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 at 37 weeks had a placental abruption. Which laboratory finding suggests she is developing disseminated intravascular coagulation (DIC)?

  1. AA low white cell count only
  2. BA high fibrinogen level and high platelets
  3. CA raised haemoglobin level
  4. DA low fibrinogen level and low platelets
2.Maternity & obstetric nursingHard

A woman at 6 weeks has vaginal spotting and one-sided pelvic pain. Her hCG rose only slightly over 48 hours and no pregnancy is seen in the uterus on transvaginal ultrasound. What is the priority concern?

  1. AAn ectopic pregnancy
  2. BA normal early pregnancy
  3. CA complete miscarriage with no further risk
  4. DA molar pregnancy
3.Dosage calculationsMedium
60 kg10 mg/kg/day4× per dayD = ? mg

A patient weighs 60 kg. The prescribed dose is 10 mg/kg per day, given in 4 equal doses. How many milligrams D are given per dose?

60 kg10 mg/kg/day4× per day
D = mg
4.Dosage calculationsHard
50%stockwater = ? mL

You must prepare 500 mL of a 2.5% (w/v) solution from a 50% (w/v) stock solution. How much water W must be added to the stock?

C₁ = 50%C₂ = 2.5%V₂ = 500 mL
W = mL
5.IV infusion ratesMedium
1170 mLleft? mL/h6 h left

1500 mL was ordered over 10 hours. After 4 hours you find that 1170 mL is still in the bag, and the order must still finish on time. To what rate R in mL/h must the pump be reset?

1500 mL / 10 hafter 4 h: 1170 mL
R = mL/h
6.IV infusion ratesHard
250 mg250 mL20 mL/h? mg/h

A bag contains 250 mg of a drug in 250 mL and runs at 20 mL/h. How many milligrams per hour D does the patient receive?

250 mg/250 mL20 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: D · A low fibrinogen level and low platelets

Why this is the answer

In DIC, widespread clotting consumes fibrinogen and platelets, leading to bleeding. Fibrinogen is normally raised in pregnancy, so a low level is especially concerning.

Answer

D · A low fibrinogen level and low platelets
2.Maternity & obstetric nursing

Answer: A · An ectopic pregnancy

Why this is the answer

A slowly rising hCG with an empty uterus at a level where a sac should be seen suggests an ectopic pregnancy. Rupture can cause life-threatening bleeding, so she needs close monitoring and urgent review.

Answer

A · An ectopic pregnancy
3.Dosage calculations

Answer: D = 150 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

10·60 = 600 mg

Per dose

D = 600/4 = 150 mg

Answer

D = 150 mg
4.Dosage calculations

Answer: W = 475 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 = 2.5·500/50 = 25 mL

Water to add

W = 500 − 25 = 475 mL

Answer

W = 475 mL
5.IV infusion rates

Answer: R = 195 mL/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.

Original rate

1500/10 = 150 mL/h

New rate

R = 1170/6 = 195 mL/h

Answer

R = 195 mL/h

This is more than a 25% increase: most hospitals require you to contact the prescriber instead of catching up, and to assess the patient for fluid overload.

6.IV infusion rates

Answer: D = 20 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

250/250 = 1 mg/mL

Dose rate

D = 1·20 = 20 mg/h

Answer

D = 20 mg/h

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