A 42-year-old woman with community-acquired pneumonia is admitted to the ICU. On day 2, she develops fever (38.8°C), hypotension (BP 88/54 mmHg), tachycardia (HR 126/min), and altered mental status (GCS 13). Lactate is 4.1 mmol/L. She has already received ceftriaxone + azithromycin for 18 hours. Central venous pressure is 8 cmH₂O and ScvO₂ is 62%. After drawing blood cultures, what is the most appropriate next step?