Question

A patient is ordered to receive sodium supplementation by intravenous infusion of a sodium phosphate dibasic solution [Na₂H PO₄ , MW=141.96 g/mol]. The patient is ordered to receive 0.5 mEq of Na + ions per hour.

A 500 mL intravenous bag is prepared that contains 47 mL of a 1% solution of sodium phosphate dibasic. What should be the infusion rate (in units of mL/min) necessary to produce the ordered dose of 0.5 mEq/hr of sodium?

(Note: Consider the total solution volume to be 500 mL. Also assume the sodium phosphate dibasic salt completely disassociates in solution. Please do not assume the specifics of this question are exactly clinically relevant due to the variability in this question.)

Answer 1

solution)

1% Na₂H PO₄  means 1 gram of Na₂H PO₄ in 100 ml of the solution .

So amount of Na₂H PO₄ in 47 ml = 1 * 47 /100= 0.47 gram = 470 mg

So number of moles of Na₂H PO₄ = 470/141.96 = 3.31 millimoles

So number of equivalents of po4- = 3.31 new

So 3.31 m Eq of po4- present in 500 ml of solution.

So 0.5 mEq present in 500/3.31 * 0.5 = 302 ml

Infusion rate per minute = 302/60 = 5.03 ml/minute.

So the infusion rate should be 5.03 ml/minute.

hence solved