital capacity is the most critical next step to monitor for impending respiratory failure in Guillain-Barré syndrome.

The correct answer addresses the most critical and life-threatening complication of Guillain-Barré syndrome (GBS): neuromuscular respiratory failure. GBS presents with ascending, symmetric, flaccid paralysis and areflexia, often preceded by a gastrointestinal or respiratory infection (e.g., Campylobacter jejuni). Because the weakness can ascend rapidly to involve the diaphragm and intercostal muscles, nearly a third of patients require mechanical ventilation. Serial bedside measurements of forced vital capacity (FVC) and negative inspiratory force (NIF) are essential. A rapid decline in FVC warrants elective intubation before the patient develops overt hypoxia or hypercapnia, as relying solely on pulse oximetry or arterial blood gas changes is dangerous and occurs too late in the course of neuromuscular failure.

Step-by-Step Solution

Analyze the clinical presentation and recent history.

The patient has acute, symmetric, ascending weakness and areflexia following a diarrheal illness (likely Campylobacter jejuni).

This establishes a high clinical suspicion for Guillain-Barré syndrome (GBS).

Identify the primary immediate threat to life in this condition.

Up to 30% of patients with GBS develop neuromuscular respiratory failure due to diaphragm and intercostal muscle weakness.

Anticipating life-threatening complications dictates the next best step in management.

Determine the appropriate intervention to address this threat.

Serial bedside measurements of forced vital capacity (FVC) and negative inspiratory force (NIF) are required to monitor respiratory muscle strength.

FVC measurement provides an objective assessment of respiratory decline, indicating when elective intubation is necessary before overt hypoxia occurs.

Key Concept

Patients with suspected Guillain-Barré syndrome require immediate and serial assessment of pulmonary function (using vital capacity and negative inspiratory force) due to the high risk of rapid, life-threatening neuromuscular respiratory failure.

Estimated Time:1m 15s

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic