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

Why is a baby of a mother with poorly controlled diabetes often large?

  1. AFetal hyperinsulinaemia acts as a growth hormone
  2. BThe baby inherits a gene for large size
  3. CDiabetes always prolongs the pregnancy
  4. DThe mother's insulin crosses the placenta
2.Maternity & obstetric nursingHard

At 18 weeks, a woman's maternal serum alpha-fetoprotein is well above the normal range for her dates. Which condition does this result most suggest?

  1. AAn open neural tube defect
  2. BPre-eclampsia
  3. CDown syndrome (trisomy 21)
  4. DGestational diabetes
3.Dosage calculationsMedium
22 kg5 mg/kg/day4× per dayD = ? mg

A patient weighs 22 kg. The prescribed dose is 5 mg/kg per day, given in 4 equal doses. How many milligrams D are given per dose?

22 kg5 mg/kg/day4× per day
D = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 2850 units of a drug that comes as 5000 units/mL. Draw up the dose in the 1 mL syringe: what volume V do you give?

2850 units5000 units/mL
V = mL
5.IV infusion ratesMedium
V = ?20 gtt/mL25 gtt/min6 h

A drip runs at 25 gtt/min through a set of 20 gtt/mL. How many millilitres V does the patient receive in 6 hours?

25 gtt/min20 gtt/mL6 h
V = mL
6.IV infusion ratesHard
1000 mg500 mL20 gtt/mL150 mg/h? gtt/min

1000 mg of a drug is diluted in 500 mL and given by gravity through a set of 20 gtt/mL. The order is 150 mg per hour. Find the drip rate R in drops per minute.

1000 mg/500 mL150 mg/h20 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · Fetal hyperinsulinaemia acts as a growth hormone

Why this is the answer

Maternal glucose crosses the placenta, so the fetal pancreas makes extra insulin, which promotes growth and fat storage. After birth this extra insulin continues and can cause neonatal hypoglycaemia.

Answer

A · Fetal hyperinsulinaemia acts as a growth hormone
2.Maternity & obstetric nursing

Answer: A · An open neural tube defect

Why this is the answer

High AFP is linked to open neural tube defects and abdominal wall defects, but also to wrong dates or twins. Low AFP is associated with trisomy 21. A detailed ultrasound is the next step.

Answer

A · An open neural tube defect
3.Dosage calculations

Answer: D = 27.5 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

5·22 = 110 mg

Per dose

D = 110/4 = 27.5 mg

Answer

D = 27.5 mg
4.Dosage calculations

Answer: V = 0.57 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.

Volume

V = 2850/5000 = 0.57 mL

On the syringe

On this 1 mL syringe every small line is 0.01 mL.

Answer

V = 0.57 mL
5.IV infusion rates

Answer: V = 450 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

25·60/20 = 75 mL/h

Volume

V = 75·6 = 450 mL

Answer

V = 450 mL
6.IV infusion rates

Answer: R = 25 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

1000/500 = 2 mg/mL

Volume per hour

150/2 = 75 mL/h

Drip rate

R = 75·20/60 = 25 gtt/min

Answer

R = 25 gtt/min

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