Question

"Zoe", a 40 kg Labrador Retriever is recovering after a liver mass resection. The doctor asks you to start "Zoe" on a fentanyl constant rate infusion at 4 micrograms per kilogram per hour (ug/kg/hr). The concentration of fentanyl is 0.05mg/mL. The fluid rate is currently set at 100 mL/hour. How much fentanyl will you add to a liter of Normosol-R?

Answer 1

32 mL

Step-by-step explanation:

Step 1: Covert pounds to kilograms. This problem's units are already in kg, so no conversion is necessary.

Step 2: Calculate the number of hours an infusion will last by dividing the volume in the bag (1 liter,or 1000 mL) by the rate per hour: 1000 mL/100 mL/h = 10 hours.

Step 3: In case the problem asks for a dose per minute, you will need to multiply the hours by 60 to convert to minutes, but this problem does not ask for it, it asks for ug/kg/hr, so no need to convert here.

Step 4: Now plug into the equation: 4 ug/40 kg/10 hr = 1600 ug.

Step 5: Now convert the ug into mg by dividing by 1000: 1600/1000 = 1.6 mg.

Step 6: Then calculate the quantity of fentanyl to add, by dividing the 1.6 mg by the concentration of the drug (0.05 mg/mL): 1.6 mg/0.05 mg/mL = 32 mL.

Note: to be truly accurate when adding drugs to bags like this, you should discard 32 mL of fluids from the bag prior to adding the 32 mL of fentanyl.