Question

A healthy male presents with altered mental status and this was attributed to his [Na+ ] being 108 mEq/L. To return the patient to normal Na+ levels, how much of a 5 wt% NaCl solution must be administered? (Normal plasma Na+ concentration = 140 mEq/L; molecular weight of NaCl is 58; 5 wt% NaCl = 5g/100mL)

Total Body Water = 42L

Extracellular Fluid = 14L

Osmolarity = 300mOsmoles/L

Intracellular Fluid = 28L

Answer 1

Answer :)

The patient’s Na+ levels = 108 mEq/L

Normal Na+ levels = 140 mEq/L

Required Na+ levels to increase = 140 – 108

Required Na+ levels to increase = 32 mEq/L

The sodium levels of 140 mEq/L is present in extracellular fluids.

The administered concentration of NaCl solution = 5 wt% or 5g NaCl in 0.1 Liter water

Number of equivalents in 5 wt% NaCl solution = Weight/ Molecular weight

Number of equivalents in 5 wt% NaCl solution = 0.086 equivalents

But, we need to provide 32 mEq/L without changing the concentration.

We know that 0.086 equivalents are present in 0.1 L solution.

Now use the following formula to find out the 32 mEq/L concentration in the 5 wt% solution.

E1V1 = E2V2

E is equivalents and V is volume

0.086/1000 x 0.1 = 32 x V2

V2 = 2.7 x 10-7 L or

V2 = 2.7 x 10-7 x 103 mL

V2 = 2.7 x 10-4 mL

The extracellular fluid is 14 L.

Therefore, total volume of NaCl required for the patient’s body = 2.7 x 10-4 mL x 14 x 1000 mL

Total volume of NaCl required for the patient’s body = 3.78 mL