Our patients often require electrolyte supplementation, and potassium supplementation is encountered most commonly.

Hypokalaemia is common in anorexic patients, patients with chronic kidney disease, and primary hyperaldosteronism (Conn's syndrome) patients amongst others - and so we as nurses should be familiar with how to supplement our fluids, and how to manage patients on supplemented fluids.

Here are my top tips for patients on KCl supplementation:

Bags containing potassium salts should be regularly rotated/agitated. Because potassium salts are dense, they will sink! If not agitated/mixed they can settle at the bottom of the bag, causing increased concentrations to enter the giving set and be administered.

Bags should be labelled with the volume (in mmol) of potassium chloride added, strength of the potassium solution and the volume (in mls) of potassium injection added. Note that there are different concentrations of potassium chloride injection available - in the UK we have 15% and 20%, and the mmol/ml will be different between them. Always double check and label clearly!

When calculating the volume to add to Hartmanns solution, you don't need to minus the amount already in the bag - as it contains very little potassium

Lines containing high-dose potassium MUST NOT be flushed or used to administer medications.

If your patient also needs a fluid bolus, or their fluid rate is changing often (e.g. if they are hypovolaemic or dehydrated and deficits are being corrected) set up two lines - a potassium supplemented line being administered at a lower rate, and a plain bag which can be bolused as needed. Always label these bags clearly

KMAX is the maximum rate at which potassium can be delivered to a patient. This is 0.5mmol/kg/hour. Anything exceeding this rate can cause significant complications including bradycardia and cardiac arrhythmias.

To work out the rate of potassium administration per kilo per hour, use the following calculation:

1. Size of bag divided by fluid rate in ml/hour = number of hours the bag will last

2. Total mmol of potassium added to bag divided by the number of hours the bag will last = mmol/hour

3. mmol/hour divided by patient bodyweight = mmol/kg/hour

For example, a 20kg dog receiving 40ml/hour of fluids, on 1 litre of Hartmanns containing 20mmol of potassium chloride:

1. 1000ml / 40ml = bag will last 25 hours

2. 20mmol of potassium / 25 hours = 0.8mmol/hour

3. 0.8 / 20kg = 0.04mmol/kg/hour

References

1. BSAVA Formulary, 8th Edition