Weight-Based Safe Ranges (Part 2) — practice set

Check yourself

50 review questions from the chapter. Try each one, then open the answer.

1. Question 351. Scenario: A 3-year-old child with a fever of 102.2°F (39°C) needs an antipyretic. Order: Acetaminophen 15 mg/kg/dose PO every 6 hours PRN for fever. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: The child weighs 32 lb. How many mg should be given per dose, and how many mL should the nurse draw up? Round the weight to the nearest tenth and the volume to the nearest tenth (oral liquid).

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   Correct answer: 217.5 mg per dose (6.8 mL) Setup (dimensional analysis): Weight: 32 lb × (1 kg / 2.2 lb) = 14.5 kg. Dose: 15 mg/kg × 14.5 kg = 217.5 mg. Volume: 217.5 mg × (5 mL / 160 mg). Raw calculation: 32 ÷ 2.2 = 14.545455 kg → 14.5 kg; 15 × 14.5 = 217.5 mg; 217.5 × (5/160) = 6.796875 mL Rounding: Weight rounded to the nearest tenth (14.5 kg). Volume 6.796875 mL is rounded to the nearest tenth for oral liquid. Final answer: 217.5 mg = 6.8 mL Rationale: Convert pounds to kilograms first, then multiply by the per-kilogram dose to get the mass (mg). Only after the mg dose is known do you convert to volume using the concentration. The 15 mg/kg/dose falls within the well-known educational acetaminophen reference range of 10–15 mg/kg/dose. Clinical pearl: Mass first, volume second — safety is judged in mg, but you administer in mL.

2. Question 352. Scenario: A 6-year-old child is being treated for acute otitis media. Order: Amoxicillin 40 mg/kg/day PO divided every 8 hours. Available: Amoxicillin oral suspension 250 mg/5 mL. Question: The child weighs 44 lb. How many mg should be given per dose, and how many mL per dose? Round the volume to the nearest tenth (oral liquid).

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   Correct answer: 266.7 mg per dose (5.3 mL) Setup (dimensional analysis): Weight: 44 lb × (1 kg / 2.2 lb) = 20 kg. Total daily dose: 40 mg/kg/day × 20 kg = 800 mg/day. Per dose (÷3): 800 mg ÷ 3 doses. Volume: per-dose mg × (5 mL / 250 mg). Raw calculation: 44 ÷ 2.2 = 20 kg; 40 × 20 = 800 mg/day; 800 ÷ 3 = 266.6667 mg/dose; 266.6667 × (5/250) = 5.3333 mL Rounding: Per-dose mg kept to the nearest tenth (266.7 mg). Volume 5.3333 mL rounded to the nearest tenth. Final answer: 266.7 mg = 5.3 mL per dose Rationale: A per-day range must first be divided by the number of daily doses to find each single dose. q8h means 3 doses per day. Dividing the 800 mg daily total by 3 gives ~266.7 mg per dose, then the concentration converts mass to volume. Clinical pearl: Read the slash — mg/kg/day is a 24-hour total, not a single dose; always divide by the number of doses first.

3. Question 353. Scenario: An adolescent is admitted with a serious infection and is started on an aminoglycoside. Order: Gentamicin 150 mg IV every 8 hours. Available: Vial: gentamicin 40 mg/mL. Question: The patient weighs 132 lb. Using a HYPOTHETICAL educational safe range of 5–7.5 mg/kg/day in divided doses every 8 hours, is this order SAFE or UNSAFE? Show the comparison.

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   Correct answer: SAFE — 450 mg/day equals the 300–450 mg/day safe range (at the maximum) Weight: 132 lb ÷ 2.2 = 60 kg Minimum safe dose (day): 5 mg/kg/day × 60 kg = 300 mg/day Maximum safe dose (day): 7.5 mg/kg/day × 60 kg = 450 mg/day Ordered dose: 150 mg/dose × 3 doses/day = 450 mg/day (150 mg per dose) Comparison: 300 ≤ 450 ≤ 450 ✓ — per-dose check: 100–150 mg/dose; 150 mg/dose is within this window. Conclusion: SAFE (ordered dose sits exactly at the maximum safe daily dose). Setup (dimensional analysis): 132 lb × (1 kg / 2.2 lb) = 60 kg; min = 5 × 60 = 300 mg/day; max = 7.5 × 60 = 450 mg/day; ordered = 150 × 3 = 450 mg/day. Raw calculation: 132 ÷ 2.2 = 60; 5 × 60 = 300; 7.5 × 60 = 450; 150 × 3 = 450 Rounding: Weight rounded to the nearest tenth; doses are whole numbers. Final answer: SAFE — 150 mg q8h = 450 mg/day, within the 300–450 mg/day hypothetical safe range (at the maximum). Rationale: When the range is per day, multiply the single dose by the number of daily doses before comparing. 150 mg × 3 = 450 mg/day, which equals the maximum safe daily dose. It is technically in range but deserves extra monitoring as a peak-renal-risk aminoglycoside at the upper limit. Clinical pearl: A dose exactly at the maximum is "safe but at the limit" — document the comparison and monitor renal function and drug levels per policy.

4. Question 354. Scenario: A child with methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is started on IV vancomycin. Order: Vancomycin 12 mg/kg/dose IV every 6 hours. Available: Vancomycin 500 mg vial reconstituted with 10 mL to yield 500 mg/20 mL (25 mg/mL). Question: The child weighs 55 lb. (a) Is 12 mg/kg/dose within the well-known educational vancomycin range of 10–15 mg/kg/dose? (b) How many mL should be administered for one dose? Round the volume to the nearest tenth.

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   Correct answer: SAFE (12 mg/kg/dose is within 10–15 mg/kg/dose); 12 mL Weight: 55 lb ÷ 2.2 = 25 kg Minimum safe dose: 10 mg/kg/dose × 25 kg = 250 mg/dose Maximum safe dose: 15 mg/kg/dose × 25 kg = 375 mg/dose Ordered dose: 12 mg/kg/dose × 25 kg = 300 mg/dose Comparison: 250 ≤ 300 ≤ 375 ✓ Conclusion: SAFE. Setup (dimensional analysis): 25 kg × 12 mg/kg = 300 mg. Volume: 300 mg × (20 mL / 500 mg). Raw calculation: 55 ÷ 2.2 = 25 kg; 12 × 25 = 300 mg; 300 × (20/500) = 12 mL Rounding: Weight to nearest tenth; volume 12 mL is a whole number (nearest tenth unchanged). Final answer: SAFE; administer 12 mL (300 mg). Rationale: 12 mg/kg/dose sits inside the 10–15 mg/kg/dose educational vancomycin window (250–375 mg/dose for this 25 kg child). After confirming safety in mg, convert to volume: 300 mg at 25 mg/mL equals 12 mL. Clinical pearl: Vancomycin is infused slowly and monitored (trough levels); confirm the reconstituted concentration on the label before drawing up, since final volume varies by how much diluent is added.

5. Question 355. Scenario: A 2-month-old infant with a congenital heart defect is to receive a loading dose of digoxin. Order: Digoxin 5 mcg/kg IV once (HYPOTHETICAL educational dose). Available: Digoxin 100 mcg/mL ampule. Question: The infant weighs 4.4 kg. How many mcg should be given, and how many mL? Which syringe is most appropriate to measure the volume? Round the volume to the nearest hundredth.

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   Correct answer: 22 mcg (0.22 mL); 1 mL tuberculin syringe Setup (dimensional analysis): Dose: 5 mcg/kg × 4.4 kg = 22 mcg. Volume: 22 mcg × (1 mL / 100 mcg). Raw calculation: 5 × 4.4 = 22 mcg; 22 ÷ 100 = 0.22 mL Rounding: Volume < 1 mL is rounded to the nearest hundredth (tuberculin-syringe precision). Final answer: 22 mcg = 0.22 mL; use a 1 mL tuberculin syringe. Rationale: mcg/kg is handled exactly like mg/kg — multiply the per-kg dose by weight. 22 mcg of a 100 mcg/mL solution is 0.22 mL, a sub-mL volume best measured with a 1 mL tuberculin (or insulin-style graduated) syringe for hundredth-mL precision. Clinical pearl: For volumes under 1 mL, a 1 mL tuberculin syringe (marked in 0.01 mL) is the right tool; a 3 mL syringe cannot reliably measure 0.22 mL.

6. Question 356. Scenario: A child in diabetic ketoacidosis (DKA) is started on a continuous regular insulin infusion. Order: Per HYPOTHETICAL protocol: regular insulin IV infusion at 0.05 units/kg/hr. Available: Regular insulin 100 units in 100 mL of 0.9% sodium chloride (1 unit/mL). Question: The child weighs 44 lb. Calculate the infusion rate in units/hr and mL/hr. Round to the nearest tenth.

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   Correct answer: 1 unit/hr (1 mL/hr) Setup (dimensional analysis): Weight: 44 lb × (1 kg / 2.2 lb) = 20 kg. Rate: 0.05 units/kg/hr × 20 kg = 1 units/hr. Volume: 1 units/hr × (1 mL / 1 unit). Raw calculation: 44 ÷ 2.2 = 20 kg; 0.05 × 20 = 1 units/hr; 1 × 1 = 1 mL/hr Rounding: Rate is exactly 1 unit/hr (1 mL/hr); nearest tenth unchanged. Final answer: 1 unit/hr = 1 mL/hr Rationale: Units/kg/hr works the same as mg/kg/hr — multiply the per-kg rate by weight. Because the admixture is 1 unit/mL, the numeric rate is identical in units/hr and mL/hr. Clinical pearl: With a 1 unit/mL insulin concentration the units/hr and mL/hr numbers match — but only for that concentration; always check the bag label.

