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 preterm baby on feeds develops a swollen abdomen, bloody stools and feeding intolerance. Which condition is suspected?

  1. AInfantile pyloric stenosis
  2. BCow's milk protein allergy
  3. CHirschsprung disease
  4. DNecrotising enterocolitis
2.Maternity & obstetric nursingHard

Ten days after birth, a woman phones to say her bleeding has suddenly become heavy and bright red with clots, with lower abdominal pain and a temperature of 38.2 °C (100.8 °F). Which response is most appropriate?

  1. AAsk her to come in now; retained tissue or infection is possible
  2. BAdvise her to use tampons so the blood loss is easier to measure
  3. CTell her it is probably her first period and needs no action
  4. DReassure her that lochia rubra often returns and review at 6 weeks
3.Dosage calculationsMedium
20%100 mLm = ? mg

How many milligrams of drug m are in 100 mL of a 20% (w/v) solution?

20% w/v100 mL
m = mg
4.Dosage calculationsHard
200 mg/5 mLV = ? mL

A child weighing 8 kg is prescribed 12.5 mg/kg per dose of an oral suspension that contains 200 mg in 5 mL. What volume V do you give?

8 kg12.5 mg/kg200 mg/5 mL
V = mL
5.IV infusion ratesMedium
500 mL10 gtt/mL3 h? gtt/min

Infuse 500 mL over 3 hours with a giving set of 10 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

500 mL3 h10 gtt/mL
R = gtt/min
6.IV infusion ratesHard
4 g500 mL? mL/h4 mg/min

A bag contains 4 g of a drug in 500 mL. The order is 4 mg per minute. At what rate R do you set the pump, in mL/h?

4 g/500 mL4 mg/min
R = mL/h

3Solutions

1.Maternity & obstetric nursing

Answer: D · Necrotising enterocolitis

Why this is the answer

Necrotising enterocolitis mainly affects preterm babies. Signs include abdominal distension, bilious aspirates, bloody stools and instability. Feeds are stopped and the baby is urgently reviewed. Breast milk lowers the risk.

Answer

D · Necrotising enterocolitis
2.Maternity & obstetric nursing

Answer: A · Ask her to come in now; retained tissue or infection is possible

Why this is the answer

Heavy bleeding between 24 hours and 12 weeks after birth is a secondary postpartum haemorrhage. With pain and fever it suggests retained placental tissue or endometritis, which needs same-day assessment and possibly ultrasound, antibiotics or evacuation. Tampons are avoided in the postnatal period.

Answer

A · Ask her to come in now; retained tissue or infection is possible
3.Dosage calculations

Answer: m = 20000 mg

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

20% = 20 g/100 mL = 200 mg/mL

Mass of drug

m = 200·100 = 20000 mg

Answer

m = 20000 mg
4.Dosage calculations

Answer: V = 2.5 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

12.5·8 = 100 mg

Volume

V = (100/200)·5 = 2.5 mL

Answer

V = 2.5 mL
5.IV infusion rates

Answer: R = 28 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

3·60 = 180 min

Drip rate

R = 500·10/180 = 27.78 ≈ 28 gtt/min

Answer

R = 28 gtt/min

At the bedside you round to the nearest whole drop: 28 gtt/min.

6.IV infusion rates

Answer: R = 30 mL/h

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

4000 mg/500 mL = 8 mg/mL

Dose per hour

4·60 = 240 mg/h

Pump rate

R = 240/8 = 30 mL/h

Answer

R = 30 mL/h

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