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 a normal pre-pregnancy BMI asks how much weight she should gain. Which range do the widely used US Institute of Medicine guidelines recommend?

  1. AAbout 11.5 to 16 kg
  2. BAbout 5 to 9 kg
  3. CAbout 18 to 23 kg
  4. DAbout 2 to 4 kg
2.Maternity & obstetric nursingHard

The partner of a woman receiving magnesium sulfate asks what the drug is for. Which answer is accurate?

  1. AIt is the main drug that lowers her blood pressure
  2. BIt stops the baby from growing too large
  3. CIt speeds up labour
  4. DIt helps prevent seizures caused by pre-eclampsia
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 240 mg. What volume V of the reconstituted solution do you give?

2 g+ 9.2 mL → 10 mL240 mg
V = mL
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 405 micrograms. The ampoule contains 0.5 mg/mL. Draw up the dose in the 1 mL syringe: what volume V do you give?

405 mcg0.5 mg/mL
V = mL
5.IV infusion ratesMedium
V = ?20 gtt/mL20 gtt/min6 h

A drip runs at 20 gtt/min through a set of 20 gtt/mL. How many millilitres V does the patient receive in 6 hours?

20 gtt/min20 gtt/mL6 h
V = mL
6.IV infusion ratesHard
200 mg250 mL30 mL/h? mg/h

A bag contains 200 mg of a drug in 250 mL and runs at 30 mL/h. How many milligrams per hour D does the patient receive?

200 mg/250 mL30 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: A · About 11.5 to 16 kg

Why this is the answer

For a normal BMI, the US Institute of Medicine (National Academy of Medicine) recommends a total gain of about 11.5 to 16 kg (25 to 35 lb), more for underweight women and less for women with obesity. The UK has no official target range; NICE focuses on healthy eating and activity.

Answer

A · About 11.5 to 16 kg
2.Maternity & obstetric nursing

Answer: D · It helps prevent seizures caused by pre-eclampsia

Why this is the answer

Magnesium sulfate is given to prevent and treat eclamptic seizures. It is not an effective antihypertensive, so severe hypertension needs separate drugs.

Answer

D · It helps prevent seizures caused by pre-eclampsia
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

2000 mg/10 mL = 200 mg/mL

Volume

V = 240/200 = 1.2 mL

Answer

V = 1.2 mL
4.Dosage calculations

Answer: V = 0.81 mL

Drawing up a dose: volume = (prescribed dose/stock strength) × stock volume. Convert to the same units first, then check that the volume fits the syringe and lands on one of its graduations.

Same units

0.5 mg/mL = 500 mcg/mL

Volume

V = 405/500 = 0.81 mL

Answer

V = 0.81 mL
5.IV infusion rates

Answer: V = 360 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

20·60/20 = 60 mL/h

Volume

V = 60·6 = 360 mL

Answer

V = 360 mL
6.IV infusion rates

Answer: D = 24 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

200/250 = 0.8 mg/mL

Dose rate

D = 0.8·30 = 24 mg/h

Answer

D = 24 mg/h

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