Potassium - Hyperkalaemia

Hyperkalaemia is defined as a serum K+ > 5.5 mmol. In its extremes it is the most dangerous of the electrolyte imbalances. It often needs urgent and emergency treatment. There is need to get an urgent ECG, and the findings dictate the needs for specific treatment such as calcium.

Causes

The causes can be categorised into 3 groups, decreased excretion, increased extracellular K+ and ionic shift.

Symptoms

The symptoms of hyperkalaemia can be categorised as neurological, GI and cardiovascular

Neurological

• Weakness, flaccid paralysis, areflexia

• Paraesthesia in hands and feet

Gastrointestinal

• Nausea, vomiting, diarrhoea, abdominal pain

Cardiovascular

• Atrial and ventricular ectopic beats

• Tachydysrhythmias

Investigations

When there is any suspicion of hyperkalaemia do an urgent ECG and send bloods, ideally a venous blood gas for expedient results. Other investigations are those of renal function, digoxin levels and looking for underlying causes depending on clinical and historical findings.

ECG Findings

ECGs with increasing K+ serum levels.

K+6.4

K+7.4

K+8.7

Source: Life In The Fast Lane - Hyperkalaemia

Management

Resuscitation and cardiac protection are the initial priorities ( emphasis again on K+ levels and ECG driving Rx).

Cardiac protection:

IV calcium if ECG shows a wide QRS

Calcium gluconate 10mLs 10%

• Cardio-protective but does not lower serum K+

• Narrows QRS within minutes

• Contains 2.2mmols

• Easier on veins

Calcium chloride 10mLs 10% IV over 2-3 mins

• Cardio-protective but does not lower serum K+

• Narrows QRS within minutes

• Contains 6.8 mmols of Calcium

• Corrosive on veins

Drive K+ into cells

• Glucose (50mLs 50%) with IV actrapid insulin (10 units) - reduces serum K+ by 1.0mmol (in the setting of renal impairment then 1 hrly BSLs required for 24 hours due to high risk of hypoglycaemia)

• Nebulised salbutamol (5mg x2) - reduces serum K+ by ~0.8mmol l-1

• Sodium bicarbonate (50mLs of 8.4%) - only if patient is acidotic

• The effect onset in 10-20 mins and lasts 2-3 hrs with broad variation

• Monitoring is the key

Increase excretion of K+

• Calcium resonium (a polystyrene GIT exchange resin) 30-60g oral or rectal

• may be repeated 4-6 hourly

• Haemodialysis if available and if hyperkalaemia severe

• Diuresis, with fluids / frusemide

Further References and Resources

1. Life In The Fast Lane - Hyperkalaemia

2. Northern Beaches Health Service - Hyperkalaemia Guidelines (including algorithm)