Published on 07/02/2015 by admin
Filed under Anesthesiology
Last modified 07/02/2015
This article have been viewed 879 times
Robert J. Friedhoff, MD
Pyloric stenosis is one of the most common gastrointestinal abnormalities occurring during the first 6 months of life. The incidence is 1 in 500 live births in whites and 1 in 2000 in blacks, with males having a two to four times increased incidence, compared with females. It is especially common in first-born sons of parents who had pyloric stenosis.
Pyloric stenosis usually presents at 3 to 5 weeks of age in the preterm or term infant. Although the cause is unknown, proposed mechanisms include an imbalance in the autonomic nervous system, humoral imbalances, infection, or edema with muscular hypertrophy. Hirschsprung first described pyloric stenosis in 1888, although he could offer no effective treatment. Ramstedt described the optimal surgical therapy in 1912. Since then, improvements in fluid therapy and anesthetic technique have decreased the mortality rate from 25% to 0.01% to 0.1%.
In pyloric stenosis, a thickening of the circular muscular fibers in the lesser curvature of the stomach and pylorus (from both hypertrophy and an increased number of fibers) causes obstruction of the pyloric lumen. The typical presentation is an infant with persistent bile-free vomiting who is dehydrated and lethargic. The skin is cool to touch, capillary refill is usually greater than 15 sec, and the eyes are sunken. The infant may present at less than its birth weight. Vomiting can be projectile (2 to 3 feet), occurring after every feeding, thus resulting in loss of hydrogen, chloride, sodium, and potassium ions from the stomach.
A metabolic alkalosis develops for several reasons. First and foremost is the loss of hydrogen ions from the stomach. The vomitus does not contain any of the alkaline secretions of the small intestine because the obstruction is proximal (at the gastric outlet). Bicarbonate is one of the ions contained in pancreatic secretions, but because little food reaches the duodenum, pancreatic output is decreased, and bicarbonate remains in plasma (instead of being secreted by the pancreas).
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