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

Where universal screening for group B streptococcus is used, when is the vaginal–rectal swab usually taken?

  1. AAfter the membranes rupture in labour
  2. BAt the first antenatal visit
  3. CAt about 20 weeks
  4. DAt about 36 to 37 weeks
2.Maternity & obstetric nursingHard

Which finding in a newborn at 6 hours requires the most urgent action?

  1. AMild moulding of the head
  2. BCentral cyanosis, fast breathing and grunting
  3. CAcrocyanosis of the hands and feet
  4. DSmall white milia on the nose and chin
3.Dosage calculationsMedium
024681010 mL

A child weighing 13 kg is prescribed 4 mg/kg of a drug. The stock solution contains 10 mg/mL. Draw up the dose: what volume V do you give?

13 kg4 mg/kg10 mg/mL
V = mL
4.Dosage calculationsHard
40 mg/1 mLV = ? mL

A patient weighs 129.8 lb. The prescription is 15 mg/kg as a single dose, and the stock contains 40 mg in 1 mL. Using 1 kg = 2.2 lb, what volume V do you give? Round to one decimal place.

129.8 lb15 mg/kg40 mg/1 mL1 kg = 2.2 lb
V = mL
5.IV infusion ratesMedium
V = ?15 gtt/mL20 gtt/min4 h

A drip runs at 20 gtt/min through a set of 15 gtt/mL. How many millilitres V does the patient receive in 4 hours?

20 gtt/min15 gtt/mL4 h
V = mL
6.IV infusion ratesHard
4 g500 mL? mL/h2 mg/min

A bag contains 4 g of a drug in 500 mL. The order is 2 mg per minute. At what rate R do you set the pump, in mL/h?

4 g/500 mL2 mg/min
R = mL/h

3Solutions

1.Maternity & obstetric nursing

Answer: D · At about 36 to 37 weeks

Why this is the answer

Colonisation can come and go, so the swab is taken late in pregnancy, close to birth. A positive result leads to intrapartum antibiotics to protect the newborn. Some countries use a risk-based approach instead.

Answer

D · At about 36 to 37 weeks
2.Maternity & obstetric nursing

Answer: B · Central cyanosis, fast breathing and grunting

Why this is the answer

Central cyanosis, tachypnoea and grunting indicate respiratory distress and need immediate assessment, oxygen and evaluation for causes such as infection, heart disease or lung problems.

Answer

B · Central cyanosis, fast breathing and grunting
3.Dosage calculations

Answer: V = 5.2 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 = 4·13 = 52 mg

Volume

V = 52/10 = 5.2 mL

On the syringe

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

Answer

V = 5.2 mL
4.Dosage calculations

Answer: V = 22.1 mL

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.

Weight in kg

129.8/2.2 = 59 kg

Dose

15·59 = 885 mg

Volume

V = (885/40)·1 = 22.13 ≈ 22.1 mL

Answer

V = 22.1 mL
5.IV infusion rates

Answer: V = 320 mL

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

20·60/15 = 80 mL/h

Volume

V = 80·4 = 320 mL

Answer

V = 320 mL
6.IV infusion rates

Answer: R = 15 mL/h

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

4000 mg/500 mL = 8 mg/mL

Dose per hour

2·60 = 120 mg/h

Pump rate

R = 120/8 = 15 mL/h

Answer

R = 15 mL/h

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