Fluid and electrolyte

Question 1

How to calculate sodium deficit

Answer 1

Na deficit = (140 - serum Na) x TBW

• TBW = (0.6 x body weight)
• 140 is normal sodium level
• 0.6 is percentage of water in body

Question 2

How to calculate sodium content in 0.9% normal saline

Answer 2

• Since normal saline contains 9 grams of NaCl, the concentration is 9 grams per litre divided by 58.4 grams per mole, or 0.154 mole per litre.
• Thus, NS contains 154 mEq/L of Na+ and the same amount of Cl-