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 at 32 weeks has varicose veins in her legs. Which advice is most appropriate?

  1. AAvoid walking until after the birth
  2. BSit with her legs crossed to support the veins
  3. CRaise the legs when resting and avoid long standing
  4. DWear tight elastic bands around the top of the thighs
2.Maternity & obstetric nursingHard

Why does the ductus arteriosus normally close after birth?

  1. ARising oxygen levels and falling prostaglandins
  2. BThe cord is cut, which closes it directly
  3. CRising prostaglandins and falling oxygen levels
  4. DPressure in the pulmonary artery rises
3.Dosage calculationsMedium
54 kgBSA = 1.46 m²135 mg/m²D = ? mg

A patient weighing 54 kg has a body surface area of 1.46 m². The prescription is 135 mg/m². Find the dose D in mg.

54 kgBSA = 1.46 m²135 mg/m²
D = mg
4.Dosage calculationsHard
25k units1000 mL? mL/h1000 units/h

An infusion contains 25000 units of a drug in 1000 mL. The prescription is 1000 units per hour. At what rate R do you set the pump, in mL/h?

25000 units/1000 mL1000 units/h
R = mL/h
5.IV infusion ratesMedium
V = ?60 gtt/mL60 gtt/min6 h

A drip runs at 60 gtt/min through a set of 60 gtt/mL. How many millilitres V does the patient receive in 6 hours?

60 gtt/min60 gtt/mL6 h
V = mL
6.IV infusion ratesHard
2 g250 mL? mL/h3 mg/min

A bag contains 2 g of a drug in 250 mL. The order is 3 mg per minute. At what rate R do you set the pump, in mL/h?

2 g/250 mL3 mg/min
R = mL/h

3Solutions

1.Maternity & obstetric nursing

Answer: C · Raise the legs when resting and avoid long standing

Why this is the answer

Leg elevation, regular walking, avoiding long standing and graduated compression stockings improve venous return. Crossing the legs and tight bands at the thigh restrict venous flow.

Answer

C · Raise the legs when resting and avoid long standing
2.Maternity & obstetric nursing

Answer: A · Rising oxygen levels and falling prostaglandins

Why this is the answer

Higher blood oxygen and lower prostaglandin levels after birth cause the ductus arteriosus to constrict. Prostaglandin infusions are used to keep it open in duct-dependent heart defects.

Answer

A · Rising oxygen levels and falling prostaglandins
3.Dosage calculations

Answer: D = 197.1 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 = 135·1.46 = 197.1 mg

Answer

D = 197.1 mg
4.Dosage calculations

Answer: R = 40 mL/h

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.

Concentration

25000/1000 = 25 units/mL

Pump rate

R = 1000/25 = 40 mL/h

Answer

R = 40 mL/h
5.IV infusion rates

Answer: V = 360 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

60·60/60 = 60 mL/h

Volume

V = 60·6 = 360 mL

Answer

V = 360 mL
6.IV infusion rates

Answer: R = 22.5 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

2000 mg/250 mL = 8 mg/mL

Dose per hour

3·60 = 180 mg/h

Pump rate

R = 180/8 = 22.5 mL/h

Answer

R = 22.5 mL/h

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