A 72-year-old man is brought to the emergency department with fever, confusion, and hypotension. Vitals: temperature 102.4 F, blood pressure 82/46 mmHg, heart rate 118 per minute, respiratory rate 26 per minute, oxygen saturation 93 percent on 2 L nasal cannula. Lactate is 4.2 mmol/L. After obtaining blood cultures, broad-spectrum antibiotics are started. What is the most appropriate initial fluid resuscitation strategy?