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

A woman at 32 weeks with known placenta praevia is admitted with bleeding. Which procedure must be avoided?

  1. AMeasuring blood pressure
  2. BStarting an IV line
  3. CContinuous fetal heart monitoring
  4. DA digital vaginal examination
2.Maternity & obstetric nursingHard

Shortly after an epidural is started, a labouring woman's blood pressure falls to 86/50 mmHg and the fetal heart rate drops. What should the nurse do first?

  1. ARaise the head of the bed to a high sitting position to improve her breathing
  2. BTurn her onto her side to move the uterus off the large vessels
  3. CIncrease the epidural infusion rate
  4. DAsk her to walk around the room
3.Dosage calculationsMedium
90 kg7.5 mg/kgD = ? mg

A patient weighs 90 kg and is prescribed 7.5 mg/kg as a single dose. Find the dose D in mg.

90 kg7.5 mg/kg
D = mg
4.Dosage calculationsHard
18 kg109 cmBSA = √(h·w/3600)250 mg/m²D = ? mg

A patient is 109 cm tall and weighs 18 kg. The prescription is 250 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

109 cm18 kg250 mg/m²
D = mg
5.IV infusion ratesMedium
500 mL20 gtt/mL8 h? gtt/min

Infuse 500 mL over 8 hours with a giving set of 20 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

500 mL8 h20 gtt/mL
R = gtt/min
6.IV infusion ratesHard
200 mg100 mL60 gtt/mL80 mg/h? gtt/min

200 mg of a drug is diluted in 100 mL and given by gravity through a set of 60 gtt/mL. The order is 80 mg per hour. Find the drip rate R in drops per minute.

200 mg/100 mL80 mg/h60 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: D · A digital vaginal examination

Why this is the answer

A digital vaginal examination can disrupt a low-lying placenta and cause severe haemorrhage. Monitoring, IV access, blood tests and an ultrasound are appropriate.

Answer

D · A digital vaginal examination
2.Maternity & obstetric nursing

Answer: B · Turn her onto her side to move the uterus off the large vessels

Why this is the answer

A lateral position relieves aortocaval compression and improves venous return and placental flow. Then increase IV fluids as ordered, notify the anaesthetist or provider and give a vasopressor if prescribed.

Answer

B · Turn her onto her side to move the uterus off the large vessels
3.Dosage calculations

Answer: D = 675 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.

Dose

7.5·90 = 675 mg

Answer

D = 675 mg
4.Dosage calculations

Answer: D = 184.6 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 = √(109·18/3600) = √0.545 = 0.7382 m²

Dose

D = 250·0.7382 = 184.6 mg

Answer

D = 184.6 mg
5.IV infusion rates

Answer: R = 21 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

8·60 = 480 min

Drip rate

R = 500·20/480 = 20.83 ≈ 21 gtt/min

Answer

R = 21 gtt/min

At the bedside you round to the nearest whole drop: 21 gtt/min.

6.IV infusion rates

Answer: R = 40 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

200/100 = 2 mg/mL

Volume per hour

80/2 = 40 mL/h

Drip rate

R = 40·60/60 = 40 gtt/min

Answer

R = 40 gtt/min

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