Not answering your question, just adding related info: within most EU countries you're already covered for "emergency treatments" thru the universal healthcare offered to all citizens AND visitors.
This, however, doesn't include everything. A good point would be to know what exactly constitutes an emergency -other than the obvious. But there I can't help you, sorry, I don't know.
In any case, if you're not an EU citizen, or from a country with bilateral agreements, you'll be billed AFTER the treatment: https://cronicaglobal.elespanol.com/vida/asistencia-sanitaria-turistas-espana-turismo-medico_138119_102.html Also to mention, especially if you're visiting from the US, that, even if you have to pay costs over here are far far! less outrageous than over there.