A 6-week-old infant is admitted with a diagnosis of hypertrophic pyloric stenosis. The infant has been vomiting for the past week and shows signs of dehydration. Which nursing intervention should be the priority before surgical correction?

Correcting fluid and electrolyte imbalances is the priority before surgery to ensure safe anesthesia and prevent complications like arrhythmias. Other options are less critical: prone positioning may not be safe, oral rehydration is contraindicated due to vomiting, and antiemetics do not address the underlying imbalance.

Understanding the Priority in Preoperative Care for Hypertrophic Pyloric Stenosis

The correct answer is 3. Correct fluid and electrolyte imbalances.

In infantile hypertrophic pyloric stenosis (IHPS), the hypertrophied pyloric muscle obstructs gastric emptying, leading to persistent, projectile, non-bilious vomiting. This physiological blockage results in a specific and dangerous sequence of metabolic derangements. The stomach contents lost through vomiting are rich in hydrochloric acid (HCl). Consequently, the infant loses hydrogen ions (H⁺) and chloride ions (Cl⁻). This loss of acid leads to a hypochloremic, hypokalemic metabolic alkalosis.

The body attempts to compensate for the alkalosis, but the priority before any surgical intervention is to restore a safe physiological state. The rationale provided by the study on preoperative fluid therapy in IHPS underscores this principle. The research highlights that infants with IHPS present with "significant metabolic derangement requiring preoperative fluid resuscitation" ^[1]. The study specifically investigated fluid therapy guided by serum chloride levels, as chloride is the key electrolyte lost in the emesis. A failure to correct these imbalances prior to administering anesthesia can lead to severe complications, including cardiac arrhythmias and respiratory depression, making surgery extremely high-risk.

Analyzing the other options clarifies why they are not the priority:
- Option 1 (Position the infant prone to prevent aspiration) is incorrect and dangerous. The priority positioning for an infant who is actively vomiting or at risk for vomiting is supine with the head of the bed elevated, or side-lying, never prone, due to the risk of sudden infant death syndrome (SIDS). While preventing aspiration is a nursing responsibility, it does not address the life-threatening metabolic condition that must be stabilized before surgery.
- Option 2 (Begin oral rehydration therapy immediately) is contraindicated. The underlying pathology is a mechanical obstruction at the pylorus. Any oral intake, including rehydration solutions, will not pass into the duodenum and will instead be vomited, worsening fluid and electrolyte losses and increasing the risk of aspiration. Preoperative resuscitation is achieved through intravenous fluid therapy, as studied in the comparison of conventional and bolus fluid therapy ^[1].
- Option 4 (Administer antiemetic medications as ordered) is not a primary intervention. The vomiting in IHPS is due to a mechanical obstruction, not a chemoreceptor trigger zone stimulation. Antiemetics are ineffective in treating the cause of the vomiting and do not correct the resultant dehydration and metabolic alkalosis. The core issue is the metabolic derangement, which requires direct correction through IV fluids.

The study comparing conventional fluid therapy (CFT) and bolus fluid therapy (BFT) explicitly states that BFT, guided by serum chloride levels, was investigated for its potential to allow "faster correction and improved outcomes" ^[1]. This confirms that the normalization of serum electrolytes, particularly chloride and the associated alkalosis, is the central goal of preoperative management. The nursing priority is to administer prescribed intravenous fluids, strictly monitor intake and output, and track the resolution of metabolic alkalosis by observing serial blood gas results, specifically looking for a rising serum chloride and a falling serum bicarbonate level. Only when the metabolic derangement is corrected, typically evidenced by a serum chloride level greater than or equal to 100 mEq/L and a bicarbonate level less than 30 mEq/L, is the infant considered optimized for the surgical pyloromyotomy.