Question

A patient is receiving an intravenous infusion
containing 40 mEq of potassium chloride in 1000
mL of dextrose 5% in half–normal saline. The
infusion has been running at a rate of 80 mL/h 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/h. The physician prescribes
potassium chloride injection (14.9% KCl) to be
added to the IV such that the patient will receive a
total of 80 mEq of potassium over the remaining
time for completion of the infusion. How many
milliliters of the potassium chloride injection
should be added by the pharmacist?

Answer 1

80 ml/hr (x) 6.5 hr = 520 ml administered (480 ml remain

480 ml/ 40 ml/hr = 12 hours of fluid available

40 mEq KCl in 1000 ml = 4 mEq per 100 ml

X mEq/520 ml =4 mEq /100 ml =20.8 mEq of KCl

40 mEq (minus) 20.8 mEq = 19.2 mEq that remain in the bag

Could also do for KCl

X mEq /480 ml =4 mEq /100 ml =19.2 mEq of KCl remaining in the bag

80 mEq (minus) 19.2 mEq = 60.8 mEq needed to add to the bag

K = 39 + Cl = 35.5 = 74.5 mg per mEq (x) 60.8 mEq = 4529.6 mg needed

14.9% = 149 mg per ml

4529.6 mg (div by) 149 mg per ml = 30.4 ml----answer