Case in the Spotlight 4 answer
ECG with a K+ 1.6mmol/L
1. The ECG demonstrates
- U waves
- Prolonged QT, or QU interval
2. The most important tests are an urgent K+ and Mg
The K+ is checked rapidly using point of care testing, or more slowly by sending to the lab – the minutes lost using the latter strategy may matter – ie “did you hear about that patient with hypokalaemia and VF arrest matters…”
Potential diagnostic pitfalls with hypokalaemia include the following:
Hypokalaemia is often associated with hypomagnesaemia, which increases the risk of malignant ventricular arrhythmias
Check potassium and magnesium in any patient with an arrhythmia
Top up the potassium to 4.0-4.5 mmol/l and the magnesium to > 1.0 mmol/l to stabilise the myocardium and protect against arrhythmias – this is standard practice in most CCUs and ICUs
See medscape reference for more details
Why do I need to always recognise this ECG?
The patient is at risk of VF
This is preventable
An absolutely fantastic summary is located below and is a must read
Here is an extract from the management section
"If the potassium level is less than 2.5 mEq/L, intravenous potassium should be given. Maintain close follow-up care, provide continuous ECG monitoring, and check serial potassium levels.
Higher dosages may increase the risk of cardiac complications. Many institutions have policies that limit the maximum amount of potassium that can be given per hour. Hospital admission or observation in the emergency department is indicated; replacement therapy takes more than a few hours.
The serum potassium level is difficult to replenish if the serum magnesium level is also low. Look to replace both."