Thu18November0317AM 7

A 70-year-old male has a serum potassium of 2.2 mmol/L (3.5-4.9).

The following statements are true:

True / False

A 12 lead ECG may show peaked T waves Correct

Up to 20 mmol of potassium chloride should be added to his daily maintenance intravenous fluids Correct

Hypokalaemia may cause cardiac arrest Correct

Oral potassium supplements will rapidly correct his deficit Correct

Potassium can safely be given by infusion at a rate of 60 mmol per hour Correct

Explanation

Hypokalaemia is defined as a serum potassium of <3.5 mmol/L and symptoms usually occur below 2.5 mmol/L. A common cause of post-operative hypokalaemia is inadequate potassium intake, e.g. intravenous fluid therapy without sufficient potassium supplementation. The daily maintenance potassium requirement is 0.5-1.0 mmol/kg per day.

ECG changes are common and include T wave inversion, S-T segment depression, Q-T and P-R prolongation and U waves. Cardiac arrest may occur if attempts to raise the serum potassium are delayed and hypokalaemia is a cause of pulseless electrical activity (PEA).

Treatment of hypokalaemia in this patient should be with intravenous potassium not oral supplementation. Up to 40 mmol of potassium chloride can be added to each litre bag of fluid (not 20), but this method may not raise the serum potassium quickly enough. Therefore, it should be given by intravenous infusion at a rate not exceeding 40 mmol/hour (not 60).

In severe cases this upper limit may be exceeded with ECG monitoring e.g. in a critical care areas, as there is a high risk of dysrrhythmias, especially ventricular fibrillation (VF).

Hypokalaemic patients often have a low serum magnesium and thus they should have their serum magnesium checked and corrected if found to be low.

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Average score: 92.32%

Times answered: 271