Fluids and Electrolytes in the
Newborn
Vandana Nayal
Body fluid composition in the
fetus and newborn
 Total Body Water = ICF + ECF
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(Intravascular+Interstitial)
As gestational age increases, TBW and ECF
decrease while ICF increases
At birth, TBW = 75% of body weight in term
infants and about 80% in premature infants
ECF decreases from 70% to 45%
At 32 wks gestation, TBW = 83% and ECF
53%
Perinatal changes
 During the first week to 10 days of life,
reduction in body weight is due to the
reduction in the ECF
 Term infants- wt loss = 5%-10% within 3-5
days of birth
 LBW infants lose about 10-15% of body
weight during the first 5 days of life

Can lead to imbalances in sodium and water
homeostasis
Sodium balance in
the newborn
 Renal sodium losses are inversely
proportional to gestational age
 Term infants have Fractional excretion of
sodium = 1% with transient increases on day
2 and 3
 At 28 weeks- Fractional excretion of Sodium
= 5% to 6%
 Preterm infants <35wks display negative
sodium balance and hyponatremia during first
2-3 wks of life
Sodium balance in the
newborn
 Preterm infants may need 4-5mEq/kg of
sodium per day to offset high renal losses
 Increased urinary sodium losses

hypoxia
 respiratory distress
 hyperbilirubinemia
 ATN
 polycythemia
 increased fluid and salt intake
 diuretics.
Sodium balance in the
newborn
 Pharmacologic agents like dopamine,
labetalol, propranolol, captopril and
enalaprilat increase urinary sodium
losses
 Fetal and postnatal kidneys exhibit
diminished responsiveness to
aldosterone compared to adult kidneys
Water balance in the newborn
 Primarily controlled by ADH which enables
water to be reabsorbed by the distal nephron
collecting duct
 Stimulation of ADH occurs when blood
volume is diminished or when serum
osmolality increases above 285mOsm/kg
 Intravascular volume has a greater influence
on ADH secretion than serum osmolality
Renal concentration and
diluting capacity
 Adults can concentrate urine up to
1500mOsm/kg of plasma water and dilute as
low as 50mOsm/kg of plasma water
 Concentrating capacity is 800 mOsm/kg in
term infants and 600 mOsm/kg in preterm
 Diluting capacity is 50 mOsm/kg in term and
70 mOsm/kg in preterm
 Newborns have reduction in GFR and
decreased activity of transporters in the early
distal tubule
Fluid requirements in the
first month of life
Birth weight
Water requirements
D 1-2
D3-7
D8-30
<750
100-200 150-200 120-180
750-1000 80-150 100-150 120-180
1000-1500 60-100 80-150
120-180
>1500
60-80 100-150 120-180
Factors affecting insensible
water losses in the neonate
 Level of maturity
 Elevated body temperature increases loss by
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10%
Radiant warmer - increased by 50%
compared to thermo-neutral with high
humidity
Phototherapy increases losses by 50%
High ambient or inspired humidity - reduced
by 30%
Double walled isolette or plastic shield
reduces losses by 10-30%
Electrolyte requirements
 Day 1-2
 Sodium or chloride are not provided in IVF due to
high content of these electrolytes in body fluids
(unless serum Na <135 mEq/l)
 Potassium is not added until urinary flow has been
established
 Day 3-7
 Na, K, Cl requirements are about 2-3mEq/kg/day
for term infants and 3-5 mEq/kg per day for
preterm infants
 After the first week
 2-3mEq/kg/day of sodium and chloride are needed
Monitoring fluid and electrolyte
balance
 Body weight
 Oral mucosal
 Fluid intake
integrity
 Heart rate and blood
pressure
 Capillary refill
 Sunken anterior
fontanelle
 Urine and stool
output
 Serum electrolytes
 Urine osmolarity or
specific gravity
Monitoring fluid and
electrolytes
 During the first few days of life
 Urine output should be about 1-3ml/kg/hour
 SG of urine 1.008-1.012
 Wt loss of 5-8% in term and 15% in VLBW infants
 Monitor serum electrolytes at 8-24 hour intervals
 After the first week
 weight gain of 20-30gm/day
 Monitor electrolytes at intervals based on use of
TPN
Hyponatremia
 Serum sodium < 130mmol/L
 Early onset in the first week is due to
excess free water or increased
vasopressin release
 perinatal
asphyxia, respiratory distress,
bilateral pneumothoraces, IVH
 Increased free water or suboptimal
sodium in formula or IV fluids
Congenital Adrenal Hyperplasia
 Cause
 Most common form of CAH is complete
absence of 21 hydroxylase activity
 Severe renal sodium wasting due to
deficient aldosterone production and
inhibition of sodium absorption in the distal
nephron
 Symptoms
 Ambiguous genitalia, hyponatremia,
hyperkalemia, and metabolic acidosis
Congenital Adrenal Hyperplasia
 Treatment
 Normal
saline or 3% saline used to correct
the sodium to at least 125mEq/L,
glucose+insulin, and NaHCO3
 Glucocorticoid and sodium replacement
Hyponatremia in late newborn
 Caused by negative sodium balance
 Excess
renal losses, SIADH, renal failure,
edema
 Low sodium intake, diuretics,
mineralocorticoid deficiency (hypoNa,
hyperK, metabolic acidosis, shock)
 Treat with water restriction and repletion
of deficit
Treatment of Hyponatremia
 Fluid restriction which results in a slow
return to normal levels
 Urgent correction necessary if serum
sodium is < 120 mEq/L b/c obtundation
or seizure activity may develop
 Hypertonic
saline 3%, 6ml/kg infused over
1 hour (increases Na by 5 mEq/L)

