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 baby is at greatest risk of early-onset group B streptococcal infection?

  1. AA baby of a GBS-positive mother with no antibiotics
  2. BA baby born at 40 weeks to a mother with no risk factors
  3. CA baby born by planned caesarean with intact membranes
  4. DA baby whose mother was GBS-negative at 36 weeks
2.Maternity & obstetric nursingHard

Six hours after birth, a woman has not passed urine. The fundus is boggy and displaced to the right, and bleeding has increased. Why is this a priority?

  1. AIt shows that the epidural is still working well
  2. BUrine retention only matters after a caesarean birth, not after a vaginal one
  3. CA full bladder is a sign of normal recovery
  4. DA full bladder prevents the uterus from contracting and increases bleeding
3.Dosage calculationsMedium
024681010 mL

A child weighing 36 kg is prescribed 3 mg/kg of a drug. The stock solution contains 20 mg/mL. Draw up the dose: what volume V do you give?

36 kg3 mg/kg20 mg/mL
V = mL
4.Dosage calculationsHard
32 kg125 cmBSA = √(h·w/3600)25 mg/m²D = ? mg

A patient is 125 cm tall and weighs 32 kg. The prescription is 25 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

125 cm32 kg25 mg/m²
D = mg
5.IV infusion ratesMedium
60 gtt/mL25 mL/h? gtt/min

An infusion is ordered at 25 mL/h, but no pump is available. It runs by gravity through a giving set of 60 gtt/mL. Find the drip rate R in drops per minute.

25 mL/h60 gtt/mL
R = gtt/min
6.IV infusion ratesHard
100 mg100 mL30 mL/h? mg/h

A bag contains 100 mg of a drug in 100 mL and runs at 30 mL/h. How many milligrams per hour D does the patient receive?

100 mg/100 mL30 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: A · A baby of a GBS-positive mother with no antibiotics

Why this is the answer

GBS colonisation, no intrapartum antibiotics, prolonged rupture of membranes, maternal fever and prematurity increase the risk. Intrapartum IV antibiotics greatly lower early-onset GBS disease.

Answer

A · A baby of a GBS-positive mother with no antibiotics
2.Maternity & obstetric nursing

Answer: D · A full bladder prevents the uterus from contracting and increases bleeding

Why this is the answer

A distended bladder pushes the uterus up and aside, causing atony and more bleeding. Help her to void, or catheterise per order, then reassess the fundus and the bleeding.

Answer

D · A full bladder prevents the uterus from contracting and increases bleeding
3.Dosage calculations

Answer: V = 5.4 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 = 3·36 = 108 mg

Volume

V = 108/20 = 5.4 mL

On the syringe

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

Answer

V = 5.4 mL
4.Dosage calculations

Answer: D = 26.35 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 = √(125·32/3600) = √1.111 = 1.054 m²

Dose

D = 25·1.054 = 26.35 mg

Answer

D = 26.35 mg
5.IV infusion rates

Answer: R = 25 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

25/60 = 0.4167 mL/min

Drip rate

R = 0.4167·60 = 25 gtt/min

Answer

R = 25 gtt/min

With a microdrip set (60 gtt/mL), gtt/min equals mL/h.

6.IV infusion rates

Answer: D = 30 mg/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.

Concentration

100/100 = 1 mg/mL

Dose rate

D = 1·30 = 30 mg/h

Answer

D = 30 mg/h

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