A 68-year-old female presents to the emergency department with confusion, fever, and rapid breathing. Her vital signs are: BP 85/50 mmHg, HR 120 bpm, RR 28/min, Temp 39.5°C (103.1°F), and SpO2 94% on room air. Which of the following is the most appropriate initial intervention?
Start vasopressors
Administer IV fluids
Obtain blood cultures
Initiate oxygen therapy