Anesthetic Considerations in Hypertrophic Pyloric Stenosis

HYPERTROPHIC PYLORIC STENOSIS

Pathophysiology

Hypertrophic pyloric stenosis impedes emptying of gastric contents. Persistent vomiting depletes potassium, chloride, hydrogen, and sodium ions, causing hypochloremic metabolic alkalo-sis. Initially, the kidney tries to compensate forthe alkalosis by excreting sodium bicarbonate in the urine. Later, as hyponatremia and dehydration worsen, the kidneys must conserve sodium even at the expense of hydrogen ion excretion (para-doxic aciduria). Correction of the volume and ion deficits and metabolic alkalosis requires hydra-tion with a sodium chloride (rather than lactated Ringer’s) solution supplemented with potassium chloride.

Anesthetic Considerations

Surgery should be delayed until fluid and electro-lyte abnormalities have been corrected. Operation for correction of pyloric stenosis is never an emer-gency. The stomach should be emptied with a nasogastric or orogastric tube; the tube should be suctioned with the patient in the supine, lateral, and prone positions. Diagnosis often requires contrast radiography, and all contrast media will need to be suctioned from the stomach before induction. Techniques for intubation and induc-tion vary, but in all cases the patient’s increased risk of aspiration must be considered. Experienced clinicians have variously advocated awake intu-bation, rapid sequence intravenous induction, and even careful inhalation induction in selected patients. Pyloromyotomy is a short procedure that requires muscle relaxation. These neonates may be at increased risk for respiratory depression and hypoventilation in the recovery room because of persistent metabolic (measurable in arterial blood) or cerebrospinal fluid alkalosis (despite neutral arterial pH).