A 62-year-old man presents with fever, productive cough, and pleuritic chest pain. He is hypotensive (BP 88/52 mmHg), tachycardic (39.5°C), and confused. Lactate is 4.5 mmol/L. You suspect septic shock secondary to pneumonia. According to Surviving Sepsis Campaign guidance adopted in Canadian practice, which intervention has the highest priority in the first hour?