7. Question 357. Scenario: A hypotensive adult in the ICU is started on a vasopressor infusion. Order: Per HYPOTHETICAL protocol: dopamine 5 mcg/kg/min IV infusion. Available: Dopamine 400 mg in 250 mL D5W. Question: The patient weighs 176 lb. Calculate the infusion rate in mL/hr. Round to the nearest whole number.

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   Correct answer: 15 mL/hr Setup (dimensional analysis): Weight: 176 lb × (1 kg / 2.2 lb) = 80 kg. mcg/min: 5 mcg/kg/min × 80 kg = 400 mcg/min. Convert to mg/hr: 400 mcg/min × 60 min/hr ÷ 1000 mcg/mg = 24 mg/hr. Concentration: 400 mg ÷ 250 mL = 1.6 mg/mL. Rate: 24 mg/hr ÷ 1.6 mg/mL. Raw calculation: 176 ÷ 2.2 = 80; 5 × 80 = 400 mcg/min; 400 × 60 ÷ 1000 = 24 mg/hr; 400 ÷ 250 = 1.6 mg/mL; 24 ÷ 1.6 = 15 mL/hr Rounding: Pump rate rounded to the nearest whole number (15 mL/hr). Final answer: 15 mL/hr Rationale: mcg/kg/min is a per-minute mass rate; convert it to mg/hr (×60, ÷1000), then divide by the mg/mL concentration to reach mL/hr. The standard 400 mg/250 mL dopamine admixture is 1.6 mg/mL. Clinical pearl: For vasoactive drips, memorize the two-step chain: mcg/kg/min → mg/hr → mL/hr; the bag concentration is the pivot.

8. Question 358. Scenario: A child is to receive a cephalosporin for a soft-tissue infection. Order: Cefazolin 25 mg/kg/day IV divided every 8 hours. Available: Cefazolin 500 mg vial. Question: The child weighs 33 lb. How many mg should be given per dose? Round to the nearest whole mg. A. 41.7 mg B. 125 mg C. 250 mg D. 375 mg

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   Correct answer: B) 125 mg Setup (dimensional analysis): Weight: 33 lb × (1 kg / 2.2 lb) = 15 kg. Daily total: 25 mg/kg/day × 15 kg = 375 mg/day. Per dose: 375 mg ÷ 3 doses. Raw calculation: 33 ÷ 2.2 = 15; 25 × 15 = 375 mg/day; 375 ÷ 3 = 125 mg/dose Rounding: 125 is already a whole number. Final answer: B) 125 mg per dose Rationale: Divide the total daily dose by the number of doses (q8h = 3). 375 mg/day ÷ 3 = 125 mg per dose. The distractors target the common mistakes of reporting the daily total (375) or mis-dividing (41.7 = ÷9, 250 = ÷1.5). Clinical pearl: q8h = 3 doses/day; q6h = 4; q12h = 2; daily = 1. Fix the doses-per-day before dividing a daily total.

9. Question 359. Scenario: A child in the emergency department has pain after a fracture reduction. Order: Ibuprofen 8 mg/kg/dose PO every 6 hours PRN for pain. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: The child weighs 55 lb. How many mL should the nurse administer? Round to the nearest tenth.

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   Correct answer: 10 mL Setup (dimensional analysis): Weight: 55 lb × (1 kg / 2.2 lb) = 25 kg. Dose: 8 mg/kg × 25 kg = 200 mg. Volume: 200 mg × (5 mL / 100 mg). Raw calculation: 55 ÷ 2.2 = 25 kg; 8 × 25 = 200 mg; 200 × (5/100) = 10 mL Rounding: 10 mL is a whole number (nearest tenth unchanged). Final answer: 10 mL Rationale: 8 mg/kg sits within the well-known educational ibuprofen range of 5–10 mg/kg/dose. At 100 mg/5 mL (20 mg/mL), 200 mg = 10 mL. Clinical pearl: 100 mg/5 mL means 20 mg/mL — half the work is recognizing the per-mL strength before setting up the fraction.

10. Question 360. Scenario: A toddler is receiving acetaminophen around the clock for post-operative pain. Order: Acetaminophen 160 mg PO every 4 hours (scheduled, 6 doses per day). Available: Acetaminophen 160 mg/5 mL suspension. Question: The child weighs 27 lb. Using the well-known educational range of 10–15 mg/kg/dose and a maximum of 75 mg/kg/day, is this regimen SAFE or UNSAFE? Show both the per-dose and per-day checks.

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    Correct answer: UNSAFE — per dose is within range but 960 mg/day exceeds the 922.5 mg/day maximum Weight: 27 lb ÷ 2.2 = 12.3 kg (rounded to tenth) Per-dose range: min 123 mg/dose; max 184.5 mg/dose Ordered per dose: 160 mg → within 123–184.5 mg/dose ✓ Ordered per day: 160 mg × 6 doses = 960 mg/day Maximum per day: 75 mg/kg/day × 12.3 kg = 922.5 mg/day Comparison: 960 > 922.5 ✗ Conclusion: UNSAFE — exceeds the daily acetaminophen maximum despite each single dose being in range. Setup (dimensional analysis): kg = 27 ÷ 2.2 = 12.3; per-dose window = 10×12.3 to 15×12.3 = 123–184.5 mg; day total = 160 × 6 = 960; day max = 75 × 12.3 = 922.5. Raw calculation: 27 ÷ 2.2 = 12.272727; 10 × 12.3 = 123; 15 × 12.3 = 184.5; 160 × 6 = 960; 75 × 12.3 = 922.5 Rounding: Weight rounded to the nearest tenth. Final answer: UNSAFE — hold and clarify with the provider; the 960 mg/day total exceeds the 922.5 mg/day maximum. Rationale: A drug can be safe per single dose yet toxic as a daily total. Each 160 mg dose is within the 10–15 mg/kg/dose window, but six doses in 24 hours (960 mg) exceed the 75 mg/kg/day cap (922.5 mg). Both the per-dose and per-day limits must be checked. Clinical pearl: For acetaminophen, always check the 24-hour total — not just each dose — because hepatotoxicity is dose-accumulating.

11. Question 361. Scenario: A child with community-acquired pneumonia is started on IV ceftriaxone. Order: Ceftriaxone 50 mg/kg/day IV once daily. Available: Ceftriaxone 1 g vial reconstituted to a concentration of 100 mg/mL. Question: The child weighs 66 lb. How many mg should be given, and how many mL? Round the volume to the nearest tenth.

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    Correct answer: 1500 mg (15 mL) Setup (dimensional analysis): Weight: 66 lb × (1 kg / 2.2 lb) = 30 kg. Dose: 50 mg/kg × 30 kg = 1500 mg. Volume: 1500 mg × (1 mL / 100 mg). Raw calculation: 66 ÷ 2.2 = 30 kg; 50 × 30 = 1500 mg; 1500 ÷ 100 = 15 mL Rounding: 15 mL is a whole number (nearest tenth unchanged). Final answer: 1500 mg (1.5 g) = 15 mL Rationale: Once-daily dosing means the per-dose amount equals the whole daily total. 50 mg/kg × 30 kg = 1500 mg; at 100 mg/mL that is 15 mL. Clinical pearl: A "once daily" weight-based order needs no division — the daily total is the single dose.

12. Question 362. Scenario: An adult with an acute pulmonary embolism is started on a low-molecular-weight heparin. Order: Enoxaparin 1 mg/kg SC every 12 hours (well-known educational treatment dose). Available: Enoxaparin 100 mg/mL prefilled syringe. Question: The patient weighs 165 lb. How many mg should be given per dose, and how many mL? Round the volume to the nearest hundredth.

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    Correct answer: 75 mg (0.75 mL) Setup (dimensional analysis): Weight: 165 lb × (1 kg / 2.2 lb) = 75 kg. Dose: 1 mg/kg × 75 kg = 75 mg. Volume: 75 mg × (1 mL / 100 mg). Raw calculation: 165 ÷ 2.2 = 75 kg; 1 × 75 = 75 mg; 75 ÷ 100 = 0.75 mL Rounding: Volume < 1 mL rounded to the nearest hundredth (0.75 mL). Final answer: 75 mg = 0.75 mL SC Rationale: Enoxaparin treatment dosing is 1 mg/kg every 12 hours; prophylaxis is typically a lower fixed dose (0.5 mg/kg or 40 mg) — always confirm the indication. 75 kg × 1 mg/kg = 75 mg = 0.75 mL of the 100 mg/mL syringe. Clinical pearl: The 100 mg/mL concentration gives a clean 1:1 conversion only for 1 mg/kg doses (kg → mg → ×0.01 mL); verify the actual concentration on the syringe.

13. Question 363. Scenario: A 3 kg neonate with hypotension requires an inotrope infusion. Order: Per HYPOTHETICAL protocol: epinephrine 0.1 mcg/kg/min IV infusion. Available: Epinephrine 0.6 mg in 100 mL of D5W. Question: Calculate the infusion rate in mL/hr. Round to the nearest tenth.

