The nurse in the labor and delivery unit is preparing to administer an oxytocin IV infusion to induce labor at the ordered initial dose of 2 milliunits per minute. The available solution is 20 units of oxytocin in 1000 mL lactated ringer’s. Which rate should the nurse set on the infusion pump in mL per hour? Round to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero. Any rounding should be completed at the end of the calculation. The answer must be numeric only. Do not add any units of measurement.

Medication administration - Intravenous labor and delivery: Nursing pharmacology

Revisores de contenido

Kelsey LaFayette, DNP, ARNP, FNP-C,Katie Arps BSN, RN,Paige Randall, MS, RN, CNE, CEN,Lisa Miklush PhD, RN, CNS

Colaboradores/as

Kelsey LaFayette, DNP, ARNP, FNP-C,Katie Arps BSN, RN,Sam Gillespie, BSc,John Gully,Patricia Nguyen, MScBMC

The administration of IV medications used during labor and delivery requires the nurse to calculate medication concentrations, infusion rates, and titration factors, along with close monitoring of how both the pregnant patient and the fetus respond to the medication. Some medications used in this setting, like magnesium sulfate and oxytocin, are considered high-alert medications, meaning they can cause significant harm if administered incorrectly. These medications are always delivered through an IV pump to ensure accuracy.

To calculate a dose using the Dimensional Analysis, or DA method, the three components you need are V, for Vehicle or the form and amount in which the medication comes, like tablets or liquid, H, for Have, or the dosage you have available; and D, for the Desired dose, or dose ordered by the health care provider; and since there’s a time component, we also have T, for Time.

Magnesium sulfate is a medication used as tocolytic to slow contractions in preterm labor or to reduce the risk of seizures in patients with preeclampsia. It's typically administered starting with a loading dose, or a higher dose given over a shorter duration, so the desired therapeutic effect is achieved more quickly. After the loading dose is administered, a maintenance dose, or a slower rate of administration is administered to maintain a therapeutic level.

Let’s look at how to calculate a loading dose of magnesium sulfate in mL/hr.

First, you’ll read the order, which is: magnesium sulfate 6 g IV in Lactated Ringer’s solution over 30 minutes.

Then, check the medication label:

The medication is available in a concentration of 40 g in 1000 mL of Lactated Ringer’s solution.

In this case, D is 6 g, which was obtained from the health care provider’s order; H is 40 g, which was obtained from the medication label; V is 1000 mL, which was also obtained from the label; and T is 30 minutes, which was obtained from the health care provider’s order.

Next, you’ll determine if a conversion factor is required. To determine this, compare the units of D with the units of H. Because both D and H are in grams, no conversion factor is needed for the dose. However, since T is in minutes and the infusion rate you’re calculating is in mL/hr, a conversion factor is needed. In this case you’ll use the following conversion factor for minutes to hours:

60 minutes = 1 hour

Now, set up your equation, where X is the infusion rate in mL per hour, written out like this:

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