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 2 hours after birth has a temperature of 37.8 °C (100.0 °F), a firm fundus and normal lochia. What is the most likely cause?

  1. ADehydration after labour
  2. BEndometritis
  3. CPulmonary embolism
  4. DMastitis
2.Maternity & obstetric nursingHard

A newborn is jaundiced at 12 hours of age. The mother is blood group O, Rh-positive and the baby is group A, Rh-positive with a positive direct Coombs test. What is the most likely cause?

  1. AABO incompatibility
  2. BRh isoimmunisation
  3. CPhysiological jaundice
  4. DBreast milk jaundice
3.Dosage calculationsMedium
30 kg25 mg/kg/day2× per dayD = ? mg

A patient weighs 30 kg. The prescribed dose is 25 mg/kg per day, given in 2 equal doses. How many milligrams D are given per dose?

30 kg25 mg/kg/day2× per day
D = mg
4.Dosage calculationsHard
90 kg181 cmBSA = √(h·w/3600)100 mg/m²D = ? mg

A patient is 181 cm tall and weighs 90 kg. The prescription is 100 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

181 cm90 kg100 mg/m²
D = mg
5.IV infusion ratesMedium
V = ?60 gtt/mL100 gtt/min2 h

A drip runs at 100 gtt/min through a set of 60 gtt/mL. How many millilitres V does the patient receive in 2 hours?

100 gtt/min60 gtt/mL2 h
V = mL
6.IV infusion ratesHard
500 mg250 mL60 gtt/mL60 mg/h? gtt/min

500 mg of a drug is diluted in 250 mL and given by gravity through a set of 60 gtt/mL. The order is 60 mg per hour. Find the drip rate R in drops per minute.

500 mg/250 mL60 mg/h60 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · Dehydration after labour

Why this is the answer

A slight rise in temperature in the first 24 hours is often due to dehydration and the effort of labour. Fluids are encouraged and temperature rechecked. A fever of 38 °C (100.4 °F) or more, especially after 24 hours, suggests infection.

Answer

A · Dehydration after labour
2.Maternity & obstetric nursing

Answer: A · ABO incompatibility

Why this is the answer

Group O mothers have anti-A and anti-B antibodies that can cross the placenta and haemolyse the red cells of a group A or B baby. Early jaundice with a positive direct Coombs test suggests haemolysis. Both are Rh-positive, so Rh disease is excluded.

Answer

A · ABO incompatibility
3.Dosage calculations

Answer: D = 375 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

25·30 = 750 mg

Per dose

D = 750/2 = 375 mg

Answer

D = 375 mg
4.Dosage calculations

Answer: D = 212.7 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).

Body surface area

BSA = √(181·90/3600) = √4.525 = 2.127 m²

Dose

D = 100·2.127 = 212.7 mg

Answer

D = 212.7 mg
5.IV infusion rates

Answer: V = 200 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

100·60/60 = 100 mL/h

Volume

V = 100·2 = 200 mL

Answer

V = 200 mL
6.IV infusion rates

Answer: R = 30 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

500/250 = 2 mg/mL

Volume per hour

60/2 = 30 mL/h

Drip rate

R = 30·60/60 = 30 gtt/min

Answer

R = 30 gtt/min

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