Critical Care & Titration (Part 1) — practice set (Q401–450)

Check yourself

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

1. Question 401. Scenario: A nurse is preparing a continuous dopamine infusion for a hypotensive patient in the ICU. Order: Dopamine 400 mg in 250 mL D5W, titrate per protocol. Available: Dopamine injection 40 mg/mL (10 mL vial) and a 250 mL bag of D5W. Question: The nurse adds the entire 10 mL vial (400 mg) to the 250 mL bag. What is the final concentration of the infusion in mcg/mL? Round to a whole number.

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   Correct answer: 1,600 mcg/mL Setup (dimensional analysis): 400 mg × (1,000 mcg / 1 mg) ÷ 250 mL Raw calculation: 400 × 1,000 = 400,000 mcg; 400,000 ÷ 250 = 1,600 mcg/mL Rounding: Whole number — 1,600 is already exact. Final answer: 1,600 mcg/mL Rationale: Converting mg to mcg (×1,000) and dividing by the total bag volume yields the concentration needed to compute mcg/kg/min titrations. A 400 mg/250 mL dopamine bag is a standard educational concentration of 1,600 mcg/mL. Clinical pearl: Always document the final concentration (mcg/mL) on the bag and in the pump before starting any vasoactive titration.

2. Question 402. Scenario: A patient in septic shock is started on a norepinephrine (Levophed) infusion. Order: Norepinephrine 4 mg in 250 mL D5W. Available: Norepinephrine 1 mg/mL (4 mL ampule) and a 250 mL bag of D5W. Question: What is the concentration of the prepared infusion in mcg/mL? Round to a whole number.

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   Correct answer: 16 mcg/mL Setup (dimensional analysis): 4 mg × (1,000 mcg / 1 mg) ÷ 250 mL Raw calculation: 4 × 1,000 = 4,000 mcg; 4,000 ÷ 250 = 16 mcg/mL Rounding: Whole number — 16 is exact. Final answer: 16 mcg/mL Rationale: A 4 mg/250 mL norepinephrine bag contains 16 mcg/mL. This is the concentration most commonly used in norepinephrine rate-to-dose conversions. Clinical pearl: Norepinephrine concentration is frequently expressed in mcg/mL, so a quick mg→mcg conversion is the first step of every titration problem.

3. Question 403. Scenario: A 154 lb patient in cardiogenic shock requires a dopamine infusion. Order: Dopamine 5 mcg/kg/min, titrate to maintain MAP ≥ 65. Available: Dopamine 400 mg in 250 mL D5W (1,600 mcg/mL). Question: What rate in mL/hr should the infusion pump be set to deliver 5 mcg/kg/min? (Convert lb → kg using 1 kg ≈ 2.2 lb; round weight to the nearest tenth, then round the pump rate to the nearest tenth of a mL/hr.)

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   Correct answer: 13.1 mL/hr Setup (dimensional analysis): Weight: 154 lb × (1 kg / 2.2 lb) = 70 kg Rate: 5 mcg/kg/min × 70 kg × 60 min/hr ÷ 1,600 mcg/mL Raw calculation: 5 × 70 × 60 = 21,000 mcg/hr; 21,000 ÷ 1,600 = 13.125 mL/hr Rounding: Weight 70.0 kg (exact). Rate 13.125 rounds to 13.1 mL/hr (nearest tenth). Final answer: 13.1 mL/hr Rationale: Convert lb to kg, then compute the pump rate by multiplying dose × weight × 60 and dividing by concentration. The result is a clinically plausible low-to-moderate dopamine rate. Clinical pearl: For weight-based vasoactive drips, always convert the weight to kg first; a missed lb→kg conversion is a common and dangerous error.

4. Question 404. Scenario: A patient weighing 80 kg is receiving dopamine 400 mg in 250 mL D5W at 12 mL/hr. Order: (infusion already running; verify the delivered dose) Available: Dopamine 400 mg in 250 mL D5W (1,600 mcg/mL). Question: What dose in mcg/kg/min is the patient actually receiving? Select one: A. 2 mcg/kg/min B. 4 mcg/kg/min C. 6 mcg/kg/min D. 8 mcg/kg/min

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   Correct answer: B — 4 mcg/kg/min Setup (dimensional analysis): 12 mL/hr × 1,600 mcg/mL ÷ 60 min/hr ÷ 80 kg Raw calculation: 12 × 1,600 = 19,200 mcg/hr; 19,200 ÷ 60 = 320 mcg/min; 320 ÷ 80 = 4 mcg/kg/min Rounding: Exact — 4 mcg/kg/min. Final answer: 4 mcg/kg/min Rationale: Reverse dose calculation (rate → dose) is verified by multiplying the pump rate by concentration, dividing by 60 to get mcg/min, then dividing by weight. 4 mcg/kg/min is a typical renal/low-dose dopamine range. Clinical pearl: To verify an unknown vasoactive dose, remember "mL/hr × concentration ÷ 60 ÷ kg."

5. Question 405. Scenario: A 75 kg patient with a pulmonary embolism is started on a heparin infusion. Order: Heparin 12 units/kg/hr. Available: Heparin 25,000 units in 250 mL D5W. Question: At what rate in mL/hr should the pump be set? Round to the nearest tenth.

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   Correct answer: 9 mL/hr Setup (dimensional analysis): 12 units/kg/hr × 75 kg ÷ 100 units/mL Raw calculation: 12 × 75 = 900 units/hr; 900 ÷ 100 = 9 mL/hr Rounding: Exact — 9 mL/hr. Final answer: 9 mL/hr Rationale: Heparin concentration (25,000 units / 250 mL = 100 units/mL) converts the weight-based hourly dose into a pump rate. Clinical pearl: Heparin bags are commonly 100 units/mL; confirming the actual bag concentration every shift prevents a 2× rate error.

