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

When should an Rh-negative woman with no anti-D antibodies routinely receive antenatal anti-D immunoglobulin?

  1. AOnly at the first antenatal visit
  2. BAfter she has formed anti-D antibodies
  3. CAt about 28 weeks of pregnancy
  4. DOnly if the baby is known to be Rh-negative
2.Maternity & obstetric nursingHard

A biophysical profile scores 4 out of 10 at 38 weeks. How should the nurse interpret this?

  1. AIt is normal and reassuring
  2. BIt is abnormal and needs prompt review
  3. CIt is equivocal and should be repeated next week
  4. DIt only means the woman needs to drink more water
3.Dosage calculationsMedium
024681010 mL

A child weighing 28 kg is prescribed 4 mg/kg of a drug. The stock solution contains 40 mg/mL. Draw up the dose: what volume V do you give?

28 kg4 mg/kg40 mg/mL
V = mL
4.Dosage calculationsHard
59 kg172 cmBSA = √(h·w/3600)60 mg/m²D = ? mg

A patient is 172 cm tall and weighs 59 kg. The prescription is 60 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

172 cm59 kg60 mg/m²
D = mg
5.IV infusion ratesMedium
500 mL15 gtt/mL10 h? gtt/min

Infuse 500 mL over 10 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

500 mL10 h15 gtt/mL
R = gtt/min
6.IV infusion ratesHard
450 mL20 gtt/mL40 gtt/mint = ? h

A drip runs at 40 gtt/min through a set of 20 gtt/mL. There are 450 mL left in the bag. How many hours t until it is empty? Round to one decimal place.

40 gtt/min20 gtt/mL450 mL
t = h

3Solutions

1.Maternity & obstetric nursing

Answer: C · At about 28 weeks of pregnancy

Why this is the answer

Routine antenatal anti-D around 28 weeks, in a single or split dose depending on the programme, protects against sensitisation from silent fetomaternal bleeds. It is given again after birth if the baby is Rh-positive.

Answer

C · At about 28 weeks of pregnancy
2.Maternity & obstetric nursing

Answer: B · It is abnormal and needs prompt review

Why this is the answer

A score of 8 to 10 is normal, 6 is equivocal, and 4 or less is abnormal and suggests fetal hypoxia. At term, a low score usually leads to prompt review and consideration of birth.

Answer

B · It is abnormal and needs prompt review
3.Dosage calculations

Answer: V = 2.8 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.

Dose from body weight

D = 4·28 = 112 mg

Volume

V = 112/40 = 2.8 mL

On the syringe

On this 10 mL syringe every small line is 0.2 mL.

Answer

V = 2.8 mL
4.Dosage calculations

Answer: D = 100.7 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).

Body surface area

BSA = √(172·59/3600) = √2.819 = 1.679 m²

Dose

D = 60·1.679 = 100.7 mg

Answer

D = 100.7 mg
5.IV infusion rates

Answer: R = 13 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.

Time in minutes

10·60 = 600 min

Drip rate

R = 500·15/600 = 12.5 ≈ 13 gtt/min

Answer

R = 13 gtt/min

At the bedside you round to the nearest whole drop: 13 gtt/min.

6.IV infusion rates

Answer: t = 3.8 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.

Rate in mL/h

40·60/20 = 120 mL/h

Time left

t = 450/120 = 3.75 ≈ 3.8 h

Answer

t = 3.8 h

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