Beside out patient department, emergency department exit in hospital world wide. It’s name said it’s importance.
In medical care the severity addressed:
i) emergency
ii) urgency
The sharp difference is "emergency" give some time to doctor but "urgency" didn’t give a nano second. Therefore, patient with urgency is more important than patient with emergency.
Next to that, patient with which organ damage or type of disease also matter.
Then, age, co-morbidity.
These are few about severe patient.
Lastly, at emergency department we generally said either give services as quick as possible" or "wait as least time as possible" because life is in danger or damage may permanent.