HESI RN Dosage Calculation IV – Focused Practice on Intravenous Medication and Fluid Rates

HESI RN Dosage Calculation IV
Question 1:
The healthcare provider prescribes cefazolin 800 mg IM every 6 hours. The available vial
is labeled, "Cefazolin 1 gram," and the instructions for reconstitution state, "For IM use,
add 2.5 mL sterile water for injection to provide a total volume of 3.0 mL." How many mL
should the nurse administer? (Enter numerical value only. If rounding is required, round
to the nearest tenth.)

Explanation

Correct Answer (mL) : 2.4

Solution

Here's how to calculate the volume (mL) of the reconstituted cefazolin solution the nurse
should administer for each dose:

1. We know the following:

Prescribed dose: 800 mg cefazolin (given)

Vial information:

Contains 1 gram cefazolin (given) = 1000 mg (since 1 gram = 1000 milligrams)

Reconstituted with 2.5 mL sterile water for injection (given)

Yields a total volume of 3.0 mL (given)

2. We need to find the concentration of cefazolin (mg/mL) in the reconstituted solution.

3. Then, we can find the volume (mL) to administer for the prescribed dose (800 mg)
considering the concentration.

Steps:

a. Calculate the concentration after reconstitution:

Total volume after reconstitution = 3.0 mL (given)

Total amount of cefazolin after reconstitution = 1 gram (from the vial) = 1000 mg

Concentration (mg/mL) = Total amount of medication (mg) / Total volume after
reconstitution (mL)

,Concentration (mg/mL) = 1000 mg / 3.0 mL

Concentration (mg/mL) = 333.33 mg/mL (round to one decimal place)

b. Calculate the volume to administer:

Volume to administer (mL) = Dose (mg) / Concentration (mg/mL)

Volume to administer (mL) = 800 mg / 333.33 mg/mL

Volume to administer (mL) = 2.4 mL (round to nearest tenth)

Therefore, the nurse should administer approximately 2.4 mL of the reconstituted
cefazolin solution intramuscularly every 6 hours.



Question 2:

The nurse is preparing a client's dose of an IM analgesic in a single syringe. The
prescription is hydromorphone 4 mg and hydroxyzine 25 mg. The
hydromorphone is available in a 10 mg/ml, ampule, and the hydroxyzine is
available in a 50 mg/ml, vial. How many total mL should the nurse administer?
(Enter the numeric value only. If rounding is required, round to the nearest tenth.)

Explanation

Correct Answer (mL) : 0.9

Solution

Here's how to calculate the total volume (mL) the nurse should administer for the
combined medication dose

1. Calculate the volume for each medication:

Hydromorphone:

Dose: 4 mg (given)

Concentration: 10 mg/mL (given)

Volume (mL) = Dose (mg) / Concentration (mg/mL)

Volume (mL) = 4 mg / 10 mg/mL

,Volume (mL) = 0.4 mL

Hydroxyzine:

Dose: 25 mg (given)

Concentration: 50 mg/mL (given)

Volume (mL) = Dose (mg) / Concentration (mg/mL)

Volume (mL) = 25 mg / 50 mg/mL

Volume (mL) = 0.5 mL

2. Add the volumes for each medication to find the total volume:

Total volume (mL) = Volume of hydromorphone (mL) + Volume of hydroxyzine (mL)

Total volume (mL) = 0.4 mL + 0.5 mL

Total volume (mL) = 0.9 mL (round to nearest tenth)

Therefore, the nurse should administer a total of 0.9 mL.


Question 3:

A client is receiving IV dextrose 5% in water (DSW) at 125 mL/hour and a secondary
infusion of pantoprazole 40 mg IV daily. The pharmacy provides a 110 mL premixed
solution of pantoprazole to be infused over 15 minutes. The nurse should program the
secondary infusion to deliver how many mL/hour? (Enter numeric value only.)
Explanation

Correct Answer (mL/hour) : 440

Solution

While the primary infusion rate (dextrose 5% in water) and the total volume of
pantoprazole solution are provided, the pantoprazole infusion doesn't directly affect the
rate of the primary DSW infusion.

Here's the breakdown:

Primary Infusion:

Dextrose 5% in water (DSW) at 125 mL/hour (given) - This rate remains constant
throughout the secondary infusion.

, Secondary Infusion:

Pantoprazole 40 mg total dose (given)

Premixed solution volume: 110 mL (given)

Infusion duration: 15 minutes (given) = 0.25 hours (convert minutes to hours)

The nurse programs the secondary infusion pump to deliver the 110 mL pantoprazole
solution over 0.25 hours, independent of the primary DSW infusion.

Therefore, the nurse should program the secondary infusion pump to deliver a rate of:

Delivery rate (mL/hour) = Total volume (mL) / Infusion time (hours)

Delivery rate (mL/hour) = 110 mL / 0.25 hours

Delivery rate (mL/hour) = 440 mL/hour (This is the rate for the pantoprazole solution
only)

In conclusion:

The primary DSW infusion rate remains at 125 mL/hour.

The secondary pantoprazole infusion rate is 440 mL/hour, but it delivers the total dose
(110 mL) over the 15-minute timeframe.


Question 4:

The healthcare provider prescribes acyclovir 800 mg by mouth (PO) every 6 hours for an
adolescent with chicken pox. The medication is available in 400 mg tablets PO. How
many tablets should the nurse administer to the client every 24 hours? (Enter the
numeric value only.)
Explanation

Correct Answer (tablets) : 8

Solution

Here's how to calculate the number of acyclovir tablets the nurse should administer
every 24 hours:

1. We know the following:

Prescribed dose per administration: 800 mg (given)