Drill one: weight, safe range, surface area, reconstitution

Ninety seconds per strip. Cancel the units on the page.

Strip 1 — Pounds first

Heparin bolus ordered at 80 units/kg. Charted weight 176 lb. 176 lb × (1 kg / 2.2 lb) = 80 kg. 80 kg × 80 units/kg = 6400 units

Strip 2 — Volume from that order

Supply: 5000 units/mL. 6400 units × (1 mL / 5000 units) = 1.28 = 1.3 mL

Strip 3 — Safe range

Infant charted at 15.4 lb. Ordered: acetaminophen 80 mg for one dose. The reference dose for this drug in this patient is 10 to 15 mg/kg/dose. 15.4 lb × (1 kg / 2.2 lb) = 7 kg. Low: 7 kg × 10 mg/kg = 70 mg. High: 7 kg × 15 mg/kg = 105 mg. The ordered 80 mg sits between 70 mg and 105 mg: safe, proceed.

Strip 4 — Volume for that dose

Supply: 160 mg per 5 mL. 80 mg × (5 mL / 160 mg) = 400 ÷ 160 = 2.5 mL

Strip 5 — Body surface area

Mosteller: BSA in m² equals the square root of (height in cm × weight in kg ÷ 3600). Child 150 cm, 48 kg. (150 × 48) ÷ 3600 = 7200 ÷ 3600 = 2. Square root of 2 = 1.41 m², rounded to hundredths before use.

Strip 6 — Dose from body surface area

Order: 40 mg/m². 1.41 m² × 40 mg/m² = 56.4 mg Round the surface area once, then multiply once. Rounding twice moves the answer.

Strip 7 — Reconstitution and displacement

Vial: ceftriaxone 1 g powder. The label directs adding 9.6 mL of diluent to yield 10 mL, because the powder itself occupies 0.4 mL. Final concentration: 1000 mg ÷ 10 mL = 100 mg/mL. Order: 500 mg. 500 mg × (1 mL / 100 mg) = 5 mL The diluent volume and the final volume are different numbers, and the label gives you both. Withdraw against the final volume, never against the diluent volume.

Watch outpowder takes up room. The label already knew. Adding 10 mL to a vial that expects 9.6 mL dilutes every dose drawn from it.

Margin notereference doses appear here only inside a problem, never as a table. → BOOK 07 · P7

Takeawayweight, range, surface area and vial label are four separate gates, each checked before the arithmetic, not after.