Shock (hypovolaemic shock in dehydration) is the failure of the heart to maintain adequate circulation due to the loss of fluid. With excessive fluid loss in the stools, the volume of fluid in the circulation falls and there is not enough fluid to allow normal blood flow to the small capillaries of the body. As a result, blood flow slows down or stops in the capillaries and the body cells do not receive enough oxygen and food. Shock presents with:

• A delayed capillary filling time
• Tachycardia (a fast heart rate)
• A weak radial pulse which is difficult to feel
• Hypothermia (low body temperature) especially cold hands and feet (cold peripheries)
• A depressed level of consciousness (lethargy and drowsiness)
• Hypotension (low blood pressure) with weak or impalpable peripheral pulses

The blood pressure may still be normal in the early stages of shock. Shock is a very serious sign and indicates that the child will probably die unless immediate treatment is started.