Sarcasm aside, there are only 3 places I’ve ever seen bleed more than 15L intra-op: portal vein injury with HPB surgery, aorta during AAA or TAAA, and pulmonary vein injury during VATS. I think each of these locations has anatomic factors which render surgical control of hemorrhage difficult. (This is excluding cardiac surgery with RV injuries during redo sternotomy, etc- it feels a bit different when you’re hemorrhaging but you can go on sucker bypass). I guess the other way to lose that much blood would be bleeding from raw surfaces or bone marrow: liver txp, major craniofacial synostosis type stuff, multi level redo scoliosis, etc. Probably need to include C-section gone wrong —> embo —> salvage hysterectomy on that list, too.
edit: forgot to add retrohepatic IVC injury to the list… I still get nightmares thinking about that one case…