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 pregnant woman takes warfarin for a mechanical heart valve. Why is she usually switched to heparin for much of the pregnancy?

  1. AHeparin can be taken as a tablet once a day
  2. BWarfarin crosses the placenta and can harm the fetus
  3. CHeparin crosses the placenta better and also protects the fetus
  4. DWarfarin is ineffective in pregnancy
2.Maternity & obstetric nursingHard

A woman at 11 weeks has heavy bleeding, cramping and an open cervical os, and she has passed some tissue. Which type of miscarriage is this?

  1. AComplete miscarriage
  2. BIncomplete miscarriage
  3. CMissed miscarriage
  4. DThreatened miscarriage
3.Dosage calculationsMedium
1 g+ 4.2 mLV = ? mL

A vial contains 1 g of powder. The label says: add 4.2 mL of water for injection to give a total volume of 5 mL. The prescription is 240 mg. What volume V of the reconstituted solution do you give?

1 g+ 4.2 mL → 5 mL240 mg
V = mL
4.Dosage calculationsHard
50k units500 mL? mL/h2000 units/h

An infusion contains 50000 units of a drug in 500 mL. The prescription is 2000 units per hour. At what rate R do you set the pump, in mL/h?

50000 units/500 mL2000 units/h
R = mL/h
5.IV infusion ratesMedium
1000 mL15 gtt/mL10 h? gtt/min

Infuse 1000 mL over 10 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute.

1000 mL10 h15 gtt/mL
R = gtt/min
6.IV infusion ratesHard
200 mg100 mL15 gtt/mL40 mg/h? gtt/min

200 mg of a drug is diluted in 100 mL and given by gravity through a set of 15 gtt/mL. The order is 40 mg per hour. Find the drip rate R in drops per minute.

200 mg/100 mL40 mg/h15 gtt/mL
R = gtt/min

3Solutions

1.Maternity & obstetric nursing

Answer: B · Warfarin crosses the placenta and can harm the fetus

Why this is the answer

Warfarin crosses the placenta and is teratogenic and can cause fetal bleeding. Heparins are large molecules that do not cross the placenta, so low molecular weight heparin is commonly used instead.

Answer

B · Warfarin crosses the placenta and can harm the fetus
2.Maternity & obstetric nursing

Answer: B · Incomplete miscarriage

Why this is the answer

An open os with some tissue passed and continued bleeding is an incomplete miscarriage. Retained tissue can cause haemorrhage and infection, so it is usually managed medically or surgically.

Answer

B · Incomplete miscarriage
3.Dosage calculations

Answer: V = 1.2 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

1000 mg/5 mL = 200 mg/mL

Volume

V = 240/200 = 1.2 mL

Answer

V = 1.2 mL
4.Dosage calculations

Answer: R = 20 mL/h

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

50000/500 = 100 units/mL

Pump rate

R = 2000/100 = 20 mL/h

Answer

R = 20 mL/h
5.IV infusion rates

Answer: R = 25 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

10·60 = 600 min

Drip rate

R = 1000·15/600 = 25 gtt/min

Answer

R = 25 gtt/min
6.IV infusion rates

Answer: R = 5 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

200/100 = 2 mg/mL

Volume per hour

40/2 = 20 mL/h

Drip rate

R = 20·15/60 = 5 gtt/min

Answer

R = 5 gtt/min

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