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

A woman at 22 weeks describes sharp pain on one side of the lower abdomen when she stands up quickly. Her vital signs and fetal heart rate are normal. What is the most likely cause?

  1. APlacental abruption
  2. BAppendicitis
  3. CRound ligament pain
  4. DPreterm labour
2.Maternity & obstetric nursingHard

A woman at 8 weeks takes valproate for epilepsy. She asks whether she should stop it. Which response is best?

  1. AHalve the dose herself to reduce the risk to the baby
  2. BStop the drug today because it causes birth defects
  3. CDo not stop it suddenly; arrange urgent specialist review
  4. DContinue as usual because epilepsy drugs are all safe in pregnancy
3.Dosage calculationsMedium
38 kgBSA = 1.13 m²100 mg/m²D = ? mg

A patient weighing 38 kg has a body surface area of 1.13 m². The prescription is 100 mg/m². Find the dose D in mg.

38 kgBSA = 1.13 m²100 mg/m²
D = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 2500 units of a drug that comes as 10000 units/mL. Draw up the dose in the 1 mL syringe: what volume V do you give?

2500 units10000 units/mL
V = mL
5.IV infusion ratesMedium
1000 mL15 gtt/mL4 h? gtt/min

Infuse 1000 mL over 4 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

1000 mL4 h15 gtt/mL
R = gtt/min
6.IV infusion ratesHard
1000 mg500 mL60 gtt/mL80 mg/h? gtt/min

1000 mg of a drug is diluted in 500 mL and given by gravity through a set of 60 gtt/mL. The order is 80 mg per hour. Find the drip rate R in drops per minute.

1000 mg/500 mL80 mg/h60 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: C · Round ligament pain

Why this is the answer

Round ligament pain is sharp, brief pain in the groin or lower abdomen with sudden movement as the uterus grows. Moving slowly and flexing the hips towards the abdomen help. Persistent or severe pain needs review.

Answer

C · Round ligament pain
2.Maternity & obstetric nursing

Answer: C · Do not stop it suddenly; arrange urgent specialist review

Why this is the answer

Valproate is strongly teratogenic, but stopping antiepileptics suddenly can cause seizures that harm mother and fetus. She needs urgent specialist review to change treatment safely, ideally before conception.

Answer

C · Do not stop it suddenly; arrange urgent specialist review
3.Dosage calculations

Answer: D = 113 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).

Dose

D = 100·1.13 = 113 mg

Answer

D = 113 mg
4.Dosage calculations

Answer: V = 0.25 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 = 2500/10000 = 0.25 mL

On the syringe

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

Answer

V = 0.25 mL
5.IV infusion rates

Answer: R = 63 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

4·60 = 240 min

Drip rate

R = 1000·15/240 = 62.5 ≈ 63 gtt/min

Answer

R = 63 gtt/min

At the bedside you round to the nearest whole drop: 63 gtt/min.

6.IV infusion rates

Answer: R = 40 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

1000/500 = 2 mg/mL

Volume per hour

80/2 = 40 mL/h

Drip rate

R = 40·60/60 = 40 gtt/min

Answer

R = 40 gtt/min

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