Formula sheets, the key method steps for every topic and 6 practice problems, with full solutions at the back.
Which finding suggests magnesium sulfate toxicity?
Which finding is a sign that the placenta is separating in the third stage of labour?
An ampoule of epinephrine (adrenaline) is labelled 1:1000 (1 mg/mL). The prescription is 0.3 mg IM for anaphylaxis. What volume V do you draw up?
A patient weighs 61.6 lb. The prescription is 0.5 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?
A drip runs at 20 gtt/min through a set of 20 gtt/mL. How many millilitres V does the patient receive in 12 hours?
1500 mL was ordered over 8 hours. After 5 hours you find that 660 mL is still in the bag, and the order must still finish on time. By what percentage Δ must the original pump rate be increased?
Answer: C · Absent deep tendon reflexes
Loss of the patellar reflex is an early sign of toxicity, followed by respiratory depression and reduced consciousness. Brisk reflexes with clonus suggest worsening pre-eclampsia, not magnesium toxicity.
Answer: D · A gush of blood and lengthening of the cord
Signs of placental separation include a gush of blood, lengthening of the cord at the vulva, and a uterus that rises and becomes firm and globular. Severe pain or collapse suggests a complication such as inversion.
Answer: V = 0.3 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.
US labels now state mg/mL (1 mg/mL = 1:1000; 0.1 mg/mL = 1:10 000). Never give 1 mg/mL epinephrine IV push.
Answer: V = 0.35 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: V = 720 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.
Answer: Δ = 17.33 %
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.
Many hospitals allow such an adjustment up to 25% without a new order; check local policy.
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