Fluid & Electrolyte balance
Elspeth Ferguson
ST4 Paediatrics
September 2011
Learning objectives
 Maintenance fluid requirements
 Deficit & Supplemental fluid requirements
 Grades of dehydration
 Types of dehydration
 Fluid & Electrolyte management
 Scenarios
How are children different?
 15 % turnover of body fluids
(adults 5%)
 Limited access to fluids
 Easier to give inappropriate fluids
Maintenance requirements
 Based on calorie requirements and fluid losses from
the body
 Insensible losses
Essential urine output
Normal urine output
1/5th
1/5th
3/5th
Maintenance requirements (Child)
Body
weight (kg)
Fluid
(ml/kg/d)
Na
(mmol/kg/d)
K
(mmol/kg/d)
Protein
(g/kg/d)
Energy
(kcal/kg/d)
<10
100
3
2
2.5
100
10-20
+50
+1.5
+1
+1.5
+75
>20
+20
+0.75
+0.4
+1
+30
Maintenance requirements (Neonates)
Day of life
Fluid(ml/kg)
Type
1
60
10%
dextrose
2
90
3
120
Na 3 mmol/kg
K 2 mmol/kg
10% dextrose
+ additives
4
150
5
180
Deficit
 Deficit = abnormal losses
 Abnormal losses
vomiting
diarrhea
fever
tachypnea
hot weather
DKA
3rd space losses
 % dehydration x 10 = ml/kg deficit
Supplemental
 Supplemental = ongoing abnormal losses
 Composition of body fluids (mmol/l)
diarrhoea 50
gastric
50
small bowel
Na
40
15
130
K
40
150
15
Cl
40
40
110
Bicarb
30
Dehydration
 History
Age
Intake
Output
Systemic illness
 Pre-illness weight comparison
 Rehydrated wt estimate
= admission wt (kg) x 100
100 - % dehydration
Grades of dehydration
1(symptoms) 5%
2(signs) 7%
3(shock) 10%
Clinical condition
Thirsty alert
restless
Lethargic irritable
drowsy
Floppy comatose
Pulse
Normal
Fast
Feeble
Respiration
Normal
Deep
Deep & Rapid
Fontanelle
Normal
Sunken
Very sunken
Systolic BP
Normal
Postural drop
Low
CRT
Normal
>2 seconds
> 3 seconds
Eyes
Normal
Sunken
Very sunken
Mucous memb
Moist
Dry
Very dry
Urine output
Normal
Deficit (ml/kg)
50
Concentrated
70
Anuria
100
Types of dehydration
 Hyponatremic (< 135 mmol/l)
greater loss of Na relative to water
deficit exaggerated by hypotonicity
seizures may occur
 Isonatremic (135-150 mmol/l)
equal losses of Na and water
 Hypernatremic (>150 mmol/l)
difficult to estimate the degree of dehydration
correct over 48 hours
Na fall should be < 10 mmol/day
Types of fluids
Fluid
Na
(mmol/l)
K
(mmol/l)
Cl
(mmol/l)
Calories
(kcal/l)
0.9% Saline
150
0
150
0
0.45% Saline
+ 5% dextrose
75
0
75
200
10% dextrose
0
0
0
400
0.45% Saline
+ 5% dextrose
+ KCl
75
40
75
200
Principles of fluid therapy
 Fluids are drugs : Check calculations !
 Add K when U&Es are back ( 40 mmol/l)
 Rehydration usually corrects metabolic acidosis
 Monitor U&Es closely
To admit or not?
 > 5 % dehydration
 Persistent vomiting
 Need for IV therapy
 Failure of outpatient management
 Diagnosis is not clear
Which route?
 Oral when possible
Dioralyte
Rehidrat
 Nasogastric fluids
 IV fluids
persistent vomiting
severe ongoing losses
Shock
Oral therapy fails
Which fluid?
 Use 0.9% saline as bolus
 Use 0.45% saline + 5 % dextrose for all types of
dehydration initially
 Then fluid composition is guided by U&Es
How much fluid?
Hourly rate
=
Maintenance + Deficit + Ongoing losses
24
Monitoring
 Intake
 Output
 Weight
 CRT
 Pulse
 BP
 Conscious level
 U&Es
Case 1
A previously healthy 11 month old infant is
referred to CAU with a 3 day history of diarrhoea
and vomiting with a poor urine output
She has sunken eyes, sunken fontanelle and dry
mucous membranes. The pulse is rapid and easily
felt. She vomits all her feeds
Calculate her fluid requirements over the next
24 hours
Case 2
A 10 year old girl has been brought by ambulance
in a semi-comatose state. She is found to have a
non-blanching rash over her trunk, neck stiffness
and an axillary temperature of 39.5°C. Her
capillary return time is 7 seconds and her systolic
BP is 90 mm/HG.
How will you manage her fluids in the emergency
setting and subsequently?
Case 3
A 6 year old boy has been referred by his GP for being unwell and
wetting his bed lately. His mothers says that he has been losing
weight since he came back from Pakistan 4 weeks ago.
His urine shows 4+ glucose and “large” ketones and a lab blood
sugar is 32.
On examination he is found to be lethargic with a capillary return
time of 5 seconds. He is afebrile with a dry mouth and a pulse of
120/min.Blood pressure is 110/70.
What is your diagnosis?
How will you write up the fluids for this child?
Case 4
A 6 month old infant of a drug addict is brought to the Children’s
Ward with a history of vomiting and excessive drowsiness. The
Health Visitor accompanying the infant fears that the mother
may have made up the feeds wrongly over the past few days.
The infant is found to have a sunken fontanelle and has not
passed urine for a few hours. The S. Na+ is 165, S. K+ is 3.5, Urea
is 8, Creatinine is 70.
How will you manage this infant?
Case 5
A 6 week old male infant who was born at 38 weeks gestation is referred by his
GP on a Saturday for non bilious vomiting after most feeds for the last two
weeks. His birth weight centile was the 10th but now is is less than the 3rd.
On examination he is alert and hungry. He looks thin and has a capillary return
time of 4-5 seconds. Abdomen palpation reveals no abnormality but you notice
that his nappy is wet.
The lab results area as follows:
Na+
132
K+
3.2
C196
HCO3
32
pH
7.45
How will you manage the fluid and electrolyte needs of this infant?
Case 6
A 5 day old baby who was a planned home birth is seen by the
Community Midwife who feels that the baby’s genitalia are odd. The baby is
seen in the clinic and has an underdeveloped phallus and scrotum. No testes
are palpable in the scrotum.
The baby has a poor perfusion and weak cry. It is admitted from clinic.
Dextrostix is 2.
The lab results are back urgently:
S. Na+
125
S. K+
7.5 (non-haemolysed sample)
Blood sugar
1.8
How will you manage this neonate’s fluids?
Summary
 Maintenance fluid requirements
 Deficit & Supplemental fluid requirements
 Grades of dehydration
 Types of dehydration
 Fluid & Electrolyte management
 Scenarios
Questions