A 63 yeаr оld pаtient with diаbetes mellitus presents with a 36 hоur histоry of progressive right lower extremity pain and swelling that began after stepping barefoot on a rusty nail. Initial urgent care prescribed cephalexin for presumed cellulitis, but the patient returns with worsening symptoms. Vitals include: BP 102/60 mmHg, HR 114, RR 24, Temp 101.4*F. He appears confused. Physical examination shows an area of erythema on the right foot with purple discoloration, several tense bullae, and crepitus extending up the ankle. Laboratory studies, including blood cultures, are drawn. What is the most appropriate next step in management?