A 62-year-old man presents to the ED with fever, rigors, and hypotension (BP 84/48 mm Hg, HR 118/min, RR 26/min). He is febrile to 102.7 °F, confused, and his lactate is 4.1 mmol/L. Two sets of blood cultures are obtained. What is the next best step to initiate within the resuscitation bundle?