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

Methylergonovine (methylergometrine) for postpartum bleeding should not be given to a woman with:

  1. AAsthma
  2. BHigh blood pressure
  3. CType 1 diabetes
  4. DAnaemia
2.Maternity & obstetric nursingHard

Why does the foramen ovale close soon after birth?

  1. ABlood flow to the lungs decreases after birth
  2. BThe umbilical vein carries more blood to the heart
  3. CProstaglandin levels rise in the newborn's blood
  4. DLeft atrial pressure rises above right atrial pressure
3.Dosage calculationsMedium
10%50 mLm = ? mg

How many milligrams of drug m are in 50 mL of a 10% (w/v) solution?

10% w/v50 mL
m = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 1440 micrograms. The ampoule contains 2 mg/mL. Draw up the dose in the 1 mL syringe: what volume V do you give?

1440 mcg2 mg/mL
V = mL
5.IV infusion ratesMedium
320 mLleft? mL/h5 h left

500 mL was ordered over 10 hours. After 5 hours you find that 320 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 5 h: 320 mL
R = mL/h
6.IV infusion ratesHard
250 mg50 mL8 mL/h? mg/h

A bag contains 250 mg of a drug in 50 mL and runs at 8 mL/h. How many milligrams per hour D does the patient receive?

250 mg/50 mL8 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: B · High blood pressure

Why this is the answer

Ergot alkaloids cause vasoconstriction and can raise blood pressure dangerously, so they are avoided in hypertension and pre-eclampsia. Carboprost is the drug to avoid in asthma.

Answer

B · High blood pressure
2.Maternity & obstetric nursing

Answer: D · Left atrial pressure rises above right atrial pressure

Why this is the answer

With the first breaths, pulmonary resistance falls and more blood returns to the left atrium, while cord clamping lowers right-sided pressure. The higher left atrial pressure pushes the flap of the foramen ovale shut.

Answer

D · Left atrial pressure rises above right atrial pressure
3.Dosage calculations

Answer: m = 5000 mg

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

10% = 10 g/100 mL = 100 mg/mL

Mass of drug

m = 100·50 = 5000 mg

Answer

m = 5000 mg
4.Dosage calculations

Answer: V = 0.72 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.

Same units

2 mg/mL = 2000 mcg/mL

Volume

V = 1440/2000 = 0.72 mL

Answer

V = 0.72 mL
5.IV infusion rates

Answer: R = 64 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 = 320/5 = 64 mL/h

Answer

R = 64 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: D = 40 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

250/50 = 5 mg/mL

Dose rate

D = 5·8 = 40 mg/h

Answer

D = 40 mg/h

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