Formula sheets, the key method steps for every topic and 6 practice problems, with full solutions at the back.
Obesity before pregnancy (BMI 40) most increases the risk of which pregnancy complication?
A woman at 8 weeks takes valproate for epilepsy. She asks whether she should stop it. Which response is best?
A child weighing 7 kg is prescribed 15 mg/kg of a drug. The stock solution contains 25 mg/mL. Draw up the dose: what volume V do you give?
A patient weighs 121 lb. The prescription is 15 mg/kg as a single dose, and the stock contains 200 mg in 5 mL. Using 1 kg = 2.2 lb, what volume V do you give? Round to one decimal place.
1500 mL was ordered over 10 hours. After 6 hours you find that 760 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?
500 mg of a drug is diluted in 250 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.
Answer: C · Gestational diabetes
Obesity raises the risks of gestational diabetes, pre-eclampsia, venous thromboembolism, macrosomia, caesarean birth and stillbirth. Early glucose testing and VTE risk assessment are often recommended.
Answer: D · Do not stop it suddenly; arrange urgent specialist review
Valproate is strongly teratogenic, but stopping antiepileptics suddenly can cause seizures that harm mother and fetus. She needs urgent specialist review to change treatment safely, ideally before conception.
Answer: V = 4.2 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.
On this 10 mL syringe every small line is 0.2 mL.
Answer: V = 20.6 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.
Answer: R = 190 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.
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.
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).
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