6. Question 406. Scenario: A nurse is preparing an insulin infusion for a patient in diabetic ketoacidosis. Order: Regular insulin 100 units in 100 mL NS. Available: Regular insulin 100 units/mL vial and a 100 mL bag of NS. Question: What is the concentration of the prepared insulin infusion in units/mL? Round to the nearest tenth.

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   Correct answer: 1 unit/mL Setup (dimensional analysis): 100 units ÷ 100 mL Raw calculation: 100 ÷ 100 = 1 unit/mL Rounding: Nearest tenth — 1.0 units/mL. Final answer: 1 unit/mL Rationale: When 100 units of regular insulin are diluted to a total volume of 100 mL, the concentration is exactly 1 unit/mL, so 1 mL/hr = 1 unit/hr. Clinical pearl: A 1 unit/mL insulin infusion lets the nurse read mL/hr directly as units/hr, which reduces conversion errors during hourly titration.

7. Question 407. Scenario: A 60 kg patient in septic shock needs a norepinephrine infusion. Order: Norepinephrine 0.05 mcg/kg/min, titrate to maintain MAP ≥ 65. Available: Norepinephrine 4 mg in 250 mL D5W (16 mcg/mL). Question: At what rate in mL/hr should the pump be started? Round to the nearest tenth.

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   Correct answer: 11.3 mL/hr Setup (dimensional analysis): 0.05 mcg/kg/min × 60 kg × 60 min/hr ÷ 16 mcg/mL Raw calculation: 0.05 × 60 × 60 = 180 mcg/hr; 180 ÷ 16 = 11.25 mL/hr Rounding: 11.25 rounds to 11.3 mL/hr (nearest tenth). Final answer: 11.3 mL/hr Rationale: The standard norepinephrine concentration of 16 mcg/mL is used to convert the ordered mcg/kg/min dose to a pump rate. Clinical pearl: Norepinephrine is a high-alert medication — independent double-checks of both the dose and the pump setting are standard practice.

8. Question 408. Scenario: An 80 kg patient is receiving norepinephrine 4 mg in 250 mL D5W at 15 mL/hr. Order: (infusion already running; verify the delivered dose) Available: Norepinephrine 4 mg in 250 mL D5W (16 mcg/mL). Question: What dose in mcg/kg/min is being delivered? Round to the nearest hundredth.

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   Correct answer: 0.05 mcg/kg/min Setup (dimensional analysis): 15 mL/hr × 16 mcg/mL ÷ 60 min/hr ÷ 80 kg Raw calculation: 15 × 16 = 240 mcg/hr; 240 ÷ 60 = 4 mcg/min; 4 ÷ 80 = 0.05 mcg/kg/min Rounding: Nearest hundredth — 0.05 mcg/kg/min. Final answer: 0.05 mcg/kg/min Rationale: Reverse calculation confirms the infusion is delivering the intended low-end norepinephrine dose. Clinical pearl: Small decimal doses (0.05 vs 0.5 mcg/kg/min) differ by a factor of ten — a decimal-place error here is potentially fatal; always re-read the order.

9. Question 409. Scenario: A 70 kg patient is prescribed a weight-based continuous infusion under a hypothetical educational protocol. Order: Infuse at 2 mg/kg/hr. Available: 500 mg in 250 mL D5W. Question: At what rate in mL/hr should the pump be set? Round to a whole number.

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   Correct answer: 70 mL/hr Setup (dimensional analysis): 2 mg/kg/hr × 70 kg ÷ 2 mg/mL Raw calculation: 2 × 70 = 140 mg/hr; 140 ÷ 2 = 70 mL/hr Rounding: Whole number — 70 mL/hr. Final answer: 70 mL/hr Rationale: This is a direct mg/kg/hr → pump-rate conversion (no minute factor needed because the dose is already per hour). Clinical pearl: mg/kg/hr orders do not use the "× 60" minute factor — that factor applies only to per-minute doses such as mcg/kg/min.

10. Question 410. Scenario: A 50 kg postoperative patient is sedated with a fentanyl infusion. Order: Fentanyl 1 mcg/kg/hr. Available: Fentanyl 2,500 mcg in 250 mL NS (10 mcg/mL). Question: At what rate in mL/hr should the pump be set? Round to the nearest tenth.

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    Correct answer: 5 mL/hr Setup (dimensional analysis): 1 mcg/kg/hr × 50 kg ÷ 10 mcg/mL Raw calculation: 1 × 50 = 50 mcg/hr; 50 ÷ 10 = 5 mL/hr Rounding: Nearest tenth — 5.0 mL/hr. Final answer: 5 mL/hr Rationale: The mcg/kg/hr dose converts directly to mL/hr via the concentration; no ×60 factor is needed because the dose is already hourly. Clinical pearl: Distinguish mcg/kg/hr (fentanyl, midazolam) from mcg/kg/min (vasopressors) — the unit of time determines whether a ×60 factor is required.

11. Question 411. Scenario: A 60 kg ventilated patient is receiving fentanyl 2,500 mcg in 250 mL NS at 6 mL/hr. Order: (infusion already running; verify the delivered dose) Available: Fentanyl 2,500 mcg in 250 mL NS (10 mcg/mL). Question: What dose in mcg/kg/hr is being delivered? Round to the nearest tenth.