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    Correct answer: 3 mL/hr Setup (dimensional analysis): mcg/min: 0.1 mcg/kg/min × 3 kg = 0.3 mcg/min. mcg/hr: 0.3 × 60 = 18 mcg/hr. Concentration: 0.6 mg × 1000 mcg/mg ÷ 100 mL = 6 mcg/mL. Rate: 18 mcg/hr ÷ 6 mcg/mL. Raw calculation: 0.1 × 3 = 0.3 mcg/min; 0.3 × 60 = 18 mcg/hr; 0.6 × 1000 ÷ 100 = 6 mcg/mL; 18 ÷ 6 = 3 mL/hr Rounding: 3 mL/hr is a whole number (nearest tenth unchanged). Final answer: 3 mL/hr Rationale: The 0.6 mg/100 mL admixture is 6 mcg/mL. A 3 kg neonate at 0.1 mcg/kg/min needs 0.3 mcg/min = 18 mcg/hr, which is 3 mL/hr. Clinical pearl: Always convert the bag concentration to the same mass unit as the dose (mcg) before dividing — a mg/mcg mismatch is a classic 1000-fold error.

14. Question 364. Scenario: A child with heart failure and fluid overload needs a loop diuretic. Order: Furosemide 1.5 mg/kg/dose IV every 12 hours (HYPOTHETICAL educational dose). Available: Furosemide 10 mg/mL injection. Question: The child weighs 22 lb. How many mg should be given per dose, and how many mL? Round the volume to the nearest tenth.

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    Correct answer: 15 mg (1.5 mL) Setup (dimensional analysis): Weight: 22 lb × (1 kg / 2.2 lb) = 10 kg. Dose: 1.5 mg/kg × 10 kg = 15 mg. Volume: 15 mg × (1 mL / 10 mg). Raw calculation: 22 ÷ 2.2 = 10 kg; 1.5 × 10 = 15 mg; 15 ÷ 10 = 1.5 mL Rounding: Volume ≥ 1 mL rounded to the nearest tenth (1.5 mL). Final answer: 15 mg = 1.5 mL Rationale: Multiply the per-kg dose by weight to get mg, then divide by the 10 mg/mL concentration for volume. 1.5 mg/kg × 10 kg = 15 mg = 1.5 mL. Clinical pearl: Furosemide doses are small in pediatrics; a 10 mg/mL concentration keeps the volume modest and measurable.

15. Question 365. Scenario: A child with an anaerobic infection is started on IV clindamycin. Order: Clindamycin 300 mg IV every 6 hours. Available: Clindamycin 150 mg/mL injection. Question: The child weighs 48 lb. Using a HYPOTHETICAL educational safe range of 20–40 mg/kg/day in divided doses every 6 hours, is this order SAFE or UNSAFE? Show the comparison.

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    Correct answer: UNSAFE — 1200 mg/day (300 mg/dose) exceeds the 436–872 mg/day safe range Weight: 48 lb ÷ 2.2 = 21.8 kg (rounded to tenth) Minimum safe dose (day): 20 mg/kg/day × 21.8 kg = 436 mg/day Maximum safe dose (day): 40 mg/kg/day × 21.8 kg = 872 mg/day Ordered dose: 300 mg/dose × 4 doses/day = 1200 mg/day (300 mg per dose) Comparison: 1200 > 872 ✗ — per-dose max = 872 ÷ 4 = 218 mg/dose; 300 mg/dose > 218 mg/dose ✗ Conclusion: UNSAFE — exceeds the maximum safe dose by both the daily and the per-dose comparison. Setup (dimensional analysis): kg = 48 ÷ 2.2 = 21.8; min = 20 × 21.8 = 436; max = 40 × 21.8 = 872; ordered/day = 300 × 4 = 1200. Raw calculation: 48 ÷ 2.2 = 21.818182 → 21.8; 20 × 21.8 = 436; 40 × 21.8 = 872; 300 × 4 = 1200 Rounding: Weight rounded to the nearest tenth. Final answer: UNSAFE — hold the dose and clarify with the provider; 300 mg q6h (1200 mg/day) exceeds the 436–872 mg/day hypothetical range. Rationale: q6h = 4 doses/day, so the ordered total is 300 × 4 = 1200 mg/day, far above the 872 mg/day maximum. The per-dose check (300 mg vs a 218 mg maximum) confirms the error independently. Clinical pearl: When an order looks too high for the child's size, check BOTH the daily total and the single dose — a mismatch in either direction is a red flag.

16. Question 366. Scenario: A child receiving chemotherapy has nausea and vomiting. Order: Ondansetron 0.15 mg/kg IV every 8 hours PRN (well-known educational range 0.1–0.15 mg/kg/dose). Available: Ondansetron 4 mg/2 mL vial. Question: The child weighs 44 lb. How many mg should be given per dose, and how many mL? Round the volume to the nearest tenth.

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    Correct answer: 3 mg (1.5 mL) Setup (dimensional analysis): Weight: 44 lb × (1 kg / 2.2 lb) = 20 kg. Dose: 0.15 mg/kg × 20 kg = 3 mg. Volume: 3 mg × (2 mL / 4 mg). Raw calculation: 44 ÷ 2.2 = 20 kg; 0.15 × 20 = 3 mg; 3 × (2/4) = 1.5 mL Rounding: Volume ≥ 1 mL rounded to the nearest tenth (1.5 mL). Final answer: 3 mg = 1.5 mL Rationale: 0.15 mg/kg is the upper end of the 0.1–0.15 mg/kg/dose educational ondansetron range. 4 mg/2 mL is 2 mg/mL, so 3 mg = 1.5 mL. Clinical pearl: A concentration like "4 mg/2 mL" should be reduced to per-mL terms (2 mg/mL) before the fraction setup.

17. Question 367. Scenario: A nurse reviews two newly written medication orders for a patient with diabetes and post-operative pain. Order: Order 1: "Regular insulin 10.0 units SC now." Order 2: "Morphine .5 mg IV every 4 hours PRN severe pain." Available: Not applicable (order-safety/notation review). Question: Identify the error(s) in each order per the Joint Commission "Do Not Use" list, and state how each should be rewritten.

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    Correct answer: Order 1 has a trailing zero ("10.0 units"); Order 2 has a missing leading zero (".5 mg"). Rewrite as "10 units" and "0.5 mg." Setup (dimensional analysis): Not applicable (order-safety/notation review). Raw calculation: Not applicable. Rounding: Not applicable. Final answer: "Regular insulin 10 units SC now" and "Morphine 0.5 mg IV every 4 hours PRN severe pain." Rationale: The Joint Commission "Do Not Use" list prohibits a trailing zero after a decimal point ("10.0" can be misread as "100") and requires a leading zero before a decimal point ("0.5 mg," not ".5 mg," which can be misread as "5 mg"). Both errors risk a 10-fold dosing error. Insulin also must be written with "units" spelled out ("U" is on the Do Not Use list). Clinical pearl: Always a leading zero for decimals less than one; never a trailing zero. Spell "units" out fully — never "U" or "IU."

18. Question 368. Scenario: A nurse administered a vancomycin dose and is now verifying it against the child's weight. Order: The nurse gave vancomycin 240 mg IV (single dose). Available: Not applicable (verification/reverse calculation). Question: The child weighs 26.4 lb. How many mg/kg/dose did the child actually receive? Using the well-known educational vancomycin range of 10–15 mg/kg/dose, was this dose SAFE or UNSAFE?

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    Correct answer: 20 mg/kg/dose — UNSAFE (exceeds the 10–15 mg/kg/dose range) Weight: 26.4 lb ÷ 2.2 = 12 kg Minimum safe dose: 10 mg/kg/dose × 12 kg = 120 mg/dose Maximum safe dose: 15 mg/kg/dose × 12 kg = 180 mg/dose Ordered/Received dose: 240 mg/dose → 240 mg ÷ 12 kg = 20 mg/kg/dose Comparison: 20 mg/kg/dose > 15 mg/kg/dose ✗ (240 mg > 180 mg maximum) ✗ Conclusion: UNSAFE — the child received twice the maximum safe per-kg dose. Setup (dimensional analysis): kg = 26.4 ÷ 2.2 = 12; mg/kg received = 240 mg ÷ 12 kg. Raw calculation: 26.4 ÷ 2.2 = 12; 240 ÷ 12 = 20 mg/kg/dose Rounding: Weight to nearest tenth; mg/kg reported to the nearest tenth. Final answer: 20 mg/kg/dose — UNSAFE; notify the provider and complete an incident report per policy. Rationale: Reverse the usual calculation: divide the administered mg by the weight to recover the mg/kg actually given. 240 mg ÷ 12 kg = 20 mg/kg/dose, double the 15 mg/kg/dose maximum. This is a serious overdose that must be reported immediately. Clinical pearl: Re-deriving the mg/kg actually given (not just the ordered mg/kg) is a powerful double-check whenever a dose seems large for the child.

19. Question 369. Scenario: A neonate with suspected sepsis is started on IV ampicillin. Order: Ampicillin 100 mg IV every 6 hours. Available: Ampicillin 250 mg vial. Question: The infant weighs 8 lb. Using a HYPOTHETICAL educational safe range of 100–200 mg/kg/day in divided doses every 6 hours, is this order SAFE or UNSAFE? Show the comparison.

