The priority intervention for an infant admitted with HPS and dehydration is fluid resuscitation and electrolyte correction, not immediate surgery. A pyloromyotomy is the definitive treatment but is an urgent, not emergent, procedure.
Priority Nursing Actions on Admission
- Establish IV Access: Secure intravenous access immediately to administer isotonic fluids (e.g., 0.9% Normal Saline) for initial volume expansion.
- Monitor Electrolytes: Assess serum electrolytes, particularly chloride and potassium, to identify the classic hypochloremic, hypokalemic metabolic alkalosis.
- Strict I/O: Maintain strict intake and output records, including daily weights, to guide fluid replacement therapy.
- NPO Status: Keep the infant NPO (nothing by mouth) to rest the stomach and prevent further vomiting and aspiration risk.
Understanding the Pathophysiology
Persistent vomiting of gastric contents leads to a predictable metabolic derangement:
- Loss of HCl: Depletes hydrogen (H⁺) and chloride (Cl⁻) ions, causing hypochloremia and metabolic alkalosis.
- Renal Compensation: The kidneys initially excrete bicarbonate, but as hypovolemia worsens, they retain sodium and excrete potassium and hydrogen, leading to paradoxical aciduria and worsening hypokalemia.
Preoperative Goal
Surgery is delayed until the infant is hemodynamically stable and electrolyte imbalances are corrected. The target is often a serum chloride level greater than 100 mEq/L and a bicarbonate level less than 30 mEq/L to ensure safe anesthesia induction.