The purpose of basic life support (abbreviated BLS) is to save lives in a variety of different situations that require immediate attention. These situations can include, but are not limited to, cardiac arrest, stroke, drowning, choking, accidental injuries, violence, severe allergic reactions, burns, hypothermia, birth complications, Drug addiction, and alcohol intoxication. The most common emergency that requires BLS is cerebral hypoxia, a shortage of oxygen to the brain due to heart or respiratory failure. A victim of cerebral hypoxia may die within 8–10 minutes without basic life support procedures. BLS is the lowest level of emergency care, followed by advanced life support and critical care.