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.

Core Nursing Explanation Key Concept Analysis: This question tests the priority preoperative management for an infant with Hypertrophic Pyloric Stenosis (HPS). HPS is a condition where the muscle of the pylorus (the outlet of the stomach) thickens, causing a mechanical obstruction. This leads to projectile, non-bilious vomiting, which results in significant loss of gastric fluids rich in hydrochloric acid (HCl) and potassium (K+). The pathophysiological consequence is a hypochloremic, hypokalemic metabolic alkalosis. The infant's dehydration and electrolyte imbalance are the most immediate threats to life and safety for anesthesia.

Answer Rationale: Key Point! The priority nursing intervention is to Correct fluid and electrolyte imbalances. Before any surgical correction (pyloromyotomy), the infant must be stabilized. Anesthesia and surgery are high-risk in a state of dehydration and alkalosis, which can lead to cardiac arrhythmias, respiratory depression, and poor wound healing. IV fluids (typically 0.45% or 0.9% Normal Saline with added potassium chloride) are administered to restore intravascular volume and correct the specific electrolyte deficits and alkalosis. This is the foundational step that makes all other care safe.

Distractor Analysis:
• Watch out for confusion! Option 1: Positioning the infant prone is contraindicated due to the increased risk of Sudden Infant Death Syndrome (SIDS). The safe position for an infant at risk for aspiration is on the right side or with the head of the bed elevated, which uses gravity to help keep gastric contents down.
• Option 2: Beginning oral rehydration is ineffective and dangerous. Because the pylorus is obstructed, oral fluids cannot pass into the intestines and will only contribute to further vomiting and aspiration risk. All fluids must be given intravenously (NPO - Nothing by mouth).
• Option 4: Administering antiemetics does not treat the mechanical obstruction. While they may reduce the urge to vomit, they do not correct the underlying life-threatening fluid and electrolyte imbalances. Surgery is the definitive treatment for the obstruction.

Related Concepts: The nursing process prioritizes physiological needs (Maslow's Hierarchy). Airway, breathing, and circulation (ABCs) are paramount. In this case, the circulatory deficit (dehydration) and its metabolic consequences (electrolyte imbalance) are the highest priority threats. Always address life-sustaining physiological stability before proceeding with diagnostic or corrective procedures. Concept Summary • Disease: Hypertrophic Pyloric Stenosis (HPS) – mechanical gastric outlet obstruction.
• Classic Symptom: Projectile, non-bilious vomiting in a 3-6 week old infant.
• Key Pathophysiology: Loss of H+ and Cl- in vomitus → Hypochloremic, Hypokalemic Metabolic Alkalosis.
• Diagnostic Sign: Palpable "olive-shaped" mass in the RUQ (Right Upper Quadrant), visible peristaltic waves.
• Definitive Treatment: Pyloromyotomy (surgical splitting of the pyloric muscle).
• Pre-op Priority: IV fluid and electrolyte replacement to correct dehydration and alkalosis.
• Post-op Care: Advance feeds gradually (clear liquids → formula/breast milk), monitor for vomiting.
Side-by-Side Comparison!

Condition	Hypertrophic Pyloric Stenosis (HPS)	Gastroesophageal Reflux (GER)
Age of Onset	3-6 weeks	Birth onward
Type of Vomiting	Projectile, non-bilious, Key Point! after feeding	Regurgitation/spitting up, often with positioning
Pathology	Mechanical obstruction (thickened muscle)	Functional immaturity of lower esophageal sphincter
Electrolyte Imbalance	Hypochloremic, hypokalemic metabolic alkalosis (pH >7.45, HCO3- high, K+ low, Cl- low)	Usually none, or mild metabolic acidosis if poor feeding
Treatment	Surgical (Pyloromyotomy)	Conservative (thickened feeds, positioning, time)

