Functions of kidney: potassium balance
What is potassium? How much is too much potassium? Why is potassium high in CKD? Why might this be a problem? What are the symptoms? And what treatment is available? We aim to answer these questions and more.
What is potassium?
Potassium is a mineral that is found in many foods (e.g. bananas, potatoes, meat and fish). The body needs potassium to work properly. It plays key roles in the use of muscles, the beating of our hearts and sending messages along nerves. However, having too much or too little potassium can be harmful. Therefore, we need to keep it within a narrow range (3.5-5.3 mmol/L). If the potassium is greater than this its caused hyperkalaemia.
Potassium and the kidneys
The kidneys play an important role in maintaining the balance of minerals, including potassium, in the body. They remove excess amounts of potassium in the urine. This helps prevent it building up and preventing the heart from working properly.
Click here to learn more about the functions of the kidneys.
1. Hyperkalaemia definition
The term hyperkalaemia is used when potassium in the blood is above 5.5 mmol/L. Hyperkalaemia is never normal and always requires action. There are three levels of severity depending on how high the potassium is:
- Mild hyperkalaemia = > 5.5 mmol/L – this requires action
- Moderate hyperkalaemia = > 6 mmol/L – this requires action soon
- Severe hyperkalaemia = > 6.5 mmol/L – this requires action today.
2. CKD and hyperkalaemia
In CKD, the kidneys are damaged and so do not remove excess potassium very well. This causes potassium levels to build up in the blood (hyperkalaemia).
3. Acute and chronic hyperkalaemia
Hyperkalaemia can be separated into ‘acute’ and ‘chronic’.
Acute hyperkalaemia is a single event of high potassium, occurring over hours to days. This usually requires emergency treatment.
Chronic hyperkalaemia develops over weeks to months. In this case high potassium may be persistent or come and go. This may require long-term monitoring and treatment.
4. Symptoms of hyperkalaemia
Symptoms of hyperkalaemia vary. They range from no symptoms, to:
- Muscle weakness (this may be severe)
- Palpitations (feeling your heart beating)
- Irregular heart rhythms
- Cardiac arrest.
“If a dialysis or transplant patient says they cannot stand up, take them seriously. It may be severe hyperkalaemia.”
5. Medication for hyperkalaemia
Medications can be used to lower potassium levels in CKD patients with high potassium. These medications include:
- ‘Potassium binders’ (e.g. calcium resonium and sodium zirconium cyclosilicate, Lokelma)
- Diuretics (e.g. furosemide and bumetanide)
6. Medications to stop
Some drugs may cause or contribute to high potassium. This is because they either contain potassium, or raise potassium levels. Taking these medications increases your risk of developing hyperkalaemia. These may need to be stopped in patients with CKD. Some can be started at a lower dose later on. These drugs include:
- Potassium-sparing diuretics (e.g. spironolactone)
- Angiotensin-converting enzyme inhibitors (ACE inhibitors, e.g. ramipril)
- Angiotensin receptor antagonists (ARBs, e.g. losartan)
- Aliskiren
- Trimethoprim and co-trimoxazole
- Ciclosporin and tacrolimus
- Potassium containing drugs or potassium supplements
- Non-steroidal anti-inflammatory drugs (NSAIDs).
7. Other treatment options (dialysis)
In moderate or severe CKD (stages 4-5), or in severe hyperkalaemia, if the above treatments are not sufficient, haemodialysis or peritoneal dialysis may be necessary. These help remove excess potassium from the blood.
They can also help with other CKD-related symptoms such as shortness-of-breath. A high potassium level can be a sign of needing to start dialysis. If you are already on dialysis, and potassium is not controlled, more frequent or longer dialysis may be necessary.
8. Dietary changes
CKD patients with hyperkalaemia may be advised to reduce the amount of high-potassium foods they eat. Speak to your renal dietitian for advice.
Click here to learn more about potassium and a CKD diet.
9. Regular monitoring
CKD patients should have regular blood tests to monitor their potassium levels and kidney function.
10. Collaboration
Managing CKD and hyperkalaemia requires working together with your doctor, sticking to treatment plans, and lifestyle changes.
Summary
We have discussed functions of kidney: potassium balance. We hope it has been helpful.
Last Reviewed on 9 March 2024