ECG changes in Electrolyte Imbalances
Electrolyte balance is important for maintenance of proper cardiac function. The nurse should be alert to changes in the electrocardiogram (ECG or EKG) which can indicate electrolyte imbalance; OR if an imbalance is present already, the nurse should investigate the possible ramifications to the ECG.
If you are a nurse in a critical care area, you already know the rapidity with which these changes can occur. If you are a med/surg nurse, or other specialty nurse, be aware of imbalance which can happen slowly. Due to the insidious nature of most electrolyte problems, you must prevent it from becoming severe.
Hyperkalemia, high blood potassium > 5.5 mEq/L
Serum potassium > 5.5 mEq/L is associated with repolarization abnormalities:
Tall tented T waves (usually the earliest sign of hyperkalaemia).
Serum potassium > 6.5 mEq/L is associated with progressive paralysis of the atria:
P wave widens and flattens.
Prolonging PR segment .
Serum potassium > 7.0 mEq/L is associated with conduction abnormalities and bradycardia:
Prolonged QRS interval with bizarre QRS morphology.
Hypokalemia, low blood potassium < 3.5 mEq/L
Changes appear when potassium level falls below about 2.7 mEq/L
ST depression and flattening of the T wave and inversion.
Prominent U waves.
Hypercalcemia, high blood calcium, speeds repolarization
The main ECG abnormality seen with hypercalcaemia is shortening of the QT interval.
In severe hypercalcaemia, Osborn waves (J waves) may be seen.
Normal serum corrected calcium = 2.1 – 2.6 mmol/L
Hypocalcemia, low blood calcium
Prolongation of the QT interval primarily by prolonging the ST segment.
The T wave is typically left unchanged.