Shock

The definition of shock is inadequate organ and tissue perfusion. This simply means that there is not enough appropriate fluid (blood) in a patient’s circulatory system able to carry oxygen and nutrients to the tissues and to remove the waste products of metabolism. The important aspects are to identify then treat the cause, to help restore the circulatory volume which may require the use of fluid therapy.

Non-Haemorrhagic: Most of the time we immediately think of haemorrhagic shock as the main cause but it is important to consider non-haemorrhagic causes of shock.

These include:

• Cardiogenic: where the heart is failing or fails to generate adequate cardiac output e.g. cardiac arrest
• Tension pneumothorax: where a build up of pressure in the pleural cavity results in pressure on the superior and inferior vena cava, restricting the return of venous blood to the heart. This results in poor cardiac output and if not relieved will lead to PEA cardiac arrest
• Neurogenic: when there is damage to the high thoracic spinal cord with loss of the sympathetic supply to the peripheries resulting in vasodilatation. This causes the circulating volume to be redistributed to the peripheries,significantly reducing venous return to the heart.
• Septic: an overwhelming inflammatory response to infection results in peripheral vasodilatation, fluid redistribution and reduced central circulation.
• Anaphylactic: an overwhelming inflammatory response to an allergen resulting in peripheral vasodilatation and capillary membranes becoming leaky, leading to tissue oedema and a significant reduction in central circulation

Haemorrhagic shock is the loss of circulatory volume (bleeding) and if not managed will result in end organ failure,it is essential to try and identify the source and if possible stop or at least reduce the blood loss as soon as possible.