Pulseless electrical activity

Pulseless electrical activity or PEA (also known by the older terms electromechanical dissociation) refers to a cardiac arrest situation in which a heart rhythm is observed on the electrocardiogram that should be producing a pulse, but is not. Under normal circumstances, electrical activation of muscle cells precedes mechanical contraction of the heart (known as electromechanical coupling). In PEA, there is electrical activity, but the heart either does not contract or there are other reasons why this results in an insufficient cardiac output to generate a pulse and supply blood to the organs.

Cardiopulmonary resuscitation is the first treatment for PEA, while potential underlying causes are identified and treated. Various drugs may be administered.

Signs and symptoms
Pulseless electrical activity leads to a loss of cardiac output, and the blood supply to the brain is interrupted. As a result, PEA is usually noticed because a person loses consciousness and stops breathing spontaneously. This is confirmed by examining the airway for obstruction, observing the chest for respiratory movement, and feeling the pulse (usually at the carotid artery) for a period of 10 seconds.

Causes
These possible causes are remembered as the 6 Hs and the 6 Ts.
 * Hypovolemia
 * Hypoxia
 * Hydrogen ions (Acidosis)
 * Hyperkalemia or Hypokalemia
 * Hypoglycemia
 * Hypothermia
 * Tablets or Toxins (Drug overdose)
 * Cardiac Tamponade
 * Tension pneumothorax
 * Thrombosis (Myocardial infarction)
 * Thrombosis (Pulmonary embolism)
 * Trauma (Hypovolemia from blood loss)

Diagnosis
The absence of a pulse confirms cardiac arrest, but PEA can only be distinguished from other causes of cardiac arrest with a device capable of electrocardiography (ECG/EKG). In PEA, there is electrical activity in the heart (as opposed to asystole), but not compatible with either ventricular fibrillation or ventricular tachycardia.

Treatment
Cardiopulmonary resuscitation is initiated immediately, although this may not take place if there has been a decision not to resuscitate. The approach in treatment of PEA is to treat the underlying cause, if known (e.g. relieving a tension pneumothorax). Where an underlying cause for PEA cannot be determined and/or reversed, the treatment of pulseless electrical activity is similar to that for asystole.

The mainstay of drug therapy for PEA is epinephrine 1 mg every 3–5 minutes. Although previously the use of atropine was recommended in the treatment of PEA/asystole, this recommendation was withdrawn in 2010 by the American Heart Association due to lack of evidence for therapeutic benefit.

Sodium bicarbonate 1meq per kilogram may be considered in this rhythm as well, although there is little evidence to support this practice. Its routine use is not recommended for patients in this context, except in special situations (e.g. preexisting metabolic acidosis, hyperkalemia, tricyclic antidepressants overdose).

All of these drugs should be administered along with appropriate CPR techniques. Defibrillators are not used for this rhythm, as the problem lies in the response of the myocardial tissue to electrical impulses.