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Child Health Guideline Identifier

Hypocalcaemia

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Objectives

  • Rapid and appropriate investigation and treatment of hypocalcaemia with symptoms in children
  • This is a dilute calcium infusion designed for peripheral IV infusion (most often in the setting of rickets with low calcium).

Definitions

Hypocalcaemia is a symptom complex, and classified as:

  1. Asymptomatic with biochemical hypocalcaemia (the majority) (oral therapy required only)
  2. Mildly symptomatic with mod-severe hypocalcaemia (normally total calcium <1.8mmol/l) (e.g.: parasthesia): may be managed with oral or IV pending clinician concern.
  3. Severely symptomatic with severe hypocalcaemia (e.g.: total calcium <1.6mmol/l, with seizures): should be managed with initial IV calcium therapy.

All children with symptomatic OR severe biochemical hypocalcaemia should be discussed with and admitted under the Paediatric Endocrinology Team.

Background

Hypocalcaemia itself in children is potentially life-threatening due to cardiac arrhythmias and stridor (usually at values of total Calcium <1.5 mmol/l).

Calcium is vital for most biological functions and hence the serum calcium level is maintained within a narrow range, at the expense of sequestration of bone (potentially leading to rickets), and retention of calcium by kidneys at the expense of phosphate loss. Hypocalcaemia in this setting is therefore a late presentation of a chronic disease process and indicates that a child has significant total body calcium depletion (or "bone hunger") and normally an acute on chronic event precipitated by illness or poor oral intake.

Hypocalcaemia, rather than treatment with IV calcium, can prolong the QT interval and be associated with cardiac arrhythmias; hence the need for an ECG/formal cardiac monitoring in the initial stages.

The daily elemental calcium estimation requirements is ≈ 73mg/kg.

Large and continuous doses of calcium are normally required for replacement when hypocalcaemia occurs; weaning of calcium infusion is usually over 24-48 hours once oral calcium and Vitamin D is initiated  (so key is to start oral replacement ASAP): stopping infusions abruptly usually results in rebound hypocalcaemia. But weaning can normally start once serum Ca2+ is >1.7-1.8 or 20% higher than when admitted.

Common Causes of Infant and Childhood Hypocalcaemia

Causes  Features
   PO4  ALP  PTH  25(OH)D3
Vitamin D deficiency  ↓  ↑  ↑  ↓↓
Hypoparathyroidism (transient or permanent)  =  N/↓  N/↓  N
Pseudohypoparathyroidism    ↑  N/↓  ↑  N

Investigations

Blood tests (required)

Draw at time of hypocalcaemia or soon after (for use in clinical notes for an admission)

Serum calcium Result:                              
Ionised calcium Result:
Phosphate Result:
ALP Result:
Albumin Result:
Creatinine Result:
Urea Result:
Magnesium Result:
PTH Result:
25(OH)D3 (25 hydroxy-vitamin D) Result:

X-rays (consider)

  • Consider wrist x-ray or long bone x-ray for rickets
  • Consider chest x-ray (looking for thymus) for hypo-parathyroidism)

Urine (consider)

Calcium, calcium/creatinine ratio and phosphate (consider aminoaciduria in some cases)

In Neonates

Check maternal PTH, 25 hydroxyvitamin D, calcium, phosphate, ALP and HbA1c (maternal diabetes)

Principles of management

  1. To stabilize serum calcium to a safe range (>1.7 - 1.8 mmol/L total Calcium or >1.0 mmol/l ionised) or > 20% from initial calcium value.
  2. To maintain calcium and avoid significant rebound hypocalcaemia while transitioning to oral therapy.
  3. To avoid complications of treatment: in particular extravasation of IV calcium infusion (must have a close watch of IV site and documentation that IV has not tissued on a 10-15 min basis).
  4. To establish the underlying cause.

Management details

  • Obtain blood for appropriate investigations before commencing treatment. 
  • Bolus or infusions of IV calcium should ONLY be given in situations where cardiac monitoring and regular checks of peripheral IV site is available (this may be N/A for central line administration unless unstable or other co-morbidities)
  • Ideally cardiac monitoring is then:CED, PICU (or PICU-HDU), 23B or 26A HDU with continuous cardiac monitoring, and where nursing allows for frequent checks of IV site due to high risk of extravasation. 
  • Discuss with paediatric endocrinologists within 12-24 hours for diagnosis and management.
  • Do not give calcium with phosphate or bicarbonate as precipitation will occur (IV).

Symptomatic Hypocalcaemia (Seizures / Tetany / Stridor)

