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 with pre-eclampsia is on magnesium sulfate. Which task can be delegated to a healthcare assistant (unlicensed assistive personnel)?

  1. AMeasuring and recording urine output
  2. BEvaluating her for signs of toxicity
  3. CAssessing her deep tendon reflexes
  4. DAdjusting the magnesium infusion rate
2.Maternity & obstetric nursingHard

Which newborn finding should prompt checks for kidney and other anomalies?

  1. AMild moulding of the head
  2. BA single umbilical artery
  3. CMilia on the nose
  4. DAcrocyanosis in the first hours
3.Dosage calculationsMedium
10%w/vV = ? mL

A dose of 300 mg is needed from a 10% (w/v) solution. What volume V contains this dose?

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

A child weighing 10 kg is prescribed 5 mg/kg per dose of an oral suspension that contains 40 mg in 1 mL. What volume V do you give? Round to one decimal place.

10 kg5 mg/kg40 mg/1 mL
V = mL
5.IV infusion ratesMedium
740 mLleft? mL/h5 h left

1500 mL was ordered over 12 hours. After 7 hours you find that 740 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: 740 mL
R = mL/h
6.IV infusion ratesHard
100 mg100 mL15 gtt/mL100 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 100 mg per hour. Find the drip rate R in drops per minute.

100 mg/100 mL100 mg/h15 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · Measuring and recording urine output

Why this is the answer

Measuring and recording output can be delegated. The nurse assesses reflexes and breathing, interprets findings and manages the infusion.

Answer

A · Measuring and recording urine output
2.Maternity & obstetric nursing

Answer: B · A single umbilical artery

Why this is the answer

A two-vessel cord can be associated with renal, cardiac and other anomalies. Milia, moulding and acrocyanosis are normal findings.

Answer

B · A single umbilical artery
3.Dosage calculations

Answer: V = 3 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 = 300/100 = 3 mL

Answer

V = 3 mL
4.Dosage calculations

Answer: V = 1.3 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.

Dose from weight

5·10 = 50 mg

Volume

V = (50/40)·1 = 1.25 ≈ 1.3 mL

Answer

V = 1.3 mL
5.IV infusion rates

Answer: R = 148 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 = 740/5 = 148 mL/h

Answer

R = 148 mL/h

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

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

100/100 = 1 mg/mL

Volume per hour

100/1 = 100 mL/h

Drip rate

R = 100·15/60 = 25 gtt/min

Answer

R = 25 gtt/min

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