Based on the details provided below, how many milliliters of the potassium chloride injection should be added by the pharmacist?

Question

A patient is receiving an intravenous infusion containing 40 mEq of potassium chloride in 1000 mL of D5 ½NS (dextrose 5% in half normal saline). The infusion has been running at a rate of 80 mL per hour for the past 6.5 hours. Following a lab report showing the patient’s serum potassium level to be 3.5 mEq/L, the physician decides to increase the potassium dose while slowing the infusion flow rate to 40 mL per hour. The physician prescribes a potassium chloride injection (14.9% KCl) to be added to the remaining IV solution, such that the patient will receive 80 mEq of potassium over the remaining time for the completion of the infusion. How many milliliters of the potassium chloride injection should be added by the pharmacist?

Answer 1

Hello Harun,

It looks like you are posting a lot of the questions. I can definitely help you in greater detail if you reach out, but below is a walkthrough of this problem:

A patient is receiving IV infusion to increase potassium levels. The concentration of the IV is 40 molar equivalent potassium chloride, which means there would be 40 moles KCl contained within a 1000mL solution (which is the exact volume of the IV bag). The key here is that this IV was administered at a rate of 80mL per hour for 6.5 hours, which means that 520 mL of total solution had been administered over this time. This leaves 480 mLs left to administer. We need to apply our molarity to this remaining solution, which will help us determine that there are 19.2 moles of KCl remaining in the solution.

Next, we need to make sure to add enough KCl to this remaining solution to bring the molarity of to 80 mEq for the duration of the infusion. This means we need to add another 19.2 moles of KCl into the solution via 14.9% KCl injection. 19.2 = 0.149x and solve for x. We need to add 128.9 mL of the injection in order to meet the 80 mEq requirement for the duration of the infusion.

Please reach out if you need extra help