Dehydration Flashcards
What are the risk factors for dehydration in children
<1yo
Low birthweight
6 or more diarrhoeal stools in 24h
3 or more vomits in 24h
Not able to tolerate fluids
Stopped breastfeeding during illness
Signs of malnutrition
What are the causes of dehydration
Excessive loss:
- Diarrhoea e.g. Gastroenteritis
- Urine loss e.g. Diabetes mellitus, DKA, diabetes insipidus
- Vomiting e.g. DKA, Pyloric stenosis, gastroenteritis
- Sweat e.g. high fever, cystic fibrosis, hot climate, extended exercise
- Body fluids e.g. surgical loss, burns
Decreased intake: stomatitis, tonsilitis
What are the signs of dehydration on examination
Dry mucous membranes, mouth
Reduced skin turgor
Depressed fontanelle
Altered mental state, lethargic
Poorly perfused (prolonged CRT)
Tachycardia
Sunken eyes
Mottled skin
How is dehydration measured
Clinical signs
Weight:
- Water loss can be estimated from the difference between actual weight and a recent weight
- 1g of body weight is roughly equivalent to 1ml of water
How should dehydration be assessed
History
Examination
Height and weight
Estimate the severity of dehydration: mild (<5% loss), moderate (5-10%), severe (>10%)
Type of dehydration: hyponatraemic, isotonic, hypernatraemic
Is it significant?
- Reduced fluid intake but have produced wet nappies (albeit less than usual), a period of observation is recommended
- Ask the parent to increase the effort and persistence with feeds and keep in (but do not admit) until the child has passed a wet nappy or taken a whole feed without vomiting
What are the features of hyponatraemic dehydration
Serum sodium <130mmol/L
Commonly seen when fluid loss has been replaced with hypotonic solutions e.g. water, fizzy drinks
Lethargic with dry skin and poor turgor
What are the features of hypernatraemic dehydration
Hypernatraemic dehydration
Serum sodium >150mmol/L
Commonly seen in breast-fed babies in the first 2 weeks of life if there is difficulty establishing feeds OR concentrated formula feeds
Initially appears hungry but few clinical signs of dehydration
Skin feels doughy
Metabolic acidosis common
What is the management for mild dehydration
Treat at home using oral rehydration therapy
First line: Dioralyte or Rehidrat (oral solution, effervescent tablets or powders, reconstituted with freshly boiled and cooled water)
+ continue to breastfeed OR return to normal bottle milk feed once diarrhoea has settled
What is the management for moderate-severe dehydration
- Admit: Those who have fluid intake below threshold (calculate exactly) AND had no wet nappies in the last 24h
- Calculate the fluid replacement required:
- Start fluid replacement: 0.45% saline with 5% dextrose
- Shock: colloid or bolus
- Non-shock: slow rehydration over 24h
- Hypernatraemia: correct over 48h (risk of cerebral oedema) - Start an input-output chart
- Weight the child 2x daily
- Frequent serum electrolyte measurement
How is fluid loss calculated
Ascertain the difference between most recent/normal weight and their current weight and use clinical signs to estimate the % dehydration
→
Deficit (mL) = (actual weight in grams × 110%) − actual weight
What are the maintenance fluid requirements for children
100 ml/kg/day for the first 10kg of weight
50 ml/kg/day for the next 10kg of weight
20 ml/kg/day for weight over 20kg
How is fluid maintenance calculated
- Calculate deficit
- Deficit (mL) = (actual weight in grams × 110%) − actual weight - Assess the maintenance fluids required
- Maintenance + deficit
- Assess any continuing losses
Why should fluids be given slowly in hypernatraemic dehydration
Risk of cerebral oedema if sodium falls to quickly
Given over 48h
Why may you use less maintenance fluids in bronchiolitis, meningitis etc.
Due to SIADH
What is the management for shock
bolus fluids (these don’t need to be subtracted from the dehydration corrections):
- 20mL/kg 0.9% NaCl over 10 minutes: most situations, new DKA guidelines
- 10mL/kg 0.9% NaCl over 60 minutes: trauma, fluid overload, heart failure
