Clinical Practice Guidelines

Hypernatraemia


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    This guideline has been adapted for statewide use with the support of the Victorian Paediatric Clinical Network

  • Definition     Serum [Na+]
    (mmol/l) 
    Hyponatraemia < 135
    Normal 135 - 145
    Mild Hypernatremia 146 - 149
    Moderate Hypernatraemia 150 - 169
    Severe Hypernatraemia ≥ 170


    Causes:

    Mild hypernatraemia is relatively common. Risk increases with level of serum sodium.

    Treatment can be complicated and potentially dangerous. Seek expert advice early.

    Most common:

    • Water loss in excess of sodium
      • Diarrhoea, especially with continuing hyperosmolar feeding/rehydration (eg: Polyjoule, home-made rehydration solutions)
      • Severe burns
    • Inability to obtain/swallow adequate water (+/- impaired renal concentrating ability) - including neonates (eg inadequate breastmilk intake)

    Less common: consider if not improving as expected with management

    • Water deficit from
      • Impaired thirst drive (e.g. Hypothalamic lesion)*
      • Diabetes insipidus*
      • Osmotic diuresis
    • Gain of sodium
      • Ingestion of large quantities of sodium (inappropriate formula concentration, high osmolarity oral rehydration solutions)
      • Iatrogenic sodium administration (hypertonic saline, sodium bicarbonate)

    *Endocrinology can provide advice on management of central Diabetes Insipidus if required.

    Assessment

    • Severe symptoms mainly develop when the serum [Na+] > 160mmol/l.
      • more severe with acute hypernatraemia
      • Chronic hypernatraemia (present > 5 days) is often well tolerated because of cerebral compensation.
    • Clinical signs may lead to underestimation of true degree of dehydration. Weight loss is more reliable.
    • The child may appear sicker than expected for the clinical signs of dehydration that are present.
    • Shock occurs late because intravascular volume is relatively preserved.
    • Look for signs of intracellular dehydration and neurological dysfunction:
      • Lethargy
      • Irritability
      • Skin feels "doughy"
      • Ataxia, tremor
      • Hyperreflexia, Seizures, reduced GCS 

    Investigations

    • Check other electrolytes and blood sugar. These may need concurrent management
    • Investigations for rare differentials (moderate/severe hypernatraemia)
      • Urine sodium and osmolality (paired with serum)
      • Collect at diagnosis, as may help identify rare differentials if not responding to management as expected
    • If seizures / neurological signs: recheck sodium urgently, consider neuroimaging, seek senior advice.

    Management

    Too rapid reduction of the sodium in hypernatraemia can cause cerebral oedema, convulsions and permanent brain injury.

    Close monitoring is critical.

    Resuscitation:

    If "shocked", resuscitate with boluses 20ml/kg of 0.9% saline as required.

    Initial management and monitoring

    Fluid management should then be based on the initial serum sodium.

    • Rate to lower sodium:
      • Aim to lower the serum sodium slowly at a rate of no more than 12mmol/L in 24 hours, (0.5mmol/L/hour).
      • An even slower rate will be required for children with chronic hypernatraemia
    • The rate of rehydration, or sodium concentration of fluids, may need to be changed if appropriate rate of correction of serum sodium is not seen (too fast or too slow). Seek specialist advice.
    • Stop any feed fortifications (such as extra scoops of formula or Polyjoule)
    • Monitor fluid status
      • urine output
      • repeat weight (initially 6 hourly, esp if infants or severe hypernatraemia).
    • Monitor other electrolytes and blood sugar
    • Measure ongoing losses (ie: vomiting or diarrhoea, excluding urine) and replace ml for ml with normal saline.
    • Careful neurological monitoring

    Rehydration: The following guide is for rehydration of patients with excess water loss for the first 12 - 24hrs. 

    Mild hypernatraemic dehydration, [Na+] 146 - 149 mmol/L.

    Rarely requires specific management. Manage underlying cause. Repeat in 4-6 hours if clinically indicated.