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    Correct answer: SAFE — 400 mg/day (100 mg/dose) is within the 360–720 mg/day safe range Weight: 8 lb ÷ 2.2 = 3.6 kg (rounded to tenth) Minimum safe dose (day): 100 mg/kg/day × 3.6 kg = 360 mg/day Maximum safe dose (day): 200 mg/kg/day × 3.6 kg = 720 mg/day Ordered dose: 100 mg/dose × 4 doses/day = 400 mg/day (100 mg per dose) Comparison: 360 ≤ 400 ≤ 720 ✓ — per-dose window 90–180 mg/dose; 100 mg/dose is within it ✓ Conclusion: SAFE. Setup (dimensional analysis): kg = 8 ÷ 2.2 = 3.6; min = 100 × 3.6 = 360; max = 200 × 3.6 = 720; ordered/day = 100 × 4 = 400. Raw calculation: 8 ÷ 2.2 = 3.636364 → 3.6; 100 × 3.6 = 360; 200 × 3.6 = 720; 100 × 4 = 400 Rounding: Weight rounded to the nearest tenth. Final answer: SAFE — 100 mg q6h (400 mg/day) falls within the 360–720 mg/day hypothetical range. Rationale: With a per-day range and q6h dosing, multiply the single dose by 4. 100 × 4 = 400 mg/day, which lies between the 360 mg/day minimum and 720 mg/day maximum. Clinical pearl: Neonatal doses are tiny but the safety logic is identical — convert weight, compute the window, compare the ordered total.

20. Question 370. Scenario: An adult with an acute deep vein thrombosis is started on a weight-based unfractionated heparin regimen. Order: Per HYPOTHETICAL protocol: heparin bolus 70 units/kg IV, then continuous infusion 17 units/kg/hr. Available: Heparin 5,000 units/mL vial (bolus); heparin 25,000 units in 500 mL (infusion). Question: The patient weighs 132 lb. Calculate (a) the bolus dose in units and mL, and (b) the infusion rate in units/hr and mL/hr. Round the bolus to the nearest hundredth and the infusion to the nearest tenth.

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    Correct answer: Bolus 4,200 units (0.84 mL); infusion 1,020 units/hr (20.4 mL/hr) Setup (dimensional analysis): Weight: 132 lb × (1 kg / 2.2 lb) = 60 kg. Bolus: 70 units/kg × 60 kg = 4200 units; 4200 units × (1 mL / 5,000 units). Infusion: 17 units/kg/hr × 60 kg = 1020 units/hr; 1020 units/hr × (500 mL / 25,000 units). Raw calculation: 132 ÷ 2.2 = 60; 70 × 60 = 4200 units; 4200 ÷ 5000 = 0.84 mL; 17 × 60 = 1020 units/hr; 1020 × (500/25000) = 20.4 mL/hr Rounding: Bolus volume < 1 mL rounded to the nearest hundredth (0.84 mL); infusion rate rounded to the nearest tenth (20.4 mL/hr). Final answer: Bolus 4,200 units = 0.84 mL; infusion 1,020 units/hr = 20.4 mL/hr Rationale: Weight-based heparin is given as a units/kg bolus plus a units/kg/hr infusion. The 5,000 units/mL vial gives the bolus volume; the 25,000 units/500 mL (50 units/mL) bag gives the infusion rate. Clinical pearl: Heparin bolus and infusion use different concentrations (5,000 units/mL vs 50 units/mL) — do not swap them; an independent double-check is standard for anticoagulants.

21. Question 371. Scenario: A child with an ear infection and fever needs an antipyretic. Order: Acetaminophen 12 mg/kg/dose PO every 4–6 hours PRN. Available: Acetaminophen 160 mg/5 mL. Question: The child weighs 33 lb. How many mg should be given per dose? A. 90 mg B. 150 mg C. 180 mg D. 360 mg

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    Correct answer: C) 180 mg Setup (dimensional analysis): Weight: 33 lb × (1 kg / 2.2 lb) = 15 kg. Dose: 12 mg/kg × 15 kg. Raw calculation: 33 ÷ 2.2 = 15 kg; 12 × 15 = 180 mg Rounding: 180 mg is a whole number. Final answer: C) 180 mg Rationale: 33 lb = 15 kg; 12 mg/kg × 15 kg = 180 mg. Distractors: 360 (doubled the per-kg), 150 (used 10 mg/kg), 90 (halved the weight). Clinical pearl: 12 mg/kg is a mid-range acetaminophen dose; 180 mg also happens to be just under one full 160 mg/5 mL teaspoon plus a partial.

22. Question 372. Scenario: A child with meningitis is started on high-dose IV ampicillin. Order: Ampicillin 100 mg/kg/day IV divided every 6 hours. Available: Ampicillin 500 mg vial reconstituted to 250 mg/mL. Question: The child weighs 20 kg. How many mg per dose, and how many mL per dose? Round the volume to the nearest tenth.

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    Correct answer: 500 mg per dose (2 mL) Setup (dimensional analysis): Daily total: 100 mg/kg/day × 20 kg = 2000 mg/day. Per dose: 2000 mg ÷ 4 doses = 500 mg. Volume: 500 mg × (1 mL / 250 mg). Raw calculation: 100 × 20 = 2000 mg/day; 2000 ÷ 4 = 500 mg/dose; 500 ÷ 250 = 2 mL Rounding: 2 mL is a whole number (nearest tenth unchanged). Final answer: 500 mg = 2 mL per dose Rationale: Divide the 2,000 mg daily total into 4 doses (q6h) = 500 mg each, then convert using the 250 mg/mL concentration to 2 mL. Clinical pearl: Reconstituting a 500 mg vial to 250 mg/mL yields 2 mL — a frequent exam pairing; check the final volume on the vial label.

23. Question 373. Scenario: A child with croup is given a single dose of a corticosteroid. Order: Dexamethasone 4 mg PO once. Available: Dexamethasone oral solution 1 mg/mL. Question: The child weighs 44 lb. Using a HYPOTHETICAL educational safe range of 0.1–0.3 mg/kg/dose, is this single dose SAFE or UNSAFE? Show the comparison.

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    Correct answer: SAFE — 4 mg is within the 2–6 mg/dose safe range Weight: 44 lb ÷ 2.2 = 20 kg Minimum safe dose: 0.1 mg/kg/dose × 20 kg = 2 mg/dose Maximum safe dose: 0.3 mg/kg/dose × 20 kg = 6 mg/dose Ordered dose: 4 mg/dose Comparison: 2 ≤ 4 ≤ 6 ✓ Conclusion: SAFE. Setup (dimensional analysis): kg = 44 ÷ 2.2 = 20; min = 0.1 × 20 = 2; max = 0.3 × 20 = 6; ordered = 4. Raw calculation: 44 ÷ 2.2 = 20; 0.1 × 20 = 2; 0.3 × 20 = 6 Rounding: Weight to nearest tenth; doses to nearest tenth. Final answer: SAFE — 4 mg once falls within the 2–6 mg/dose hypothetical range. Rationale: Croup corticosteroids are typically given as a single dose. 0.1–0.3 mg/kg for a 20 kg child yields a 2–6 mg window, and the ordered 4 mg sits comfortably inside it. Clinical pearl: Single-dose regimens still need the same min/max safety check — the fact that it is "just one dose" does not waive the calculation.

24. Question 374. Scenario: A child with post-operative pain needs IV opioid analgesia. Order: Morphine 0.1 mg/kg IV every 4 hours PRN (well-known educational range 0.1–0.2 mg/kg/dose). Available: Morphine 2 mg/mL vial. Question: The child weighs 33 lb. How many mL should be administered? Which syringe is most appropriate to measure this volume? Round the volume to the nearest hundredth. A. 1 mL syringe B. 3 mL syringe C. 5 mL syringe D. 10 mL syringe

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    Correct answer: 0.75 mL; A) 1 mL syringe Setup (dimensional analysis): Weight: 33 lb × (1 kg / 2.2 lb) = 15 kg. Dose: 0.1 mg/kg × 15 kg = 1.5 mg. Volume: 1.5 mg × (1 mL / 2 mg). Raw calculation: 33 ÷ 2.2 = 15 kg; 0.1 × 15 = 1.5 mg; 1.5 ÷ 2 = 0.75 mL Rounding: Volume < 1 mL rounded to the nearest hundredth (0.75 mL). Final answer: 0.75 mL using a 1 mL syringe. Rationale: 0.1 mg/kg × 15 kg = 1.5 mg; at 2 mg/mL that is 0.75 mL. A 1 mL syringe (marked in 0.01 mL) measures 0.75 mL accurately, whereas 3–10 mL syringes are too coarse for sub-mL opioid volumes. Clinical pearl: Match the syringe to the volume: <1 mL → 1 mL (tuberculin) syringe; ≥1 mL → 3 mL syringe; reserve larger syringes for larger volumes.

25. Question 375. Scenario: A child with a skin infection is started on IV cefazolin. Order: Cefazolin 50 mg/kg/day IV divided every 8 hours. Available: Cefazolin 1 g vial. Question: The child weighs 66 lb. How many mg should be given per dose? A. 500 mg B. 750 mg C. 1,000 mg D. 1,500 mg

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    Correct answer: A) 500 mg Setup (dimensional analysis): Weight: 66 lb × (1 kg / 2.2 lb) = 30 kg. Daily total: 50 mg/kg/day × 30 kg = 1500 mg/day. Per dose: 1500 mg ÷ 3. Raw calculation: 66 ÷ 2.2 = 30; 50 × 30 = 1500 mg/day; 1500 ÷ 3 = 500 mg/dose Rounding: 500 mg is a whole number. Final answer: A) 500 mg Rationale: 66 lb = 30 kg; 50 mg/kg/day × 30 kg = 1,500 mg/day; divided into 3 doses = 500 mg per dose. Distractors: 1,500 (daily total), 1,000 (÷1.5), 750 (÷2). Clinical pearl: The daily-total distractor is the most common wrong answer — always ask yourself "per dose or per day?" before selecting.