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    Correct answer: 1 mcg/kg/hr Setup (dimensional analysis): 6 mL/hr × 10 mcg/mL ÷ 60 kg Raw calculation: 6 × 10 = 60 mcg/hr; 60 ÷ 60 = 1 mcg/kg/hr Rounding: Nearest tenth — 1.0 mcg/kg/hr. Final answer: 1 mcg/kg/hr Rationale: Rate × concentration gives mcg/hr; dividing by weight gives mcg/kg/hr. Clinical pearl: For mcg/kg/hr reverse checks, divide the total hourly mcg by kg only (no minute factor).

12. Question 412. Scenario: A nurse is preparing a norepinephrine infusion for a patient in shock. Order: Norepinephrine 8 mg in 250 mL D5W. Available: Norepinephrine 4 mg/4 mL vials. Question: How many mL of norepinephrine must be added to the 250 mL D5W bag to supply 8 mg? Round to a whole number.

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    Correct answer: 8 mL Setup (dimensional analysis): 8 mg × (4 mL / 4 mg) Raw calculation: 8 × 1 = 8 mL Rounding: Whole number — 8 mL. Final answer: 8 mL Rationale: Each 4 mg/4 mL vial supplies 1 mg/mL. To add 8 mg, draw up 8 mL (two full 4 mL vials). Clinical pearl: Norepinephrine ampules/vials are available in different strengths (e.g., 1 mg/mL vs 4 mg/4 mL) — verify the vial label before drawing up.

13. Question 413. Scenario: An 80 kg patient presents with an acute DVT. The provider initiates the following (hypothetical) heparin protocol. Order: (Hypothetical protocol) Bolus 80 units/kg IV, then begin a continuous infusion of 18 units/kg/hr. Check aPTT in 6 hours. Available: Heparin 25,000 units in 250 mL D5W (100 units/mL) for the infusion; heparin 5,000 units/mL vials for the bolus. Question: (a) How many mL from the 5,000 units/mL vial are needed for the bolus? Round to the nearest hundredth. (b) At what rate in mL/hr should the infusion be started? Round to the nearest tenth.

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    Correct answer: (a) 1.28 mL bolus; (b) 14.4 mL/hr Setup (dimensional analysis): (a) Bolus dose: 80 units/kg × 80 kg = 6,400 units; 6,400 units × (1 mL / 5,000 units) (b) Infusion: 18 units/kg/hr × 80 kg ÷ 100 units/mL Raw calculation: (a) 80 × 80 = 6,400 units; 6,400 ÷ 5,000 = 1.28 mL (b) 18 × 80 = 1,440 units/hr; 1,440 ÷ 100 = 14.4 mL/hr Rounding: (a) 1.28 mL (nearest hundredth, tuberculin syringe); (b) 14.4 mL/hr (nearest tenth). Final answer: (a) 1.28 mL; (b) 14.4 mL/hr Rationale: The bolus is drawn from the concentrated 5,000 units/mL vial (a small, precise volume), while the infusion is prepared from the 100 units/mL bag. Clinical pearl: Heparin boluses come from a different, more concentrated vial than the drip — using the drip concentration to compute a bolus volume would cause a serious overdose.

14. Question 414. Scenario: A 70 kg patient with a pulmonary embolism is started on a heparin drip using the following complete (hypothetical) protocol. Order: (Hypothetical protocol) - Bolus 70 units/kg IV. - Initial infusion 15 units/kg/hr (use heparin 25,000 units in 250 mL = 100 units/mL). - Check aPTT every 6 hours. - aPTT < 50 sec: repeat bolus 70 units/kg and increase infusion by 4 units/kg/hr. - aPTT 50–100 sec: no change. - aPTT > 100 sec: decrease infusion by 3 units/kg/hr. Available: Heparin 25,000 units in 250 mL D5W (100 units/mL); heparin 5,000 units/mL vials. Question: Six hours later the aPTT is 45 sec. (a) How many units are in the repeat bolus? (b) What is the new infusion rate in units/hr and in mL/hr? Round mL/hr to the nearest tenth.

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    Correct answer: (a) 4,900 units; (b) 1,330 units/hr = 13.3 mL/hr Setup (dimensional analysis): (a) Repeat bolus: 70 units/kg × 70 kg (b) New rate: (15 + 4) units/kg/hr × 70 kg ÷ 100 units/mL Raw calculation: (a) 70 × 70 = 4,900 units (b) 19 × 70 = 1,330 units/hr; 1,330 ÷ 100 = 13.3 mL/hr Rounding: (a) whole number; (b) 13.3 mL/hr (nearest tenth). Final answer: (a) 4,900 units; (b) 1,330 units/hr = 13.3 mL/hr Rationale: An aPTT of 45 sec is below the therapeutic window (50–100 sec), so the protocol calls for a repeat bolus and a 4 units/kg/hr rate increase. The new rate is 19 units/kg/hr. Clinical pearl: Protocol-driven adjustments require the nurse to compute a new weight-based rate after every lab draw — recalculate the rate from scratch rather than "bumping" the pump by an arbitrary amount.

15. Question 415. Scenario: A patient in diabetic ketoacidosis is started on an insulin infusion using the following complete (hypothetical) protocol. Order: (Hypothetical protocol) Regular insulin 100 units in 100 mL NS (1 unit/mL). - Start at 2 units/hr. - Recheck blood glucose (BG) hourly: - BG > 250 mg/dL: increase by 2 units/hr. - BG 181–250 mg/dL: increase by 1 unit/hr. - BG 70–180 mg/dL: no change. - BG < 70 mg/dL: stop infusion and notify provider. Available: Regular insulin 100 units in 100 mL NS (1 unit/mL). Question: The most recent BG is 265 mg/dL. (a) What is the new rate in units/hr? (b) What is the new pump rate in mL/hr? Round to the nearest tenth.

