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

Which reflex causes the newborn's toes to fan out when the sole is stroked from heel to toe?

  1. ABabinski reflex
  2. BStepping reflex
  3. CPlantar grasp reflex
  4. DMoro reflex
2.Maternity & obstetric nursingHard

A woman at 30 weeks is in a minor car accident. She feels fine and has no bleeding. What should the nurse advise?

  1. AStay at home because there is no bleeding
  2. BCome in for fetal monitoring even without symptoms
  3. CTake a warm bath and rest
  4. DCome in only if she bleeds within a week
3.Dosage calculationsMedium
2%100 mLm = ? mg

How many milligrams of drug m are in 100 mL of a 2% (w/v) solution?

2% w/v100 mL
m = mg
4.Dosage calculationsHard
47 kg130 cmBSA = √(h·w/3600)250 mg/m²D = ? mg

A patient is 130 cm tall and weighs 47 kg. The prescription is 250 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

130 cm47 kg250 mg/m²
D = mg
5.IV infusion ratesMedium
15 gtt/mL60 mL/h? gtt/min

An infusion is ordered at 60 mL/h, but no pump is available. It runs by gravity through a giving set of 15 gtt/mL. Find the drip rate R in drops per minute.

60 mL/h15 gtt/mL
R = gtt/min
6.IV infusion ratesHard
50 mg500 mL3 mL/h? mcg/min

An infusion of 50 mg in 500 mL runs at 3 mL/h. How many micrograms per minute D does the patient receive?

50 mg/500 mL3 mL/h
D = mcg/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · Babinski reflex

Why this is the answer

The Babinski reflex, fanning of the toes with dorsiflexion of the big toe, is normal in infants until about 1 year. Pressing the sole near the toes gives the plantar grasp instead.

Answer

A · Babinski reflex
2.Maternity & obstetric nursing

Answer: B · Come in for fetal monitoring even without symptoms

Why this is the answer

Even minor trauma can cause placental abruption, sometimes without bleeding. Pregnant women after trauma are usually monitored with CTG for several hours. Rh-negative women may need anti-D.

Answer

B · Come in for fetal monitoring even without symptoms
3.Dosage calculations

Answer: m = 2000 mg

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.

Concentration

2% = 2 g/100 mL = 20 mg/mL

Mass of drug

m = 20·100 = 2000 mg

Answer

m = 2000 mg
4.Dosage calculations

Answer: D = 325.7 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 = √(130·47/3600) = √1.697 = 1.303 m²

Dose

D = 250·1.303 = 325.7 mg

Answer

D = 325.7 mg
5.IV infusion rates

Answer: R = 15 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.

Millilitres per minute

60/60 = 1 mL/min

Drip rate

R = 1·15 = 15 gtt/min

Answer

R = 15 gtt/min
6.IV infusion rates

Answer: D = 5 mcg/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

50000 mcg/500 mL = 100 mcg/mL

Dose per hour

3·100 = 300 mcg/h

Dose per minute

D = 300/60 = 5 mcg/min

Answer

D = 5 mcg/min

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