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

What does the acronym HELLP stand for?

  1. AHyperglycaemia, elevated lactate, low potassium
  2. BHypertension, elevated lipids, low protein
  3. CHaemolysis, elevated liver enzymes, low platelets
  4. DHaemorrhage, eclampsia, low pressure
2.Maternity & obstetric nursingHard

A woman at 41 weeks has a Bishop score of 3 and is booked for induction. What is the most likely first step?

  1. AAn immediate amniotomy at the bedside
  2. BA high-dose oxytocin infusion straight away
  3. CCervical ripening with a prostaglandin
  4. DAn emergency caesarean
3.Dosage calculationsMedium
2 g+ 9.2 mLV = ? mL

A vial contains 2 g of powder. The label says: add 9.2 mL of water for injection to give a total volume of 10 mL. The prescription is 160 mg. What volume V of the reconstituted solution do you give?

2 g+ 9.2 mL → 10 mL160 mg
V = mL
4.Dosage calculationsHard
50%stockwater = ? mL

You must prepare 1000 mL of a 0.5% (w/v) solution from a 50% (w/v) stock solution. How much water W must be added to the stock?

C₁ = 50%C₂ = 0.5%V₂ = 1000 mL
W = mL
5.IV infusion ratesMedium
V = ?20 gtt/mL40 gtt/min12 h

A drip runs at 40 gtt/min through a set of 20 gtt/mL. How many millilitres V does the patient receive in 12 hours?

40 gtt/min20 gtt/mL12 h
V = mL
6.IV infusion ratesHard
1000 mg250 mL60 gtt/mL80 mg/h? gtt/min

1000 mg of a drug is diluted in 250 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/250 mL80 mg/h60 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: C · Haemolysis, elevated liver enzymes, low platelets

Why this is the answer

HELLP syndrome is a serious complication of pre-eclampsia. Right upper quadrant or epigastric pain, nausea and malaise are typical, and blood pressure is not always very high.

Answer

C · Haemolysis, elevated liver enzymes, low platelets
2.Maternity & obstetric nursing

Answer: C · Cervical ripening with a prostaglandin

Why this is the answer

A low Bishop score means the cervix is not ready. Cervical ripening with prostaglandins or a balloon catheter is done before oxytocin or amniotomy, which may not be possible with a closed cervix.

Answer

C · Cervical ripening with a prostaglandin
3.Dosage calculations

Answer: V = 0.8 mL

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.

Concentration after mixing

2000 mg/10 mL = 200 mg/mL

Volume

V = 160/200 = 0.8 mL

Answer

V = 0.8 mL
4.Dosage calculations

Answer: W = 990 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 = 0.5·1000/50 = 10 mL

Water to add

W = 1000 − 10 = 990 mL

Answer

W = 990 mL
5.IV infusion rates

Answer: V = 1440 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

40·60/20 = 120 mL/h

Volume

V = 120·12 = 1440 mL

Answer

V = 1440 mL
6.IV infusion rates

Answer: R = 20 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

1000/250 = 4 mg/mL

Volume per hour

80/4 = 20 mL/h

Drip rate

R = 20·60/60 = 20 gtt/min

Answer

R = 20 gtt/min

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