Maternity Nursing: cram pack

Formula sheets, the key method steps for every topic and 6 practice problems, with full solutions at the back.

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1Formulas and methods

Maternity & obstetric nursing

Method

  1. Place the woman in time: weeks of pregnancy, stage of labour or day after birth, and decide what is normal at that point.
  2. Look for the patient in danger: the mother, the fetus or the newborn, or more than one of them.
  3. Link the finding to its cause: VEAL CHOP for decelerations, the four Ts for bleeding, BUBBLE-HE after birth.
  4. Choose the action that improves blood flow and oxygen first (side-lying, stopping oxytocin, fundal massage), then escalate.

Dosage calculations

Dose from strength
volume = dose / strength
Weight-based dose
dose = mg/kg × body weight
Tablets
number = dose / tablet strength
Units
1 g = 1000 mg, 1 mg = 1000 mcg

Method

  1. Convert the ordered dose and the stock strength to the same unit.
  2. Use desired over have times quantity: (D/H) × Q.
  3. For weight-based doses, multiply by the weight in kg first, then divide the daily dose by the number of doses.
  4. Estimate first and check that the answer is reasonable.

IV infusion rates

Pump rate
mL/h = volume (mL)/time (h)
Drip rate
drops/min = volume (mL) × drop factor / time (min)
Infusion time
time (h) = volume (mL)/rate (mL/h)

Method

  1. Pump rate in mL/h: volume divided by time in hours.
  2. Drip rate in drops/min: volume × drop factor divided by time in minutes.
  3. For time remaining: volume left divided by the rate.
  4. Round as the question or the equipment requires.

2Practice problems

1.Maternity & obstetric nursingMedium

In fetal circulation, what is the function of the foramen ovale?

  1. AIt shunts blood from the right atrium to the left atrium
  2. BIt carries blood from the aorta back to the placenta
  3. CIt carries blood from the pulmonary artery to the aorta
  4. DIt lets blood from the umbilical vein bypass the liver
2.Maternity & obstetric nursingHard

A woman on a magnesium sulfate infusion has a respiratory rate of 10/min and absent patellar reflexes. What should the nurse do first?

  1. AStop the infusion and call the provider urgently, with calcium gluconate ready
  2. BRecheck the reflexes in 2 hours
  3. CIncrease the infusion rate, because these signs show her pre-eclampsia is worsening
  4. DGive a dose of naloxone
3.Dosage calculationsMedium
500 mg+ 1.8 mLV = ? mL

A vial contains 500 mg of powder. The label says: add 1.8 mL of water for injection to give a total volume of 2 mL. The prescription is 100 mg. What volume V of the reconstituted solution do you give?

500 mg+ 1.8 mL → 2 mL100 mg
V = mL
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 3200 units of a drug that comes as 5000 units/mL. Draw up the dose in the 1 mL syringe: what volume V do you give?

3200 units5000 units/mL
V = mL
5.IV infusion ratesMedium
20 gtt/mL30 mL/h? gtt/min

An infusion is ordered at 30 mL/h, but no pump is available. It runs by gravity through a giving set of 20 gtt/mL. Find the drip rate R in drops per minute.

30 mL/h20 gtt/mL
R = gtt/min
6.IV infusion ratesHard
250 mg100 mL5 mL/h? mg/h

A bag contains 250 mg of a drug in 100 mL and runs at 5 mL/h. How many milligrams per hour D does the patient receive?

250 mg/100 mL5 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: A · It shunts blood from the right atrium to the left atrium

Why this is the answer

The foramen ovale shunts blood from the right to the left atrium. The ductus arteriosus links the pulmonary artery to the aorta, and the ductus venosus lets umbilical venous blood bypass the liver.

Answer

A · It shunts blood from the right atrium to the left atrium
2.Maternity & obstetric nursing

Answer: A · Stop the infusion and call the provider urgently, with calcium gluconate ready

Why this is the answer

Respiratory depression and absent reflexes indicate magnesium toxicity. Stop the infusion, support breathing, obtain help, check the magnesium level and prepare calcium gluconate as ordered.

Answer

A · Stop the infusion and call the provider urgently, with calcium gluconate ready
3.Dosage calculations

Answer: V = 0.4 mL

Dose calculation: the amount to give equals what is prescribed divided by what you have, times the quantity it comes in: amount = (desired dose/stock strength) × stock volume. Always keep the units the same (convert g to mg, mg to mcg first) and check that the answer is sensible.

Concentration after mixing

500 mg/2 mL = 250 mg/mL

Volume

V = 100/250 = 0.4 mL

Answer

V = 0.4 mL
4.Dosage calculations

Answer: V = 0.64 mL

Drawing up a dose: volume = (prescribed dose/stock strength) × stock volume. Convert to the same units first, then check that the volume fits the syringe and lands on one of its graduations.

Volume

V = 3200/5000 = 0.64 mL

On the syringe

On this 1 mL syringe every small line is 0.01 mL.

Answer

V = 0.64 mL
5.IV infusion rates

Answer: R = 10 gtt/min

Infusion rates: a pump is set in mL/h = volume/time in hours. A gravity drip is counted in drops per minute: gtt/min = volume (mL) × drop factor (gtt/mL)/time (min). The drop factor is printed on the tubing package: macrodrip sets deliver 10, 15 or 20 gtt/mL (blood sets often 10 gtt/mL in the US, 15 in the UK) and microdrip sets 60 gtt/mL. Always use the drop factor the question or package gives.

Millilitres per minute

30/60 = 0.5 mL/min

Drip rate

R = 0.5·20 = 10 gtt/min

Answer

R = 10 gtt/min
6.IV infusion rates

Answer: D = 12.5 mg/h

Infusion rates: a pump is set in mL/h = volume/time in hours. A gravity drip is counted in drops per minute: gtt/min = volume (mL) × drop factor (gtt/mL)/time (min). The drop factor is printed on the tubing package: macrodrip sets deliver 10, 15 or 20 gtt/mL (blood sets often 10 gtt/mL in the US, 15 in the UK) and microdrip sets 60 gtt/mL. Always use the drop factor the question or package gives.

Concentration

250/100 = 2.5 mg/mL

Dose rate

D = 2.5·5 = 12.5 mg/h

Answer

D = 12.5 mg/h

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