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Pediatrics·CA-1

Peds: Pyloric Stenosis

6-week-old infant for pyloromyotomy. Focus on electrolyte optimization and aspiration risk.

The stem

A 6-week-old male presents with projectile, non-bilious vomiting. He appears lethargic and dehydrated. Labs show Na 132, K 3.1, Cl 88, and a metabolic alkalosis. The surgeon wants to proceed immediately with pyloromyotomy...

Focus

Medical optimization before surgical intervention, electrolyte correction, and aspiration risk in newborns.

Examination relevance

A classic test of 'not rushing to the OR' until the patient is medically optimized.

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Expert sample response

Pyloric stenosis is never a surgical emergency; it is a medical emergency. My first priority is correcting the patient's metabolic alkalosis and dehydration before any anesthetic is administered.

I will cancel the immediate surgical request and initiate aggressive fluid resuscitation with 20cc/kg boluses of normal saline until the patient is making urine and shows improved skin turgor. I will replace potassium (K+) and chloride (Cl-) to restore the metabolic balance. Only once the chloride is >100 mEq/L and the bicarbonate is <30 mEq/L will I proceed. For the induction, I will perform a 'modified' Rapid Sequence Induction (RSI) after emptying the stomach with an OG tube in multiple positions (left, right, supine), as these infants are at high risk for aspiration of curdled milk.

Full walkthrough

What the Examiner Is Testing

This case tests a classic principle: pyloric stenosis is never a surgical emergency. It's a medical one. The examiner wants to hear you push back on the surgeon, articulate why the metabolic derangement must be corrected first, and then describe a safe aspiration-risk induction in a neonate.

The Board Trap

The trap is agreeing to proceed to the OR because "the baby is crying and the surgeon is ready." Hypokalemic, hypochloremic metabolic alkalosis causes central respiratory depression — inducing anesthesia in this metabolic state increases the risk of post-operative apnea dramatically. The second trap is doing a standard RSI without emptying the stomach first.

Walk-Through: How This Case Plays Out

Examiner: The surgeon says the pyloromyotomy needs to happen in the next hour. How do you respond?

Me: I would tell the surgeon we are not going to the OR yet. This is not a surgical emergency — it's a medical one. The baby has a chloride of 88 and potassium of 3.1. I need to fix the metabolic alkalosis before I can safely induce anesthesia. We're going to resuscitate with normal saline boluses, replace potassium, and I won't clear this patient for the OR until the chloride is above 100 and bicarb is below 30.

Examiner: It's six hours later. Labs now show Cl 102, K 3.5, bicarb 28. Are you ready to proceed?

Me: Yes, that's acceptable. We're close enough to normal that the respiratory drive will be adequate post-op. My plan is an awake oral gastric tube placement before induction — I'll pass it in multiple positions, left lateral, right lateral, and supine, to empty the curdled milk that's been sitting in there. Then I'll do a rapid sequence induction with cricoid pressure.

Examiner: During induction, you use succinylcholine and the infant develops masseter rigidity. What do you do?

Me: I would not proceed immediately — masseter rigidity in a child raises the concern for MH susceptibility. I'd complete the intubation since the airway is the priority, but I'd switch off sevoflurane if I'm using it, move to TIVA, call for dantrolene, and start monitoring ETCO2 and temperature carefully. I'd have the MH cart available immediately.

Examiner: The case goes smoothly. The baby is extubated in the OR. What's your post-op concern?

Me: Post-op apnea is my main concern. These neonates can have central apnea from residual metabolic alkalosis and opioid sensitivity. I want minimal opioids — I'd use a sucrose pacifier, acetaminophen rectally, and a small amount of regional if possible. I'd keep the baby on apnea monitoring for at least 12 hours.

Key Phrases That Score Points

  • "Pyloric stenosis is never a surgical emergency — we fix the metabolic alkalosis first."
  • "Chloride above 100, bicarb below 30 — those are my clearance criteria before induction."
  • "OG tube in three positions to empty the stomach — left, right, and supine."
  • "Post-op apnea monitoring for at least 12 hours — I'm not sending this neonate to the floor without it."
  • "Minimal opioids post-op — the risk of apnea from opioids in a neonate is real and I'm not taking it."

Why This Case Appears on the Boards

This case is a test of clinical judgment over surgical urgency. It forces you to hold your ground against external pressure and demonstrate that you understand why metabolic optimization protects the patient during emergence and recovery — not just during induction.