Diarrhoea and dehydration

Question 1

Define dehydration and list the three general mechanisms by which it occurs

Answer 1

Decrease in total body water

Mechanisms

1) Decreased intake
2) increased output
3) insensible losses

Question 2

Contrast isonatreaemic, hyponatraemic and hypernatraemic fluid loss

Answer 2

Isonatraemia volume depletion is the most common form of volume depletion and results from relatively equal losses of sodium and water from the extracellular space - there is no change in body fluid tonisity or redistruction. GIT loss is the mose common cause

Hyponatreamic volume depletion results from sodium loss in excess of free water loss.- Free water than moves intracellularly from the extracellular space to maintain osmolarity - leading to decrease in intravascular volume and potentional HD compromise– GIT also the most common but with replacement by free water
-SIADH also common

Hypernatraemic volume depletion arises from the loss of more free water than sodium – occurs with salty fluid replacement or icnrease insusensible losses – usually assocaited with at least a 10% dehydration

Both hyper and hyponatraemia cause fluid shift in the brain leading to potential neurological sequalae

Question 3

Discuss clinical features of dehydration in children

Answer 3

Often incorrectly assessed by the emergency physician – can just assume 5%

The three most useful signs to determine dehydration of more than 5% are prolonged cap refill time, abnormal skin turgor and abnormal respiratory pattern

Mild dehydration 30-50ml/kg
-Dry mucous membrane 
-normal skin tufor 
-nil dpressed anterior fontanel 
-Alert 
-nil sunken eyballs 
-nil resp pattern 
cap refill >2

Moderate 60-100ml/kg

• Dry mucous membranes
• mildly reduced skin turgor
• depressed fontanel
• irritable
• sukne eyeballs
• hyperpnea
• tachy
• cap refill >2

Severe (Shocked) >10% 90-150ml-kg

• Dry mucous membranes
• marked reduction in skin turgor
• depressed anterior fontanel
• lethargic
• sunken eyeballs
• hypernea
• hypotension
• increased pulse rate
• cap refill > 2seconds

Question 4

Discuss IX of dehydration

Answer 4

Role of ultrasound in paeds is uncertain - IVC collapsibility has not been shown to correlate with hydration status – IVC to aorta ratio of less than 0.8 has been found to improve diagnosis

Question 5

Discuss management of dehydration in the ED

Answer 5

Emergent fluid repletion phase

• required for children with severe hyovolaemia
• requies 20ml/kg of isotonic saline IV at a rapid rate
• should see signs of reversal of shock in 5-15 minutes.
• If end points are not met (normotensive, UO and mentatiting) – further boluses of 10-20ml/kg of fluid should be administered
• if getting to 60ml/kg wihtout signs of imrpovement need to start pressors and look for DDX of cause
• Consider glucose and electrolytes and replace as required

Repletion phase

• ORT therapy si the preferred treatment for children with mild to moderate dehydration or as the 2nd phase of treatment of children with severe dehydration
• Calculation of desired replacement takes place at 10ml/kg/%dehydration estimated
• give 25% of the voluem of oral rehydration to replaced every hour for the first 4 horus
• Continue to replace ongoing losses and maintenance over the next 20 hours

Question 6

List Aetiology of gastroenteritis in children

Answer 6

Viruses

• Rota
• Norwalk
• enteric adenovirus

Bacteril

• Salmonella
• C.jejuni
• Shigella
• E.coli
• Yersinia
• Vibrio cholerea

Parasites

• Cryptosporidium
• Giardia lamblia
• entamoeba histolytica

It is more likely to be a bacterial cause if there is

1) blood or mucous in the stool
2) significant abdominal pain
3) there is a high grade fever

Question 7

Discuss Gorelick et al signs of dehydration

Answer 7

1) decreased skin elasticity
2) general appearance (ill, irritable, apathetic)
3) absent tears
4) sunken eyes
5) Dry MM
6) abdnormal respirations
7) cap refil > 2sec
8) abnormal radial pulse
9) tachycardia >150
10) decreased UO

<3 of correlates with <5%
3-6 with 5-9%
>7 with >10%

Question 8

Give DDX of diarrhoea

Answer 8

1) gastro-enteritis viral, bacterial or secondary to lactase deficiency
2) viral illness - non specific
3) antibiotic associated diarrhoea
4) constipation with overlfow
5) septicaemia
6) meingitis/encephalitis
7) appendicitis
8) intussuscpetion
9) malabsorprtion
10) colitits ‘-IBD, or pseudomembranous
11) endocrine disorders

Question 9

Discuss management of mild gastro-enteritis

Answer 9

Most can be managed as in a OPD setting if the child is able to tolerate a TOF

Essential things to ensure are

• the parent knows the appropriate oral fluids to give
• the parent knows how and is able to five oral fluids correctly
• the parent will have the child reviewed by the local doctor within 48 hours
• the parents knows what worrying signs and symptoms to look for that would require re-presentaiton.

The important message is to give small amounts of fluid frequently for example 0.5ml/kg every 5 minutes. The child is far more likely to tolerate small amounts of fluid than a whole bottle at once

For breast fed infants - breast feeing should continue throughout the episodes of gastro including the rehydration pahse
Formual fed infants - full strength normal formula should be started as soon as the infant is rehydrated. This can be supplemented with an ORS for ongoing lossess.
Early refeeding is good dose not worsen or prolong the duration of diarrhoea nor increase vomiting or lactose intolerance and leads to significantly higher weight gain after rehydration.

Question 10

Discuss management of moderate dehydration

Answer 10

Some can still be rehydrated with oral fluids as described above. Some require ORT via NGT,
ORT infusions should not be used if the child has an ileus
For children with moderate dehydration and simple disease rapid rehydration can be used with 10ml/kg/hour for 4% and 25ml/kg/hour for 10% every hour for 4 hours
Rapid rehydration is not suitable for
-respiratory illness, meinigoencephalitis or severe electrolyte derangement
-if less than 6 montsh not suitable if severe abdominal pain or co-morbidities

Slow rehydration involves replacement of 5% of the first 6 hours and than maintenance fluid after that
Loss should be replaced ml for ml over an hour period or over 4 hour periods

IV therapy should be used for child who fail NGT rehydration
The volume for replacement is calculated using the formula (% dehydration x 10 x weight) + maintenance fluids. They are then divided to get an hourly rate. Preferred fluid is normal saline with5% glucose and 20mmol of K. If the child is significantly hypernatremic the rate of fluid needs to be reduced to replace over 48-72 hours.

Question 11

Discuss management of the severely dehydrated child

Answer 11

This child is usually shocked and needs imediate acess and resus of 20ml/kg of saline - this should be repeated if the child remains shocked.

Bloods should be taken

After initial resus the rest of management is as per the above levels of dehydration.

Single dose of ondansetron is in the state guidelines of many states. It is not recommended if the child is less tahn 6 months or weight <8 kg
2mg for children 8-15kg
4 mg for children >15kg