As he leaves the hospital, Caldwell carries the fire helmet given to him by Manny Schecter back in Season 3. Manny was one of the three firefighters Caldwell treated as burn victims.
Referring to Caldwell's AIDS diagnosis, Dr Craig says, "I never thought of you as a fag." Caldwell emphasizes that he's straight, but Craig's comment reflects the popular misconception in the 1980s that AIDS was exclusively (or at least primarily) a "gay disease".
Mentions are made of AIDS testing related to "HTLV-III" antibodies. HTLV-III (human T-lymphotropic virus, type III) was the earlier nomenclature for the virus now known as HIV.