Cardiac arrhythmias are seen in?

VSSC Nursing Officer - 2021

Medical & Surgical Nursing

Easy

Appeared in: VSSC Nursing Officer - 2021

Explanation

Hypokalemia (serum potassium below 3.5 mEq/L) alters the resting membrane potential of myocardial cells, increasing their excitability.
This increased cardiac irritability can lead to various life-threatening arrhythmias, including premature ventricular contractions (PVCs), ventricular tachycardia (VT), and ventricular fibrillation (VF).
Classic ECG changes associated with hypokalemia include flattened or inverted T-waves, the appearance of a prominent U-wave, and ST-segment depression.

Option A: Hyponatremia (low sodium) primarily causes neurological symptoms such as confusion, headache, and seizures due to cerebral edema. It does not have a specific, characteristic effect on the ECG.
Option B: Hypernatremia (high sodium) also primarily causes neurological symptoms like lethargy, irritability, and seizures due to brain cell shrinkage. Significant cardiac effects are not a primary feature.
Option C: Hypocalcemia's main ECG effect is prolonging the ST segment, which leads to a prolonged QT interval. While this can predispose to Torsades de Pointes, it is less associated with the broad range of arrhythmias seen in hypokalemia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Effects of electrolyte imbalances on cardiac electrical activity as background academic context rather than a clinical decision trigger.
Nurses must recognize that patients on diuretics (especially loop and thiazide), or those with significant GI losses (vomiting, diarrhea), are at high risk for hypokalemia and subsequent arrhythmias.
When administering IV potassium, it must be diluted and infused slowly (never as an IV push) to prevent sudden, fatal hyperkalemia. The maximum infusion rate is typically 10 mEq/hr on a general ward.
What if? If the patient also had low magnesium (hypomagnesemia), correcting the hypokalemia would be difficult. The nurse should anticipate the need to replace magnesium first or concurrently, as magnesium is a cofactor for potassium uptake.

How to Approach the Question

First, identify the core concept of the question, which is the link between a specific condition (cardiac arrhythmias) and its potential causes among the options.
This is a factual recall question. Systematically review the primary effects of each electrolyte imbalance listed.
Recall that potassium (K+) plays a critical role in cardiac muscle and nerve cell function, specifically in electrical conduction.
Contrast this with sodium (Na+), which primarily affects fluid balance and neurological function, and calcium (Ca2+), which is key for muscle contraction and has a distinct effect on the QT interval.
Select the electrolyte whose imbalance is most famously and directly linked to a wide range of cardiac arrhythmias.

Concept Tested & Keywords

Concept Tested: Effects of electrolyte imbalances on cardiac electrical activity
Stem keywords: Cardiac arrhythmias
Lead-in keywords: seen in

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E6 Nursing Fundamentals Taylor p. 779-781

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 52-54