Question:medium
30 y/F, 70 kg man with serum sodium = 120 mEq/L. Calculate total sodium deficit.
30 y/F, 70 kg man with serum sodium = 120 mEq/L. Calculate total sodium deficit.
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Use the formula: Na deficit = 0.6 x weight (kg) x (desired Na - actual Na) with desired Na = 140 mEq/L.
Updated On: Jun 23, 2026
- 420
- 840
- 1400
- 280
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The Correct Option is B
Solution and Explanation
Formula-based calculation:
Given: Weight = 70 kg, Serum Na = 120 mEq/L, Target Na = 140 mEq/L.
Sodium deficit formula:
$\text{Na deficit} = \text{TBW} \times (\text{Desired Na} - \text{Actual Na})$
Where TBW = $0.6 \times \text{body weight (kg)}$
Calculation:
$\text{TBW} = 0.6 \times 70 = 42 \text{ L}$
$\text{Na deficit} = 42 \times (140 - 120) = 42 \times 20 = 840 \text{ mEq}$
Clinical note: Sodium correction rate should not exceed 8-10 mEq/L per 24 hours to prevent osmotic demyelination syndrome. For chronic hyponatremia, maximum correction is 8 mEq/L/day. Rapid correction can cause central pontine myelinolysis (CPM), characterized by dysarthria, dysphagia, and quadriplegia.
\[\boxed{840 \text{ mEq}}\]
Given: Weight = 70 kg, Serum Na = 120 mEq/L, Target Na = 140 mEq/L.
Sodium deficit formula:
$\text{Na deficit} = \text{TBW} \times (\text{Desired Na} - \text{Actual Na})$
Where TBW = $0.6 \times \text{body weight (kg)}$
Calculation:
$\text{TBW} = 0.6 \times 70 = 42 \text{ L}$
$\text{Na deficit} = 42 \times (140 - 120) = 42 \times 20 = 840 \text{ mEq}$
Clinical note: Sodium correction rate should not exceed 8-10 mEq/L per 24 hours to prevent osmotic demyelination syndrome. For chronic hyponatremia, maximum correction is 8 mEq/L/day. Rapid correction can cause central pontine myelinolysis (CPM), characterized by dysarthria, dysphagia, and quadriplegia.
\[\boxed{840 \text{ mEq}}\]
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