    Moderate hypernatraemic dehydration, [Na+] 150 - 169 mmol/L.

    After initial resuscitation, replace the deficit plus maintenance slowly at a uniform rate over 48 hours.


    • Nasogastric rehydration is preferred. Use oral solution (eg: Gastrolyte),
      • Note: Gastrolyte has a low sodium concentration (60mmol/L).
      • Carefully regulate fluid intake - do not allow excessive intake in a thirsty child.
      • If the serum sodium falls too rapidly (>0.5mmol/L/hr) slow the rate of rehydration (for example, by 20%) or change to intravenous fluids.
    • If needing intravenous rehydration use Plasma-Lyte 148 and 5% Glucose OR 0.9% sodium chloride (normal saline) and 5% Glucose. Add maintenance KCl once urine output established. See table below.
    • Check U&E's and glucose hourly intially.
    • If after 6 hours of rehydration therapy the sodium is decreasing at a steady rate then check the U&Es and glucose 4 hourly.
    • If serum sodium is falling faster than 1 mmol/L/hr - seek specialist advice

    Severe hypernatraemic dehydration [Na+] ≥ 170

    A medical emergency. Tertiary referral and contact Intensive Care for consideration of admission.

     After initial resuscitation, aim to replace deficit and maintenance with Plasma-Lyte 148 and 5% Glucose OR 0.9% sodium chloride (normal saline) and 5% Glucose over 72 - 96 hours.

    Table for fluid replacement:

    • Use only when hypernatraemia is associated with dehydration
    • This table advises starting rate, which may need to change depending on progress - seek specialist advice
    • Ongoing losses (eg: profuse diarrhoea) need to be replaced in addition

    Weight (kg)

    Moderate hypernatraemia [Na+] 150 - 169

    NG: Gastrolyte OR

    iv: Plasma-Lyte 148 and 5% Glucose OR

    0.9% sodium chloride (normal saline) and 5% Glucose

    Rate of fluids ml/hr

    (replacing deficit over 48hrs)
    (calc on 7% dehydration)

    Severe hypernatraemia

    [Na+] > 170

    iv: Plasma-Lyte 148 and 5% Glucose OR

    0.9% sodium chloride (normal saline) and 5% Glucose

    Rate of fluids ml/hr

    (replacing deficit over 96hrs)
    (calc on 10% dehydration)

    4

    22

    21

    5

    27

    25

    6

    33

    30

    7

    38

    35

    8

    44

    40

    10

    55

    50

    12

    62

    56

    14

    68

    62

    16

    75

    68

    18

    82

    75

    20

    90

    80

    22

    96

    87

    24

    100

    90

    26

    105

    95

    28

    110

    98

    30

    114

    100

    32

    120

    105

    34

    124

    110

    36

    128

    113

    38

    133

    117

    40

    138

    122

    45

    150

    132

    50

    160

    142

    55

    175

    152

    60

    187

    162

    65

    195

    168

    70

    200

    173


    Notes

    If seizures or other signs of cerebral oedema occur during treatment: recheck serum sodium urgently.Hypertonic saline may be required to partially reverse the reduction in serum sodium. Seek specialist advice.

    Seizures may be due to venous sinus thrombosis or cerebral infarction. Consider imaging with a contrast CT scan.

    Consider peritoneal dialysis if the serum [Na+] > 180mmol/l.  

    Consultation with local paediatric team: 

    • Any child with hypernatraemia  

    When to consider transfer to tertiary centre:

    • Child with moderate hypernatraemia where cause is unclear, or cause other than dehydration
    • Any child with severe hypernatraemia
    • Hypernatraemia not responding as expected to management
    • Child requiring care beyond the comfort level of the hospital.

      For emergency advice and paediatric or neonatal ICU transfers, call the Paediatric Infant Perinatal Emergency Retrieval (PIPER) Service: 1300 137 650.

    Last updated December 2012

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