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    Correct answer: (a) 4 units/hr; (b) 4 mL/hr Setup (dimensional analysis): (a) BG 265 > 250 → increase by 2 units/hr: 2 + 2 = 4 units/hr (b) 4 units/hr ÷ 1 unit/mL Raw calculation: (a) 4 units/hr; (b) 4 ÷ 1 = 4 mL/hr Rounding: Nearest tenth — 4.0 units/hr and 4.0 mL/hr. Final answer: (a) 4 units/hr; (b) 4 mL/hr Rationale: The BG of 265 mg/dL falls in the "> 250" arm of the protocol, triggering a 2 unit/hr increase from the 2 unit/hr starting rate. At 1 unit/mL, units/hr and mL/hr are numerically identical. Clinical pearl: With a 1 unit/mL insulin drip, the pump rate in mL/hr equals the dose in units/hr — but still label and document both clearly.

16. Question 416. Scenario: A 70 kg patient in septic shock is receiving norepinephrine titrated to a MAP goal. Order: Norepinephrine — start at 0.05 mcg/kg/min; if MAP < 65 after 5 minutes, increase by 0.05 mcg/kg/min; maximum 0.3 mcg/kg/min. Available: Norepinephrine 4 mg in 250 mL D5W (16 mcg/mL). Question: (a) At what rate in mL/hr is the infusion started? (b) After one upward titration, what is the new rate in mL/hr? Round both to the nearest tenth.

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    Correct answer: (a) 13.1 mL/hr; (b) 26.3 mL/hr Setup (dimensional analysis): (a) 0.05 mcg/kg/min × 70 kg × 60 min/hr ÷ 16 mcg/mL (b) 0.1 mcg/kg/min × 70 kg × 60 min/hr ÷ 16 mcg/mL Raw calculation: (a) 0.05 × 70 × 60 = 210 mcg/hr; 210 ÷ 16 = 13.125 mL/hr (b) 0.1 × 70 × 60 = 420 mcg/hr; 420 ÷ 16 = 26.25 mL/hr Rounding: (a) 13.1 mL/hr; (b) 26.3 mL/hr (both nearest tenth). Final answer: (a) 13.1 mL/hr; (b) 26.3 mL/hr Rationale: Each 0.05 mcg/kg/min step doubles the delivered dose; doubling the dose doubles the required pump rate. Clinical pearl: When a vasopressor is titrated in equal steps, verify the new pump rate scales proportionally — a mismatch is an early warning of a programming error.

17. Question 417. Scenario: A patient weighing 198 lb is receiving dopamine 400 mg in 250 mL D5W at 20 mL/hr. Order: (infusion already running; verify the delivered dose) Available: Dopamine 400 mg in 250 mL D5W (1,600 mcg/mL). Question: What dose in mcg/kg/min is being delivered? (Convert lb → kg using 1 kg ≈ 2.2 lb; round weight to the nearest tenth, then round the dose to the nearest tenth.)

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    Correct answer: 5.9 mcg/kg/min Setup (dimensional analysis): Weight: 198 lb × (1 kg / 2.2 lb) = 90 kg Dose: 20 mL/hr × 1,600 mcg/mL ÷ 60 min/hr ÷ 90 kg Raw calculation: 20 × 1,600 = 32,000 mcg/hr; 32,000 ÷ 60 = 533.33 mcg/min; 533.33 ÷ 90 = 5.926 mcg/kg/min Rounding: Weight 90.0 kg (exact). Dose 5.926 rounds to 5.9 mcg/kg/min (nearest tenth). Final answer: 5.9 mcg/kg/min Rationale: Converting lb→kg first, then reversing the pump rate, confirms a moderate dopamine dose. Clinical pearl: When verifying a drip on a patient documented in pounds, convert to kg before any dose-per-kg calculation.

18. Question 418. Scenario: An 80 kg patient is receiving heparin 25,000 units in 500 mL D5W at 20 mL/hr. Order: (infusion already running; verify the delivered dose) Available: Heparin 25,000 units in 500 mL D5W (50 units/mL). Question: What dose in units/kg/hr is being delivered? Round to the nearest tenth.

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    Correct answer: 12.5 units/kg/hr Setup (dimensional analysis): 20 mL/hr × 50 units/mL ÷ 80 kg Raw calculation: 20 × 50 = 1,000 units/hr; 1,000 ÷ 80 = 12.5 units/kg/hr Rounding: Nearest tenth — 12.5 units/kg/hr. Final answer: 12.5 units/kg/hr Rationale: This heparin bag is 50 units/mL (25,000 units/500 mL). Rate × concentration gives units/hr, which divided by weight gives units/kg/hr. Clinical pearl: Heparin bags come in both 25,000 units/250 mL (100 units/mL) and 25,000 units/500 mL (50 units/mL) — always confirm which bag is hanging before computing.

19. Question 419. Scenario: An 80 kg patient with acute decompensated heart failure is started on dobutamine. Order: Dobutamine 5 mcg/kg/min, titrate per protocol. Available: Dobutamine 250 mg in 250 mL D5W. Question: (a) What is the concentration of the infusion in mcg/mL? (b) At what rate in mL/hr should the pump be started? Round both to a whole number.

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    Correct answer: (a) 1,000 mcg/mL; (b) 24 mL/hr Setup (dimensional analysis): (a) 250 mg × (1,000 mcg / 1 mg) ÷ 250 mL (b) 5 mcg/kg/min × 80 kg × 60 min/hr ÷ 1,000 mcg/mL Raw calculation: (a) 250,000 ÷ 250 = 1,000 mcg/mL (b) 5 × 80 × 60 = 24,000 mcg/hr; 24,000 ÷ 1,000 = 24 mL/hr Rounding: (a) 1,000 mcg/mL (whole); (b) 24 mL/hr (whole). Final answer: (a) 1,000 mcg/mL; (b) 24 mL/hr Rationale: Dobutamine 250 mg/250 mL = 1 mg/mL = 1,000 mcg/mL. The pump rate is computed from that concentration. Clinical pearl: Dobutamine bags are often 250 mg or 500 mg per 250 mL — compute the concentration from the actual bag you are hanging, not from memory.

