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

Which drug is a known teratogen that must be stopped before a planned pregnancy?

  1. AIsotretinoin
  2. BLevothyroxine
  3. CParacetamol (acetaminophen)
  4. DFolic acid
2.Maternity & obstetric nursingHard

A preterm baby born at 28 weeks is at risk of intraventricular haemorrhage. Which nursing measure reduces this risk?

  1. ARapid fluid boluses to support blood pressure
  2. BMinimal handling with the head in midline
  3. CKeeping the head of the cot lower than the feet
  4. DFrequent handling and stimulation to keep the baby alert
3.Dosage calculationsMedium
10%20 mLm = ? mg

How many milligrams of drug m are in 20 mL of a 10% (w/v) solution?

10% w/v20 mL
m = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 4050 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?

4050 units5000 units/mL
V = mL
5.IV infusion ratesMedium
V = ?60 gtt/mL100 gtt/min12 h

A drip runs at 100 gtt/min through a set of 60 gtt/mL. How many millilitres V does the patient receive in 12 hours?

100 gtt/min60 gtt/mL12 h
V = mL
6.IV infusion ratesHard
250 mg250 mL15 gtt/mL40 mg/h? gtt/min

250 mg of a drug is diluted in 250 mL and given by gravity through a set of 15 gtt/mL. The order is 40 mg per hour. Find the drip rate R in drops per minute.

250 mg/250 mL40 mg/h15 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: A · Isotretinoin

Why this is the answer

Isotretinoin causes severe birth defects, so pregnancy must be prevented during treatment and for a period afterwards. Paracetamol is the usual analgesic in pregnancy, and levothyroxine should be continued.

Answer

A · Isotretinoin
2.Maternity & obstetric nursing

Answer: B · Minimal handling with the head in midline

Why this is the answer

Preterm babies have fragile germinal matrix vessels. Minimal handling, midline head position, slight elevation of the head and avoiding rapid fluid or pressure changes help prevent bleeding into the ventricles.

Answer

B · Minimal handling with the head in midline
3.Dosage calculations

Answer: m = 2000 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 = 100·20 = 2000 mg

Answer

m = 2000 mg
4.Dosage calculations

Answer: V = 0.81 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 = 4050/5000 = 0.81 mL

On the syringe

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

Answer

V = 0.81 mL
5.IV infusion rates

Answer: V = 1200 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

100·60/60 = 100 mL/h

Volume

V = 100·12 = 1200 mL

Answer

V = 1200 mL
6.IV infusion rates

Answer: R = 10 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 = 40·15/60 = 10 gtt/min

Answer

R = 10 gtt/min

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