Hyperkalaemia

Question 1

Normal range for potassium?

Answer 1

3.5mmol/l - 5.5mmol/l

Question 2

What are the causes of hyperkalaemia?

Answer 2

post-operative AKI
Repeated blood transfusions
Drugs - potassium sparing diuretics, spironolactone, ACEi, ARB
Excessive potassium treatment
Rhabdomyolysis
Dehydration

Question 3

When do symptoms occur? What are they?

Answer 3

7.0mmol/l

Paraesthesia, muscle weakness, nausea and vomiting, palpitations

Question 4

What investigations are required for hyperkalaemia?

Answer 4

Routine bloods, U&E, calcium, phosphate, magnesium
VBG - immediate result of potassium
ECG
Catheterisation if necessary for fluid balance monitoring
Review abs, fluid status, medication

Question 5

What are the ECG changes in mild, moderate and severe hyperkalaemia? Values?

Answer 5

Mild (5.5-6.5mmol/l):
Tall tented T waves (across leads)
Prolonged PR segment (normally 120-200ms)

Moderate (6.5-7.5mmol/l)
Decreased or flattened P wave
Prolonged QRS complex (normally <120ms)

Severe (>7.5mmol/l)
Progressive widening of the QRS complex
Axial deviation
BBB

Subsequent VF or systole may follow as QRS widens and merges with T wave forming sine wave

SO:
Tall tented T
Then flattened P
Then QRS widening
Then Axial deviation/BBB
Then sine wave pattern

Question 6

How are hyperkalemia patients managed?

Answer 6

Stabilisation of the myocardium
Reduction in serum potassium
Reduction in total body potassium

Assess underlying cause
Repeat blood testing and ECG

Question 7

How is the myocardium stabilised?

Answer 7

IV calcium gluconate or calcium chloride (10ml of 10%) when ECG changes are present or in all moderate - severe hyperkalaemia

Continuous cardiac monitoring is required following stabilisation treatment

Question 8

How is serum potassium reduced?

Answer 8

Variable rate insulin with dextrose infusion (200ml of 20% glucose with 10Units of insulin over 30 mins) acting to increase cellular uptake of potassium and reduce serum conc.
Short term as K will leave cells within 30-60mins so repeated doses may be requried

Salbutamol nebulisers may be added for further reduction - moves potassium from ECF to ICF

Question 9

How is total body potassium reduced?

Answer 9

Identify reversible underlying cause
Referral to renal physicians
Potential haemodialuysis