Dose calculation
The nurse's calculations: unit conversions, percentage concentrations, the rule of three, weight-based doses, infusion rates in mL/h and drops per minute, syringe pumps and insulin, with prescriptions to work out and the traps behind errors.
- 33 cards
- 3 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- Scenarios
- Understand
A few cards from the deck
Mass conversions: what is it?
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1 g = 1,000 mg; 1 mg = 1,000 µg.
A conversion error multiplies or divides the dose by a thousand.
Prescription: paracetamol 15 mg/kg for a 20 kg child. What dose?
- 300 mg
- 150 mg
- 3 g
- 35 mg
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300 mg
Dose per kilo × weight: 15 × 20 = 300 mg.
Volume conversions: what is it?
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1 L = 1,000 mL.
Always write the unit next to the number.
Why is a high-risk dose calculation double-checked?
- To slow the care
- A single decimal or unit slip can multiply the dose tenfold
- It is not useful
- Because doctors are always wrong
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A single decimal or unit slip can multiply the dose tenfold
Insulin, potassium, heparin and morphine are high-risk drugs.
Percentage concentration: what is it?
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Grams per 100 mL: a 5 % solution holds 5 g per 100 mL.
It is the key to infusions and ampoules.
A vial holds 500 mg in 10 mL. 200 mg must be given. What volume?
- 2 mL
- 4 mL
- 5 mL
- 0.4 mL
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4 mL
200 × 10 / 500 = 4 mL.