  1. Always perform ABC and basic resuscitation if necessary
  2. Treat seizures with anti-epileptics as per seizure protocol
  3. Continuous cardiac monitoring - if arrhythmia discuss with Cardiologist 
  4. Treat severe hypocalcaemia with acute severe symptoms with IV calcium (See below for dosing) 
    1. Bolus if tetany, seizures or stridor, then continuous infusion (minority of cases)
    2. Continuous infusion (no bolus), asymptomatic but very low Ca2+ < 1.6 mmol/L (Discuss with SMO)
  5. If serum Mg2+ is ≤ 0.6 mmol/L consider IV magnesium sulphate (2 mmol/mL). 
    Has a permissive effect on PTH release, so may not be useful in the setting of hypo-parathyroidism).
     Dose: 0.2 - 0.4 mmol/kg every 12 hours as slow IV infusion. See Paediatric Medication Administration Guideline ADHB intranet only. 
  6. Monitoring:
    1. Check Ca2+  level at 6-8 hours to ensure improvement, then 12 hourly as indicated
    2. Aim to keep Ca2+ >1.7-1.8 mmol/L, and then gradually wean the infusion as GI absorption of Ca2+ improves; suggest reducing infusion in 25% increments as calcium normalises (but ensure that oral calcium and vitamin D has been started).
    3. Stopping the calcium infusion is likely to result in a rapid fall in serum Ca2+ level due to uptake into bone ("bone hunger"). Aim to wean off over 24-48 hours, or sooner if oral treatment has been initiated.
    4. Oral Therapy (Assuming Vitamin D deficient rickets or hypo-parathyroidism)
       It is important to commence oral calcium AND vitamin D supplementation early (ASAP) as it takes ≈ 2 days to fully increase absorption from the GI system.
      Oral calcium supplementation
      Dose: 100mg/kg/day of elemental calcium in 4 divided doses
      (some SMO may use higher doses up to 200mg/kg/day initially in some cases)

      (Note: 1mmol elemental calcium = 40.1mg elemental calcium)

      NB: Other calcium such as calcium Sandoz is under restriction
      Calcium gluconate and carbonate
      Administration:
      CalSource Ca 1000® brand contains 1000mg elemental calcium per effervescent tablet)
      For part doses, a full tablet may be dissolved in 20mL of water (= 50mg/mL of elemental calcium) to administer the required dose.
      Tablets should not be divided.
      Calcium carbonate
      Administration: 1.25g tablet (contains 500mg elemental calcium)
      These tablets are NOT soluble, round doses to nearest whole tablet. Tablets should not be divided.
      Oral vitamin D supplementation

      In children <12 month simplest dosing is to use One-Alpha drops 


      (Some SMO may use higher doses for first 2-3 days to encourage optimal calcium absorption)

      Note: Calcitriol is the most active form of vitamin D and increases absorption of calcium in 1-2 days
      Calcitriol (1,25-dihydroxycholecalciferol)
      Administration:0.25mcg and 0.5mcg gel capsules
      Dose: Use 0.05 micrograms/kg/day rounded to the nearest whole capsule (maximum dose 1-2 micrograms per day)
      (initial management only, aiming to reduce once stabilised)
      Alfacalcidol (1α-hydroxycholecalciferol)
      Administration: One-Alpha drops® 2mcg/mL or 0.25mcg and 1mcg capsules
      Dose: 100 nanograms/kg/day (=0.05mL/kg/day of One-Alpha drops®)
      Drops to be prescribed by dose volume to the nearest 0.05mL, be careful with the number of drops to avoid inaccurate dosing associated with dropper choice

Calcium Infusion via peripheral IV

Note: 

  • Calcium gluconate is available as 10% standard stock solution (=1g/10mL = 2.2 mmol/10mL elemental Ca).
  • For peripheral infusions always make calcium to a 1% solution as follows: 1 part 10% calcium gluconate added to 9 parts of "water for injection".
  • (Also compatible with 5% glucose (less irritant), 0.9% sodium chloride, and glucose saline solutions).
  • More concentrated solutions may be used via central lines.
  • Only administer if secure IV access is obtained

    TETANY or SEIZURES 
    BOLUS IV calcium
    Six (6) mL/kg of 1% Calcium gluconate solution (diluted as above) over 2 hours

    Ensure cardiac monitoring, followed by an continuous infusion (see below). 
    This bolus dose equates to ~ 0.13 mmol/kg, then followed by the continuous infusion (see below).
    This will ameliorate tetany for ≥ 15 minutes to several hours.
    Can repeat if required. 
    NB: Seizures need treating with anticonvulsants
      See Concentrations of calcium gluconate.

    As above always make calcium to a 1% solution for peripheral administration:

    CONTINUOUS INFUSION IV calcium
    Sixty (60) mL/kg/DAY of the 1% calcium gluconate solution (diluted as above) over 24 hours
    • Ensure cardiac monitoring
    • Repeat Calcium levels at 8 hours then 8-12 hourly accordingly
    • Adjusting calcium total to >1.7 - 1.8 mmol/l to start reducing infusion rate
      eg 5kg child = 5 x 60 = 300mL/Day = 12.5mL/Hour.

Monitoring and observation

  • Monitor ECG in case of arrythmia: unusual with this protocol (SHO/Reg to document QT and rhythm in notes)
  • Monitor the IV site for local reaction/redness - must be directly observed regularly as risk of tissue necrosis if any extravasation occurs
  • Review IV site if patient complains of pain (and stop if any concerns)
  • Monitor Blood pressure
  • Monitor serum calcium's as described above

Other

  • Do not add any other medications as calcium precipitation may occur
  • If IV calcium gluconate not available, can use calcium chloride. Calcium chloride is available as 10% injection (=1g/10mL = 6.8mmol/10mL elemental calcium). Note: This contains 3x more elemental calcium than calcium gluconate

References

  • Sperling MA. Pediatric Endocrinology. 2nd Edition.
  • Lifshitz F. Pediatric Endocrinology. 3rd Edition.
  • Hospital for Sick Children Resuscitation Card 2003-2004

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Document Control

  • Date last published: 23 January 2019
  • Document type: Clinical Guideline
  • Services responsible: Paediatric Endocrinology
  • Author(s): Craig Jefferies
  • Owner: Craig Jefferies
  • Editor: Greg Williams
  • Review frequency: 2 years

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