OB math calculations
please show your work!
1. A patient is ordered Ancef for treatment of GBS positive culture. The patient is to receive a bolus of 2 g
in 100 mL Normal Saline to be administered over 30 minutes followed by a maintenance dose of 1 g
every 8 hours.
At what rate should the nurse program the pump for the initial dose?
How many g will the patient receive in the first 24 hours of treatment?
2. A patient with a history of opioid abuse is on Methadone, with a daily dose of 60 mg. The doctor has
placed an order for the patient to receive a dose every 4 hours. How many mg will the patient receive at
each dose?
3. An African American patient with a history of two preterm births is to receive betamethasone to
stimulate fetal surfactant production. The provider order reads: 12.5 mg betamethasone IM every 24
hours for two doses. The betamethasone vial is labeled as 25 mg/mL with a total volume of 1 mL. How
many mL will the nurse draw up into the syringe for each dose ordered?
4. An obese patient who weighs 198 pounds has been diagnosed with a deep vein thrombosis (DVT) in her
left leg and needs to be heparinized. The provider orders a bolus of 80 units/kg to be infused now and
followed by a maintenance infusion. Solution is labeled as 25,000 units heparin/1000 mL D5W.
Order: Heparin bolus at 80 units/kg x 1.
Order: Run a maintenance rate of 1500 units per hour. What rate should the infusion pump be set
at? How many mL/hr?
5. Sylvia has a history of pyelonephritis. The nurse practitioner prescribes 75 mg nitrofurantoin PO to be
taken twice daily (BID) as a prophylactic. Sylvia requests the liquid formulation. The suspension label
reads 25 mg/5 mL. The nurse is instructing Sylvia as to how to take this medication if she uses a
medicine cup labeled for 2 tablespoons (30 mL) at full capacity with increments of tablespoons and
corresponding mL. How many tablespoons is needed for each dose? How many mL?
6. Nickie comes to the OB office stating she is nauseous and is having difficulty keeping food down. The
nurse asks her about her nutrient intake and teaches her to eat small, bland foods. Nickie requests
something else to help her with her nausea. Knowing
nurse
practitioner orders 25 mg promethazine IM. The nurse obtains the vial of promethazine and checks the
expiration date and the label. The vial reads 50 mg/5 mL. How many mL will the nurse inject into
Nickie hip?
7. Magnolia is admitted to the hospital with hyperemesis gravidarum. The hospitalist orders 20 mEq
potassium chloride to be infused over one hour for serum potassium of 3.0. The solution is labeled 20
mEq KCl / 100 mL NS. What rate will the nurse set the infusion pump to run?
8. Magnolia has a second order for a 500 mL bolus infusion of Lactated Ringers in 30 mins. At what rate
will the nurse set this infusion to run?
9. Finally, the hospitalist orders D5W 50 mL with 20 mEq KCl to infuse at 8 mEq KCl/hr per IV pump.
How many mL/hr of solution will the nurse set on the IV pump?
10. Jennifer arrives on Labor and Delivery in active labor and quickly delivers a baby boy precipitously. She
did not receive an IV prior to delivery so the delivering provider orders 10 units Pitocin to be
administered IM. The vial available in the Pyxis reads 40 u/mL. How many mL would the nurse
11. Ana presents to her 28th week antepartum visit with a blood pressure of 145/88. The obstetrician orders
lab work to evaluate for preeclampsia. All urine protein, liver function tests, and platelets are all within
the normal range and preeclampsia is ruled out. The nurse instructs Ana to call the office or go to the ER
if she develops headaches or visual changes. On her 33rd
is 150/ 88, but
still has no other signs of preeclampsia and her lab work remains normal. Since Ana does not have
asthma, the obstetrician orders the antihypertensive drug labetolol, a nonselective beta blocker to
. The prescription reads 100 mg labetolol by mouth,
three times each day (TID). The available dose is 200 mg tablets.
How many tablets will Ana take with each dose?
How many tablets will Ana need until her next appointment a week from now?
12. At the next appointment 1 week later, Ana begins to show clinical signs of preeclampsia: the urine
dipstick shows 2+ protein and she complains of a headache and sees spots. Her blood pressure is now
168/98 and the obstetrician admits her to the hospital. The orders received include labetalol 20mg IV
now and magnesium sulfate bolus of 6 g to be infused over 30 minutes.
The labetalol concentration is 5mg/mL
o How many mL will the nurse administer IV?
The magnesium sulfate solution reads 40 g in 1000 mL LR
o What infusion rate would the nurse set the pump on to deliver the bolus dose?
An additional order is received to infuse magnesium sulfate at 2 g per hour after bolus dose.
o What infusion rate would the nurse set the pump to deliver 2 g per hour from the
same IV solution?