NORCET 2 - 2021 (shif…: What is the cause of tetany in a newborn?

NORCET 2 - 2021 (shift-1)

Child Health Nursing (Pediatrics)

Easy

Appeared in: NORCET 2 - 2021 (shift-1)

Explanation

Tetany, characterized by involuntary muscle spasms and neuromuscular irritability, is a classic sign of hypocalcemia.
Low levels of extracellular calcium decrease the electrical threshold required for nerve cell depolarization, leading to spontaneous firing and muscle contractions.
In newborns, this can manifest as jitteriness, twitching, a high-pitched cry, and in severe cases, carpopedal spasms, laryngospasm, or seizures.

Option B: Hypokalemia (low potassium) leads to hyperpolarization of muscle cells, making them less excitable. This results in muscle weakness, hypotonia, and arrhythmias, not the hyperexcitability of tetany.
Option C: Hypercalcemia (high calcium) raises the threshold for nerve depolarization, making neuromuscular transmission more difficult. This causes symptoms opposite to tetany, such as muscle weakness (hypotonia), lethargy, constipation, and poor feeding.
Option D: Hyperkalemia (high potassium) primarily affects cardiac muscle conductivity, leading to life-threatening arrhythmias (e.g., peaked T-waves, ventricular fibrillation). While it can cause muscle weakness, it does not cause the characteristic spasms of tetany.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Causes of Neonatal Tetany and Electrolyte Imbalances as background academic context rather than a clinical decision trigger.
Recognizing tetany as a sign of hypocalcemia is a critical nursing skill, as it requires immediate intervention to prevent life-threatening complications like seizures and laryngospasm.
When administering IV calcium gluconate, nurses must infuse it slowly and monitor the heart rate continuously. Rapid infusion can cause severe bradycardia or cardiac arrest.
What if? If a newborn's tetany does not resolve after correcting the calcium level, the nurse should anticipate an order to check the serum magnesium level. Hypomagnesemia is a common cause of refractory hypocalcemia as it is required for PTH release and action.

How to Approach the Question

First, identify the key clinical sign and patient population in the question: 'tetany' in a 'newborn'.
Recall the major electrolyte imbalances and their primary effects on neuromuscular excitability.
Associate tetany (muscle hyperexcitability and spasms) with low levels of electrolytes that stabilize nerve membranes. Calcium is the primary cation responsible for this stabilization.
Systematically evaluate each option: Does hypokalemia cause spasms? No, it causes weakness. Does hypercalcemia cause spasms? No, it causes weakness and hypotonia. Does hyperkalemia cause spasms? No, it causes arrhythmias and weakness.
Conclude that hypocalcemia is the only option that directly causes the increased neuromuscular excitability that manifests as tetany.

Concept Tested & Keywords

Concept Tested: Causes of Neonatal Tetany and Electrolyte Imbalances
Stem keywords: tetany, newborn, cause
Lead-in keywords: What is
Clinical cues: The term 'newborn' points to neonatal-specific physiology and common causes.
Negative lead-in flag: false