20. Question 420. Scenario: An 80 kg ventilated patient is sedated with a midazolam infusion. Order: (infusion already running; verify the delivered dose) Available: Midazolam 25 mg in 50 mL NS (500 mcg/mL) running at 4 mL/hr. Question: What dose in mcg/kg/hr is being delivered? Round to a whole number.

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    Correct answer: 25 mcg/kg/hr Setup (dimensional analysis): 4 mL/hr × 500 mcg/mL ÷ 80 kg Raw calculation: 4 × 500 = 2,000 mcg/hr; 2,000 ÷ 80 = 25 mcg/kg/hr Rounding: Whole number — 25 mcg/kg/hr. Final answer: 25 mcg/kg/hr Rationale: Midazolam 25 mg/50 mL = 500 mcg/mL. Rate × concentration ÷ weight yields the sedation dose in mcg/kg/hr. Clinical pearl: Sedative infusions are frequently ordered in mcg/kg/hr; verify whether the pump rate reflects the hourly (not per-minute) dose.

21. Question 421. Scenario: A 60 kg patient in a hypertensive emergency is started on nitroprusside (Nipride). Order: Nitroprusside 0.5 mcg/kg/min, titrate to a target MAP; do not exceed 10 mcg/kg/min (maximum). Available: Nitroprusside 50 mg in 250 mL D5W (200 mcg/mL). Question: (a) At what rate in mL/hr should the infusion start? (b) What is the maximum safe rate in mL/hr? Round both to a whole number.

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    Correct answer: (a) 9 mL/hr; (b) 180 mL/hr (maximum) Setup (dimensional analysis): (a) 0.5 mcg/kg/min × 60 kg × 60 min/hr ÷ 200 mcg/mL (b) 10 mcg/kg/min × 60 kg × 60 min/hr ÷ 200 mcg/mL Raw calculation: (a) 0.5 × 60 × 60 = 1,800 mcg/hr; 1,800 ÷ 200 = 9 mL/hr (b) 10 × 60 × 60 = 36,000 mcg/hr; 36,000 ÷ 200 = 180 mL/hr Rounding: Whole numbers — 9 and 180 mL/hr. Final answer: (a) 9 mL/hr; (b) 180 mL/hr Rationale: Nitroprusside 50 mg/250 mL = 200 mcg/mL. The maximum rate (10 mcg/kg/min) produces a 180 mL/hr cap that should never be exceeded. Clinical pearl: Nitroprusside is a rapid-acting, high-alert vasodilator with a hard maximum dose — always note the maximum rate (mL/hr) on the pump and the MAR.

22. Question 422. Scenario: A 100 kg patient is receiving epinephrine 1 mg in 250 mL NS at 15 mL/hr for refractory anaphylaxis. Order: (infusion already running; verify the delivered dose) Available: Epinephrine 1 mg in 250 mL NS (4 mcg/mL). Question: What dose in mcg/kg/min is being delivered? Round to the nearest hundredth.

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    Correct answer: 0.01 mcg/kg/min Setup (dimensional analysis): 15 mL/hr × 4 mcg/mL ÷ 60 min/hr ÷ 100 kg Raw calculation: 15 × 4 = 60 mcg/hr; 60 ÷ 60 = 1 mcg/min; 1 ÷ 100 = 0.01 mcg/kg/min Rounding: Nearest hundredth — 0.01 mcg/kg/min. Final answer: 0.01 mcg/kg/min Rationale: Epinephrine 1 mg/250 mL = 4 mcg/mL. The delivered weight-based dose is 0.01 mcg/kg/min, typical for refractory anaphylaxis support. Clinical pearl: Epinephrine infusions use very low mcg/kg/min doses; a misplaced decimal (0.1 vs 0.01) is a ten-fold error.

23. Question 423. Scenario: A 100 kg patient with an acute coronary syndrome is started on a heparin infusion. Order: Heparin 18 units/kg/hr. Available: Heparin 25,000 units in 500 mL D5W (50 units/mL). Question: At what rate in mL/hr should the pump be set? Round to a whole number.

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    Correct answer: 36 mL/hr Setup (dimensional analysis): 18 units/kg/hr × 100 kg ÷ 50 units/mL Raw calculation: 18 × 100 = 1,800 units/hr; 1,800 ÷ 50 = 36 mL/hr Rounding: Whole number — 36 mL/hr. Final answer: 36 mL/hr Rationale: Heparin 25,000 units/500 mL = 50 units/mL. The weight-based hourly dose is converted to mL/hr using this concentration. Clinical pearl: Heavier patients with the same units/kg/hr order require a higher mL/hr rate — always recompute, never copy a neighbor's pump setting.

24. Question 424. Scenario: A 50 kg patient is receiving a weight-based continuous infusion. Order: (infusion already running; verify the delivered dose) Available: 250 mg in 100 mL D5W (2.5 mg/mL) running at 40 mL/hr. Question: What dose in mg/kg/hr is being delivered? Round to the nearest tenth.

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    Correct answer: 2 mg/kg/hr Setup (dimensional analysis): 40 mL/hr × 2.5 mg/mL ÷ 50 kg Raw calculation: 40 × 2.5 = 100 mg/hr; 100 ÷ 50 = 2 mg/kg/hr Rounding: Nearest tenth — 2.0 mg/kg/hr. Final answer: 2 mg/kg/hr Rationale: 250 mg/100 mL = 2.5 mg/mL. The delivered weight-based hourly dose is 2 mg/kg/hr. Clinical pearl: For mg/kg/hr reverse checks, no minute conversion is needed — divide the hourly mg by kg directly.

