Hypocalcemia is characterized by all of the following features except:
1. Numbness and tingling of circumoral region.
2. Hyperactive tendon reflexes.
3. Shortening of Q-T interval in ECG.
4. Carpopedal spasm.
Answer
3. Shortening of Q-T interval in ECG.
Reference
Harrison 15th Edition Chapter 341 and 340
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Discussion
A decrease in the concentration of free calcium ions in plasma results in
- increased neuromuscular irritability and tetany.
- This syndrome is characterized by peripheral and perioral paresthesia,
- carpal spasm, pedal spasm,
- anxiety, seizures,
- bronchospasm, laryngospasm,
- Chvostek's sign, Trousseau's sign, and
- Erb's sign, and
- lengthening of the QT interval of the electrocardiogram.
- In infants tetany may be manifested only by irritability and lethargy.
- The level of calcium ions that determines which features of tetany will be manifested varies among individuals. Tetany is also influenced by other components of the ECF; e.g., hypomagnesemia and alkalosis lower whereas hypokalemia and acidosis raise the threshold for tetany.
Explanation
1. Numbness and tingling of circumoral region is present.
2. Hyperactive tendon reflexes is present. This is the basis of asking the patients to hyperventilate when we are not able to elicit a reflex. Hyperventilation causes Alkalosis which causes tetany
3. of Q-T interval in ECG is prolonged.
4. Carpopedal spasm is present.
Comments
Increases in total serum calcium concentration are usually accompanied by increases in free calcium levels and may be associated with
- anorexia, nausea, vomiting,
- constipation,
- hypotonia,
- depression, and occasionally lethargy and coma.
- Persistent hypercalcemia, especially when accompanied by normal or elevated levels of serum phosphate, may cause
- ectopic deposition of a solid phase of calcium and phosphate in
- walls of blood vessels,
- connective tissue about the joints,
- gastric mucosa,
- cornea, and
- renal parenchyma.
- Hypercalcemia per se alters renal function in addition to the pathologic effects of calcium phosphate deposition.
Tips
One formula that approximates the amount of calcium bound to protein is
% of Protein bound Calcium = 0.8 x albumin (g/L) + 0.2 x globulin(g/L) + 3
A simplified correction is The correction is to add 1 mg/dL to the serum calcium level for every 1 g/dL by which the serum albumin level is below 4.0 g/dL. If the serum calcium level, for example, is 7.8 mg/dL (a subnormal value) and the serum albumin level is only 3.0 g/dL, then the stated serum calcium level is corrected by adding 1 mg/dL; the corrected value of 8.8 mg/dL is within the normal range.
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Source of this Question: RxPG AIPG 2004
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