Loss of consciousness

In the emergency department, the patient complained of shortness of breath but denied chest pain, cough, fever, headache, weakness, or previous neurological difficulty. He had no significant past medical history and had been well before losing consciousness.

Loss of consciousness refers to a state in which an individual lacks normal awareness of self and the surrounding environment. The patient is not responsive and will not react to any activity or stimulation. Syncope is the medical term for temporary loss of consciousness. Unconsciousness can last from several seconds to longer periods of time and occurs due to a shortage of oxygen in the brain, which can happen for a variety of reasons.
Causes
Causes of unconsciousness specific to fainting can be found in the Fainting topic.
Diabetes affects blood sugar, and too much sugar (hyperglycemia) and too little sugar (hypoglycemia) can lead to unconsciousness in the form of diabetic coma or insulin shock, respectively.
Substance abuse and alcohol abuse, straining during bowel movement, coughing hard, and breathing quickly (hyperventilating) may all cause unconsciousness.
Common causes of unconsciousness include:
Alcohol (drunkenness)
A hit on the head or chest (getting knocked out)
Shock
Seizures
Poisoning
Fainting (from fright, weakness, low blood sugar, etc.)
Heat stroke
Stroke
Heart attack
A car accident
Severe blood loss
A drug overdose
Hyperventilating
Dehydration
Symptoms
A person who is unconsciousness may be
Drowsy and/or disoriented; he/she may come in and out of consciousness.
Confused and incoherent.
In a coma; he/she may be completely motionless.
Medical emergency

Seek emergency medical care if the person:
Has stopped breathing.
Does not regain consciousness quickly (ie, within 5 minutes).
Has been injured, especially if he/she is bleeding.
Has diabetes.
Is pregnant.
Is aged greater than 50.
Is having chest pain, pressure, discomfort, or a pounding or irregular heartbeat.
Cannot speak, has vision problems, or can’t move his/her arms or legs.
Has a seizure.
Experiences loss of bowel control.