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 pregnant woman taking iron says her stools have turned black. What is the best response?

  1. AAdvise her to go to the emergency department now
  2. BTell her to double the dose of the tablets
  3. CExplain that this is an expected effect of iron
  4. DTell her to stop the iron immediately
2.Maternity & obstetric nursingHard

A labouring woman has a temperature of 38.5 °C (101.3 °F), and the fetal baseline has risen from 140 to 170 bpm over the last hour. What is the most likely explanation?

  1. AFetal tachycardia due to a maternal opioid
  2. BReassuring fetal response to contractions
  3. CFetal tachycardia due to maternal fever or infection
  4. DFetal head compression
3.Dosage calculationsMedium
42 kgBSA = 1.24 m²250 mg/m²D = ? mg

A patient weighing 42 kg has a body surface area of 1.24 m². The prescription is 250 mg/m². Find the dose D in mg.

42 kgBSA = 1.24 m²250 mg/m²
D = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 2100 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?

2100 units5000 units/mL
V = mL
5.IV infusion ratesMedium
500 mL15 gtt/mL12 h? gtt/min

Infuse 500 mL over 12 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

500 mL12 h15 gtt/mL
R = gtt/min
6.IV infusion ratesHard
1000 mg250 mL20 gtt/mL240 mg/h? gtt/min

1000 mg of a drug is diluted in 250 mL and given by gravity through a set of 20 gtt/mL. The order is 240 mg per hour. Find the drip rate R in drops per minute.

1000 mg/250 mL240 mg/h20 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: C · Explain that this is an expected effect of iron

Why this is the answer

Iron supplements commonly make stools dark green or black. This is harmless, unlike tarry stools with signs of bleeding such as dizziness.

Answer

C · Explain that this is an expected effect of iron
2.Maternity & obstetric nursing

Answer: C · Fetal tachycardia due to maternal fever or infection

Why this is the answer

Maternal fever, often from intra-amniotic infection, is a common cause of fetal tachycardia. The provider is informed, and treatment of fever and infection is expected. Opioids reduce variability rather than raise the rate.

Answer

C · Fetal tachycardia due to maternal fever or infection
3.Dosage calculations

Answer: D = 310 mg

Body-surface-area dosing: many cytotoxic and some paediatric doses are prescribed per square metre of body surface area: dose (mg) = dose per m² × BSA (m²). The Mosteller formula estimates BSA = √(height (cm) × weight (kg)/3600).

Dose

D = 250·1.24 = 310 mg

Answer

D = 310 mg
4.Dosage calculations

Answer: V = 0.42 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 = 2100/5000 = 0.42 mL

On the syringe

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

Answer

V = 0.42 mL
5.IV infusion rates

Answer: R = 10 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

12·60 = 720 min

Drip rate

R = 500·15/720 = 10.42 ≈ 10 gtt/min

Answer

R = 10 gtt/min

At the bedside you round to the nearest whole drop: 10 gtt/min.

6.IV infusion rates

Answer: R = 20 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

1000/250 = 4 mg/mL

Volume per hour

240/4 = 60 mL/h

Drip rate

R = 60·20/60 = 20 gtt/min

Answer

R = 20 gtt/min

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