IGNOU PB Bsc Entrance-2022
Medical & Surgical Nursing
Hard
Tetany or tetanic seizures in chronic renal failure is caused by:
Appeared in: IGNOU PB Bsc Entrance-2022
Explanation
- In chronic renal failure, the kidneys fail to activate Vitamin D, which is necessary for intestinal calcium absorption, leading to lower calcium intake.
- The failing kidneys also retain phosphate (hyperphosphatemia). Excess phosphate binds to free calcium in the blood, further reducing its active, ionized form.
- Low levels of ionized calcium (hypocalcemia) increase the excitability of nerve and muscle cell membranes, lowering the threshold for depolarization.
- This neuromuscular hyperexcitability manifests clinically as tetany, characterized by involuntary muscle contractions, cramps, and potentially seizures.
Why Other Options Were Wrong
- Option A: Metabolic acidosis is common in renal failure, but it actually increases the level of ionized (active) calcium by causing it to unbind from albumin. This effect would counteract or protect against tetany, not cause it.
- Option C: Potassium retention (hyperkalemia) is a life-threatening complication of renal failure that primarily affects cardiac muscle, leading to arrhythmias and cardiac arrest, and skeletal muscle, causing weakness or paralysis, not the hyperexcitability of tetany.
- Option D: While sodium imbalances can occur in renal failure, sodium chloride depletion (hyponatremia) typically causes neurological symptoms related to cerebral edema, such as confusion, lethargy, and headache, rather than the specific peripheral neuromuscular irritability of tetany.
Related Visual
Clinical Relevance
- Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of electrolyte imbalances in chronic renal failure as background academic context rather than a clinical decision trigger.
- Nurses must be vigilant in assessing patients with CRF for early signs of hypocalcemia, such as paresthesias (tingling) around the mouth and in the fingertips, as well as testing for Chvostek's and Trousseau's signs.
- Implementing seizure precautions (e.g., padded side rails, keeping suction equipment at the bedside) is a critical patient safety intervention for individuals with severe hypocalcemia.
- Continuous ECG monitoring is crucial because hypocalcemia can prolong the QT interval, predisposing the patient to life-threatening ventricular arrhythmias like Torsades de Pointes.
How to Approach the Question
- First, identify the key clinical terms in the question: 'tetany' (which signifies neuromuscular hyperexcitability) and 'chronic renal failure' (a state of progressive loss of kidney function).
- Recall the primary electrolyte and acid-base disturbances associated with chronic renal failure. These include hyperkalemia, hyperphosphatemia, hypocalcemia, and metabolic acidosis.
- Connect the specific symptom (tetany) to its direct physiological cause. Remember that calcium ions stabilize nerve membranes. A deficit of calcium (hypocalcemia) lowers the firing threshold, leading to spontaneous nerve activity and muscle contraction.
- Systematically evaluate each option based on this understanding:
- Acidosis? No, this tends to increase ionized calcium.
- Calcium depletion? Yes, this is the classic cause of tetany.
Concept Tested & Keywords
- Concept Tested: Pathophysiology of electrolyte imbalances in chronic renal failure
- Stem keywords: tetany, tetanic seizures, chronic renal failure
- Lead-in keywords: caused by
- Negative lead-in flag: false
Question ID
Q4VMiI8qTIwJWihj6Nek0f
Reference Book
E6 Nursing Fundamentals Taylor p. 779-781
E6 Medicine Harrison 22e Part 1 p. 415-417
Practise the full IGNOU PB Bsc Entrance-2022
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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