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

Why is mild anaemia common in the second trimester even in healthy women?

  1. AThe bone marrow stops producing red cells during pregnancy
  2. BThe fetus breaks down maternal red blood cells
  3. CIron is lost in the urine because kidney filtration rises
  4. DPlasma volume rises more than red cell mass
2.Maternity & obstetric nursingHard

A woman at 9 weeks has hCG levels that are much higher than expected, a uterus large for dates, severe vomiting and dark brown spotting. Which condition should be suspected?

  1. AA missed miscarriage
  2. BAn ectopic pregnancy
  3. CA threatened miscarriage
  4. DA hydatidiform (molar) pregnancy
3.Dosage calculationsMedium
18 kg7.5 mg/kgD = ? mg

A patient weighs 18 kg and is prescribed 7.5 mg/kg as a single dose. Find the dose D in mg.

18 kg7.5 mg/kg
D = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 1000 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?

1000 units5000 units/mL
V = mL
5.IV infusion ratesMedium
1220 mLleft? mL/h6 h left

1500 mL was ordered over 8 hours. After 2 hours you find that 1220 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?

1500 mL / 8 hafter 2 h: 1220 mL
R = mL/h
6.IV infusion ratesHard
100 mg50 mL25 mL/h? mg/h

A bag contains 100 mg of a drug in 50 mL and runs at 25 mL/h. How many milligrams per hour D does the patient receive?

100 mg/50 mL25 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: D · Plasma volume rises more than red cell mass

Why this is the answer

Plasma volume increases more than red cell mass, so haemoglobin concentration falls (physiological or dilutional anaemia). Iron deficiency can add to this and should still be checked.

Answer

D · Plasma volume rises more than red cell mass
2.Maternity & obstetric nursing

Answer: D · A hydatidiform (molar) pregnancy

Why this is the answer

A molar pregnancy causes very high hCG, a uterus larger than dates, hyperemesis and bleeding. Ectopic and failing pregnancies usually have lower than expected hCG.

Answer

D · A hydatidiform (molar) pregnancy
3.Dosage calculations

Answer: D = 135 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.

Dose

7.5·18 = 135 mg

Answer

D = 135 mg
4.Dosage calculations

Answer: V = 0.2 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 = 1000/5000 = 0.2 mL

On the syringe

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

Answer

V = 0.2 mL
5.IV infusion rates

Answer: R = 203.3 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

1500/8 = 187.5 mL/h

New rate

R = 1220/6 = 203.3 mL/h

Answer

R = 203.3 mL/h

Many hospitals allow such an adjustment up to 25% without a new order; check local policy.

6.IV infusion rates

Answer: D = 50 mg/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.

Concentration

100/50 = 2 mg/mL

Dose rate

D = 2·25 = 50 mg/h

Answer

D = 50 mg/h

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