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 24 weeks reports burning on urination and urinary frequency. What is the priority action?

  1. AReassure her that urinary frequency is normal in pregnancy
  2. BCollect a urine sample for culture and inform the provider
  3. CAdvise her to drink less to reduce frequency
  4. DAdvise cranberry juice and no further action
2.Maternity & obstetric nursingHard

A newborn passed no meconium by 48 hours and has a swollen abdomen and green vomiting. Which condition should be suspected?

  1. APhysiological jaundice
  2. BErythema toxicum
  3. CHirschsprung disease
  4. DDevelopmental hip dysplasia
3.Dosage calculationsMedium
5%w/vV = ? mL

A dose of 50 mg is needed from a 5% (w/v) solution. What volume V contains this dose?

50 mg5% w/v
V = mL
4.Dosage calculationsHard
29 kg117 cmBSA = √(h·w/3600)250 mg/m²D = ? mg

A patient is 117 cm tall and weighs 29 kg. The prescription is 250 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

117 cm29 kg250 mg/m²
D = mg
5.IV infusion ratesMedium
10 gtt/mL30 mL/h? gtt/min

An infusion is ordered at 30 mL/h, but no pump is available. It runs by gravity through a giving set of 10 gtt/mL. Find the drip rate R in drops per minute.

30 mL/h10 gtt/mL
R = gtt/min
6.IV infusion ratesHard
2 g250 mL? mL/h3 mg/min

A bag contains 2 g of a drug in 250 mL. The order is 3 mg per minute. At what rate R do you set the pump, in mL/h?

2 g/250 mL3 mg/min
R = mL/h

3Solutions

1.Maternity & obstetric nursing

Answer: B · Collect a urine sample for culture and inform the provider

Why this is the answer

Dysuria suggests a urinary tract infection, which needs culture and treatment with a pregnancy-safe antibiotic. Untreated UTIs can progress to pyelonephritis and preterm labour.

Answer

B · Collect a urine sample for culture and inform the provider
2.Maternity & obstetric nursing

Answer: C · Hirschsprung disease

Why this is the answer

Delayed meconium, abdominal distension and bilious vomiting suggest bowel obstruction, such as Hirschsprung disease. Bilious vomiting in a newborn is always an emergency.

Answer

C · Hirschsprung disease
3.Dosage calculations

Answer: V = 1 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

5% = 50 mg/mL

Volume

V = 50/50 = 1 mL

Answer

V = 1 mL
4.Dosage calculations

Answer: D = 242.7 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).

Body surface area

BSA = √(117·29/3600) = √0.9425 = 0.9708 m²

Dose

D = 250·0.9708 = 242.7 mg

Answer

D = 242.7 mg
5.IV infusion rates

Answer: R = 5 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.

Millilitres per minute

30/60 = 0.5 mL/min

Drip rate

R = 0.5·10 = 5 gtt/min

Answer

R = 5 gtt/min
6.IV infusion rates

Answer: R = 22.5 mL/h

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

2000 mg/250 mL = 8 mg/mL

Dose per hour

3·60 = 180 mg/h

Pump rate

R = 180/8 = 22.5 mL/h

Answer

R = 22.5 mL/h

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