Cardiac Arrest

Cardiac arrest refers to a condition in which the heart stops pumping blood to the body. It occurs due to one of three main reasons, as will be explained.

The first is ventricular fibrillation/pulseless ventricular tachycardia. In this case, the heart shakes rapidly but does not pump blood (ventricular fibrillation), or it tries to pump so rapidly (pulseless ventricular tachycardia) it does not allow blood to flow in, or effectively flow out.

The second type is called pulseless electrical activity (also known as electromechanical dissociation). In this case there is normal electrical conduction in the heart, but the heart does not contract.

The third type is called asystole, in which there is no electrical activity or muscle activity of the heart.

Individual is unconscious

Skin may be pale, clammy, or gray

There is no pulse

Ventricular fibrillation/pulseless ventricular tachycardia

Myocardial Infarction (heart attack)
Myocardial ischemia
Hypoxia (low oxygen blood level)
Hypokalemia (low blood Potassium)
Other electrolyte abnormalities
Medications (e.g., Verapamil given to patients with Wolff-Parkinson-White syndrome)

Pulseless electrical activity

Volume loss (e.g., bleeding from GI tract)
Tension Pneumothorax
Massive Myocardial Infarction (large heart attack)
Cardiac Tamponade (blood or fluid gets into the sac that holds the heart)
Hypoxia (low oxygen)
Massive Pulmonary Embolism (massive blood clot in the lungs)
Hyperkalemia (high Potassium)
Severe acidosis
Drug overdose
Hypothermia (low body temperature)

Asystole

Hypoxia (low oxygen)

Acidosis

Drug overdose

Hypokalemia (low Potassium)

Hyperkalemia (high Potassium)

Hypothermia (low body temperature, e.g., cold exposure)

Prolonged cardiac arrest from another cause above (ventricular fibrillation/tachycardia or pulseless electrical activity)

Airway is checked to make sure patent

Breathing is checked to see if present

Pulse, Heart and lungs are checked

Rhythm strip will help determine the cause -- in asystole, 2 separate leads should be checked to make sure truly asystole

Generally, the American Heart Association's Guidelines for advanced cardiac life support are followed. These are algorithms for management of these conditions (though the physician may make adjustments for individual cases as needed).
Listed below are some typical treatment courses. This is for informational purposes only. Advanced cardiac life support should only be performed by highly trained professions (e.g., physicians, nurses, etc.)
Ventricular Fibrillation/Pulseless Ventricular Tachycardia

Defibrillation (three Shocks of 200J, 300J, 360J, as needed)
Intubation
Epinephrine (given at repeated intervals)
Repeat defibrillation at 360J
Lidocaine
Repeat defibrillation at 360J
Bretylium
Repeated defibrillation at 360J as needed with consideration for repeat doses of antiarrythmic medications

Pulseless Electrical Activity

Intubation
Epinephrine
Quickly try to identify the cause
Volume trial often given (since volume loss is the most common cause)
Carefully examine lungs for Pneumothorax
Consider empirical pericardial tap
Consider other causes

Asystole

Confirm in 2 separate monitor leads (we do not want to mistakenly miss ventricular fibrillation)

Intubate

Epinepherine

Atropine

Consider transcutaneous pacing

Special considerations

Ventricular fibrillation/pulseless ventricular tachycardia is the most common cause of cardiac arrest and is best treated by rapid defibrillation. Defibrillation is the absolute priority in adult cardiac arrest. If cardiac arrest occurs at home and there is only one other person present -- call 911 first, then begin CPR (if more than one person is present, one may call 911 while another begins CPR).
Some public arenas (such as sports stadiums) and airplanes now have defibrillators available and are specially designed to be used by lay people. The best chance for someone to survive cardiac arrest is for defibrillation to begin within the first four minutes of arrest. For infants and children, see separate section (please note children/infants are treated completely differently).

For your information

Defibrillation means giving an electrical Shock to the heart to change the rhythm back to normal (since the rhythm is called fibrillation, hence we are "defibrillating"). Also note, atrial fibrillation is a completely different type of rhythm from ventricular fibrillation, and is treated differently. Atrial fibrillation does not usually cause cardiac arrest (see section on atrial fibrillation for more details).