25. Question 425. Scenario: A nurse is preparing a magnesium sulfate infusion for a patient in torsades de pointes. Order: Magnesium sulfate 2 g in 50 mL D5W, infuse over 10 minutes. Available: Magnesium sulfate 1 g/2 mL (50%) vials. Question: What is the concentration of the prepared infusion in mg/mL? Round to a whole number.

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    Correct answer: 40 mg/mL Setup (dimensional analysis): 2 g × (1,000 mg / 1 g) ÷ 50 mL Raw calculation: 2,000 ÷ 50 = 40 mg/mL Rounding: Whole number — 40 mg/mL. Final answer: 40 mg/mL Rationale: Magnesium sulfate 2 g (2,000 mg) diluted to 50 mL yields 40 mg/mL. Clinical pearl: Magnesium is ordered in grams but concentrations are often reported in mg/mL — convert g→mg before dividing by volume.

26. Question 426. Scenario: A nurse is preparing a higher-strength norepinephrine infusion. Order: Norepinephrine 8 mg in 250 mL D5W. Available: Norepinephrine 4 mg/4 mL vials and a 250 mL bag of D5W. Question: What is the concentration of the prepared infusion in mcg/mL? Round to a whole number.

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    Correct answer: 32 mcg/mL Setup (dimensional analysis): 8 mg × (1,000 mcg / 1 mg) ÷ 250 mL Raw calculation: 8,000 ÷ 250 = 32 mcg/mL Rounding: Whole number — 32 mcg/mL. Final answer: 32 mcg/mL Rationale: An 8 mg/250 mL norepinephrine bag is "double-strength" at 32 mcg/mL. Clinical pearl: Double-strength norepinephrine (32 mcg/mL) is used to minimize volume in fluid-restricted patients — the higher concentration halves the mL/hr for the same dose, so verify concentration before programming.

27. Question 427. Scenario: An 85 kg patient is receiving norepinephrine 8 mg in 250 mL D5W at 10 mL/hr. Order: (infusion already running; verify the delivered dose) Available: Norepinephrine 8 mg in 250 mL D5W (32 mcg/mL). Question: What dose in mcg/kg/min is being delivered? Round to the nearest thousandth (three decimal places).

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    Correct answer: 0.063 mcg/kg/min Setup (dimensional analysis): 10 mL/hr × 32 mcg/mL ÷ 60 min/hr ÷ 85 kg Raw calculation: 10 × 32 = 320 mcg/hr; 320 ÷ 60 = 5.333 mcg/min; 5.333 ÷ 85 = 0.0627 mcg/kg/min Rounding: 0.0627 rounds to 0.063 mcg/kg/min (nearest thousandth). Final answer: 0.063 mcg/kg/min Rationale: With the double-strength bag (32 mcg/mL), the pump rate delivers a low-end norepinephrine dose of about 0.063 mcg/kg/min. Clinical pearl: When documenting mcg/kg/min doses that fall below 0.1, carry three decimal places to avoid clinically significant rounding loss.

28. Question 428. Scenario: An 82 kg patient with heart failure is started on dobutamine. Order: Dobutamine 7.5 mcg/kg/min. Available: Dobutamine 500 mg in 250 mL D5W (2,000 mcg/mL). Question: At what rate in mL/hr should the pump be set? Round to the nearest tenth.

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    Correct answer: 18.5 mL/hr Setup (dimensional analysis): 7.5 mcg/kg/min × 82 kg × 60 min/hr ÷ 2,000 mcg/mL Raw calculation: 7.5 × 82 × 60 = 36,900 mcg/hr; 36,900 ÷ 2,000 = 18.45 mL/hr Rounding: 18.45 rounds to 18.5 mL/hr (nearest tenth). Final answer: 18.5 mL/hr Rationale: Dobutamine 500 mg/250 mL = 2,000 mcg/mL. The ordered dose converts to 18.45 mL/hr, rounded to 18.5. Clinical pearl: Smart pumps generally accept one decimal place for vasoactive infusions — round once, at the end, to the pump's precision.

29. Question 429. Scenario: A patient in diabetic ketoacidosis is continued on an insulin infusion. Order: Regular insulin 5 units/hr. Available: Regular insulin 100 units in 100 mL NS (1 unit/mL). Question: At what rate in mL/hr should the pump be set? Round to the nearest tenth.

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    Correct answer: 5 mL/hr Setup (dimensional analysis): 5 units/hr ÷ 1 unit/mL Raw calculation: 5 ÷ 1 = 5 mL/hr Rounding: Nearest tenth — 5.0 mL/hr. Final answer: 5 mL/hr Rationale: At 1 unit/mL, a 5 units/hr order runs at 5 mL/hr. Clinical pearl: Insulin is a high-alert medication; two nurses should independently verify the pump setting before infusion start.

30. Question 430. Scenario: A nurse must give a heparin bolus to a patient with an acute coronary syndrome. Order: Heparin 4,000 units IV bolus now. Available: Heparin 5,000 units/mL vial. Question: (a) What volume in mL should be drawn up? Round to the nearest tenth. (b) Which syringe allows the most accurate measurement of this volume: a 1 mL tuberculin syringe, a 3 mL syringe, a 5 mL syringe, or a 10 mL syringe?

