Hyperkalemia and Hypokalemia

Potassium is the major intracellular cation and a central determinant of the resting membrane potential. A change in the serum potassium concentration can alter myocardial excitability and conduction before the patient reports symptoms. Hyperkalemia is a serum potassium level above 5.2 mmol/L. Potassium above 5.5 mmol/L with ECG changes or severe renal impairment is an emergency. Hypokalemia is below 3.5 mmol/L; severe hypokalemia is below 2.5 mmol/L, or below 3.0 mmol/L when symptoms or ECG abnormalities are present. The priority is not to memorize an isolated waveform or laboratory value. It is to connect the potassium result with the ECG, renal function, symptoms, rate of change, and likely cause. A patient can look well while developing a life-threatening dysrhythmia, so new ECG changes require urgent action even when the patient denies chest pain or palpitations. For an RPN, safe care includes focused assessment, cardiac monitoring, implementation of prescribed treatment or approved protocols, reassessment, documentation, and timely escalation to the RN, prescriber, or emergency response team according to the patient’s condition and local policy.