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

Methylergonovine (methylergometrine) for postpartum bleeding should not be given to a woman with:

  1. AHigh blood pressure
  2. BType 1 diabetes
  3. CAsthma
  4. DAnaemia
2.Maternity & obstetric nursingHard

A woman at 9 weeks has hCG levels that are much higher than expected, a uterus large for dates, severe vomiting and dark brown spotting. Which condition should be suspected?

  1. AA threatened miscarriage
  2. BA missed miscarriage
  3. CAn ectopic pregnancy
  4. DA hydatidiform (molar) pregnancy
3.Dosage calculationsMedium
024681010 mL

A child weighing 18 kg is prescribed 2 mg/kg of a drug. The stock solution contains 20 mg/mL. Draw up the dose: what volume V do you give?

18 kg2 mg/kg20 mg/mL
V = mL
4.Dosage calculationsHard
50%stockV₁ = ? mL

You must prepare 250 mL of a 0.5% (w/v) solution from a 50% (w/v) stock solution. What volume of stock V₁ do you need?

C₁ = 50%C₂ = 0.5%V₂ = 250 mL
V₁ = mL
5.IV infusion ratesMedium
570 mLleft? mL/h5 h left

1000 mL was ordered over 10 hours. After 5 hours you find that 570 mL is still in the bag, and the order must still finish on time. To what rate R in mL/h must the pump be reset?

1000 mL / 10 hafter 5 h: 570 mL
R = mL/h
6.IV infusion ratesHard
380 mLleft? mL/h4 h left

500 mL was ordered over 6 hours. After 2 hours you find that 380 mL is still in the bag, and the order must still finish on time. By what percentage Δ must the original pump rate be increased?

500 mL / 6 hafter 2 h: 380 mL
Δ = %

3Solutions

1.Maternity & obstetric nursing

Answer: A · High blood pressure

Why this is the answer

Ergot alkaloids cause vasoconstriction and can raise blood pressure dangerously, so they are avoided in hypertension and pre-eclampsia. Carboprost is the drug to avoid in asthma.

Answer

A · High blood pressure
2.Maternity & obstetric nursing

Answer: D · A hydatidiform (molar) pregnancy

Why this is the answer

A molar pregnancy causes very high hCG, a uterus larger than dates, hyperemesis and bleeding. Ectopic and failing pregnancies usually have lower than expected hCG.

Answer

D · A hydatidiform (molar) pregnancy
3.Dosage calculations

Answer: V = 1.8 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 = 2·18 = 36 mg

Volume

V = 36/20 = 1.8 mL

On the syringe

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

Answer

V = 1.8 mL
4.Dosage calculations

Answer: V₁ = 2.5 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 = 0.5·250/50 = 2.5 mL

Answer

V₁ = 2.5 mL
5.IV infusion rates

Answer: R = 114 mL/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.

Original rate

1000/10 = 100 mL/h

New rate

R = 570/5 = 114 mL/h

Answer

R = 114 mL/h

Many hospitals allow such an adjustment up to 25% without a new order; check local policy.

6.IV infusion rates

Answer: Δ = 14 %

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.

Original rate

500/6 = 83.33 mL/h

New rate

R = 380/4 = 95 mL/h

Percentage change

Δ = (95 − 83.33)/83.33·100% = 14%

Answer

Δ = 14%

Many hospitals allow such an adjustment up to 25% without a new order; check local policy.

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