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    Correct answer: (a) 0.8 mL; (b) 1 mL tuberculin syringe Setup (dimensional analysis): 4,000 units × (1 mL / 5,000 units) Raw calculation: 4,000 ÷ 5,000 = 0.8 mL Rounding: Nearest tenth — 0.8 mL. Final answer: (a) 0.8 mL; (b) 1 mL tuberculin syringe Rationale: The concentrated vial (5,000 units/mL) means the bolus is only 0.8 mL. A 1 mL tuberculin syringe is graduated in hundredths and measures 0.8 mL far more accurately than a 3–10 mL syringe. Clinical pearl: Small, high-risk volumes (heparin boluses, insulin) should be measured in a tuberculin or insulin syringe, not a large general-purpose syringe.

31. Question 431. Scenario: A 95 kg patient with a DVT is managed on a heparin drip using the following complete (hypothetical) protocol. Order: (Hypothetical protocol) - Bolus 80 units/kg IV. - Infusion 18 units/kg/hr (heparin 25,000 units in 250 mL = 100 units/mL). - Check aPTT every 6 hours: - aPTT > 110 sec: hold infusion 30 min, then restart at a rate 3 units/kg/hr lower. Available: Heparin 25,000 units in 250 mL D5W (100 units/mL); heparin 5,000 units/mL vials. Question: Four hours later the aPTT is 120 sec. (a) How many units are in the initial bolus? (b) At what rate in mL/hr was the infusion started? (c) At what rate in mL/hr should the infusion be restarted after the hold? Round mL/hr to the nearest tenth.

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    Correct answer: (a) 7,600 units; (b) 17.1 mL/hr; (c) 14.3 mL/hr Setup (dimensional analysis): (a) 80 units/kg × 95 kg (b) 18 units/kg/hr × 95 kg ÷ 100 units/mL (c) (18 − 3) units/kg/hr × 95 kg ÷ 100 units/mL Raw calculation: (a) 80 × 95 = 7,600 units (b) 18 × 95 = 1,710 units/hr; 1,710 ÷ 100 = 17.1 mL/hr (c) 15 × 95 = 1,425 units/hr; 1,425 ÷ 100 = 14.25 mL/hr Rounding: (b) 17.1 mL/hr; (c) 14.25 → 14.3 mL/hr (nearest tenth). Final answer: (a) 7,600 units; (b) 17.1 mL/hr; (c) 14.3 mL/hr Rationale: An aPTT of 120 sec is supratherapeutic (> 110 sec), so the protocol requires holding the infusion and restarting 3 units/kg/hr lower (15 units/kg/hr). Clinical pearl: Supratherapeutic aPTT signals bleeding risk; the protocol-driven decrease is a safety intervention — hold the drip, then restart at the reduced, recalculated rate.

32. Question 432. Scenario: A 70 kg patient has an order for norepinephrine 0.1 mcg/kg/min. The pump is running norepinephrine 4 mg in 250 mL D5W at 21 mL/hr. Order: Norepinephrine 0.1 mcg/kg/min. Available: Norepinephrine 4 mg in 250 mL D5W (16 mcg/mL). Question: (a) What dose in mcg/kg/min is actually being delivered? Round to the nearest hundredth. (b) Is the patient receiving the ordered dose? Explain.

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    Correct answer: (a) 0.08 mcg/kg/min; (b) No — the patient is receiving less than the ordered dose Setup (dimensional analysis): 21 mL/hr × 16 mcg/mL ÷ 60 min/hr ÷ 70 kg Raw calculation: 21 × 16 = 336 mcg/hr; 336 ÷ 60 = 5.6 mcg/min; 5.6 ÷ 70 = 0.08 mcg/kg/min Rounding: Nearest hundredth — 0.08 mcg/kg/min. Final answer: (a) 0.08 mcg/kg/min; (b) No — the pump is delivering 0.08 mcg/kg/min, below the ordered 0.1 mcg/kg/min Rationale: The pump is set to 21 mL/hr, but 0.1 mcg/kg/min would require 26.3 mL/hr (0.1 × 70 × 60 ÷ 16). At 21 mL/hr the patient is receiving 0.08 mcg/kg/min — an under-delivery that could leave the patient hypotensive. Clinical pearl: When a vasopressor is not achieving its effect, first verify the actual delivered dose against the order rather than automatically titrating upward.

33. Question 433. Scenario: A 75 kg patient is receiving a low-dose dopamine infusion. Order: (infusion already running; verify the delivered dose) Available: Dopamine 400 mg in 250 mL D5W (1,600 mcg/mL) running at 5.6 mL/hr. Question: What dose in mcg/kg/min is being delivered? Round to the nearest tenth.

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    Correct answer: 2 mcg/kg/min Setup (dimensional analysis): 5.6 mL/hr × 1,600 mcg/mL ÷ 60 min/hr ÷ 75 kg Raw calculation: 5.6 × 1,600 = 8,960 mcg/hr; 8,960 ÷ 60 = 149.33 mcg/min; 149.33 ÷ 75 = 1.991 mcg/kg/min Rounding: 1.991 rounds to 2.0 mcg/kg/min (nearest tenth). Final answer: 2 mcg/kg/min Rationale: The low pump rate of 5.6 mL/hr corresponds to a renal-range dopamine dose of about 2 mcg/kg/min. Clinical pearl: Low-dose ("renal") dopamine runs at low mL/hr rates; the same bag at a higher rate would deliver a very different dose.

34. Question 434. Scenario: A patient in vasodilatory shock is started on vasopressin. Order: Vasopressin 0.04 units/min (note: vasopressin is ordered per minute, not per kg). Available: Vasopressin 20 units in 100 mL NS (0.2 units/mL). Question: At what rate in mL/hr should the pump be set? Round to a whole number.

