Which among the following electrolytes is lethal in impaired renal function?

AIIMS Delhi NO-2016

Medical & Surgical Nursing

Medium

Appeared in: AIIMS Delhi NO-2016

Explanation

In impaired renal function, the kidneys cannot effectively excrete potassium, leading to its accumulation in the blood (hyperkalemia).
Potassium is the most abundant intracellular cation, and its balance is crucial for neuromuscular and cardiac function.
High serum potassium levels are directly cardiotoxic, interfering with the heart's electrical conduction.
Severe hyperkalemia (serum potassium greater than 7.0 mEq/L) can lead to fatal cardiac arrhythmias, including ventricular fibrillation and asystole (cardiac arrest).

Option A: Sodium imbalances in renal failure primarily cause fluid shifts, leading to hypertension, edema, or dehydration. While these conditions are serious, they are not as acutely life-threatening as the cardiac effects of hyperkalemia.
Option C: Impaired renal function typically leads to hypocalcemia (low calcium) due to decreased vitamin D activation and hyperphosphatemia. Hypocalcemia causes neuromuscular irritability (tetany, seizures), not immediate cardiac arrest.
Option D: While magnesium is excreted by the kidneys and levels can rise (hypermagnesemia), it is less common and develops more slowly than life-threatening hyperkalemia. Significant toxicity usually occurs only with very high levels, often due to intake of magnesium-containing medications.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Electrolyte Imbalances in Renal Failure as background academic context rather than a clinical decision trigger.
Nurses must be vigilant in monitoring serum potassium levels in any patient with renal insufficiency or failure. This is a critical patient safety parameter.
Patient education is a key nursing role. Teaching patients with chronic kidney disease about dietary potassium restrictions is essential to prevent life-threatening complications.
Recognizing the early ECG signs of hyperkalemia (peaked T-waves) on a cardiac monitor allows the nurse to intervene quickly and prevent cardiac arrest.

How to Approach the Question

First, identify the core concepts of the question: 'lethal', 'impaired renal function', and 'electrolytes'.
Think about the primary functions of the kidney. A major role is filtering blood and excreting waste products and excess electrolytes.
Consider each electrolyte option. How is it primarily regulated and excreted by the body?
Recall or deduce which electrolyte is most dependent on renal excretion and which becomes most dangerous when it accumulates.
Potassium is almost entirely excreted by the kidneys. Its accumulation (hyperkalemia) directly affects cardiac muscle and electrical conduction, making it the most acutely lethal.
Contrast this with the other options. Sodium issues cause fluid problems, calcium is usually low, and magnesium elevation is less common and slower to become critical. This confirms potassium as the correct answer.

Concept Tested & Keywords

QbKfRSohzJrNsb2cXqobYi

E6 Pharmacology Nursing Lilley 11e Part 2 p. 164-166

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1048-1050

E6 Medicine Davidson Principles Practice 24e p. 438-440