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 baseline variability is considered moderate (normal)?

  1. AAn amplitude of 6 to 25 bpm
  2. BAn amplitude of 3 to 5 bpm
  3. CAn amplitude of more than 25 bpm
  4. DAn amplitude of 0 to 2 bpm
2.Maternity & obstetric nursingHard

Just after her membranes rupture in labour, a woman suddenly becomes very breathless, cyanosed and hypotensive. Which condition should be suspected?

  1. AAmniotic fluid embolism
  2. BA panic attack
  3. CNormal response to a strong contraction
  4. DSupine hypotension
3.Dosage calculationsMedium
10%w/vV = ? mL

A dose of 250 mg is needed from a 10% (w/v) solution. What volume V contains this dose?

250 mg10% w/v
V = mL
4.Dosage calculationsHard
40 mg/1 mLV = ? mL

A patient weighs 81.4 lb. The prescription is 0.5 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 two decimal places.

81.4 lb0.5 mg/kg40 mg/1 mL1 kg = 2.2 lb
V = mL
5.IV infusion ratesMedium
500 mL15 gtt/mL5 h? gtt/min

Infuse 500 mL over 5 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute.

500 mL5 h15 gtt/mL
R = gtt/min
6.IV infusion ratesHard
500 mg500 mL20 gtt/mL30 mg/h? gtt/min

500 mg of a drug is diluted in 500 mL and given by gravity through a set of 20 gtt/mL. The order is 30 mg per hour. Find the drip rate R in drops per minute.

500 mg/500 mL30 mg/h20 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · An amplitude of 6 to 25 bpm

Why this is the answer

Moderate variability (6–25 bpm) shows an oxygenated fetus with a functioning autonomic nervous system. Minimal (5 bpm or less) or absent variability can mean hypoxia, sleep or medication effects; more than 25 bpm is marked variability.

Answer

A · An amplitude of 6 to 25 bpm
2.Maternity & obstetric nursing

Answer: A · Amniotic fluid embolism

Why this is the answer

Amniotic fluid embolism causes sudden breathlessness, hypoxia, hypotension and often bleeding from coagulopathy. It is an emergency: call the emergency team and start resuscitation as needed.

Answer

A · Amniotic fluid embolism
3.Dosage calculations

Answer: V = 2.5 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.

Concentration

10% = 100 mg/mL

Volume

V = 250/100 = 2.5 mL

Answer

V = 2.5 mL
4.Dosage calculations

Answer: V = 0.46 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

81.4/2.2 = 37 kg

Dose

0.5·37 = 18.5 mg

Volume

V = (18.5/40)·1 = 0.4625 ≈ 0.46 mL

Answer

V = 0.46 mL
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.

Time in minutes

5·60 = 300 min

Drip rate

R = 500·15/300 = 25 gtt/min

Answer

R = 25 gtt/min
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

500/500 = 1 mg/mL

Volume per hour

30/1 = 30 mL/h

Drip rate

R = 30·20/60 = 10 gtt/min

Answer

R = 10 gtt/min

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