Question

A patient requires 40 mEq of potassium and 12 mmol of phosphate to be diluted and given intravenously. The pharmacy has a stock of vials of potassium phosphate injection (90 mmol phosphate and 141 mEq potassium per 30 mL vial) and large quantities of concentrated 15% (w/v) potassium chloride solution. (MW KCl = 74.5). How many mL each of potassium phosphate solution and of concentrated potassium chloride solution are required to fill this order? Round each final answer to one decimal place.

Answer 1

The order is potasium 40meq and the phosphate 12mmol.

The paharmacy stock is potasium phosphate 30 ml which has 90mmol of phosphate and 141 meq od potassium

To calculate the required ml of potasium phosphate to give 12mmol of phosphate is

What we want devided by what we multiplyied by the quantity

so when we put the value in the formula,it become

(12mmol / 90mmol) x 30 = 4ml

So when we the 4ml of the soulution it has the required amount of phosphate that is 12mmol

Now we have to see how much potasium is there in 4ml of this soulution

here 30ml = 141 meq

4 ml = x meq

x = (141 x 4) / 30 = 18.8meq

So we need the remaining of 18.8meq out of 40meq is needed ( thet means 21.2meq)

In 15% of potasium chloride each ml contains 2meq of potasium (15% w/v means 15g in 100ml of solution.That means 15000mg in 100 ml,so each ml has 150mg ,it is given that MW is 74.5mg/mmol so the formula to calculate the meq is (milligram x valance) / MW,the valance of kcl is 1 so when we put the values in the formula (150 x 1) / 74.5 =2.01=2meq,so each ml is 2meq)

1ml = 2meq

x ml = 21.2meq

x = (1 x 21.2) / 2 = 10.6ml

so we have to take 4ml of potasium phosphate and 10.6 ml of potasium chloride.