Question

1. Medication order: Loading dose, mix magnesium sulfate 20 g in 1000 mL D₅W. Infuse 4 g over 30 minutes, then maintain at 1 g/hr. Maintain primary IV 1000 mL D₅W at 60 mL/hr after magnesium sulfate loading dose.
   Available: Magnesium sulfate 50% in 10 mL vials

Calculate the secondary rate for the loading dose.

Answer ________________ 400

Explain to me

Answer 1

Ans) Step 1:

Order: Mix magnesium sulfate 20g in 1000 mL.

1000 mL = 20 g

Infusion order = 4 g over 30 minutes.

Therefore,

Amount = Ordered dose / Dose on hand X volume

= 4 / 20 X 1000

Amount = 200 mL

Hence 200 mL contains 4 g of magnesium sulfate to be infused over 30 minutes.

Step 2:

1 hour = 60 minutes.

Ordered time = 30 minutes

mL/hr = 60 / 30 X 200

mL/hr = 400

The infusion pump to be set 400 mL/hr to infuse 4 g of magnesium sulfate for over 30 minutes.

Step 3:

Ordered secondary loading dose = 1g/hr.

200 mL contains 4g

Therefore 1g = 200 / 4

1g = 50 mL/hr

or

Ordered dose = 1g

Available dose = 20g

Volume = 1000 mL

Amount = Ordered dose / Dose on hand X Volume

Amount = 1 / 20 X 1000

Amount = 50 mL /hr

The infusion should be set as 50 mL/hr for secondary loading Dose.