Paediatric Acute care Guidelines PMH Emergency Department

Hyperkalaemia is defined as a serum potassium (K+) of more than 5.5 mmol/L

Background

  • Serum K+ over 6.5 – 7 mmol/L, especially when associated with ECG changes is potentially life-threatening, and should be treated as an emergency
  • Cardiac toxicity is enhanced by hypocalcaemia, hyponatraemia or acidosis, and patients with these abnormalities may experience complications at lower potassium levels

General

In children, severe hyperkalaemia may result from:

  • drug ingestions (e.g. digoxin, ACE-inhibitors, oral potassium)
  • acute renal failure
  • massive tissue damage (major trauma or burns, tumour lysis syndrome, haemolysis)
  • severe metabolic acidosis
  • adrenogenital syndromes

Assessment

  • Perform an ECG
  • Exclude an erroneus high potassium (pseudo-hyperkalaemia) due to haemolysis during collection or transport of the specimen

History

Clinical features of hyperkalaemia relate to potassium’s effect on cellular membrane polarisation

  • Early symptoms include nausea, vomiting and paraesthesia

Examination

Assess for:

  • Muscle weakness, progressing to flaccid paralysis and respiratory failure
  • Cardiac conduction disturbance, resulting in wide complex tachycardia, ventricular fibrillation and circulatory failure

Investigations

ECG Changes

In acute hyperkalaemia, cardiac conduction disturbance results in ECG changes which correlate roughly with serum K+ levels.

 
K+ > 6 mmol/L Kgreaterthan6mmol
  • Tall, symmetrical peaked T-waves
K+ > 7.5 mmol/L Kgreaterthan7.5mmol
  • PR interval lengthens (1st degree AV block)
  • Widened QRS (intraventricular block)
K+ > 9 mmol/L Kgreaterthan9mmol
  • Absent P-wave
  • Pre-arrest, QRS and T-waves merge to form a sine wave

 

Management

  • Hyperkalaemia should be treated when serum K+ is over 7 mmol/L, or at levels lower than this if ECG changes are present
  • Emergency management of hyperkalaemia should include early consultation with the Paediatric Intensive Care Unit (PICU)

Initial management

Step 1: Protect the myocardium from the effects of hyperkalaemia

  • Discontinue any potassium supplement and potassium-containing IV fluids
Calcium
  • Doesn’t lower the serum K+, but is cardioprotective in that it stabilises the myocardium, reducing the risk of arrhythmias
  • Contraindicated in digitalis toxicity and hypercalcaemia
  • Dose can be repeated after 15 minutes if ECG is still abnormal
  • Can be given as either calcium gluconate or calcium chloride

10% calcium gluconate 0.5mL/kg (maximum 20mL) IV over 2-5 minutes (10% calcium gluconate = 2.2mmol in 10ml)

OR

10% calcium chloride 0.2mL/kg (maximum 10mL) IV over 2-5 minutes

 

Step 2: Lower the serum potassium level urgently

  • Note: All of  these methods act by shifting potassium intracellularly, thereby reducing the serum K+ level. None of these methods actually reduce total body potassium.
Salbutamol
  • Nebulised or intravenous
  • As effective as glucose and insulin
  • Acts within 60 minutes and lasts about 6 hours
Nebulised:
5 mg (child > 5 years) or 2.5mg (child < 5 years)

IV:
5 micrograms/kg/minute for 1 hour, then 1 microgram/kg/min

Glucose
  • Similar onset and duration of effect to salbutamol
  • Patients endogenous insulin drives potassium intracellularly

10% glucose at 2mL/kg slow IV bolus

then commence

10% glucose + 0.9% saline infusion at maintenance rate

Insulin
  • Discuss with a senior doctor before commencing
  • Insulin is only to be given once the glucose infusion has commenced
  • Onset of action 15 minutes
  • Monitor glucose every 30-60 minutes

Insulin short acting infusion at 0.1units/kg/hr

Make up 50 units of Actrapid or Humulin R in 50mL 0.9% saline (1unit/mL).

Prime line with 20mL of solution before commencing the infusion. 

Sodium bicarbonate
  • Discuss with Emergency Department Senior Doctor or PICU prior to use
  • Not routine, but can be used in emergency even in the absence of metabolic acidosis
  • Do not administer via same line as calcium
  • Contraindicated in alkalosis, hypernatraemia
  • Any hypocalcaemia must first be corrected
Infuse at 1 mmol/kg intravenous over 30 minutes
Frusemide  Consider (in consultation with PICU)  1mg/kg (IV)

 

Step 3: Promote elimination of potassium from the body

Sodium polystyrene sulphonate
(Kayexelate / Resonium)
  • Cease Resonium treatment when the serum potassium is less than 5 mmol/L
    (to avoid hypokalaemia)
Oral dose:
0.5 – 1g/kg (max 60g daily). Administer in a small volume of water or lactulose

Rectal dose: 
0.5 – 1 g/kg (max 30g daily). To administer, mix each 1g of resin with 5mL of water or 10% dextrose.  Irrigate the colon after 8 to 12 hours to remove the resin.

Dialysis  Peritoneal dialysis or haemodialysis  

 

Nursing

  • Continuous ECG monitoring is required due to the risk of lethal dysrhythmias

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