An organ is a discrete anatomical structure composed of two or more different tissue types that together form a structural and functional unit, performing one or more specific physiological roles. Examples include the heart, lungs, liver, kidneys, brain, stomach, and intestines. Most organs are part of larger systems (such as the cardiovascular system or respiratory system) that work together to maintain the body’s functions.
The heart is the most directly relevant organ in the context of cardiac arrest: it is the pumping organ of the cardiovascular system, circulating blood to all other organs. When the heart arrests, all organs are deprived of oxygen and begin to fail within minutes. The brain is most vulnerable, sustaining irreversible damage within 4 to 6 minutes without circulation. This is why speed of response is critical in cardiac arrest.
Major organ systems affected by cardiac arrest and its aftermath include the brain (hypoxic-ischaemic brain injury), the kidneys (acute kidney injury from hypoperfusion), the liver (ischaemic hepatitis in severe cases), and the lungs (pneumonia and ARDS in ventilated patients). The term ‘multi-organ failure’ describes simultaneous failure of two or more organ systems, which may occur as a complication of post-cardiac arrest syndrome.
Organ donation is also relevant in the context of cardiac arrest: some patients who cannot be resuscitated may be considered for organ donation, where their organs can save the lives of others. Specialist organ donation teams and the NHS Blood and Transplant infrastructure support this process, which operates alongside the family’s grieving and is handled with great care and sensitivity.
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