Pediatric Fluids and
Electrolytes
Katinka Kersten
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 fluid management for patients with
 Isonatremic dehydration
 Hyponatremic dehydration
 Hypernatremic dehydration
 Know contents of different intravenous and oral
rehydration solutions
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
Developmental Differences in
Children
 Increased fluid intake and output relative to
size. 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
ECF and ICF Composition
ICF (mEq/L)
Sodium
20
Potassium 150
Chloride
--Bicarbonate 10
Phosphate 110-115
Protein
75
ECF (mEq/L)
135-145
3-5
98-110
20-25
5
10
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
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
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
Holliday-Segar Method
Most widely used method
Landmark paper by 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
Holliday-Segar
 FLUID 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
REPLACEMENT
OF DEFICIT
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
Clinical signs of Dehydration
Type
Percent
Very mild
Mild
<3
3-5
Moderate
5-7
Severe
Very severe
7-12
>12
Symptoms
Thirst may be present
Dry mucous membranes
and conjunctiva
Sunken eyes, decreased
fontanelle
Tenting of skin
Shock
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
Electrolytes in Popular
Drinks
Apple juice
Coke
Gatorade
Milk
OJ
Pedialyte
WHO ORS
Na (mEq/L) K (mEq/L)
0.4
26
4.3
0.1
21
2.5
22
36
0.2
49
45
20
90
20
Isotonic dehydration (Na 130-145 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?
Isotonic Dehydration Example
Maintenance (Holiday/Segar)
Total deficit = 1000 ml
Extracellular fluid deficit
(50% of total)
Intracellular fluid deficit
(50% of total)
Total
H2O
(ml)
1000
Na
(mEq)
30
500
70
500
2000
K
(mEq)
20
75
100
95
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%
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+ -145 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
Hypertonic Dehydration Example
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?
Hypertonic Dehydration Example
H2O
(ml)
500
Maintenance (Holiday/Segar)
Total deficit = 500 ml
½ of Free Water Deficit
{(165-145)x5x4x½}
200
Remainder of deficit
{(500-200) = 300 ml}
180
Extracellular (60%)
120
Intracellular (40%)
Total
1000
Na
K
(mEq) (mEq)
15
10
25
18
40
28
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.
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.
Hypotonic Dehydration Example
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?
Hypotonic Dehydration Example
Maintenance (Holliday/Segar)
Deficit (7% of 14 kg)
Extracellular fluid (80%)
Intracellular fluid (20%)
Additional sodium
{(135-120) x 0.6 x 14}
Total
H2O Na K
(ml) (mEq)(mEq)
1200 36 24
800
200
112
126
2200 274
30
54
Electrolytes in Body Fluids (mEq/L)
Na
Gastric juice
140
Small-intestinal juice 140
Diarrhea
40
Sweat
70
K
15
15
40
15
Cl
155
155
40
60
HCO3
0
40
40
0
Composition of Parenteral Fluids
Fluid
cal/L
Na
D5W
170
0
D10W
340
0
NS
0
154
1/2 NS
0
77
D5 1/4 NS 170
34
LR
0
130
Alb. 25% 1000 100-160
K
4
CL
0
0
154
77
34
109
<120
HCO3
28