Prevention. The fewer people coming through the hospital, the less waste generated.
If someone comes in with a problem that can be solved permanently (e.g. type 2 diabetes), solve it the first time so that they won't be back.
EDIT: Anyone on the hospital staff, nurse or receptionist or janitor, can share information that could help someone to avoid repeat hospital visits. Just give a disclaimer like "I'm not a doctor, so don't take this as medical advice, but..." and then tell the patient with diabetes or atherosclerosis about the benefits of a low-fat plant-based diet (and maybe give them a simple link like pcrm.org), or direct the biker with the fractured skull to a source of quality motorcycle helmets, or provide the addict who overdosed with the contact information of a local support group... We never really know how big a difference our actions can make.