Potassium Balance Disorders

Key Points

• Normal serum potassium is 3.5 to 5.1 mEq/L.
• Hyperkalemia is potassium greater than 5.1 mEq/L and can progress to dysrhythmia or cardiac arrest.
• Hypokalemia is potassium less than 3.5 mEq/L and often presents with weakness, lethargy, and weak pulse findings.
• IV potassium administration requires hydration, adequate renal function, and careful infusion safety controls.

Pathophysiology

Potassium is the most abundant intracellular electrolyte and is essential for cardiac rhythm, neuromuscular function, and cellular excitability. Potassium distribution is maintained by active transport through the sodium-potassium pump, and total potassium balance is strongly influenced by renal handling and aldosterone effects.

Hyperkalemia raises risk for electrical instability in the myocardium. Hypokalemia decreases membrane excitability and contributes to muscle and cardiovascular dysfunction. Because both states can cause serious cardiac effects, trend-based assessment and rapid intervention are core nursing priorities.

Classification

• Hyperkalemia: Serum potassium greater than 5.1 mEq/L; cues include irritability, GI cramping, diarrhea, and peaked T waves.
• Hypokalemia: Serum potassium less than 3.5 mEq/L; cues include muscle weakness, lethargy, and thready pulse.

Nursing Assessment

NCLEX Focus

Prioritize ECG changes, renal clearance status, and current potassium trend before initiating or advancing replacement.

• Trend serial serum-potassium values and correlate with symptom progression.
• Monitor ECG for peaked T waves or rhythm instability in hyperkalemia.
• Assess for weakness, lethargy, and pulse quality changes in hypokalemia.
• Confirm urine output and renal status before potassium replacement because potassium is renally excreted.
• Review causes including vomiting, diarrhea, diuretic class, metabolic-acidosis, renal failure, and potassium supplement exposure.

Nursing Interventions

• Escalate severe hyperkalemia findings promptly due to risk for life-threatening cardiac-dysrhythmias.
• For mild hyperkalemia, support medication and intake adjustments as ordered.
• For severe hyperkalemia, support ordered therapies such as potassium binding therapy and dialysis-level escalation.
• For hypokalemia, implement ordered oral or IV potassium replacement with strict infusion safeguards.
• Recheck post-treatment potassium levels from a different line than infusion access.

IV Potassium Safety

Verify adequate hydration and renal function before IV potassium. Infuse slowly and do not exceed 20 mEq/hr to reduce arrhythmia and arrest risk.

Pharmacology

Drug Class	Examples	Key Nursing Considerations
cation-exchange-resin	Sodium polystyrene (Kayexalate)	Used for severe hyperkalemia to bind potassium in the GI tract for excretion.
potassium-supplements	Oral or IV potassium replacement	Confirm urine output before administration and follow infusion safety limits.
diuretics	Potassium-sparing or potassium-wasting agents	Diuretic type can raise or lower potassium and should be reviewed during cause analysis.

Clinical Judgment Application

Clinical Scenario

A patient with poor urine output develops potassium of 5.2 mEq/L with new ECG changes.

Recognize Cues: Potassium is above 5.1 mEq/L and rhythm risk markers are present. Analyze Cues: Hyperkalemia with reduced renal clearance is likely driving electrical instability. Prioritize Hypotheses: Immediate risk is progression to life-threatening dysrhythmia. Generate Solutions: Escalate care, initiate ordered potassium-lowering treatment, and intensify monitoring. Take Action: Implement urgent protocol and coordinate repeat labs and ECG reassessment. Evaluate Outcomes: Potassium falls toward normal and rhythm stabilizes.

Related Concepts

• serum-potassium - Primary laboratory marker for diagnosis and treatment response.
• hyperkalemia - High potassium state with major cardiac risk.
• hypokalemia - Low potassium state with neuromuscular and cardiovascular effects.
• electrocardiogram - Essential tool for detecting potassium-related conduction changes.
• kidney-function-monitoring - Renal clearance determines risk during replacement and correction.

Self-Check

1. Which ECG finding in hyperkalemia indicates urgent cardiac risk?
2. Why must urine output be confirmed before giving potassium replacement?
3. What infusion limit improves IV potassium safety in this source?