Administer to increase Na to 120-125mEq/L
and eliminate seizures
Correction of hyponatremia
 Based on sodium deficit X volume of
distribution of sodium
 mEq Na needed = (Goal Na-Serum Na) X
TBW (60%) X body weight in kg

Prevents rapid correction (no more than 0.5
mEq/L/h)
 mEq Na = (140-serum Na) X 0.6 X body
weight
Hypernatremia
 Serum sodium > 150mEq/L
 Most often in ELBW infants
 High rates of insensible water losses and reduced
ECF volume
 Treat by reducing sodium administration and
increasing free water
 Rapid correction of more than 0.5mEq/L/h
should be avoided

causes cerebral edema, seizures, and death
Hypokalemia
 Serum Potassium < 3mEq/L
 Causes
 Diuretic use, renal tubular defects, NG tube
drainage, or ileostomy
 Can lead to weakness, paralysis, ileus,
conduction defects (ST depression, low
voltage T waves, U waves)
 Treat by increasing the intake by 1-2 mEq/kg

If severe, 0.5-1mEq/kg is infused IV over 1 hour
with EKG monitoring
Hyperkalemia
 Serum potassium > 6mEq/L
 Causes
 renal
failure, CAH, IVH, cephalohematoma,
hemolysis, excess administration
 EKG- Peaked T waves, flat P waves,
increased PR interval, widening of QRS
 Bradycardia, SVT, VT may occur
Treatment of Hyperkalemia
 D/C K in IVF
 Reverse the effect of hyperkalemia on the cell
membranes

infuse 10% Calcium gluconate (100mg/kg/dose)
 Promote movement of K from the ECF into
the cells

NaHCO3 1-2 mEq/kg IV over 5-10 min
 Insulin-0.05 units/kg with 2ml/kg/hr of D10
 Furosemide 1mg/kg/dose if there is adequate
renal function to increase renal excretion
 Peritoneal dialysis in case of oliguria/anuria
Fluid and electrolyte therapy
in common conditions
 Perinatal asphyxia resulting in ATN
 Fluid
restriction = urine output+insensible
losses, no potassium
 Anuric term infant = 30ml/kg/day
 Anuric preterm = 80ml/kg/day
 If the cause of the anuria is unclear give
10ml/kg of crystalloid or colloid