It says in the scenario assume all four patients are of equal medical severity. Hence, isn't this an ethical dilemma, not based on medical knowledge?given the triage system cannot work in this case.Universities have moved away from these questions because at the end of the day it will help immensely if you had medical knowledge.
The defintion of DNR is that you do not resuscitate the patient if they go into cardiac arrest. All other measures in keeping them alive are determined by their advanced care directive if they had one or their next of kin. Just because they have life threatening injuries doesn't mean you cannot treat the patient.
In these kind of scenarios, the order would either score you minimal or no marks. It's testing your biases, sensitivity, ethical reasoning etc.. It doesn't matter if the wound or injury was self-inflicted your duty of care as a doctor is to provide equal access to care where possible. Just because a patient "ate fatty foods" or if the incident was "an accident" doesn't justify who gets seen first. It's always going to be treating the most severe injuries first as per the Triage system set up in emergency departments.
From a medical perspective imo the burns victim is probably most severe or the pregnant lady (depends on the situation). Again its very circumstantial as vital sign stability is the key component to assessment. If they are stable then you can treat the problem temporarily to buy you more time until it can be treated later. For example with the bleeding, pressure and retraction of the skin/tissue over the bleed will stem the flow of blood. I've seen AMI patients walk around for days before presenting to ED and on the other hand I have had to perform CPR on those that have arrested.