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Fluids and Electrolytes in the Newborn


Renal sodium losses are inversely proportional to ... excretion of Sodium = 5% to 6 ... may need 4-5mEq/kg of sodium per day to offset high renal losses ... – PowerPoint PPT presentation

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Title: Fluids and Electrolytes in the Newborn

Fluids and Electrolytes in the Newborn
  • Vandana Nayal

Body fluid composition in the fetus and
  • Total Body Water ICF ECF (IntravascularInters
  • 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
  • LBW infants lose about 10-15 of body weight
    during the first 5 days of life
  • Can lead to imbalances in sodium and water

Sodium balance in the
  • 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 lt35wks display negative sodium
    balance and hyponatremia during first 2-3 wks of

Sodium balance in the
  • 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
  • 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

Water balance in the newborn
  • Primarily controlled by ADH which enables water
    to be reabsorbed by the distal nephron collecting
  • 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

Fluid requirements in the first
month of life
  • Birth weight Water requirements
  • D 1-2 D3-7
  • lt750 100-200 150-200 120-180
  • 750-1000 80-150 100-150 120-180
  • 1000-1500 60-100 80-150 120-180
  • gt1500 60-80 100-150 120-180

Factors affecting insensible water losses in the
  • Level of maturity
  • Elevated body temperature increases loss by 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
  • 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 lt135 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
  • Body weight
  • Fluid intake
  • Urine and stool output
  • Serum electrolytes
  • Urine osmolarity or specific gravity
  • Oral mucosal integrity
  • Heart rate and blood pressure
  • Capillary refill
  • Sunken anterior
  • fontanelle

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

  • Serum sodium lt 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, glucoseinsulin, and
  • 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,
  • Treat with water restriction and repletion of

Treatment of Hyponatremia
  • Fluid restriction which results in a slow return
    to normal levels
  • Urgent correction necessary if serum sodium is lt
    120 mEq/L b/c obtundation or seizure activity may
  • 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 Na (140-serum Na) X 0.6 X body weight

  • Serum sodium gt 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

  • Serum Potassium lt 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

  • Serum potassium gt 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
  • 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 outputinsensible
    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
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