Why have I been given potassium after heart surgery?

Potassium is an important mineral that helps your body function normally, especially your muscles and nerves.

This includes your heart, which is a muscle controlled by the nervous system.

If your potassium levels are too high or too low this can affect the way it works.

This might include abnormal heart rhythms such as atrial fibrillation, which you’re already at an increased risk of following heart surgery, such as a coronary artery bypass graft (CABG) or a heart valve procedure.

This is why doctors will prescribe potassium supplements if your potassium is below the normal range after heart surgery. You may be given it via a vein (intravenously) in hospital or as a pill, usually dissolved in water.

Some doctors also prescribe potassium supplements for a short time after heart surgery because they believe it helps prevent atrial fibrillation, even if potassium levels are in the normal range.

However, new research from the UK and Germany shows that doing so in people who have had a CABG does not lead to fewer cases of atrial fibrillation.

The study, called TIGHT-K, included 1,690 people undergoing a CABG – half were given potassium supplements to maintain high-normal levels, and half were given them only if their potassium levels fell below the normal range.

The results, presented at the 2024 European Society of Cardiology Congress, showed no difference in the number of people in each group who developed atrial fibrillation in the five days following a CABG, or before they were discharged from hospital, whichever was sooner. 

This suggests that potassium supplements do not prevent atrial fibrillation as long as your potassium levels are within the normal range.

So, if you’re having heart surgery, speak to your doctor about whether you’ll need potassium supplements afterwards.

As with any medication, you may experience side effects with potassium supplements. The most common include diarrhoea, nausea and stomach pain or wind.

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