1. Pediatric Fluids and Electrolytes
Katinka Kersten

2. Learning Objectives
Recognize that fluid and electrolyte homeostasis is different in infants, children and adults
Know contents of different fluid compartments in body
Know how to estimate maintenance fluid and electrolyte needs
Know contents of different intravenous and oral rehydration solutions
Know fluid management for patients with
Isonatremic dehydration
Hyponatremic dehydration
Hypernatremic dehydration

3. ECF and ICF Body has two fluid compartments
Extracellular fluid (ECF) space makes up 1/3 of our body fluids
Intracellular fluid (ICF) space makes up 2/3 of our body fluids
Extracellular space refers to fluids outside our cells which may be interstitial fluid or plasma or
CSF
Total body water = 0.6 X weight (kg) for children and adults and 0.78 X weight (kg) for neonates and infants

5. Developmental Differences in Children
Total body fluid of infants is 20% more than adults
Greater surface area relative to size and therefore more water loss through skin
Increased metabolic rate
Immature kidney function that requires more fluid to excrete waste

6. ECF and ICF Composition
ICF (mEq/L) ECF (mEq/L)
Sodium
Potassium
Chloride
Bicarbonate
Phosphate
Protein

7. Approach to Fluid Calculations
1. Maintenance: Determined by a ‘system’:
a. Caloric expenditure method
b. Holliday-Segar method c. Surface area method
LOW AMOUNT OF ELECTROLYTES IN FLUID
2. Deficit: Determined by acute weight change or clinical estimate
HIGH AMOUNT OF ELECTROLYTES IN FLUID
3. Ongoing losses: Determined by measuring

8. Basal Metabolism
Daily fluid and electrolyte need is related to daily average energy requirement.
Daily energy requirement is determined by Resting Energy Expenditure (REE) plus correction factor for activity, fever, trauma, injury and growth.
When compared to body weight the Resting Energy Expenditure (REE) is high in the newborn, and lower in adults

9. Maintenance Fluid Simplification
It’s impossible to know Resting Energy Expenditure and average daily energy needs for different ages and sizes and most people rely on existing tables.
Two systems have been proposed to relate maintenance fluid and electrolyte needs to the body weight.
Surface area method
Holliday-Segar method

10. Holliday Segar Method
Most widely used method in pediatrics to estimate maintenance fluid need
Landmark paper by Drs. Holliday and Segar in 1957
Studies done on healthy infants and children
Assumes that for each 100 calories metabolized, 100 ml H2O will be required (50 ml/100 calories for insensible loss, 67 ml/100 calories for urine and 17 ml/100 calories gained from metabolism)
Not suitable for newborns

11. Holliday-Segar FLUID REQUIREMENTS ElECTROLYTE REQUIREMENTS
For first 10 kg 100 ml/kg/day (4ml/kg/hr)
For second 10 kg 50 ml/kg/day (2ml/kg/hr)
Each additional kg 20 ml/kg/day (1ml/kg/hr)
ElECTROLYTE REQUIREMENTS
Na+ 3 mEq/100ml
Cl- 4 mEq/100ml
K+ 2 mEq/100ml

12. Replacement of Deficit

13. ECF and ICF Contributions to Loss
If losses occur over very short period most of the
loss is from ECF
If losses occur over long period of time losses are
about 50/50 ICF and ECF

14. Clinical Signs of Dehydration
Type Percent Symptoms
Very mild <3 Thirst may be present
Mild Dry mucous membranes
and conjunctiva
Moderate Sunken eyes, decreased
fontanelle
Severe Tenting of skin
Very severe >12 Shock

15. Oral Rehydration Therapy
Safest way to rehydrate patient is by the enteral route
Best to use ORS as this is least hyponatremic. However many patients don’t take this because salty. Pedialyte decent as well and thirdly Gatorate
Can not do this in patients with
Severe altered mental status
Persistent severe vomiting
Intestinal obstruction

16. Electrolytes in Popular Drinks
Na (mEq/L) K (mEq/L)
Apple juice
Coke
Gatorade
Milk OJ
Pedialyte
WHO ORS

17. Electrolytes in Body Fluids
Na K Cl HCO3
Gastric juice
Small-intestinal juice
Diarrhea
Sweat

18. Composition of Parenteral Fluids
Fluid cal/L Na K CL HCO3
D5W
D10W NS
1/2 NS
D5 1/4 NS LR
Alb. 25% <120

19. Isotonic Dehydration (Na 135-`45 mEq/L)
A 2 year old has a 6-day history of gastroenteritis,
poor fluid intake and infrequent urination. On exam you
find dryness of the mucous membranes, sunken eyes
with mild tenting of the skin. The serum sodium
is 137 mEq/L.
The weight is 10 kg.
You determine the child is suffering from about 10%
dehydration.
What are the fluid and electrolyte requirements?

20. Isotonic Dehydration H2O Na K (ml) (mEq) (mEq)
Maintenance (Holiday/Segar)
Total deficit = 1000 ml
Extracellular fluid deficit
(50% of total)
Intracellular fluid deficit
Total

21. Hypertonic Dehydration (Na > 145 mEq/L)
Mortality can be high
Often iatrogenic
The intravascular volume (extracellular space) is
preserved at the expense of the intracellular volume
The patient looks better than you would expect
based on fluid loss
Always assume total fluid deficit of at least 10%

22. Free Water Deficit Use 4 ml/kg of body weight for each mEq of Na+
above 145 mEq/L as the
Free Water Deficit
(Serum Na mEq/) x weight x 4
= total amount of free water needed to dilute the serum to get a normal concentration Na+
Only correct half of total Free Water Deficit in first 24 hours if Na+ < 175 mEq/L
For Na+ > 175 mEq/L you do not want to correct
faster than 1 mEq/L/hr

23. Hypertonic Dehydration
6-month-old suffering for 3 days from severe
diarrhea.
Mucous membranes are dry, skin feels doughy
and the child is somnolent and lethargic.
The serum Na+ is 165 mEq/L.
The child weighs 5 kg and you assume the fluid deficit
is at least 10%.
What are the fluid and electrolyte requirements?

24. Hypertonic Dehydration
H2O Na K
(ml) (mEq) (mEq)
Maintenance (Holiday/Segar)
Total deficit = 500 ml
½ of Free Water Deficit
{( )x5x4x½}
Remainder of deficit
{( ) = 300 ml}
Extracellular (60%)
Intracellular (40%)
Total
200

25. Hypotonic Dehydration (Na < 135 mEq/L)
Children with vomiting and diarrhea who have received
hypotonic fluids as oral replacement
Shock is an early symptom.
Physical exam findings usually exaggerate
amount of dehydration.

26. Additional Na+ needed
To calculate the Na+ Deficit, multiply 0.6 mEq/kg of body weight for each mEq of Na+ below 135 mEq/L.

27. Hypotonic Dehydration
A 3-year-old has had diarrhea and vomiting for
1 day. Examination shows sunken eyes and
marked tenting of the skin but the child is not in shock.
The serum Na+ is 120 mEq/L.
The weight 14 kg.
You estimate the deficit as 7%.
What are the fluid and electrolyte requirements for this patient?

28. Hypotonic Dehydration
H2O Na K
(ml) (mEq) (mEq)
Maintenance (Holliday/Segar)
Deficit (7% of 14 kg)
Extracellular fluid (80%)
Intracellular fluid (20%)
Additional sodium
{( ) x 0.6 x 14}
Total
126