A 15 kg, 4-year-old girl presents for exploratory laparotomy for small bowel perforation. She is somnolent and her mother reports that she has been wetting herself even though she was previously potty-trained. Her labs include: glucose 350 mg/dL, potassium 3 mg/dL, bicarbonate 5 mEq/L, and beta-hydroxybutyrate 4 mmol/L. Administration of which of the following fluids is MOST appropriate?