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 pre-eclampsia is on magnesium sulfate. Why does the nurse monitor her urine output closely?

  1. AMagnesium causes a large diuresis that leads to dehydration
  2. BLow urine output shows that the magnesium is working
  3. CUrine output tells the nurse exactly when to stop the infusion after the birth
  4. DMagnesium is cleared by the kidneys, so oliguria raises the risk of toxicity
2.Maternity & obstetric nursingHard

A labouring woman has a temperature of 38.5 °C (101.3 °F), and the fetal baseline has risen from 140 to 170 bpm over the last hour. What is the most likely explanation?

  1. AFetal tachycardia due to a maternal opioid
  2. BFetal tachycardia due to maternal fever or infection
  3. CReassuring fetal response to contractions
  4. DFetal head compression
3.Dosage calculationsMedium
70 kg7.5 mg/kgD = ? mg

A patient weighs 70 kg and is prescribed 7.5 mg/kg as a single dose. Find the dose D in mg.

70 kg7.5 mg/kg
D = mg
4.Dosage calculationsHard
25%stockV₁ = ? mL

You must prepare 200 mL of a 1% (w/v) solution from a 25% (w/v) stock solution. What volume of stock V₁ do you need?

C₁ = 25%C₂ = 1%V₂ = 200 mL
V₁ = mL
5.IV infusion ratesMedium
V = ?60 gtt/mL100 gtt/min3 h

A drip runs at 100 gtt/min through a set of 60 gtt/mL. How many millilitres V does the patient receive in 3 hours?

100 gtt/min60 gtt/mL3 h
V = mL
6.IV infusion ratesHard
25 mg250 mL15 mL/h? mcg/min

An infusion of 25 mg in 250 mL runs at 15 mL/h. How many micrograms per minute D does the patient receive?

25 mg/250 mL15 mL/h
D = mcg/min

3Solutions

1.Maternity & obstetric nursing

Answer: D · Magnesium is cleared by the kidneys, so oliguria raises the risk of toxicity

Why this is the answer

Magnesium is cleared by the kidneys, so oliguria, which is common in pre-eclampsia, allows levels to rise. The nurse also monitors reflexes, respiratory rate and level of consciousness.

Answer

D · Magnesium is cleared by the kidneys, so oliguria raises the risk of toxicity
2.Maternity & obstetric nursing

Answer: B · Fetal tachycardia due to maternal fever or infection

Why this is the answer

Maternal fever, often from intra-amniotic infection, is a common cause of fetal tachycardia. The provider is informed, and treatment of fever and infection is expected. Opioids reduce variability rather than raise the rate.

Answer

B · Fetal tachycardia due to maternal fever or infection
3.Dosage calculations

Answer: D = 525 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.

Dose

7.5·70 = 525 mg

Answer

D = 525 mg
4.Dosage calculations

Answer: V₁ = 8 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 = 1·200/25 = 8 mL

Answer

V₁ = 8 mL
5.IV infusion rates

Answer: V = 300 mL

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.

Rate in mL/h

100·60/60 = 100 mL/h

Volume

V = 100·3 = 300 mL

Answer

V = 300 mL
6.IV infusion rates

Answer: D = 25 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

25000 mcg/250 mL = 100 mcg/mL

Dose per hour

15·100 = 1500 mcg/h

Dose per minute

D = 1500/60 = 25 mcg/min

Answer

D = 25 mcg/min

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