These lecture notes accompany the MBChB Year 5 case-based tutorial on abnormal electrolytes (2025). They are an adjunct to the tutorial and may not make complete sense in isolation.
hyperkalaemia is usually caused by renal failure and drugs that interfere with the RAAS
[K+] < 6 mM rarely requires treatment
stablise the myocardium > shift K+ into cells > encourage elimination
Causes of hyperkalaemia
Plasma potassium concentration is tightly controlled by aldosterone, which acts to promote potassium excretion by the kidneys (distal renal tubule).
The commonest causes are acute or chronic kidney failure and drugs inhibiting the renin-angiotensin-aldosterone system (RAAS).1 Plasma potassium concentration is also strongly influenced by shifts into and out of cells. However, with intact kidneys and a functioning renin-angiotensin-aldosterone system, potassium shifted out of cells should be promptly excreted in the urine.
Management
Severe hyperkalaemia is a medical emergency because it can cause life-threatening cardiac dysrhythmia.
Remember that any abnormal ECG in the context of hyperkalaemia is likely to be significant.2 For example, hyperkalaemia can sometimes cause junctional rhythms that are easy to miss unless you are looking for them.
Treatment is almost never required with K < 6 mM (although it may be worth reviewing medications and optimising kidney function if potassium levels are creeping up).
shifting potassium into cells (a temporary holding measure)
enhancing potassium removal from the body (in the urine or using renal replacement therapy)
For mild-to-moderate hyperkalaemia, it is important to weigh the benefits of potassium-lowering therapy against the iatrogenic risks. These risks include hypoglycaemia (after insulin therapy) and decompensated heart failure (after stopping RAS inhibitors).
Additional reading
Core materials
You should ensure that you are familiar with the UK Kidney Association one-page treatment algorithms:
hyperkalaemia algorithm in hospital
hyperkalaemia algorithm in primary care
hyperkalaemia algorithm during cardiac arrest
(There are appendices 6, 7 and 8 in the guidelines.)
Additional materials (consult only if interested)
The UK Kidney Association hyperkalaemia guidelines contain everything you could ever need wish to know about the management of hyperkalaemia in adults. The full guideline is over 150 pages long.
This open access review article has additional information on the causes and consequences of hyperkalaemia, including an explanation of the mechanisms driving ECG changes.
