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In this lesson, we're going to cover a type of cardiac arrest known as pulseless electrical activity or PEA for short. At the end of the lesson, we'll provide you with an in-depth Word about the underlying causes of cardiac arrest (and PEA), otherwise known as the H's and T's.
PEA is an organized rhythm without a pulse where the electrical activity of the heart may appear normal, but the heart muscle is not responding. What is super unique about PEA is that the heart muscle is completely disassociated from the electrical activity.
Pro Tip #1: Any rhythm can deteriorate into PEA. So, it's really important to closely monitor the patient's pulse, blood pressure, and any underlying conditions he or she might have.
Remember, performing high-quality CPR is the initial treatment for PEA. In addition to CPR, identifying the underlying causes early, such as the H's and T's, and providing treatment quickly, is the key to reversing most pulseless electrical activity.
As mentioned above, some of the more common reversible causes of PEA can be more easily remembered by the H's and T's.
The H's and T's
PEA is associated with many conditions. As healthcare providers, you should memorize the list of common causes to keep from overlooking an obvious cause of PEA that might be reversed by appropriate treatment.
The most common causes of cardiac arrest are presented as H's and T's as indicated below.
The H's |
The T's |
| Hypovolemia | Tension pneumothorax |
| Hypoxia | Tamponade (cardiac) |
| Hydrogen ion (acidosis) | Toxins |
| Hypokalemia | Thrombosis (pulmonary) |
| Hyperkalemia | Thrombosis (coronary) |
| Hypothermia |
Of the H's and T's, hypovolemia and hypoxia are the two most common underlying and potentially reversible causes of PEA. Which is why it's important to look for evidence of these problems as you assess the patient.
In these two cases – hypovolemia and hypoxia – it's vital to recognize the condition early and treat for it quickly with volume replacement and oxygen therapy.
Pro Tip #2: Remember, pulseless electrical activity is not a shockable rhythm. Treatment involves high-quality CPR, proper airway management, IV or IO therapy, and the appropriate medication therapy.
The primary medication to treat PEA is 1mg of epinephrine 1:10,000 concentration every 3 to 5 minutes via rapid IV or IO push. However, in order to correct PEA, the ultimate goal will always be to identify and treat the underlying cause of the cardiac arrest.
A Word About the Underlying Causes of Cardiac Arrest
In this Word section, we're going to take a closer look at the H's and T's, since they are so vitally important in treating PEA and other types of cardiac arrest.
Hypovolemia
Look for: a history of trauma or severe dehydration, flat jugular veins, and ECG is rapid with narrow ORS complexes.
Treat with: give a 500ml bolus of normal saline and then reassess.
Hypoxia
Look for: profound cyanosis, suggestive blood gas readings, and airway problems.
Treat with: effective oxygenation and ventilation.
Hydrogen ion (acidosis)
Look for: a history of diabetes, such as hyperglycemic ketoacidosis, suggestive blood gas readings, bicarbonate-responsive preexisting acidosis, and renal failure.
Treat with: effective oxygenation and ventilation first, then consider sodium bicarbonate.
Hyperkalemia/hypokalemia
Look for: a history of renal failure, recent dialysis, diuretic use, and abnormal ECG findings.
Treat with: calcium chloride and sodium bicarbonate for hyperkalemia, and cautious infusion of potassium and magnesium for hypokalemia.
Hypothermia (spontaneous or environmental)
Look for: a history of recent exposure to cold environment and low core body temperature.
Treat with: remove from the cold environment, perform active internal rewarming, and limit defibrillations to one attempt and withhold cardiac medications until the core body temperature is raised above 86°F (30°C).
Toxins (intentional/accidental overdose)
Look for: a history of ingestion, empty bottles at the scene, abnormal neurologic exam, bradycardia, tachycardia, and a prolonged Q-T interval.
Treat with: intubation, activated charcoal, antidotes specific to ingestion (naloxone for narcotics and sodium bicarbonate for tricyclic antidepressants), and hemodialysis for certain agents.
Tamponade (cardiac)
Look for: a history of thoracic trauma or invasive cancer, pulses not palpable during CPR, and jugular venous distention.
Treat with: pericardiocentesis.
Tension pneumothorax
Look for: a history of thoracic trauma, pulses not palpable during CPR, jugular venous distention, absent breath sounds on the affected side, decreased compliance when ventilating, and contralateral tracheal shift (late)
Treat with: needle decompression (thoracentesis)
Thrombosis (coronary, ACS)
Look for: a history suggestive of acute myocardial infarction (AMI) and ST-segment and T-wave changes
Treat with: PCI or fibrinolytics
Thrombosis (pulmonary)
Look for: a sudden onset of dyspnea and pleuritic chest pain shortly before the arrest, cyanosis that persists despite supplemental oxygen, pulses not palpable during CPR, and jugular venous distention.
Treat with: anticoagulation or fibrinolytic therapy.