Anatomy, Physiology & Pharmacology Points • Anatomy: The pylorus is the muscular valve connecting the stomach to the duodenum. In HPS, it becomes hypertrophied and stenotic.
• Physiology: Gastric fluid contains H+ (acid) and Cl- (chloride). Vomiting this fluid leads to loss of acid, causing the blood to become alkaline (metabolic alkalosis). The kidneys excrete K+ and H+ to retain Na+, worsening the hypokalemia.
• Lab Values: Expect low serum chloride (< 98 mEq/L), low potassium (< 3.5 mEq/L), and elevated bicarbonate (> 26 mEq/L) indicating metabolic alkalosis.
• Pharmacology (IV Fluids): The fluid of choice is often 0.45% or 0.9% Sodium Chloride with added Potassium Chloride (KCl). Potassium is added only after urine output is confirmed to prevent hyperkalemia.
Memory Tips • Acronym for HPS Symptoms: Projectile vomiting, Olive (palpable mass), Labs show alkalosis, Oldest is 6 weeks, Right Upper Quadrant mass, Urine output down, Surgery needed. (POLORUS – like pylorus!)
• Metabolic Alkalosis Cause: Think "Lost my HCl" → Hypochloremic, Hypokalemic, Metabolic Alkalosis.
• Pre-op Priority: "Fix the mix before the fix!" (Fix the fluid/electrolyte mix before the surgical fix).
High-Frequency NCLEX Topics NCLEX loves to test priority-setting and pediatric surgical conditions. HPS is a classic. Remember: Physiological stability (ABCs, fluid/electrolytes) always comes before surgery or diagnostic procedures. You will also be tested on safe infant positioning (back to sleep, side-lying for aspiration risk) and contraindications (no prone positioning).
Watch Out for Question Variations! • Instead of asking for the priority intervention, the question could ask: "Which laboratory finding would the nurse expect?" (Answer: Metabolic alkalosis with hypochloremia and hypokalemia).
• Or: "The nurse is preparing the infant for surgery. Which finding indicates the infant is ready?" (Answer: Fluid and electrolyte imbalances are corrected, urine output is adequate).
• Or: "The parent asks why the baby can't have a bottle before surgery. What is the nurse's best response?" (Explain NPO status and risk of aspiration due to obstruction).

Nursing Clinical Practice Guide Clinical Scenario: You are the nurse in the pediatric unit admitting Michael, a 6-week-old male with a 5-day history of worsening vomiting after feeds. The vomit is forceful, shoots across the bassinet, and never has a greenish color. On assessment, he has poor skin turgor, a sunken fontanelle, and few wet diapers. The pediatric surgeon palpates a small, firm, olive-shaped mass in his right upper abdomen and orders an ultrasound to confirm HPS.

Nursing Intervention Strategy:
1. Assessment: Perform a thorough head-to-toe assessment focusing on hydration status (vital signs, weight, fontanelle, mucous membranes, skin turgor, capillary refill, urine output). Monitor for visible peristaltic waves. Strictly measure and document all intake (IV only) and output (emesis, urine).
2. Nursing Diagnosis: Fluid Volume Deficit related to active loss (projectile vomiting). Risk for Aspiration related to vomiting. Anxiety (parental) related to infant's illness and impending surgery.
3. Planning & Implementation: The priority plan is to restore fluid and electrolyte balance. Insert an IV line and administer prescribed IV fluids (e.g., D5 0.45% NS with 20 mEq KCl/L). Never add potassium to a bag until you have confirmed the infant has voided! Maintain strict NPO status. Position the infant on the right side or with the head elevated to minimize aspiration risk. Provide emotional support and clear education to the parents about the condition and the planned surgery.
4. Evaluation: The infant is ready for surgery when hydration is restored (good skin turgor, moist mucous membranes, fontanelle flat), electrolytes are within normal limits, and urine output is at least 1-2 mL/kg/hr.

Patient Safety and Precautions:
• Airway: Always have suction equipment at the bedside. Never leave the infant unattended on his back immediately after a vomiting episode.
• Positioning: Prone positioning is contraindicated. Follow "Back to Sleep" guidelines for SIDS prevention. For aspiration risk, use right side-lying or semi-upright positioning.
• Medication/IV: Use an IV pump for precise fluid delivery. Double-check potassium chloride additives with another nurse. Monitor the IV site closely for infiltration.
Nursing Procedure & Medication Flow Preoperative Management for HPS:
1. Admit & Assess: Obtain weight, vital signs, full physical. Insert IV catheter.
2. Lab Work: Draw blood for electrolytes (Chem 7). Expect results showing alkalosis.
3. IV Therapy:
  a. Hang maintenance IV fluids as ordered (e.g., D5 0.45% NS).
  b. After confirming the infant has voided, add prescribed KCl to the IV bag.
  c. Calculate drip rate based on weight (e.g., 100 mL/kg/day for maintenance + deficit replacement).
4. NPO & Positioning: Place "NPO" sign. Position infant on right side.
5. Parent Education: Explain why the baby cannot eat, the purpose of IV fluids, and what to expect with surgery.
6. Pre-op Checklist: Once labs normalize and hydration is restored, complete surgical consent, pre-op vital signs, and ensure NPO time has been met.
A Word from Your Senior Nurse "Nursing is not just about carrying out physician orders — it's about being the frontline guardian for your patients! In clinical practice, recognizing subtle changes in a patient's vital signs early can prevent deterioration. With this little one, your vigilant monitoring of his fontanelle, skin, and urine output is what tells you if the IV fluids are working. When studying for your boards, don't just memorize — connect everything to a real patient situation and always ask 'why?' That mindset will not only earn you a great score on the NCLEX but will make you a truly confident, professional nurse! Remember, in peds, they can't tell you how they feel, so your assessment skills are everything."