Hypokalemia (K+ <2.5)

1. ECG stat to look for hypokalemic changes
2. 1g KCLin 100cc NS over 2hour (according to K+ level0 with continous cardiac monitoring
3. add KCL in drip if any, mist KCL 15mls TDS/t slow K 600mg/1.2g OD
4. off K supplements once K>4
5. repeat 1 hour post correction
6. Repeat cm?

ECG changes in Hypokalemia

• Increased amplitude and width of the P wave
• Prolongation of the PR interval
• T wave flattening and inversion
• ST depression
• Prominent U waves (best seen in the precordial leads)
• Apparent long QT interval due to fusion of the T and U waves (= long QU interval)

With worsening hypokalaemia…

• Frequent supraventricular and ventricular ectopics
• Supraventricular tachyarrhythmias: AF, atrial flutter, atrial tachycardia
• Potential to develop life-threatening ventricular arrhythmias, e.g. VT, VF and Torsades de Pointes

Handy tips

• 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

Hyperkalemia (K+ >5.5)

1. ECG stat to look for hyperkalemic changes
2. off K supplements
3. 10cc of 10% calcium gluconate in 10 minutes with cardiac monitoring + 50cc d50% glucose + 10 unit actrapid
4. t kalimate 5-10g TDS
5. off kalimate once K <5
6. repeat 1 hour post chase
7. repeat cm?

ECG manifestations in hyperkalaemia

• Peaked T waves
• Prolonged PR segment
• Loss of P waves
• Bizarre QRS complexes
• Sine wave

Effects of hyperkalaemia on the ECG

Serum potassium > 5.5 mEq/L is associated with repolarization abnormalities:

• Peaked T waves (usually the earliest sign of hyperkalaemia)

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Serum potassium > 6.5 mEq/L is associated with progressive paralysis of the atria:

• P wave widens and flattens
• PR segment lengthens
• P waves eventually disappear

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Serum potassium > 7.0 mEq/L is associated with conduction abnormalities and bradycardia:

• Prolonged QRS interval with bizarre QRS morphology
• High-grade AV block with slow junctional and ventricular escape rhythms
• Any kind of conduction block (bundle branch blocks, fascicular blocks)
• Sinus bradycardia or slow AF
• Development of a sine wave appearance (a pre-terminal rhythm)

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Serum potassium level of > 9.0 mEq/L causes cardiac arrest due to:

• Asystole
• Ventricular fibrillation
• PEA with bizarre, wide complex rhythm

Handy Tips

Suspect hyperkalaemia in any patient with a new bradyarrhythmia or AV block, especially patients with renal failure, on haemodialysis or taking any combination of ACE inhibitors, potassium-sparing diuretics and potassium supplements.

credit: Life in the fast lane ECG and sources from study crew