Emergency medication isn't dosed by gender, it's dosed by weight. It really would only matter with certain drugs in pregnancy.

It is helpful to know the original gender for some things because certain illnesses present differently in men V women and not all of that changes post transition so if you are treating a man it would be helpful to know that he was born a woman so you don't brush off certain symptoms as minor if in fact in a women they would be very alarming. For example, men having heart attacks are more likely to present with the classic chest pain radiating to their arm. Women can have chest pain, but often present as sudden onset of nausea and vomiting with no pain. That's a rare presentation of a heart attack in a man, so a man complaining of severe nausea is more likely to be thought of as GI in nature, but if you know he's trans then alarm bells start screaming that this might be cardiac and you need to do an EKG now.

But in an unconscious trauma patient, it doesn't really matter. If a trans man still has a uterus then that's an additional organ to be damaged that might not be expected, but that's not something that's going to be caught in the ambulance either way because we don't have a CT scanner hanging out in the cabinets.