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

After rupture of the membranes, the amniotic fluid is green. What does this suggest?

  1. AThere is bleeding from the placenta
  2. BThe fluid is normal at term
  3. CThe fetus has passed meconium
  4. DThe mother has an infection with group B streptococcus
2.Maternity & obstetric nursingHard

A woman received an opioid IV 30 minutes ago. The tracing now shows minimal variability but no decelerations. What is the most likely cause?

  1. APlacental abruption
  2. BSevere fetal anaemia from Rh disease
  3. CProlapse of the umbilical cord
  4. DThe opioid's effect on the fetal brain
3.Dosage calculationsMedium
15 kg25 mg/kg/day3× per dayD = ? mg

A patient weighs 15 kg. The prescribed dose is 25 mg/kg per day, given in 3 equal doses. How many milligrams D are given per dose?

15 kg25 mg/kg/day3× per day
D = mg
4.Dosage calculationsHard
120 mg/5 mLV = ? mL

A child weighing 8 kg is prescribed 20 mg/kg per dose of an oral suspension that contains 120 mg in 5 mL. What volume V do you give? Round to one decimal place.

8 kg20 mg/kg120 mg/5 mL
V = mL
5.IV infusion ratesMedium
V = ?15 gtt/mL20 gtt/min3 h

A drip runs at 20 gtt/min through a set of 15 gtt/mL. How many millilitres V does the patient receive in 3 hours?

20 gtt/min15 gtt/mL3 h
V = mL
6.IV infusion ratesHard
4 g1000 mL? mL/h3 mg/min

A bag contains 4 g of a drug in 1000 mL. The order is 3 mg per minute. At what rate R do you set the pump, in mL/h?

4 g/1000 mL3 mg/min
R = mL/h

3Solutions

1.Maternity & obstetric nursing

Answer: C · The fetus has passed meconium

Why this is the answer

Green fluid means meconium was passed in the uterus. It is more common after term and can occur with fetal stress, so the fetal heart rate is watched closely and the team prepares for the birth.

Answer

C · The fetus has passed meconium
2.Maternity & obstetric nursing

Answer: D · The opioid's effect on the fetal brain

Why this is the answer

Opioids, magnesium sulfate and fetal sleep can temporarily reduce variability. Without decelerations, it is likely drug-related, but the tracing should be watched for return of variability.

Answer

D · The opioid's effect on the fetal brain
3.Dosage calculations

Answer: D = 125 mg

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.

Total per day

25·15 = 375 mg

Per dose

D = 375/3 = 125 mg

Answer

D = 125 mg
4.Dosage calculations

Answer: V = 6.7 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.

Dose from weight

20·8 = 160 mg

Volume

V = (160/120)·5 = 6.667 ≈ 6.7 mL

Answer

V = 6.7 mL
5.IV infusion rates

Answer: V = 240 mL

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.

Rate in mL/h

20·60/15 = 80 mL/h

Volume

V = 80·3 = 240 mL

Answer

V = 240 mL
6.IV infusion rates

Answer: R = 45 mL/h

Dose-based infusions: concentration = amount of drug in the bag/bag volume. Pump rate (mL/h) = dose per hour/concentration, and dose per hour = mL/h × concentration. Convert per-minute doses to per-hour (× 60) and keep the mass units the same (1 g = 1000 mg, 1 mg = 1000 mcg).

Concentration

4000 mg/1000 mL = 4 mg/mL

Dose per hour

3·60 = 180 mg/h

Pump rate

R = 180/4 = 45 mL/h

Answer

R = 45 mL/h

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