Paediatricsmiddle twist
A 5-week-old boy, first child, has had one week of vomiting that occurs within 30 minutes of every feed and is now forceful, landing well away from him. The vomit is milk, never green. He is hungry immediately afterwards and takes the next feed eagerly. He has lost 300 g since his last weigh at 3 weeks. He has had no wet nappy for eight hours; his fontanelle is sunken and his mucous membranes are dry. Blood tests: sodium 133 mmol/L, potassium 2.8 mmol/L (3.5–5.0), chloride 86 mmol/L (98–108), bicarbonate 37 mmol/L (22–28), pH 7.53. An ultrasound confirms a thickened, elongated pylorus.
Which one of the following is the most appropriate initial management?