Reversible causes of cardiac arrest – the four Hs and four Ts

A cardiac arrest occurs when the heart stops beating in a co-ordinated fashion resulting in the cessation of blood flow around the body.

The main treatment for cardiac arrest is made up of CPR and defibrillation. However first aiders and first responders should also have an awareness of some of the reversible underlying causes of a cardiac arrest.

In some situations it can be possible to identify and treat a reversible cause. Combined with effective CPR and defibrillation, this maximises the chances of the patient surviving the cardiac arrest.

What are the reversible causes of cardiac arrest?

The reversible causes of cardiac arrest can be remembered by using the “Four Hs and Four Ts”:

  • Hypoxia (low levels of oxygen)
  • Hypovolemia (shock)
  • Hyperkalemia/hypokalemia/hypoglycemia/hypocalcemia (+ other metabolic disturbances)
  • Hypothermia
  • Thrombosis (coronary or pulmonary)
  • Tension pneumothorax
  • Tamponade (cardiac)
  • Toxins

Although first aiders may not be able to correct some of these reversible causes, it is important that they are considered during the resuscitation attempt whilst high quality CPR is ongoing.

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John Furst

JOHN FURST is an experienced emergency medical technician and qualified first aid and CPR instructor. John is passionate about first aid and believes everyone should have the skills and confidence to take action in an emergency situation.

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