26. Question 376. Scenario: An adolescent with a migraine is prescribed a single dose of an NSAID. Order: Ketorolac 20 mg IV once. Available: Ketorolac 30 mg/mL injection. Question: The patient weighs 88 lb. Using a HYPOTHETICAL educational dose of 0.5 mg/kg/dose (maximum single dose 30 mg), is this order SAFE or UNSAFE? Show the comparison.

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    Correct answer: SAFE — 20 mg equals the calculated 0.5 mg/kg dose (within the 30 mg single-dose cap) Weight: 88 lb ÷ 2.2 = 40 kg Calculated dose: 0.5 mg/kg × 40 kg = 20 mg Maximum single dose (hypothetical): 30 mg Ordered dose: 20 mg Comparison: 20 mg = 20 mg ✓ and 20 mg ≤ 30 mg ✓ Conclusion: SAFE. Setup (dimensional analysis): kg = 88 ÷ 2.2 = 40; 0.5 × 40 = 20 mg. Raw calculation: 88 ÷ 2.2 = 40; 0.5 × 40 = 20 Rounding: Weight to nearest tenth; dose to nearest whole. Final answer: SAFE — 20 mg matches 0.5 mg/kg and is under the 30 mg single-dose cap. Rationale: Ketorolac is a weight-based single dose with an absolute maximum. 0.5 mg/kg × 40 kg = 20 mg, which equals the order and respects the 30 mg cap. Clinical pearl: Some weight-based drugs carry a flat maximum (cap) regardless of weight — check both the mg/kg result and the ceiling.

27. Question 377. Scenario: An ICU nurse is verifying what dose a running vasopressor is actually delivering. Order: Dopamine infusion running at 15 mL/hr. Available: Dopamine 400 mg in 250 mL D5W. Question: The patient weighs 80 kg. How many mcg/kg/min is the patient actually receiving? Round to the nearest tenth.

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    Correct answer: 5 mcg/kg/min Setup (dimensional analysis): Concentration: 400 mg ÷ 250 mL = 1.6 mg/mL. mg/hr: 15 mL/hr × 1.6 mg/mL = 24 mg/hr. mcg/min: 24 mg/hr × 1000 mcg/mg ÷ 60 min/hr = 400 mcg/min. Per kg: 400 mcg/min ÷ 80 kg. Raw calculation: 400 ÷ 250 = 1.6 mg/mL; 15 × 1.6 = 24 mg/hr; 24 × 1000 ÷ 60 = 400 mcg/min; 400 ÷ 80 = 5 mcg/kg/min Rounding: mcg/kg/min rounded to the nearest tenth (5). Final answer: 5 mcg/kg/min Rationale: Reverse the usual chain: mL/hr → mg/hr (× concentration) → mcg/min (×1000 ÷60) → mcg/kg/min (÷ weight). 15 mL/hr of a 1.6 mg/mL drip is 24 mg/hr = 400 mcg/min = 5 mcg/kg/min for an 80 kg patient. Clinical pearl: "What dose is this drip actually giving?" is answered by running the mcg/kg/min formula backward from the pump rate.

28. Question 378. Scenario: A nurse must weigh a child before a weight-based medication is given. Order: Weight obtained: 88 lb. Available: Not applicable (conversion only). Question: Convert 88 lb to kilograms. Round to the nearest tenth. A. 38.6 kg B. 40 kg C. 44 kg D. 193.6 kg

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    Correct answer: B) 40 kg Setup (dimensional analysis): kg = lb ÷ 2.2 = 88 lb × (1 kg / 2.2 lb). Raw calculation: 88 ÷ 2.2 = 40 kg Rounding: 40 kg is a whole number (nearest tenth unchanged). Final answer: B) 40 kg Rationale: 88 ÷ 2.2 = 40 kg exactly. Distractors: 193.6 (multiplied by 2.2 instead of dividing), 44 (halved), 38.6 (used 2.28 as divisor). Clinical pearl: Divide (not multiply) by 2.2 to go from pounds to kilograms — a backwards conversion is a frequent error that propagates into every downstream dose.

29. Question 379. Scenario: A child is to receive IV vancomycin for a bloodstream infection. Order: Vancomycin 10 mg/kg/dose IV every 6 hours. Available: Vancomycin 500 mg vial. Label: "Add 10 mL Sterile Water for Injection to yield 50 mg/mL." Question: The child weighs 33 lb. How many mg per dose, and how many mL should be drawn up? Round the volume to the nearest tenth.

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    Correct answer: 150 mg (3 mL) Setup (dimensional analysis): Weight: 33 lb × (1 kg / 2.2 lb) = 15 kg. Dose: 10 mg/kg × 15 kg = 150 mg. Volume: 150 mg × (1 mL / 50 mg). Raw calculation: 33 ÷ 2.2 = 15 kg; 10 × 15 = 150 mg; 150 ÷ 50 = 3 mL Rounding: 3 mL is a whole number (nearest tenth unchanged). Final answer: 150 mg = 3 mL Rationale: The label gives the final concentration directly (50 mg/mL after adding 10 mL), so no total-volume math is needed. 150 mg ÷ 50 mg/mL = 3 mL. Clinical pearl: Read the reconstitution label carefully — it may state the concentration (50 mg/mL) rather than the total final volume, which changes the setup.

30. Question 380. Scenario: An infant with heart failure is started on maintenance digoxin. Order: Digoxin 20 mcg PO every 12 hours. Available: Digoxin pediatric elixir 50 mcg/mL. Question: The infant weighs 6 kg. Using a HYPOTHETICAL educational safe range of 5–10 mcg/kg/day in two divided doses, is this order SAFE or UNSAFE? Show the comparison.

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    Correct answer: SAFE — 40 mcg/day (20 mcg/dose) is within the 30–60 mcg/day safe range Weight: 6 kg (given in kg) Minimum safe dose (day): 5 mcg/kg/day × 6 kg = 30 mcg/day Maximum safe dose (day): 10 mcg/kg/day × 6 kg = 60 mcg/day Ordered dose: 20 mcg/dose × 2 doses/day = 40 mcg/day (20 mcg per dose) Comparison: 30 ≤ 40 ≤ 60 ✓ — per-dose window 15–30 mcg/dose; 20 mcg/dose is within it ✓ Conclusion: SAFE. Setup (dimensional analysis): min = 5 × 6 = 30; max = 10 × 6 = 60; ordered/day = 20 × 2 = 40. Raw calculation: 5 × 6 = 30; 10 × 6 = 60; 20 × 2 = 40 Rounding: mcg doses kept as whole numbers. Final answer: SAFE — 20 mcg q12h (40 mcg/day) falls within the 30–60 mcg/day hypothetical range. Rationale: Digoxin is dosed in mcg/kg — the same workflow with a smaller unit. 5–10 mcg/kg/day for 6 kg is 30–60 mcg/day; the ordered 40 mcg/day is mid-range, and each 20 mcg dose is within the 15–30 mcg per-dose window. Clinical pearl: Never confuse mg and mcg — a "5 mg" reading of this order would be a 1,000-fold overdose; digoxin is a high-alert medication.

31. Question 381. Scenario: A nurse is checking a PRN acetaminophen order before giving it. Order: Acetaminophen 320 mg PO every 4 hours PRN. Available: Acetaminophen 160 mg/5 mL. Question: The child weighs 44 lb. How many mg/kg/dose does this order represent? Using the well-known educational range of 10–15 mg/kg/dose, is the order SAFE or UNSAFE?

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    Correct answer: 16 mg/kg/dose — UNSAFE (exceeds the 15 mg/kg/dose maximum) Weight: 44 lb ÷ 2.2 = 20 kg Minimum safe dose: 10 mg/kg/dose × 20 kg = 200 mg/dose Maximum safe dose: 15 mg/kg/dose × 20 kg = 300 mg/dose Ordered dose: 320 mg/dose → 320 mg ÷ 20 kg = 16 mg/kg/dose Comparison: 16 mg/kg/dose > 15 mg/kg/dose ✗ (320 mg > 300 mg maximum) ✗ Conclusion: UNSAFE — exceeds the per-dose maximum. Setup (dimensional analysis): kg = 44 ÷ 2.2 = 20; mg/kg = 320 mg ÷ 20 kg. Raw calculation: 44 ÷ 2.2 = 20; 320 ÷ 20 = 16 mg/kg/dose Rounding: Weight to nearest tenth; mg/kg to nearest tenth. Final answer: UNSAFE — 16 mg/kg/dose exceeds the 15 mg/kg/dose maximum; hold and clarify with the provider. Rationale: Divide the ordered mg by the weight to express it as mg/kg. 320 mg ÷ 20 kg = 16 mg/kg/dose, above the 15 mg/kg/dose upper limit. The dose would need to be ≤300 mg to be within range. Clinical pearl: Converting a fixed mg order into mg/kg (dividing by weight) is the fastest way to spot an oversized PRN dose.

