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Introduction to Dehydration


It is really important to have a good understanding of this subject because dehydration is a huge cause for concern for parents. With children who have had a bit of diarrhoea and vomiting, the main thing parents worry about is, ‘Are they getting dry?’. Tina Newton, a Children’s Emergency Medicine Consultant, will guide you through your next topic, dehydration.

The aims of this session are:

  • To understand the common causes of, and initial management priorities in dehydration
  • To help you recognise the signs of dehydration in children
  • To think about shock, and how you recognise shock

When we talk about dehydration we are talking about loss of total body water, and this can happen in a number of situations. Among the most common reasons are diarrhoea and vomiting, sore throats, mouth ulcers, and viral respiratory tract illnesses (colds, bronchiolitis) in small infants. In the latter group the reason they get dry is that, when they feed they breathe through their noses. If the nose is blocked it becomes difficult for them to take adequate amounts of fluid.

Another thing that can either be confused with, or coexist with dehydration is shock. Most children with dehydration due to things like gastroenteritis do not end up shocked; if they do, you need to consider whether the initial diagnosis was correct or if you are dealing with another condition entirely. Shock and dehydration are different because shock is caused by a loss of circulating volume and shocked children are generally much more unwell. Lack of circulating volume can happen not just because that volume is lost (blood loss, fluid leak in sepsis) but also because the tone in the blood vessels is reduced, meaning that the return of fluid to the heart is impaired (this is what is seen in warm septic shock) or if the heart (the pump) fails. When a child is shocked, oxygen delivery to the tissues is reduced and waste products (like carbon dioxide and lactate) build up in the blood. These two issues will lead to a rapid deterioration in the child indicated by a fast heart rate, prolonged central capillary refill time (in warm septic shock the peripheral capillary refill time may still be brisk), low blood pressure and possible altered conscious level.

So the important thing is to recognise a dehydrated patient, assess how dehydrated they are and think about possible causes. You then need to think what you are going to do about it. In patients who appear shocked, your management is going to be different as true shock is a medical emergency and needs appropriate treatment.

The 999 Call

“Please help me. My 4 year old has been unwell for a few days with a fever. Today he has complained of really bad tummy pain and he has vomited several times. He looked awful. His lips are dry, he has been very sleepy and he seemed to be struggling to breathe.”

A crew is dispatched.

  • This is quite an interesting combination of symptoms. The one thing that seems out of the norm is the struggling to breathe. What do you think that might indicate?
  • What do you think their differential diagnosis is going to be?
  • What will their initial priorities be when they reach the child?
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Emergency and Urgent Care for Children: a Survival Guide

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