A 42-year-old man with acute renal failure is confused. His serum potassium is 8.1 mEq/L . The most likely abnormal ECG finding is:
a) T wave inversion
b) PR interval of 300ms
c) QT interval of 0.4s
d) U wave
e) Tall tented T waves
The correct answer is E
The earliest ECG evidence of hyperkalemia usually appears in the T waves The variety of changes include: Increased amplitude and peaking of the T wave PR interval prolongation QRS interval prolongation Flattening of the P wave. A plasma potassium of >6.5mmol/l should be treated urgently unless it is an artefact.
Hyperkalemia may have a variety of causes: Renal failure; Excess potassium replacement therapy;Acidosis from any one of various causes (diabetic ketoacidosis, lactic acidosis, etc.); Presence of insufficient corticosteroids (Addison’s disease). As in hypokalemia, there may be a poor correlation between serum potassium levels and the typical ECG changes.