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

At station +2, where is the presenting part?

  1. A2 cm below the ischial spines
  2. B2 cm above the ischial spines
  3. CFloating above the pelvic inlet
  4. DAt the level of the ischial spines
2.Maternity & obstetric nursingHard

A small for gestational age baby is born at term. Which complications should the nurse anticipate?

  1. AHyperglycaemia, fever and anaemia
  2. BHypoglycaemia, hypothermia and polycythaemia
  3. CMacrosomia and shoulder dystocia
  4. DRespiratory distress from surfactant deficiency only
3.Dosage calculationsMedium
37 kgBSA = 1.14 m²20 mg/m²D = ? mg

A patient weighing 37 kg has a body surface area of 1.14 m². The prescription is 20 mg/m². Find the dose D in mg.

37 kgBSA = 1.14 m²20 mg/m²
D = mg
4.Dosage calculationsHard
50k units250 mL? mL/h800 units/h

An infusion contains 50000 units of a drug in 250 mL. The prescription is 800 units per hour. At what rate R do you set the pump, in mL/h?

50000 units/250 mL800 units/h
R = mL/h
5.IV infusion ratesMedium
1500 mL10 gtt/mL10 h? gtt/min

Infuse 1500 mL over 10 hours with a giving set of 10 gtt/mL. Find the drip rate R in drops per minute.

1500 mL10 h10 gtt/mL
R = gtt/min
6.IV infusion ratesHard
250 mg250 mL60 gtt/mL40 mg/h? gtt/min

250 mg of a drug is diluted in 250 mL and given by gravity through a set of 60 gtt/mL. The order is 40 mg per hour. Find the drip rate R in drops per minute.

250 mg/250 mL40 mg/h60 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · 2 cm below the ischial spines

Why this is the answer

Station is measured in centimetres relative to the ischial spines. Negative numbers are above them, 0 is at their level and positive numbers are below them, towards the outlet.

Answer

A · 2 cm below the ischial spines
2.Maternity & obstetric nursing

Answer: B · Hypoglycaemia, hypothermia and polycythaemia

Why this is the answer

SGA babies have low glycogen and fat stores, leading to hypoglycaemia and hypothermia. Chronic intrauterine hypoxia increases red cell production, causing polycythaemia.

Answer

B · Hypoglycaemia, hypothermia and polycythaemia
3.Dosage calculations

Answer: D = 22.8 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 = 20·1.14 = 22.8 mg

Answer

D = 22.8 mg
4.Dosage calculations

Answer: R = 4 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

50000/250 = 200 units/mL

Pump rate

R = 800/200 = 4 mL/h

Answer

R = 4 mL/h
5.IV infusion rates

Answer: R = 25 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

10·60 = 600 min

Drip rate

R = 1500·10/600 = 25 gtt/min

Answer

R = 25 gtt/min
6.IV infusion rates

Answer: R = 40 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

250/250 = 1 mg/mL

Volume per hour

40/1 = 40 mL/h

Drip rate

R = 40·60/60 = 40 gtt/min

Answer

R = 40 gtt/min

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