32. Question 382. Scenario: An adult on a weight-based heparin infusion has a subtherapeutic aPTT. Order: Per HYPOTHETICAL protocol: heparin infusion 18 units/kg/hr; if aPTT is subtherapeutic, increase by 2 units/kg/hr and recheck. Available: Heparin 25,000 units in 500 mL (50 units/mL). Question: The patient weighs 70 kg. The aPTT is subtherapeutic, so the rate is increased by 2 units/kg/hr. What is the new infusion rate in units/hr and mL/hr? Round to the nearest whole number.

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    Correct answer: 1,400 units/hr (28 mL/hr) Setup (dimensional analysis): New rate: (18 + 2) units/kg/hr × 70 kg = 1400 units/hr. Volume: 1400 units/hr × (500 mL / 25,000 units). Raw calculation: (18 + 2) × 70 = 1400 units/hr; 1400 × (500/25000) = 28 mL/hr Rounding: mL/hr rounded to the nearest whole number (28 mL/hr). Final answer: 1,400 units/hr = 28 mL/hr Rationale: The protocol adjustment adds 2 units/kg/hr to the baseline 18 units/kg/hr, giving 20 units/kg/hr × 70 kg = 1,400 units/hr. At 50 units/mL, that is 28 mL/hr. Clinical pearl: Protocol titration is still a units/kg calculation — read the adjustment step, apply it to the per-kg rate, then convert to mL/hr.

33. Question 383. Scenario: A child with a high fever needs an antipyretic. Order: Ibuprofen 10 mg/kg/dose PO every 8 hours PRN. Available: Ibuprofen 100 mg/5 mL. Question: The child weighs 44 lb. How many mg should be given per dose?

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    Correct answer: 200 mg Setup (dimensional analysis): Weight: 44 lb × (1 kg / 2.2 lb) = 20 kg. Dose: 10 mg/kg × 20 kg. Raw calculation: 44 ÷ 2.2 = 20 kg; 10 × 20 = 200 mg Rounding: 200 mg is a whole number. Final answer: 200 mg Rationale: 10 mg/kg is the top of the well-known educational ibuprofen range (5–10 mg/kg/dose). 10 × 20 kg = 200 mg. Clinical pearl: At the upper end of a range, confirm the dose is appropriate for the indication and that daily limits are not exceeded.

34. Question 384. Scenario: A child needs an antipyretic for a persistent fever. Order: Acetaminophen 15 mg/kg/dose PO now. Available: Acetaminophen 160 mg/5 mL. Question: The child weighs 30 kg. How many mL should be administered? Round to the nearest tenth. A. 4.7 mL B. 9.4 mL C. 14.1 mL D. 18.8 mL

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    Correct answer: C) 14.1 mL Setup (dimensional analysis): Dose: 15 mg/kg × 30 kg = 450 mg. Volume: 450 mg × (5 mL / 160 mg). Raw calculation: 15 × 30 = 450 mg; 450 × (5/160) = 14.0625 mL Rounding: Volume ≥ 1 mL rounded to the nearest tenth (14.1 mL). Final answer: C) 14.1 mL Rationale: 15 mg/kg × 30 kg = 450 mg; 450 mg × (5 mL/160 mg) = 14.0625 mL → 14.1 mL. Distractors reflect halving the dose (4.7), using 10 mg/kg (9.4), or rounding errors (18.8). Clinical pearl: 450 mg is a large single dose — always pair the mL with a reasonableness check against the child's weight and the per-kg range.

35. Question 385. Scenario: An adult in septic shock is started on a vasopressor infusion. Order: Per HYPOTHETICAL protocol: norepinephrine 0.1 mcg/kg/min IV infusion, titrated to effect. Available: Norepinephrine 4 mg in 250 mL D5W. Question: The patient weighs 60 kg. (a) Calculate the infusion rate in mL/hr (round to the nearest tenth). (b) If the infusion is started at 0800, at what time will the 250 mL bag be empty?

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    Correct answer: 22.5 mL/hr; bag empty at about 1907 Setup (dimensional analysis): mcg/min: 0.1 mcg/kg/min × 60 kg = 6 mcg/min. mcg/hr: 6 × 60 = 360 mcg/hr. Concentration: 4 mg × 1000 mcg/mg ÷ 250 mL = 16 mcg/mL. Rate: 360 ÷ 16.0. Duration: 250 mL ÷ rate. Raw calculation: 0.1 × 60 = 6 mcg/min; 6 × 60 = 360 mcg/hr; 4 × 1000 ÷ 250 = 16 mcg/mL; 360 ÷ 16 = 22.5 mL/hr; 250 ÷ 22.5 = 11.1111 hr Rounding: Rate to the nearest tenth (22.5 mL/hr); 11.1111 hr ≈ 11 hr 7 min. Final answer: 22.5 mL/hr; 0800 + 11 hr 7 min = about 1907 Rationale: A 4 mg/250 mL bag is 16 mcg/mL. At 0.1 mcg/kg/min a 60 kg patient needs 6 mcg/min = 360 mcg/hr = 22.5 mL/hr. A 250 mL bag at 22.5 mL/hr lasts about 11.1 hours, so an 0800 start empties near 1907. Clinical pearl: Convert the 0.1 hr fraction to minutes (0.111 hr × 60 = ~7 min) when adding infusion duration to a clock time.

36. Question 386. Scenario: A child with a Clostridioides difficile infection is started on IV metronidazole. Order: Metronidazole 150 mg IV every 6 hours. Available: Metronidazole 500 mg/100 mL premixed bag. Question: The child weighs 44 lb. Using a HYPOTHETICAL educational safe range of 30 mg/kg/day in divided doses every 6 hours, is this order SAFE or UNSAFE? Show the comparison.

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    Correct answer: SAFE — 600 mg/day (150 mg/dose) exactly matches the 600 mg/day safe range Weight: 44 lb ÷ 2.2 = 20 kg Safe daily dose: 30 mg/kg/day × 20 kg = 600 mg/day → 150 mg/dose (÷4) Ordered dose: 150 mg/dose × 4 doses/day = 600 mg/day (150 mg per dose) Comparison: 600 mg/day = 600 mg/day ✓ — per dose: 150 mg = 150 mg ✓ Conclusion: SAFE (ordered dose exactly equals the calculated safe dose). Setup (dimensional analysis): kg = 44 ÷ 2.2 = 20; day = 30 × 20 = 600 mg/day; per dose = 600 ÷ 4 = 150 mg; ordered/day = 150 × 4 = 600 mg. Raw calculation: 44 ÷ 2.2 = 20; 30 × 20 = 600; 600 ÷ 4 = 150; 150 × 4 = 600 Rounding: Weight to nearest tenth; doses whole numbers. Final answer: SAFE — 150 mg q6h (600 mg/day) equals the 600 mg/day hypothetical dose. Rationale: The hypothetical range is a single 30 mg/kg/day value, so the expected daily total is 30 × 20 = 600 mg/day, or 150 mg q6h. The order matches exactly. Clinical pearl: A single mg/kg/day figure is a target, not a range — compute it and confirm each divided dose matches.

37. Question 387. Scenario: A child with a severe infection is started on once-daily IV ceftriaxone. Order: Ceftriaxone 75 mg/kg/day IV once daily. Available: Ceftriaxone 1 g vial reconstituted to a total volume of 10 mL (100 mg/mL). Question: The child weighs 33 lb. How many mg should be given, and how many mL? Round the volume to the nearest tenth.

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    Correct answer: 1,125 mg (11.3 mL) Setup (dimensional analysis): Weight: 33 lb × (1 kg / 2.2 lb) = 15 kg. Dose: 75 mg/kg × 15 kg = 1125 mg. Volume: 1125 mg × (10 mL / 1000 mg). Raw calculation: 33 ÷ 2.2 = 15 kg; 75 × 15 = 1125 mg; 1125 × (10/1000) = 11.25 mL Rounding: Volume ≥ 1 mL rounded to the nearest tenth (11.3 mL). Final answer: 1,125 mg = 11.3 mL Rationale: Once-daily dosing means the whole daily total is given at once. 75 × 15 kg = 1,125 mg. The 1 g/10 mL vial is 100 mg/mL, so 1,125 mg = 11.25 mL → 11.3 mL. Clinical pearl: When the label gives total volume ("1 g in 10 mL"), convert to mg/mL (100 mg/mL) or set up the fraction with 10 mL/1,000 mg directly.

38. Question 388. Scenario: A nurse reviews a discharge medication list for an older adult. Order: "Acetaminophen 325 mg PO QD for arthritis." Available: Not applicable (order-safety/notation review). Question: Identify the abbreviation that must be rewritten per the Joint Commission "Do Not Use" list, and write the corrected order.

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    Correct answer: "QD" must be written as "daily" — "Acetaminophen 325 mg PO daily." Setup (dimensional analysis): Not applicable (order-safety/notation review). Raw calculation: Not applicable. Rounding: Not applicable. Final answer: "Acetaminophen 325 mg PO daily." Rationale: The Joint Commission "Do Not Use" list prohibits "Q.D."/"QD"/"q.d."/"qd" (meaning daily) because the period can be mistaken for an "O" and misread as "QOD" (every other day) — a doubling error. Write "daily" instead. Clinical pearl: For every order on the Do Not Use list there is an unambiguous plain-English substitute: QD → daily, QOD → every other day, U → units, IU → international units.

