Which is the first-line treatment for the following intestinal infection? A 36-year-old male presents with 1 day of diarrhea (10+ watery stools), vomiting 2-3 times. Stool Gram stain shows parallel-arranged Gram-negative curved bacilli resembling fish schools, suggesting suspected paracholera. After rapid IV infusion of 500 mL dextran and 2000 mL isotonic saline plus 3000 mL glucose solution, the patient develops palpitations, dyspnea, and inability to lie flat. Exam shows cyanotic lips, orthopnea, heart rate 140 bpm, and basal lung rales.