Hyperkalaemia

Hyperkalaemia is defined as a serum potassium level of > 5.2 mmol/L.
ECG changes generally do not manifest until there is a moderate degree of hyperkalaemia (≥ 6.0 mmol/L).
The earliest manifestation of hyperkalaemia is an increase in T wave amplitude.

Causes:

Hyperkalaemia as an artefact of collection process or technique
Decreased excretion (frequent cause)
- Renal diseases: Acute/chronic renal failure, renal anomaly
- Adrenal mineralocorticoid deficiency
Transcellular shift
- Acidosis eg Diabetic ketoacidosis, lactic acidosis
Increased production (Most often if in association with renal dysfunction)
- Extensive trauma, rhabdomyolysis (crush injury, convulsion, infection), haemolysis, tumour lysis syndrome, burns
Exogenous source
- Iatrogenic potassium administration (oral, IV)
- Increased ingestion
- Massive transfusion
Medication
- eg NSAID, trimethoprim, heparin, chemotherapy, K-sparing diuretic, ACE inhibitor, beta blockers, succinylcholine, digoxin, mannito

ECG features of hyperkalaemia
- Peaked T waves
- P wave widening/flattening, PR prolongation
- Bradyarrhythmias: sinus bradycardia, high-grade AV block with slow junctional and ventricular escape rhythms, slow AF
- Conduction blocks (bundle branch block, fascicular blocks)
- QRS widening with bizarre QRS morphology
With worsening hyperkalaemia… (> 9.0 mmol/L):
- Development of sine wave appearance (pre-terminal rhythm)
- Ventricular fibrillation
- PEA with bizarre, wide complex rhythm
- Asystole

Note: Serum potassium level may not correlate closely with ECG changes. Patients with a relatively normal ECG can suffer sudden hyperkalaemia cardiac arrest. In any patient who has suffered a bradycardia PEA arrest, suspect and treat for hyperkalaemia.

An easy way to remember the usual order of ECG changes seen is by following the ECG trace logically – effects begin on the T wave and move forwards to the P wave / PR interval, and subsequently to the QRS complex with QRS widening and conduction blocks.

Classification of severity of hyperkalaemia

Degree of hyperkalaemia	Potassium level (mmol/L)
Mild	5.3 – 6.0
Moderate	6.0 – 6.9
Severe	≥ 7.0

Treatment

Stop any source of potassium intake
- IV fluid
- parenteral alimentation
- dietary supplement (including NGT feeding)
- potassium-sparing medication

Severe hyperkalaemia

K+ >7.0 mEq/L or at risk of increasing and/or
Patient symptomatic and/or
ECG disturbance

Calcium IV
Salbutamol neb
Insulin/glucose IV
Bicarbonate IV if metabolic acidosis
Dialysis:
- Urgent if unstable
- Rapid if stable but symptomatic or abnormal ECG
- Consider if asymptomatic but severe hyperkalaemia
Resonium (Polystyrene sulfonate) PR (if dialysis unavailable)
Consider hydrocortisone 1-2 mg/kg IV if suspicion of adrenal insufficiency

Moderate hyperkalaemia

K+ 6-7
Patient asymptomatic
Normal ECG

Salbutamol neb
Insulin/glucose IV
Resonium (Polystyrene sulfonate) PR or oral
Bicarbonate IV if metabolic acidosis

Mild hyperkalaemia

K+ >5.5
Patient asymptomatic
Normal ECG

Consider no treatment
Stop K supplements
Recheck result
Salbutamol neb
Polystyrene sulfonate PR or oral (resonium)
Bicarbonate IV if metabolic acidosis

Therapies:

Calcium:
- 2 solutions :
  - Calcium gluconate 10%: 0.5 mL/kg slow IV injection
    - 2-5 minutes if unstable, over 15-20 min if stable (Max: 20 mL)
    - Preferable if only peripheral line available
  - Calcium Chloride 10% : 0.1-0.2 mL/kg slow IV injection (as above) (Max: 10 mL)

Note: Give under cardiac monitoring, discontinue if HR dropping significantly
Avoid extravasations
NOT to be given simultaneously with bicarbonate
NOT to be given if digoxin toxicity

Onset of Action: <3 minutes, should see normalisation of ECG. If not: repeat dose (twice)
Duration: ~30 minutes

Salbutamol:
- Salbutamol: nebulisation
  - Less than 25 kg : 2.5 mg neb 1-2 hourly
  - More than 25 kg : 5 mg neb (Adu max 10-20 mg) 1-2 hourly
- Salbutamol : IV *Only if severe hyperkalaemia after discussion with senior doctor from tertiary centre with monitoring for tachycardia
- Onset of Action: 30 minutes
- Duration: 2-3 hours

Insulin/glucose
to be given at the same time
If severe hyperkalaemia:
- Dextrose 10% : 5 mL/kg IV bolus (if no hyponatraemia)
- Insulin short action: 0.1 U/kg IV bolus (max 10 units)
- Then followed by infusion insulin/glucose – Insulin short action infusion : 0.1 U/kg/h IV
If moderate hyperkalaemia:
- Dextrose 10% IV at maintenance with 0.9% sodium chloride (normal saline)

Onset of Action: 15 minutes
Duration: peak 60 minutes, 2-3 hours

Bicarbonate
In metabolic acidosis only
Severe hyperkalamia and metabolic acidosis
- Sodium Bicarbonate 8.4% 1 mmol/mL : 1-3ml/kg IV over 5 minutes
Mild to moderate hyperkalaemia and metabolic acidosis:
- Sodium Bicarbonate 8.4% 1 mmol/mL : 1 mL/kg slow IV infusion over 30 minutes
Note: Do NOT give simultaneously with Calcium
Onset of Action: 30-60 minutes
Duration: 2-3 hours

Resonium
- Mild effect, multiple doses necessary, may be used as long term agent
- Polystyrene sulfonate (resonium) 0.3-1 g/kg 6 hourly (max 15-30 g)
- PR or oral (with lactulose)
- Note: NOT to be used if ileus, recent abdominal surgery, perforation, hypernatraemia
- Onset of Action: 1 hour PR, 4-6 hours oral
- Duration: variable

ECG Examples