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 18 weeks asks about safe exercise. Which advice is correct?

  1. AExercise should be stopped completely during pregnancy
  2. BContact sports and scuba diving are safe if she did them before
  3. CModerate exercise like walking or swimming is encouraged
  4. DExercise lying flat on her back is best after 20 weeks
2.Maternity & obstetric nursingHard

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

  1. AFetal polycythaemia only
  2. BFetal macrosomia
  3. CA fetal heart rate below 100 bpm
  4. DFetal tachycardia and poor growth
3.Dosage calculationsMedium
12 kg10 mg/kg/day4× per dayD = ? mg

A patient weighs 12 kg. The prescribed dose is 10 mg/kg per day, given in 4 equal doses. How many milligrams D are given per dose?

12 kg10 mg/kg/day4× per day
D = mg
4.Dosage calculationsHard
25%stockV₁ = ? mL

You must prepare 500 mL of a 1% (w/v) solution from a 25% (w/v) stock solution. What volume of stock V₁ do you need?

C₁ = 25%C₂ = 1%V₂ = 500 mL
V₁ = mL
5.IV infusion ratesMedium
380 mLleft? mL/h2 h left

1000 mL was ordered over 6 hours. After 4 hours you find that 380 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?

1000 mL / 6 hafter 4 h: 380 mL
R = mL/h
6.IV infusion ratesHard
50 mg500 mL12 mL/h? mcg/min

An infusion of 50 mg in 500 mL runs at 12 mL/h. How many micrograms per minute D does the patient receive?

50 mg/500 mL12 mL/h
D = mcg/min

3Solutions

1.Maternity & obstetric nursing

Answer: C · Moderate exercise like walking or swimming is encouraged

Why this is the answer

Moderate exercise is safe and beneficial for most pregnant women. Contact sports, activities with a high fall risk and scuba diving are avoided, as is lying flat on the back for long periods later in pregnancy.

Answer

C · Moderate exercise like walking or swimming is encouraged
2.Maternity & obstetric nursing

Answer: D · 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

D · Fetal tachycardia and poor growth
3.Dosage calculations

Answer: D = 30 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

10·12 = 120 mg

Per dose

D = 120/4 = 30 mg

Answer

D = 30 mg
4.Dosage calculations

Answer: V₁ = 20 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 = 1·500/25 = 20 mL

Answer

V₁ = 20 mL
5.IV infusion rates

Answer: R = 190 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

1000/6 = 166.7 mL/h

New rate

R = 380/2 = 190 mL/h

Answer

R = 190 mL/h

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

6.IV infusion rates

Answer: D = 20 mcg/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

50000 mcg/500 mL = 100 mcg/mL

Dose per hour

12·100 = 1200 mcg/h

Dose per minute

D = 1200/60 = 20 mcg/min

Answer

D = 20 mcg/min

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