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

What is a "reactive" non-stress test?

  1. ALate decelerations with every contraction
  2. BA baseline heart rate above 160 bpm
  3. CNo accelerations of the fetal heart rate within 40 minutes
  4. DAt least 2 fetal heart rate accelerations within 20 minutes
2.Maternity & obstetric nursingHard

A large for gestational age newborn of a mother with diabetes is also very red and has a high haematocrit. Which complication of this finding should the nurse watch for?

  1. ANeural tube defects
  2. BDehydration caused by vomiting
  3. CHypothermia caused by sweating
  4. DJaundice
3.Dosage calculationsMedium
1:10 000ampouleV = ? mL

A prefilled syringe of epinephrine (adrenaline) is labelled 1:10 000 (0.1 mg/mL). The prescription is 1 mg IV in cardiac arrest. What volume V do you give?

1:10 0001 mg
V = mL
4.Dosage calculationsHard
200 mg/5 mLV = ? mL

A patient weighs 85.8 lb. The prescription is 10 mg/kg as a single dose, and the stock contains 200 mg in 5 mL. Using 1 kg = 2.2 lb, what volume V do you give? Round to one decimal place.

85.8 lb10 mg/kg200 mg/5 mL1 kg = 2.2 lb
V = mL
5.IV infusion ratesMedium
250 mL60 gtt/mL8 h? gtt/min

Infuse 250 mL over 8 hours with a giving set of 60 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

250 mL8 h60 gtt/mL
R = gtt/min
6.IV infusion ratesHard
500 mg50 mL20 mL/h? mg/h

A bag contains 500 mg of a drug in 50 mL and runs at 20 mL/h. How many milligrams per hour D does the patient receive?

500 mg/50 mL20 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: D · At least 2 fetal heart rate accelerations within 20 minutes

Why this is the answer

A reactive non-stress test shows at least two qualifying accelerations in 20 minutes and indicates fetal well-being. A non-reactive test needs further testing, such as a biophysical profile.

Answer

D · At least 2 fetal heart rate accelerations within 20 minutes
2.Maternity & obstetric nursing

Answer: D · Jaundice

Why this is the answer

Polycythaemia is common in infants of diabetic mothers and SGA babies. Breakdown of the extra red cells raises bilirubin, and high viscosity can cause poor feeding, lethargy or thrombosis.

Answer

D · Jaundice
3.Dosage calculations

Answer: V = 10 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

1:10 000 = 1 g/10000 mL = 0.1 mg/mL

Volume

V = 1/0.1 = 10 mL

Answer

V = 10 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: V = 9.8 mL

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.

Weight in kg

85.8/2.2 = 39 kg

Dose

10·39 = 390 mg

Volume

V = (390/200)·5 = 9.75 ≈ 9.8 mL

Answer

V = 9.8 mL
5.IV infusion rates

Answer: R = 31 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

8·60 = 480 min

Drip rate

R = 250·60/480 = 31.25 ≈ 31 gtt/min

Answer

R = 31 gtt/min

At the bedside you round to the nearest whole drop: 31 gtt/min.

6.IV infusion rates

Answer: D = 200 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

500/50 = 10 mg/mL

Dose rate

D = 10·20 = 200 mg/h

Answer

D = 200 mg/h

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