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 with hyperemesis gravidarum has been vomiting for weeks. Which vitamin is given before glucose-containing fluids to prevent Wernicke encephalopathy?

  1. AAscorbic acid (vitamin C)
  2. BVitamin D
  3. CPhytomenadione (vitamin K)
  4. DThiamine (vitamin B1)
2.Maternity & obstetric nursingHard

Just after the membranes rupture, there is painless vaginal bleeding and the fetal heart rate drops sharply. The mother's vital signs are normal. Which condition is most likely?

  1. ARuptured vasa praevia
  2. BUterine rupture
  3. CBloody show
  4. DPlacental abruption
3.Dosage calculationsMedium
22 kg5 mg/kg/day4× per dayD = ? mg

A patient weighs 22 kg. The prescribed dose is 5 mg/kg per day, given in 4 equal doses. How many milligrams D are given per dose?

22 kg5 mg/kg/day4× per day
D = mg
4.Dosage calculationsHard
69 kg153 cmBSA = √(h·w/3600)25 mg/m²D = ? mg

A patient is 153 cm tall and weighs 69 kg. The prescription is 25 mg/m². Using the Mosteller formula BSA = √(height (cm) × weight (kg)/3600), find the dose D in mg.

153 cm69 kg25 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
400 mg500 mL10 mL/h? mg/h

A bag contains 400 mg of a drug in 500 mL and runs at 10 mL/h. How many milligrams per hour D does the patient receive?

400 mg/500 mL10 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: D · Thiamine (vitamin B1)

Why this is the answer

Prolonged vomiting depletes thiamine. Giving glucose without thiamine can trigger Wernicke encephalopathy, with confusion, ataxia and eye movement problems.

Answer

D · Thiamine (vitamin B1)
2.Maternity & obstetric nursing

Answer: A · Ruptured vasa praevia

Why this is the answer

Rupture of the membranes can tear unprotected fetal vessels in vasa praevia. Fetal blood loss causes rapid bradycardia while the mother stays stable. An emergency caesarean is needed.

Answer

A · Ruptured vasa praevia
3.Dosage calculations

Answer: D = 27.5 mg

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.

Total per day

5·22 = 110 mg

Per dose

D = 110/4 = 27.5 mg

Answer

D = 27.5 mg
4.Dosage calculations

Answer: D = 42.81 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 = √(153·69/3600) = √2.933 = 1.712 m²

Dose

D = 25·1.712 = 42.81 mg

Answer

D = 42.81 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: D = 8 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

400/500 = 0.8 mg/mL

Dose rate

D = 0.8·10 = 8 mg/h

Answer

D = 8 mg/h

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