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 30 weeks, which fundal height is consistent with expected growth?

  1. A22 cm
  2. B36 cm
  3. C18 cm
  4. D29 cm
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. BMacrosomia and shoulder dystocia
  3. CRespiratory distress from surfactant deficiency only
  4. DHypoglycaemia, hypothermia and polycythaemia
3.Dosage calculationsMedium
1:1000ampouleV = ? mL

An ampoule of epinephrine (adrenaline) is labelled 1:1000 (1 mg/mL). The prescription is 0.3 mg IM for anaphylaxis. What volume V do you draw up?

1:10000.3 mg
V = mL
4.Dosage calculationsHard
101 kg190 cmBSA = √(h·w/3600)135 mg/m²D = ? mg

A patient is 190 cm tall and weighs 101 kg. The prescription is 135 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

190 cm101 kg135 mg/m²
D = mg
5.IV infusion ratesMedium
190 mLleft? mL/h3 h left

500 mL was ordered over 10 hours. After 7 hours you find that 190 mL is still in the bag, and the order must still finish on time. To what rate R in mL/h must the pump be reset?

500 mL / 10 hafter 7 h: 190 mL
R = mL/h
6.IV infusion ratesHard
200 mg100 mL20 gtt/mL150 mg/h? gtt/min

200 mg of a drug is diluted in 100 mL and given by gravity through a set of 20 gtt/mL. The order is 150 mg per hour. Find the drip rate R in drops per minute.

200 mg/100 mL150 mg/h20 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: D · 29 cm

Why this is the answer

The expected fundal height at 30 weeks is about 28–32 cm. A difference of more than 2–3 cm from the gestational age should be followed up, usually with an ultrasound.

Answer

D · 29 cm
2.Maternity & obstetric nursing

Answer: D · 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

D · Hypoglycaemia, hypothermia and polycythaemia
3.Dosage calculations

Answer: V = 0.3 mL

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

1:1000 = 1 g/1000 mL = 1 mg/mL

Volume

V = 0.3/1 = 0.3 mL

Answer

V = 0.3 mL

US labels now state mg/mL (1 mg/mL = 1:1000; 0.1 mg/mL = 1:10 000). Never give 1 mg/mL epinephrine IV push.

4.Dosage calculations

Answer: D = 311.7 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 = √(190·101/3600) = √5.331 = 2.309 m²

Dose

D = 135·2.309 = 311.7 mg

Answer

D = 311.7 mg
5.IV infusion rates

Answer: R = 63.33 mL/h

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.

Original rate

500/10 = 50 mL/h

New rate

R = 190/3 = 63.33 mL/h

Answer

R = 63.33 mL/h

This is more than a 25% increase: most hospitals require you to contact the prescriber instead of catching up, and to assess the patient for fluid overload.

6.IV infusion rates

Answer: R = 25 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

200/100 = 2 mg/mL

Volume per hour

150/2 = 75 mL/h

Drip rate

R = 75·20/60 = 25 gtt/min

Answer

R = 25 gtt/min

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