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

Hypocalcemia, or low serum calcium, is the primary cause of tetany in newborns.
Low calcium levels increase the permeability of neuronal membranes to sodium ions, leading to progressive depolarization, which increases the possibility of action potentials. This results in nerve and muscle hyperexcitability, manifesting as tetany (involuntary muscle spasms).
According to pediatric guidelines, neonatal hypocalcemia is defined as a serum total calcium level below 8.5 mg/dL and an ionic calcium level below 4.4 mg/dL.
Other signs of neonatal hypocalcemia include jitteriness, poor feeding, and seizures.

Option B: Hypokalemia (low potassium) typically causes muscle weakness, fatigue, and cardiac arrhythmias, not the hyperexcitability and spasms seen in tetany.
Option C: Hypercalcemia (high calcium) has a calming or depressive effect on neuromuscular excitability, leading to symptoms like hypotonia (decreased muscle tone), lethargy, and poor feeding.
Option D: Hyperkalemia (high potassium) is a life-threatening condition that primarily affects the heart, causing dangerous cardiac arrhythmias. It does not cause tetany.

Visual 1: Diagram: Pathophysiology of Hypocalcemia. A flowchart showing how low extracellular calcium leads to increased sodium influx, neuronal hyperexcitability, and muscle tetany.
Visual 2: Table: Electrolyte Imbalances in Newborns. A comparison table showing the causes, signs, and symptoms of hypocalcemia, hypercalcemia, hypokalemia, and hyperkalemia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Neonatal electrolyte imbalances and their clinical manifestations as background academic context rather than a clinical decision trigger.
Recognizing tetany as a sign of hypocalcemia is a critical nursing assessment skill. Prompt reporting and intervention are necessary to prevent more severe complications like seizures and laryngospasm.
Nursing responsibilities during IV calcium gluconate administration include continuous cardiac monitoring for bradycardia (a common side effect), ensuring slow infusion, and monitoring the IV site for extravasation, which can cause severe tissue necrosis.
What if? If the newborn with tetany also had a difficult birth with asphyxia, the nurse should have a high index of suspicion for early-onset hypocalcemia and also check blood glucose, as hypoglycemia can present with similar neurological signs.

How to Approach the Question

First, identify the key terms in the question: 'tetany' and 'newborn'.
Recall the function of major electrolytes (Calcium, Potassium) in the body, specifically their role in muscle and nerve function.
Analyze the term 'tetany,' which implies neuromuscular hyperexcitability and spasms.
Evaluate the options: Calcium is directly involved in regulating the excitability threshold of nerves and muscles. Low calcium (hypocalcemia) lowers this threshold, causing hyperexcitability.
Contrast this with potassium imbalances: Hypokalemia causes weakness, while hyperkalemia primarily affects the heart. Hypercalcemia causes decreased excitability (hypotonia).
Conclude that hypocalcemia is the direct cause of the described symptom.

Concept Tested & Keywords

Concept Tested: Neonatal electrolyte imbalances and their clinical manifestations.
Stem keywords: tetany, newborn
Lead-in keywords: cause of
Clinical cues: Symptom: Tetany
Clinical cues: Patient: Newborn

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