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Transient tachypnea of the newborn — USMLE Step 2 CK MCQ

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HardPediatricsTransient tachypnea of the newbornUSMLE Step 2 CK

A 5-week-old boy has progressively forceful nonbilious vomiting and ultrasound-confirmed hypertrophic pyloric stenosis. He is lethargic, capillary refill is 4 seconds, chloride is 84 mEq/L, potassium is 2.9 mEq/L, and bicarbonate is 38 mEq/L. What should be done before pyloromyotomy?

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Correct answer: A — Restore intravascular volume and correct chloride and potassium deficits

Pyloric stenosis is a medical resuscitation problem before it is a surgical problem. Repeated loss of gastric hydrochloric acid causes hypochloremic, hypokalemic metabolic alkalosis and volume depletion; anesthesia before correction increases respiratory and cardiac risk. Isotonic chloride-containing fluid is given first, potassium is added after urine output is established, and pyloromyotomy follows adequate resuscitation. Acetazolamide does not replace chloride or volume. Enteral feeding worsens obstruction, and atropine is not preferred definitive therapy for a suitable surgical candidate.

Reference: NCBI Bookshelf: Pyloric stenosis. https://www.ncbi.nlm.nih.gov/books/NBK555931/