[9] Hyperkalaemia Flashcards
What is classified as hyperkalaemia?
A serum potassium of greater than 5.5mmol/L
When is hyperkalaemia usually asymptomatic?
At relatively low levels
Why is hyperkalaemia a very important condition to identify and treat early?
Due to cardiac and other complications that can arise
What are the causes of hyperkalaemia?
- Oliguric renal failure
- Potassium sparing diuretics
- Rhabdomyolysis
- Metabolic acidosis
- Excess potassium therapy
- Addison’s disease
- Massive blood transfusion
- Burns
- Drugs
- Artefactual result
Give an example of a drug that can cause hyperkalaemia?
ACE inhibitors
What should be done if a patient is found on testing to be hyperkalaemic but they do not display any signs or symptoms of hyperkalaemia?
The test should be repeated urgently, as it may be artefactual
What can cause an artefactual hyperkalaemia result?
- Haemolysis
- Contamination with potassium EDTA in FBC bottles
- Thrombocythaemia
- Delayed analysis
What can cause haemolysis leading to an artefactual hyperkalaemia result?
- Difficult venepuncture
- Patient clenching their fist
How can thrombocythaemia cause an artefactual hyperkalaemia result?
Because potassium leaks out from platelets during clotting
How can delayed analysis lead to an artefactual hyperkalaemia result?
Potassium leaks out of RBCs
Below what serum potassium concentration are symptoms rare in hyperkalamia?
Less than 7.0mmol/L
What are the signs and symptoms of hyperkalaemia?
- Fast, irregular pulse
- Chest pain
- Weakness
- Palpitations
- Light-headedness
- Paresthesia
When should clinical assessment in hyperkalaemia take place?
Needs to be timely, and is often performed simultaneously with treatment
What is involved in the clinical assessment of hyperkalaemia?
- Urine output
- Review of potassium intake
- Review of drugs
- Review history for possible causes of renal disease or major tissue destruction
- Fluid status
- Review recent biochemistry results, in particular renal function and potassium levels
What sources of potassium intake need to be reviewed in hyperkalaemia?
- IV fluids
- Potassium supplements
- Diet
What drugs should be reviewed in hyperkalaemia?
- ACE inhibitors
- Angiotensin II receptor blockers
- Potassium sparing diuretics
What should be involved in a fluid status assessment?
Look for signs of dehydration or fluid overload
Describe the importance of ECG in hyperkalaemia
The ECG is vital in the assessment of hyperkalaemia, with the findings progressing with increasing serum potassium levels
Describe the relationship between serum potassium concentration and ECG
While ECG findings can generally be correlated to serum potassium concentration, potentially life-threatening arrhythmias can occur without warning at almost any level of hyperkalaemia
What is considered to be mild hyperkalaemia?
5.5-6.5mmol/L
What are the ECG findings in mild hyperkalaemia?
- Tall ‘tented’ T waves seen across the precordial leads
- Prolonged PR segment
What is considered to be moderate hyperkalaemia?
6.5-7.5mmol/L
What are the ECG findings in moderate hyperkalaemia?
- Decreased or ‘flattened’ P wave
- Prolonged QRS complex
What is considered to be severe hyperkalaemia?
>7.5mmol/L
What are the ECG findings in severe hyperkalaemia?
- Progressive widening of QRS complex
- Axial deviation and bundle branch blocks
What may eventually happen to the ECG in hyperkalaemia?
The progressively widened QRS eventually merges with the T wave, forming a sine wave pattern. Subsequent ventricular fibrillation or asystole may then follow
When should you seek expert renal advice in hyperkalaemia?
If potassium is >6.5mmol/L or there are ECG changes, and the patient is oligo/anuric
How should hyperkalaemia be managed when potassium is >6.5mmol/L, or there are ECG changes?
- Monitor cardiac rhythm
- Calcium gluconate 10% 10ml undiluted over 5 mins. Repeat at 5 min intervals as needed, until ECG is normal, with a maximum of 3 doses in total
- 10 units insulin + glucose 50% 50ml, give into large vein over 30 minutes
- Salbutamol 10mg nebuliser
- Stop all potassium containing/sparing drugs, and treat hypotension
What monitoring should be done when you give a patient 10 units insulin + glucose 50% 50ml?
Monitor BMs after 15 and 30 minutes, then hourly
When should you exercise caution in giving patients salbutamol in hyperkalaemia?
In patients with a history of arrhythmias in IHD
When should you consider giving sodium bicarbonate in hyperkalaemia?
If pH <7.2
How often should you recheck potassium in hyperkalaemia when potassium is >6.5mmolL or there are ECG changes?
Every 2 hours
When might a patient with hyperkalaemia need dialysis?
If they develop renal failure, or are oligo/anuric
How is hyperkalaemia managed when potassium 6.0-6.5mmol/L with no ECG changes?
- Exclude pseudohyperkalaemia
- Stop all potassium containing/sparing drugs
- Low potassium diet
- Ensure adequate hydration, and monitor urine output
- Monitor renal function
- Remove excess potassium using calcium resonium 15g PO
When should you stop calcium resonium?
Consider stopping when <6.0mmol/L. Stop when <5.5mmol/L
How is hyperkalaemia managed if potassium <6.0mmol/L and renal function is stable?
No urgent action is required, arrange dietary modification and medication review
