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 postpartum woman who is not immune to rubella receives the vaccine before discharge. What advice is essential?

  1. AHave the vaccine repeated in 6 months
  2. BStop breastfeeding for 4 weeks
  3. CKeep away from her newborn for 2 days
  4. DAvoid becoming pregnant for at least 4 weeks
2.Maternity & obstetric nursingHard

A newborn is apnoeic after being warmed, dried and stimulated. What is the next step?

  1. AStart positive-pressure ventilation with a bag and mask
  2. BWait and assess the 5-minute APGAR score before doing anything
  3. CHold the baby upside down and slap the back
  4. DStart chest compressions immediately
3.Dosage calculationsMedium
59 kgBSA = 1.54 m²100 mg/m²D = ? mg

A patient weighing 59 kg has a body surface area of 1.54 m². The prescription is 100 mg/m². Find the dose D in mg.

59 kgBSA = 1.54 m²100 mg/m²
D = mg
4.Dosage calculationsHard
25%stockV₁ = ? mL

You must prepare 1000 mL of a 2% (w/v) solution from a 25% (w/v) stock solution. What volume of stock V₁ do you need?

C₁ = 25%C₂ = 2%V₂ = 1000 mL
V₁ = mL
5.IV infusion ratesMedium
500 mL60 gtt/mL6 h? gtt/min

Infuse 500 mL over 6 hours with a giving set of 60 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

500 mL6 h60 gtt/mL
R = gtt/min
6.IV infusion ratesHard
50 mg500 mL30 mL/h? mcg/min

An infusion of 50 mg in 500 mL runs at 30 mL/h. How many micrograms per minute D does the patient receive?

50 mg/500 mL30 mL/h
D = mcg/min

3Solutions

1.Maternity & obstetric nursing

Answer: D · Avoid becoming pregnant for at least 4 weeks

Why this is the answer

The rubella vaccine contains a live attenuated virus, so pregnancy should be avoided for at least 4 weeks after vaccination. It is compatible with breastfeeding.

Answer

D · Avoid becoming pregnant for at least 4 weeks
2.Maternity & obstetric nursing

Answer: A · Start positive-pressure ventilation with a bag and mask

Why this is the answer

If the newborn is apnoeic or gasping, or the heart rate is below 100/min after the initial steps, positive-pressure ventilation starts within the first minute. Effective ventilation is the most important step in newborn resuscitation.

Answer

A · Start positive-pressure ventilation with a bag and mask
3.Dosage calculations

Answer: D = 154 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 = 100·1.54 = 154 mg

Answer

D = 154 mg
4.Dosage calculations

Answer: V₁ = 80 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.

Volume of stock

V₁ = 2·1000/25 = 80 mL

Answer

V₁ = 80 mL
5.IV infusion rates

Answer: R = 83 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

6·60 = 360 min

Drip rate

R = 500·60/360 = 83.33 ≈ 83 gtt/min

Answer

R = 83 gtt/min

At the bedside you round to the nearest whole drop: 83 gtt/min.

6.IV infusion rates

Answer: D = 50 mcg/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

50000 mcg/500 mL = 100 mcg/mL

Dose per hour

30·100 = 3000 mcg/h

Dose per minute

D = 3000/60 = 50 mcg/min

Answer

D = 50 mcg/min

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