A 30-year-old man with type 1 diabetes presents with nausea, abdominal pain, and polyuria. He has missed multiple insulin doses. Vitals: temperature 99.0 F, heart rate 120 per minute, blood pressure 102/64 mm Hg, respiratory rate 26 per minute with Kussmaul respirations. Labs: glucose 480 mg per dL, anion gap 22, bicarbonate 12 mEq per L, potassium 5.2 mEq per L. What is the most appropriate initial fluid resuscitation?