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
Life In The Fast Lane - Hyperkalaemia