39. Question 389. Scenario: An ICU nurse is verifying the insulin dose a patient is actually receiving. Order: Regular insulin infusion running at 6 mL/hr. Available: Regular insulin 100 units in 100 mL of 0.9% sodium chloride (1 unit/mL). Question: The patient weighs 60 kg. How many units/kg/hr is the patient receiving? Round to the nearest hundredth.

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    Correct answer: 0.1 units/kg/hr Setup (dimensional analysis): units/hr: 6 mL/hr × (1 unit / 1 mL) = 6 units/hr. Per kg: 6 units/hr ÷ 60 kg. Raw calculation: 6 × 1 = 6 units/hr; 6 ÷ 60 = 0.1 units/kg/hr Rounding: units/kg/hr rounded to the nearest hundredth (0.1). Final answer: 0.1 units/kg/hr Rationale: At 1 unit/mL, 6 mL/hr is 6 units/hr. Divided by 60 kg, that is 0.1 units/kg/hr — a common DKA infusion starting rate. Clinical pearl: When the concentration is 1 unit/mL, mL/hr and units/hr are numerically identical; the per-kg rate still requires dividing by weight.

40. Question 390. Scenario: A nurse is checking the upper limit of a vancomycin dose before administration. Order: Vancomycin IV every 6 hours. Available: Not applicable (maximum-dose calculation). Question: The child weighs 26.4 lb. Using the well-known educational vancomycin range of 10–15 mg/kg/dose, what is the MAXIMUM safe single dose in mg? A. 120 mg B. 150 mg C. 180 mg D. 240 mg

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    Correct answer: C) 180 mg Setup (dimensional analysis): Weight: 26.4 lb × (1 kg / 2.2 lb) = 12 kg. Maximum: 15 mg/kg/dose × 12 kg. Raw calculation: 26.4 ÷ 2.2 = 12 kg; 15 × 12 = 180 mg Rounding: 180 mg is a whole number. Final answer: C) 180 mg Rationale: The maximum is the high end of the range (15 mg/kg/dose) × weight. 15 × 12 kg = 180 mg. Distractors: 120 (minimum = 10 mg/kg), 240 (20 mg/kg), 150 (12.5 mg/kg). Clinical pearl: "Maximum safe dose" = high end of range × kg; "minimum safe dose" = low end × kg — know which end the question asks for.

41. Question 391. Scenario: A toddler with fever and discomfort is receiving ibuprofen around the clock. Order: Ibuprofen 100 mg PO every 6 hours (4 doses per day). Available: Ibuprofen 100 mg/5 mL suspension. Question: The child weighs 28 lb. Using the well-known educational range of 5–10 mg/kg/dose and a maximum of 40 mg/kg/day, determine whether the regimen is SAFE or UNSAFE (check both per dose and per day). If safe, calculate the mL per dose (round to the nearest tenth).

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    Correct answer: SAFE — 100 mg/dose and 400 mg/day are both within range; 5 mL per dose Weight: 28 lb ÷ 2.2 = 12.7 kg (rounded to tenth) Minimum safe dose: 5 mg/kg/dose × 12.7 kg = 63.5 mg/dose Maximum safe dose: 10 mg/kg/dose × 12.7 kg = 127 mg/dose Ordered per dose: 100 mg → within 63.5–127 mg/dose ✓ Ordered per day: 100 mg × 4 = 400 mg/day Maximum per day: 40 mg/kg/day × 12.7 kg = 508 mg/day Comparison: 400 ≤ 508 ✓ Conclusion: SAFE. Setup (dimensional analysis): kg = 28 ÷ 2.2 = 12.7; per-dose window = 5×12.7 to 10×12.7 = 63.5–127 mg; day = 100 × 4 = 400; day max = 40 × 12.7 = 508; volume = 100 mg × (5 mL / 100 mg). Raw calculation: 28 ÷ 2.2 = 12.727273 → 12.7; 5 × 12.7 = 63.5; 10 × 12.7 = 127; 100 × 4 = 400; 40 × 12.7 = 508; 100 × (5/100) = 5 mL Rounding: Weight to nearest tenth; volume 5 mL is a whole number (nearest tenth unchanged). Final answer: SAFE; administer 5 mL (100 mg) per dose. Rationale: This integrates the full workflow: each 100 mg dose is within the 63.5–127 mg per-dose window, and the 400 mg daily total is under the 508 mg/day cap. Only then do we compute volume — 100 mg at 20 mg/mL is 5 mL. Clinical pearl: A complete safe-range question checks per-dose AND per-day limits, then converts to volume — in that order, every time.

42. Question 392. Scenario: A child in status epilepticus requires a loading dose of an anticonvulsant. Order: Fosphenytoin 20 mg/kg IV once (HYPOTHETICAL educational loading range 15–20 mg/kg). Available: Fosphenytoin 50 mg PE/mL injection. Question: The child weighs 20 kg. How many mg should be given, and how many mL? Round the volume to the nearest tenth.

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    Correct answer: 400 mg (8 mL) Setup (dimensional analysis): Dose: 20 mg/kg × 20 kg = 400 mg. Volume: 400 mg × (1 mL / 50 mg). Raw calculation: 20 × 20 = 400 mg; 400 ÷ 50 = 8 mL Rounding: 8 mL is a whole number (nearest tenth unchanged). Final answer: 400 mg = 8 mL Rationale: A loading dose is a single, larger dose to reach therapeutic levels quickly; 20 mg/kg is the top of the 15–20 mg/kg loading range. 20 × 20 kg = 400 mg; at 50 mg/mL that is 8 mL. Clinical pearl: Loading doses are given once and are intentionally at the high end of the range — but still must be checked against the mg/kg ceiling before administration.

43. Question 393. Scenario: An infant is to begin maintenance digoxin therapy. Order: Digoxin 8 mcg/kg/day PO divided every 12 hours (HYPOTHETICAL educational dose). Available: Digoxin pediatric elixir 50 mcg/mL. Question: The infant weighs 5 kg. How many mcg should be given per dose? A. 10 mcg B. 20 mcg C. 40 mcg D. 80 mcg

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    Correct answer: B) 20 mcg Setup (dimensional analysis): Daily total: 8 mcg/kg/day × 5 kg = 40 mcg/day. Per dose: 40 mcg ÷ 2 doses. Raw calculation: 8 × 5 = 40 mcg/day; 40 ÷ 2 = 20 mcg/dose Rounding: 20 mcg is a whole number. Final answer: B) 20 mcg Rationale: 8 mcg/kg/day × 5 kg = 40 mcg/day, divided into two doses (q12h) = 20 mcg per dose. Distractors: 40 (daily total), 80 (failed to divide AND doubled), 10 (÷4). Clinical pearl: With digoxin, the mcg/day total and the mcg/dose are easy to confuse — always state both and label which is which.

44. Question 394. Scenario: A child is to receive a weight-based medication. Order: Medication X 4 mg/kg/dose PO (HYPOTHETICAL educational dose). Available: Medication X 20 mg/mL oral solution. Question: The child weighs 55 lb. How many mg should be given per dose?

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    Correct answer: 100 mg Setup (dimensional analysis): Weight: 55 lb × (1 kg / 2.2 lb) = 25 kg. Dose: 4 mg/kg × 25 kg. Raw calculation: 55 ÷ 2.2 = 25 kg; 4 × 25 = 100 mg Rounding: 100 mg is a whole number. Final answer: 100 mg Rationale: 55 lb = 25 kg; 4 mg/kg × 25 kg = 100 mg. Clinical pearl: When the question asks only for mg (not mL), stop at the mass — do not convert to volume unless the question asks for it.

45. Question 395. Scenario: A neonate with sepsis is started on IV cefotaxime. Order: Cefotaxime 200 mg IV every 6 hours. Available: Cefotaxime 500 mg vial. Question: The infant weighs 9 lb. Using a HYPOTHETICAL educational safe range of 100–200 mg/kg/day in divided doses every 6 hours, is this order SAFE or UNSAFE? Show the comparison.

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    Correct answer: SAFE — 800 mg/day (200 mg/dose) is within the 410–820 mg/day safe range Weight: 9 lb ÷ 2.2 = 4.1 kg (rounded to tenth) Minimum safe dose (day): 100 mg/kg/day × 4.1 kg = 410 mg/day Maximum safe dose (day): 200 mg/kg/day × 4.1 kg = 820 mg/day Ordered dose: 200 mg/dose × 4 doses/day = 800 mg/day (200 mg per dose) Comparison: 410 ≤ 800 ≤ 820 ✓ — per-dose window 102.5–205 mg/dose; 200 mg/dose is within it ✓ Conclusion: SAFE (near the maximum). Setup (dimensional analysis): kg = 9 ÷ 2.2 = 4.1; min = 100 × 4.1 = 410; max = 200 × 4.1 = 820; ordered/day = 200 × 4 = 800. Raw calculation: 9 ÷ 2.2 = 4.090909 → 4.1; 100 × 4.1 = 410; 200 × 4.1 = 820; 200 × 4 = 800 Rounding: Weight rounded to the nearest tenth. Final answer: SAFE — 200 mg q6h (800 mg/day) is within the 410–820 mg/day hypothetical range. Rationale: 9 lb = 4.1 kg; the safe daily window is 410–820 mg. The ordered 200 mg q6h totals 800 mg/day, which is within range (near the top). Clinical pearl: A dose just under the maximum is safe but warrants the same monitoring vigilance as one at the limit.

