Shock is a loss of effective circulation resulting in impaired tissue oxygen and nutrient delivery and causes life threatening organ failure. Any seriously ill or seriously injured person is at risk of developing shock.
Absolute fluid loss can result from either internal or external bleeding where there is damage to the circulatory system or loss of body fluids through severe burns, severe vomiting, or severe diarrhea, etc. This can lead to an inadequate supply of oxygenated blood to the cells and tissue. The onset of shock starts to occur when a casualty loses approximately 15% (approximately 750 ml for an adult) of the circulating blood volume.
Loss of circulating blood volume (hypovolaemic shock), e.g.:
Cardiac failure occurs when the heart is suffering from either injury or disease and is unable to pump effectively or efficiently. The heart has its own blood supply coming from the coronary arteries.
If this blood supply is interrupted by blockages or narrowing, as occurs in a heart attack, the heart will not be able to function correctly. The result is a lack of oxygenated blood to the cells and tissue.
Cardiac arrest occurs because of an electrical problem in the heart disrupts its normal rhythm. During cardiac arrest, the electrical signals to the heart become erratic. Blood flow to the brain is reduced and the victim loses consciousness. Death will follow unless emergency treatment is begun.
Cardiac causes (cardiogenic shock), e.g.:
Abnormal dilation of blood vessels (distributive shock), e.g.:
Blockage of blood flow in or out of heart (obstructive shock), e.g.:
Early recognition of the seriously ill or seriously injured person should alert the first aider to the risk of developing shock. The symptoms, signs, and rate of onset of shock vary depending on the nature and severity of the underlying cause. Shock is a condition that may be difficult to identify.