I had actually started this series of Emergency Aid posts with an article on fractures (broken bones), but I realized I was going about this in the wrong order...
First things first, the ABC's of First-Aid/Emergency-Aid.
Whenever an incident occurs where you will personally be the first person on the scene, the VERY FIRST thing you should do is secure the area. No treatment you could ever possibly render would make the situation any more tragic than if the 'rescuer-needs-rescue'. These situations are very scene specific and can be as simple as having someone direct traffic at an accident scene or making sure the overhead area is free from falling debris in a construction/logging accident. Always take a few moments to stop, look around and understand what is actually going on before you act.
Ok, with that established and hopefully understood...I will move on to what the ABC acyronm means. Whenever you encounter someone who has been injured, you need to make a quick assessment that can truly mean the difference between stabilization or death in moments.
A = Airway, check the individual to see if the pathway from the mouth to lungs is clear. If the person is concious, ask the patient to talk to you. Ask questions like "What's your name?" "Where do you hurt?" When you hear paramedics ask these questions, they're not only asking them for their records. If you have a patient who is unresponsive (with the exception of possible spinal injuries), open the person's mouth and look for any obstruction, pay careful attention to the positioning of the tongue.
B = Breathing, if the patient is screaming and/or communicating verbally, chances are they are breathing normally. When in doubt, CAREFULLY listen for respirations from the nose or mouth. If you cannot hear anything from an unconcious patient, perform a mandibular jaw thrust (Another Method) paying careful attention to avoid excessive movement in any situation where you may suspect spinal injury. Another commonly overlooked part of the breathing assessment is make sure the injured has bilateral respirations (breathing properly from both lungs). You may either use the stethoscope or simply place your ear over the ribcage just under the pectoral region and listen for clean respirations.
C = Circulation, check for a pulse, below are two pictures for the best areas on the body to check for a pulse without moving a patient.
Count the beats you feel for 15 seconds, then multiply by four...this will give you your patients heartrate in bpm, keep a record of this figure. As well as pulse, you'll want to take notes of other circulatory problem signatures. How is the patient's color? Pale, flushed, cold/clammy skin?
Depending on your level of first-aid training, the C also refers to the control of any openly bleeding injuries. Watch for a future edition on the methods of hemorrage control.
As long as you verify the ABC's and can act accordingly if one of the three have not been met, the injured should have a good baseline for survival until emergency professionals arrive. Keeping a blanket around to keep the person warm won't hurt either.