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

After an amniotomy, why is the time of rupture of the membranes recorded?

  1. AIt is used to work out the baby's gestational age
  2. BInfection risk rises the longer the membranes are ruptured
  3. CIt is needed to calculate the woman's Bishop score
  4. DIt predicts exactly when the placenta will deliver
2.Maternity & obstetric nursingHard

A woman has hyperthyroidism in pregnancy. Which finding in the fetus should be monitored?

  1. AFetal polycythaemia only
  2. BA fetal heart rate below 100 bpm
  3. CFetal tachycardia and poor growth
  4. DFetal macrosomia
3.Dosage calculationsMedium
024681010 mL

A child weighing 8 kg is prescribed 7.5 mg/kg of a drug. The stock solution contains 10 mg/mL. Draw up the dose: what volume V do you give?

8 kg7.5 mg/kg10 mg/mL
V = mL
4.Dosage calculationsHard
25%stockwater = ? mL

You must prepare 500 mL of a 2% (w/v) solution from a 25% (w/v) stock solution. How much water W must be added to the stock?

C₁ = 25%C₂ = 2%V₂ = 500 mL
W = mL
5.IV infusion ratesMedium
710 mLleft? mL/h5 h left

1500 mL was ordered over 12 hours. After 7 hours you find that 710 mL is still in the bag, and the order must still finish on time. To what rate R in mL/h must the pump be reset?

1500 mL / 12 hafter 7 h: 710 mL
R = mL/h
6.IV infusion ratesHard
100 mg100 mL15 gtt/mL40 mg/h? gtt/min

100 mg of a drug is diluted in 100 mL and given by gravity through a set of 15 gtt/mL. The order is 40 mg per hour. Find the drip rate R in drops per minute.

100 mg/100 mL40 mg/h15 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: B · Infection risk rises the longer the membranes are ruptured

Why this is the answer

Once the membranes are ruptured, organisms can ascend into the uterus, and the risk of intra-amniotic infection rises with time. The nurse records the time with the colour, odour and amount of fluid (COAT) and monitors temperature and fetal heart rate.

Answer

B · Infection risk rises the longer the membranes are ruptured
2.Maternity & obstetric nursing

Answer: C · Fetal tachycardia and poor growth

Why this is the answer

In Graves' disease, maternal antibodies can cross the placenta and cause fetal hyperthyroidism, with tachycardia, goitre and growth restriction. Antithyroid drugs also cross the placenta, so the fetus is monitored.

Answer

C · Fetal tachycardia and poor growth
3.Dosage calculations

Answer: V = 6 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 = 7.5·8 = 60 mg

Volume

V = 60/10 = 6 mL

On the syringe

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

Answer

V = 6 mL
4.Dosage calculations

Answer: W = 460 mL

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.

Volume of stock

V₁ = 2·500/25 = 40 mL

Water to add

W = 500 − 40 = 460 mL

Answer

W = 460 mL
5.IV infusion rates

Answer: R = 142 mL/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.

Original rate

1500/12 = 125 mL/h

New rate

R = 710/5 = 142 mL/h

Answer

R = 142 mL/h

Many hospitals allow such an adjustment up to 25% without a new order; check local policy.

6.IV infusion rates

Answer: R = 10 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

100/100 = 1 mg/mL

Volume per hour

40/1 = 40 mL/h

Drip rate

R = 40·15/60 = 10 gtt/min

Answer

R = 10 gtt/min

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