46. Question 396. Scenario: An adolescent in diabetic ketoacidosis (DKA) is on a two-stage insulin infusion protocol. Order: Per HYPOTHETICAL protocol: regular insulin 0.1 units/kg/hr until serum glucose < 250 mg/dL, then reduce to 0.05 units/kg/hr. Available: Regular insulin 100 units in 100 mL of 0.9% sodium chloride (1 unit/mL). Question: The patient weighs 66 kg. The serum glucose is now 200 mg/dL, so the nurse reduces the rate per protocol. What is the new infusion rate in units/hr and mL/hr? Round to the nearest tenth.

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    Correct answer: 3.3 units/hr (3.3 mL/hr) Setup (dimensional analysis): New rate: 0.05 units/kg/hr × 66 kg = 3.3 units/hr. Volume: 3.3 units/hr × (1 mL / 1 unit). Raw calculation: 0.05 × 66 = 3.3 units/hr; 3.3 × 1 = 3.3 mL/hr Rounding: Rate rounded to the nearest tenth (3.3). Final answer: 3.3 units/hr = 3.3 mL/hr Rationale: The protocol drops the insulin rate by half once glucose falls below 250 mg/dL: 0.05 units/kg/hr × 66 kg = 3.3 units/hr. With a 1 unit/mL admixture, the mL/hr figure is identical. Clinical pearl: DKA insulin is titrated on glucose AND anion gap trends — never change the rate on a single value alone; follow the protocol's thresholds.

47. Question 397. Scenario: A child with a serious Gram-positive infection needs IV vancomycin. Order: Vancomycin 15 mg/kg/dose IV every 6 hours. Available: Vancomycin 1 g vial. Label: "Add 20 mL Sterile Water for Injection to yield 50 mg/mL." Question: The child weighs 40 lb. How many mg per dose, and how many mL should be drawn up? Round the weight to the nearest tenth and the volume to the nearest tenth.

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    Correct answer: 273 mg (5.5 mL) Setup (dimensional analysis): Weight: 40 lb × (1 kg / 2.2 lb) = 18.2 kg. Dose: 15 mg/kg × 18.2 kg = 273 mg. Volume: 273 mg × (1 mL / 50 mg). Raw calculation: 40 ÷ 2.2 = 18.181818 → 18.2 kg; 15 × 18.2 = 273 mg; 273 ÷ 50 = 5.46 mL Rounding: Weight to nearest tenth (18.2 kg); volume 5.46 mL rounded to the nearest tenth (5.5 mL). Final answer: 273 mg = 5.5 mL Rationale: 40 lb ÷ 2.2 = 18.2 kg; 15 mg/kg × 18.2 kg = 273 mg. The label's 50 mg/mL concentration converts that to 5.46 mL → 5.5 mL. Clinical pearl: "Add 20 mL to yield 50 mg/mL" states the concentration directly; multiply by 50 to see the vial's total drug (1 g), which you can use to sanity-check the math.

48. Question 398. Scenario: An adult with cardiogenic shock is started on a low-dose vasopressor infusion. Order: Per HYPOTHETICAL protocol: dopamine 3 mcg/kg/min IV infusion. Available: Dopamine 400 mg in 250 mL D5W. Question: The patient weighs 198 lb. Calculate the infusion rate in mL/hr. Round to the nearest tenth.

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    Correct answer: 10.1 mL/hr Setup (dimensional analysis): Weight: 198 lb × (1 kg / 2.2 lb) = 90 kg. mcg/min: 3 mcg/kg/min × 90 kg = 270 mcg/min. mg/hr: 270 mcg/min × 60 min/hr ÷ 1000 mcg/mg = 16.2 mg/hr. Concentration: 400 mg ÷ 250 mL = 1.6 mg/mL. Rate: 16.2 mg/hr ÷ 1.6 mg/mL. Raw calculation: 198 ÷ 2.2 = 90; 3 × 90 = 270 mcg/min; 270 × 60 ÷ 1000 = 16.2 mg/hr; 400 ÷ 250 = 1.6 mg/mL; 16.2 ÷ 1.6 = 10.125 mL/hr Rounding: Pump rate rounded to the nearest tenth (10.1 mL/hr). Final answer: 10.1 mL/hr Rationale: 198 lb = 90 kg; 3 mcg/kg/min = 270 mcg/min = 16.2 mg/hr. At 1.6 mg/mL, that is 10.125 mL/hr → 10.1 mL/hr. Clinical pearl: The 400 mg/250 mL dopamine bag (1.6 mg/mL) is a fixed standard — recognize it so the mL/hr result can be mentally cross-checked.

49. Question 399. Scenario: A child is being treated for high-dose (severe) otitis media. Order: Amoxicillin 500 mg PO every 8 hours. Available: Amoxicillin 400 mg/5 mL suspension. Question: The child weighs 48 lb. Using the well-known educational high-dose amoxicillin range of 80–90 mg/kg/day in divided doses every 8 hours, work through the 7-step safe-dose workflow and state whether the order is SAFE or UNSAFE.

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    Correct answer: UNSAFE — 68.8 mg/kg/day is below the 80–90 mg/kg/day range (underdose) Weight (Step 1): 48 lb ÷ 2.2 = 21.8 kg (rounded to tenth) Read the range (Step 2): 80–90 mg/kg/day (a daily range, divided q8h). Minimum safe dose (Step 3): 80 mg/kg/day × 21.8 kg = 1,744 mg/day Maximum safe dose (Step 4): 90 mg/kg/day × 21.8 kg = 1,962 mg/day Ordered dose (Step 5): 500 mg/dose × 3 doses/day = 1500 mg/day → 1500 ÷ 21.8 = 68.8 mg/kg/day Comparison (Step 6): 68.8 mg/kg/day < 80 mg/kg/day ✗ Conclusion (Step 7): UNSAFE — the ordered total is BELOW the minimum (an underdose for high-dose otitis media). Setup (dimensional analysis): kg = 48 ÷ 2.2 = 21.8; min = 80 × 21.8 = 1744; max = 90 × 21.8 = 1962; ordered/day = 500 × 3 = 1500; mg/kg/day = 1500 ÷ 21.8. Raw calculation: 48 ÷ 2.2 = 21.818182 → 21.8; 80 × 21.8 = 1744; 90 × 21.8 = 1962; 500 × 3 = 1500; 1500 ÷ 21.8 = 68.807 mg/kg/day Rounding: Weight to nearest tenth; mg/kg/day to nearest tenth. Final answer: UNSAFE (underdose) — 1,500 mg/day = 68.8 mg/kg/day, below the 80–90 mg/kg/day range; clarify with the provider. Rationale: Unsafe is not always "too much." The 7-step workflow compares the ordered mg/kg/day (68.8) against the 80–90 mg/kg/day window and finds it falls below the minimum — an underdose that would undertreat the infection. Both under- and over-dosing require provider clarification. Clinical pearl: High-dose amoxicillin (80–90 mg/kg/day) for resistant otitis media is DOUBLE the standard dose — failing to recognize the indication-specific range causes underdosing.

50. Question 400. Scenario: A 4-year-old child with a urinary tract infection is prescribed an oral cephalosporin. Order: Cefdinir 7 mg/kg/dose PO every 12 hours. Available: Cefdinir 125 mg/5 mL oral suspension. Question: The child weighs 35 lb. (a) Confirm the dose is within the well-known educational cefdinir total of 14 mg/kg/day (7 mg/kg/dose q12h) — state mg/kg/dose and mg/kg/day. (b) Calculate the mL per dose. Round the weight to the nearest tenth and the volume to the nearest tenth.

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    Correct answer: 7 mg/kg/dose = 14 mg/kg/day (SAFE); 4.5 mL per dose Weight: 35 lb ÷ 2.2 = 15.9 kg (rounded to tenth) Ordered per dose: 7 mg/kg/dose × 15.9 kg = 111.3 mg/dose Ordered per day: 111.3 mg × 2 doses = 222.6 mg/day → 222.6 ÷ 15.9 = 14 mg/kg/day Comparison: 7 mg/kg/dose and 14 mg/kg/day match the educational reference ✓ Conclusion: SAFE. Setup (dimensional analysis): kg = 35 ÷ 2.2 = 15.9; dose = 7 × 15.9 = 111.3 mg; day = 111.3 × 2 = 222.6 mg; volume = 111.3 mg × (5 mL / 125 mg). Raw calculation: 35 ÷ 2.2 = 15.909091 → 15.9; 7 × 15.9 = 111.3 mg; 111.3 × 2 = 222.6 mg/day; 222.6 ÷ 15.9 = 14 mg/kg/day; 111.3 × (5/125) = 4.452 mL Rounding: Weight to nearest tenth; volume 4.452 mL rounded to the nearest tenth (4.5 mL). Final answer: SAFE — 111.3 mg/dose = 14 mg/kg/day; administer 4.5 mL. Rationale: Cefdinir's educational dosing is 7 mg/kg/dose twice daily, i.e., 14 mg/kg/day. 7 × 15.9 kg = 111.3 mg per dose (222.6 mg/day = 14 mg/kg/day), confirming the order. The 125 mg/5 mL suspension delivers 111.3 mg in 4.45 mL → 4.5 mL. Clinical pearl: This question ties every skill together — weight conversion, mg/kg/dose and mg/kg/day checks, SAFE/UNSAFE comparison, and administration-volume follow-up.