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. CMoro reflex
  4. DPlantar grasp reflex
2.Maternity & obstetric nursingHard

Just after the membranes rupture, there is painless vaginal bleeding and the fetal heart rate drops sharply. The mother's vital signs are normal. Which condition is most likely?

  1. ABloody show
  2. BPlacental abruption
  3. CUterine rupture
  4. DRuptured vasa praevia
3.Dosage calculationsMedium
70 kg7.5 mg/kg/day4× per dayD = ? mg

A patient weighs 70 kg. The prescribed dose is 7.5 mg/kg per day, given in 4 equal doses. How many milligrams D are given per dose?

70 kg7.5 mg/kg/day4× per day
D = mg
4.Dosage calculationsHard
29 kg101 cmBSA = √(h·w/3600)50 mg/m²D = ? mg

A patient is 101 cm tall and weighs 29 kg. The prescription is 50 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

101 cm29 kg50 mg/m²
D = mg
5.IV infusion ratesMedium
250 mL15 gtt/mL5 h? gtt/min

Infuse 250 mL over 5 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

250 mL5 h15 gtt/mL
R = gtt/min
6.IV infusion ratesHard
200 mL60 gtt/mL25 gtt/mint = ? h

A drip runs at 25 gtt/min through a set of 60 gtt/mL. There are 200 mL left in the bag. How many hours t until it is empty?

25 gtt/min60 gtt/mL200 mL
t = h

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: D · Ruptured vasa praevia

Why this is the answer

Rupture of the membranes can tear unprotected fetal vessels in vasa praevia. Fetal blood loss causes rapid bradycardia while the mother stays stable. An emergency caesarean is needed.

Answer

D · Ruptured vasa praevia
3.Dosage calculations

Answer: D = 131.3 mg

Dose calculation: the amount to give equals what is prescribed divided by what you have, times the quantity it comes in: amount = (desired dose/stock strength) × stock volume. Always keep the units the same (convert g to mg, mg to mcg first) and check that the answer is sensible.

Total per day

7.5·70 = 525 mg

Per dose

D = 525/4 = 131.3 mg

Answer

D = 131.3 mg
4.Dosage calculations

Answer: D = 45.1 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 = √(101·29/3600) = √0.8136 = 0.902 m²

Dose

D = 50·0.902 = 45.1 mg

Answer

D = 45.1 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

5·60 = 300 min

Drip rate

R = 250·15/300 = 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 = 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

25·60/60 = 25 mL/h

Time left

t = 200/25 = 8 h

Answer

t = 8 h

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