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

At a booking visit, a woman says she drinks heavily most weekends. Which nursing response is most appropriate?

  1. ATell her the damage is done, so stopping will not help
  2. BAdvise her to change to beer, which has less alcohol
  3. CReassure her that weekend drinking is safe if she avoids weekdays
  4. DExplain the risks and refer her for support to stop
3.Dosage calculationsMedium
47 kgBSA = 1.26 m²375 mg/m²D = ? mg

A patient weighing 47 kg has a body surface area of 1.26 m². The prescription is 375 mg/m². Find the dose D in mg.

47 kgBSA = 1.26 m²375 mg/m²
D = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 1150 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?

1150 units5000 units/mL
V = mL
5.IV infusion ratesMedium
250 mL60 gtt/mL5 h? gtt/min

Infuse 250 mL over 5 hours with a giving set of 60 gtt/mL. Find the drip rate R in drops per minute.

250 mL5 h60 gtt/mL
R = gtt/min
6.IV infusion ratesHard
1000 mg250 mL20 gtt/mL240 mg/h? gtt/min

1000 mg of a drug is diluted in 250 mL and given by gravity through a set of 20 gtt/mL. The order is 240 mg per hour. Find the drip rate R in drops per minute.

1000 mg/250 mL240 mg/h20 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · 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

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

Answer: D · Explain the risks and refer her for support to stop

Why this is the answer

Alcohol can harm the fetus throughout pregnancy, and stopping at any point reduces the risk. The nurse gives clear, non-judgemental information and refers her to support services.

Answer

D · Explain the risks and refer her for support to stop
3.Dosage calculations

Answer: D = 472.5 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 = 375·1.26 = 472.5 mg

Answer

D = 472.5 mg
4.Dosage calculations

Answer: V = 0.23 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 = 1150/5000 = 0.23 mL

On the syringe

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

Answer

V = 0.23 mL
5.IV infusion rates

Answer: R = 50 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

5·60 = 300 min

Drip rate

R = 250·60/300 = 50 gtt/min

Answer

R = 50 gtt/min
6.IV infusion rates

Answer: R = 20 gtt/min

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

1000/250 = 4 mg/mL

Volume per hour

240/4 = 60 mL/h

Drip rate

R = 60·20/60 = 20 gtt/min

Answer

R = 20 gtt/min

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