/ Hs and Ts

The Hs and Ts Made Simple: Memorize in Minutes

One of the secrets to acing your ACLS certification exam is memorization.

To accomplish this, most students rely on mnemonic devices, which is a learning technique that helps the brain retain and retrieve information.

Two of the most common ones in ACLS certification training are the H’s and T’s, which enable students to remember the causes of cardiac arrest.

The ability to quickly identify what contributed to the arrhythmia enables a health care provider to follow the appropriate steps to treat the patient and provide the best chance at survival.

Whether you are just beginning your journey with ACLS training or could simply use a refresher, here’s everything you need to know about the H’s and T’s.

While H’s and T’s are most frequently associated with what’s known as pulseless electrical activity (PEA), they can also contribute to ventricular fibrillation (VF), ventricular tachycardia (VT) and asystole.

Because there are multiple angles to approach things, it’s important that the individual delivering care assess the patient’s medical history, evaluate his or her ECG and take into consideration any situational or environmental factors.

This facilitates a more accurate diagnosis and subsequent treatment plan.

The H’s of ACLS




The loss of fluid volume in the circulatory system, a common cause of PEA (Pulseless Electrical Activity). Look for any blood loss in the patient with PEA, it could be a good indicator of Hypovolemia. After CPR, obtain intravenous access. A fluid challenge could also help determine if the cardiac arrest was caused by Hypovolemia.


A deficiency in the amount of oxygen that reaches the tissues - a contributing cause to cardiac arrest. Adequate ventilation and oxygenation is vital to reverse Hypoxia. Ensure the airway is open, check for proper rising and falling of the chest and for bilateral breath sounds and make sure that the oxygen source is connected correctly.

Hydrogen Ions (Acidosis)

An abnormal pH in the body resulting from lactic acidosis which can be a result of prolonged Hypoxia. Acidosis can be either respiratory or metabolic. To diagnose respiratory acidosis, perform an arterial blood gas evaluation (respiratory acidosis can be prevented by providing adequate ventilation). If the acidosis is metabolic, treatment with sodium bicarbonate is recommended.

Hyperkalemia / Hypokalemia (Potassium)

Too much (hyper) or too little (hypo) potassium in the body.


A low core body temperature defined clinically as 95 degrees Fahrenheit (35 degrees Celsius). Defibrillation, CPR, or any drug therapy may prove to be ineffective for a hypothermic patient. Hence, the primary objective would be to warm the body.

The T’s of ACLS



Tension Pneumothorax

Refers to air in the pleural space (around the lung) that has no way to escape, causing collapse of the lung on the affected side. This reduces the return of blood flow to the heart and causes low blood pressure and hemodynamic collapse. This emergency can be treated with needle thoracotomy, which is performed by placing an 18-gauge needle in the second intercostal space in the midclavicular line.

Tamponade (Cardiac)

A condition in which fluid or blood accumulates in the pericardium. The buildup puts pressure on the heart and prevents proper pumping of the blood which can lead to cardiac arrest.


Toxic ingestions or environmental exposure to toxic substances can lead to cardiac arrest. These conditions can be diagnosed by specific groups of symptoms known as toxidromes. Recognition of a toxic cause of arrest can lead to appropriate treatment and a better outcome. In the case of uncommon toxic ingestion or exposure, poison control is a valuable and timely resource. While treating a victim of cardiac arrest that is caused dur to exposure to an environmental toxin, the rescuer must ensure the scene is safe before providing aid. Decontamination of the victim is critical.

Thrombosis (Pulmonary Embolus)

Blockage of the lung’s main artery (pulmonary artery).

Thrombosis (Acute Coronary Syndrome)

Blockage of the heart’s coronary artery/arteries.


Studying and memorizing the causes and treatment methods for the above conditions will prepare you for your ACLS exam and serve you well throughout your medical career.