Pulseless electrical activity (PEA), also known as electromechanical dissociation, is a clinical condition characterized by unresponsiveness and impalpable pulse in the presence of sufficient electrical discharge. A lack of ventricular impulse often points to the absence of ventricular contraction, but the contrary is not always true. It means that the electrical activity is pertinent, but not sufficient, condition for contraction. In the case of cardiac arrest, the organized ventricular electrical activity does not usually follow sufficient ventricular response. The word “sufficient” is being used to describe a degree of ventricular mechanical activity that is adequate to generate a palpable pulse.
Pulseless electrical activity does not necessarily mean the lack of mechanical activity. There can be ventricular contractions and detectable pressures in the aorta which are also known as pseudo-PEA. True pulseless electrical activity is a state in which cardiac contractions are lacking in the presence of coordinated electrical impulses. Pulseless electrical activity can include a number of organized cardiac rhythms that may be supraventricular in origin (sinus versus nonsinus) or ventricular in origin (accelerated idioventricular or escape). An impalpable pulse should not always be taken as a pulseless electrical activity because it may be due to severe peripheral vascular abnormality. 
The etiology of pulseless electrical activity is classified into primary/cardiac and secondary/noncardiac causes.
Causes of secondary pulseless electrical activity include the famous "5 Hs and 5 Ts." These are as follows:
The incidence of pulseless electrical activity varies among different United States patient populations. It accounts for approximately 20% of sudden cardiac deaths outside of the hospital setting.
A study found that 68% of the recorded in-hospital deaths and 10% of all in-hospital deaths were attributed to pulseless electrical activity. In addition, hospitalized patients are more likely to have pulmonary embolism among other complications. Pulseless electrical activity is the first documented rhythm in 30 to 38% of adults with in-hospital cardiac arrest. Beta blockers and calcium channel blockers may alter contractility, leading to increased susceptibility and resistance to treatment. Women are more likely to develop pulseless electrical activity as compared to the male population. The risk of pulseless electrical activity increases over the age of 70, especially in the female population.
Pulseless electrical activity occurs when an insult involving the cardiovascular, gastrointestinal or the respiratory system results in the inability of the cardiac muscle to generate adequate force in response to electrical depolarization. This adverse event decreases cardiac contractility, and the situation gets severe by potential acidosis, hypoxia, and worsening vagal tone. More compromise of the inotropic state of the cardiac muscle leads to insufficient mechanical activity, despite the presence of electrical activity. It causes degeneration of cardiac rhythm, and eventually, death follows.
Transient coronary occlusion usually does not cause pulseless electrical activity unless hypotension or other arrhythmias are involved. Respiratory failure leading to hypoxia is one of the most common causes of pulseless electrical activity, responsible for about half of the PEA cases. The following are other mechanisms for pulseless electrical activity:
Decreased cardiac contractility has been related to changes in intracellular calcium levels, which explains why patients with beta blockers or calcium channel blockers are more prone to developing pulseless electrical activity and may become unresponsive to therapy.
A thorough yet quick history should be reviewed while paying special attention to the following:
Physical findings, as the name indicates, include an absence of palpable pulses is the foremost finding.
Depending upon the cause, one may see the following:
Investigations should include an EKG, arterial blood gas analysis, serum electrolytes, core body temperature, chest X-ray, and echocardiogram.
The first step in managing pulseless electrical activity is to begin chest compressions according to ACLS protocol followed by administrating epinephrine every 3 to 5 minutes, while simultaneously looking for any reversible causes. Once a diagnosis is made, begin immediate specific management i.e., decompression of pneumothorax, pericardial drain for tamponade, fluids infusion for hypovolemia, correction of body temperature for hypothermia, administration of thrombolytics for myocardial infarction or pulmonary embolism. An arterial blood gas and serum electrolytes should be obtained during the resuscitation process.
Epinephrine should be administered in 1 mg doses intravenously/intraosseously every 3 to 5 minutes during pulseless electrical activity arrest. Each dose should be followed by 20 ml of flush and elevating the arm for 10 to 20 seconds for better perfusion. Higher doses of epinephrine have not shown to improve survival or neurologic outcomes in most patients. Selected patients, like those with beta blockers or calcium channel blockers overdose, may benefit from higher-dose epinephrine. It can also be given via endotracheal tube after mixing 2 mg in 10 ml of normal saline.
If the detected rhythm is bradycardia that is associated with hypotension, then atropine (1 mg IV every 3-5 min, up to three doses) should be administered. This is considered the optimal dose, beyond which no further benefit will occur. Note that atropine may cause pupillary dilation; therefore, this sign cannot be used to assess neurologic function.
Sodium bicarbonate may be used only in patients with severe, systemic acidosis, hyperkalemia, or tricarboxylic acid overdose. The dose is 1 mEq/kg. Avoid routine administration of sodium bicarbonate as it worsens intracellular and intracerebral acidosis without affecting mortality.
Pericardial drainage and emergent surgery may be lifesaving in appropriate patients with pulseless electrical activity. In a patient with a refractory case and chest trauma, a thoracotomy may be performed. Near pulseless electrical activity or a very low-output state may also be managed with the circulatory assistance (e.g., intra-aortic balloon pump, extracorporeal membrane oxygenation, cardiopulmonary bypass, and ventricular assist device).
The chances of a successful outcome depend on a very coordinated resuscitation process. There should be a specific person responsible for specific steps and a good team leader.
Patients who have sudden cardiac arrest due to pulseless electrical activity have a poor outcome. In one study of 150 such patients, 23% were resuscitated and survived to hospital admission; only 11% survived until hospital discharge.
Rib fracture due to chest compression
Ischemia of extremities due to poor perfusion
Anoxic injury to the brain
Usually, patients are sent to the Intensive care and managed by the intensivist
Vascular surgery consult if a large pulmonary embolus is detected
Toxicologist for poisoning
Cardiothoracic surgery for tamponade
Cardiologist for Myocardial infarction
Most of the cardiac arrests are preceded by changes in the vital signs including tachycardia, hypoxia, and tachypnea.
Health care professional should pay attention to such changes and look into the causes and treat them and prevent a potential cardiac arrest due to PEA
All healthcare workers, especially emergency department physicians, nurses, urgent care workers, internists, intensivists and trauma specialists must be certified in ALS. While there are many causes of cardiac arrest, one needs to be aware of pulseless electrical activity, which carries a high mortality rate.
The first step in managing pulseless electrical activity is to start chest compressions according to ACLS protocol along with using epinephrine, while simultaneously looking for any reversible causes. Once a diagnosis is made, begin immediate management i.e., decompression of pneumothorax, pericardial drain for tamponade, fluids infusion, correction of body temperature, administration of thrombolytics, or surgical embolectomy for pulmonary embolus. A successful outcome very much depends on the combined efforts of the multidisciplinary team.
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