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

Why is a copper intrauterine device a good contraceptive option for many breastfeeding mothers?

  1. AIt must be replaced every month
  2. BIt increases milk production
  3. CIt protects against sexually transmitted infections
  4. DIt is hormone-free and very effective
2.Maternity & obstetric nursingHard

A woman at 11 weeks has heavy bleeding, cramping and an open cervical os, and she has passed some tissue. Which type of miscarriage is this?

  1. AComplete miscarriage
  2. BMissed miscarriage
  3. CThreatened miscarriage
  4. DIncomplete miscarriage
3.Dosage calculationsMedium
52 kgBSA = 1.41 m²375 mg/m²D = ? mg

A patient weighing 52 kg has a body surface area of 1.41 m². The prescription is 375 mg/m². Find the dose D in mg.

52 kgBSA = 1.41 m²375 mg/m²
D = mg
4.Dosage calculationsHard
10%stockwater = ? mL

You must prepare 500 mL of a 1% (w/v) solution from a 10% (w/v) stock solution. How much water W must be added to the stock?

C₁ = 10%C₂ = 1%V₂ = 500 mL
W = mL
5.IV infusion ratesMedium
V = ?20 gtt/mL50 gtt/min2 h

A drip runs at 50 gtt/min through a set of 20 gtt/mL. How many millilitres V does the patient receive in 2 hours?

50 gtt/min20 gtt/mL2 h
V = mL
6.IV infusion ratesHard
1 g500 mL? mL/h0.5 mg/min

A bag contains 1 g of a drug in 500 mL. The order is 0.5 mg per minute. At what rate R do you set the pump, in mL/h?

1 g/500 mL0.5 mg/min
R = mL/h

3Solutions

1.Maternity & obstetric nursing

Answer: D · It is hormone-free and very effective

Why this is the answer

The copper IUD contains no hormones, does not affect milk supply and is highly effective for many years. It does not protect against sexually transmitted infections.

Answer

D · It is hormone-free and very effective
2.Maternity & obstetric nursing

Answer: D · Incomplete miscarriage

Why this is the answer

An open os with some tissue passed and continued bleeding is an incomplete miscarriage. Retained tissue can cause haemorrhage and infection, so it is usually managed medically or surgically.

Answer

D · Incomplete miscarriage
3.Dosage calculations

Answer: D = 528.8 mg

Body-surface-area dosing: many cytotoxic and some paediatric doses are prescribed per square metre of body surface area: dose (mg) = dose per m² × BSA (m²). The Mosteller formula estimates BSA = √(height (cm) × weight (kg)/3600).

Dose

D = 375·1.41 = 528.8 mg

Answer

D = 528.8 mg
4.Dosage calculations

Answer: W = 450 mL

Solution strengths: a percentage strength is grams per 100 mL, so 1% = 1 g/100 mL = 10 mg/mL. A ratio strength 1:1000 means 1 g in 1000 mL = 1 mg/mL; 1:10 000 is 0.1 mg/mL. For a dilution the amount of drug stays the same: C₁·V₁ = C₂·V₂.

Volume of stock

V₁ = 1·500/10 = 50 mL

Water to add

W = 500 − 50 = 450 mL

Answer

W = 450 mL
5.IV infusion rates

Answer: V = 300 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

50·60/20 = 150 mL/h

Volume

V = 150·2 = 300 mL

Answer

V = 300 mL
6.IV infusion rates

Answer: R = 15 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

1000 mg/500 mL = 2 mg/mL

Dose per hour

0.5·60 = 30 mg/h

Pump rate

R = 30/2 = 15 mL/h

Answer

R = 15 mL/h

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