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    Correct answer: 12 mL/hr Setup (dimensional analysis): 0.04 units/min × 60 min/hr ÷ 0.2 units/mL Raw calculation: 0.04 × 60 = 2.4 units/hr; 2.4 ÷ 0.2 = 12 mL/hr Rounding: Whole number — 12 mL/hr. Final answer: 12 mL/hr Rationale: Vasopressin is a fixed (non-weight-based) dose ordered in units/min. Converting to units/hr then dividing by concentration gives the pump rate. Clinical pearl: Vasopressin is not weight-based — do not multiply by the patient's weight; only convert units/min to units/hr.

35. Question 435. Scenario: A 70 kg patient with acute decompensated heart failure is started on milrinone. Order: Milrinone 0.5 mcg/kg/min. Available: Milrinone 20 mg in 100 mL D5W (200 mcg/mL). Question: At what rate in mL/hr should the pump be set? Select one: A. 1.05 mL/hr B. 5.25 mL/hr C. 10.5 mL/hr D. 21 mL/hr

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    Correct answer: C — 10.5 mL/hr Setup (dimensional analysis): 0.5 mcg/kg/min × 70 kg × 60 min/hr ÷ 200 mcg/mL Raw calculation: 0.5 × 70 × 60 = 2,100 mcg/hr; 2,100 ÷ 200 = 10.5 mL/hr Rounding: 10.5 mL/hr (already one decimal). Final answer: 10.5 mL/hr Rationale: Milrinone 20 mg/100 mL = 200 mcg/mL. The weight-based dose converts to 10.5 mL/hr. Distractors reflect omitting the ÷60 (21), omitting the ÷2 for mg→mcg (5.25), and a decimal slip (1.05). Clinical pearl: Milrinone is dosed in mcg/kg/min like the pressors, but its higher concentration (mg, not mcg, per bag) means the mL/hr is lower than many nurses expect.

36. Question 436. Scenario: A 70 kg patient with acute decompensated heart failure requires a milrinone loading dose followed by a continuous infusion. Order: Milrinone loading dose 50 mcg/kg IV over 10 minutes, then begin 0.5 mcg/kg/min. Available: Milrinone 20 mg in 100 mL D5W (200 mcg/mL). Question: (a) How many mL are required for the loading dose? Round to the nearest tenth. (b) At what rate in mL/hr should the continuous infusion run? Round to the nearest tenth.

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    Correct answer: (a) 17.5 mL; (b) 10.5 mL/hr Setup (dimensional analysis): (a) 50 mcg/kg × 70 kg ÷ 200 mcg/mL (b) 0.5 mcg/kg/min × 70 kg × 60 min/hr ÷ 200 mcg/mL Raw calculation: (a) 50 × 70 = 3,500 mcg = 3.5 mg; 3,500 ÷ 200 = 17.5 mL (b) 0.5 × 70 × 60 = 2,100 mcg/hr; 2,100 ÷ 200 = 10.5 mL/hr Rounding: (a) 17.5 mL; (b) 10.5 mL/hr (nearest tenth). Final answer: (a) 17.5 mL; (b) 10.5 mL/hr Rationale: The loading dose (a fixed mcg/kg total) is a volume, while the continuous infusion (mcg/kg/min) is a rate. The two require different formulas. Clinical pearl: A loading dose is a total amount (mg or mL), while an infusion is a rate (mL/hr or mcg/kg/min) — do not confuse the two when programming.

37. Question 437. Scenario: An 80 kg patient with a DVT is started on a heparin infusion. Order: Heparin 10 units/kg/hr. Available: Heparin 20,000 units in 500 mL D5W (40 units/mL). Question: At what rate in mL/hr should the pump be set? Round to a whole number.

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    Correct answer: 20 mL/hr Setup (dimensional analysis): 10 units/kg/hr × 80 kg ÷ 40 units/mL Raw calculation: 10 × 80 = 800 units/hr; 800 ÷ 40 = 20 mL/hr Rounding: Whole number — 20 mL/hr. Final answer: 20 mL/hr Rationale: Heparin 20,000 units/500 mL = 40 units/mL. The weight-based dose converts to 20 mL/hr. Clinical pearl: Always compute the bag's units/mL (total units ÷ total mL) before converting a units/kg/hr order to mL/hr.

38. Question 438. Scenario: An 80 kg patient is started on epinephrine for refractory anaphylaxis. Order: Epinephrine 0.1 mcg/kg/min. Available: Epinephrine 2 mg in 250 mL NS (8 mcg/mL). Question: At what rate in mL/hr should the pump be set? Select one: A. 6 mL/hr B. 30 mL/hr C. 60 mL/hr D. 120 mL/hr

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    Correct answer: C — 60 mL/hr Setup (dimensional analysis): 0.1 mcg/kg/min × 80 kg × 60 min/hr ÷ 8 mcg/mL Raw calculation: 0.1 × 80 × 60 = 480 mcg/hr; 480 ÷ 8 = 60 mL/hr Rounding: Whole number — 60 mL/hr. Final answer: 60 mL/hr Rationale: Epinephrine 2 mg/250 mL = 8 mcg/mL. The ordered dose converts to 60 mL/hr. Distractors reflect common decimal (6), half-weight (30), and double-dose (120) errors. Clinical pearl: Epinephrine infusion rates are often surprisingly high in mL/hr because of the low concentration — confirm the bag's mcg/mL before programming.

39. Question 439. Scenario: A 100 kg patient is receiving a concentrated dopamine infusion. Order: (infusion already running; verify the delivered dose) Available: Dopamine 800 mg in 250 mL D5W (3,200 mcg/mL) running at 15 mL/hr. Question: What dose in mcg/kg/min is being delivered? Round to a whole number.

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    Correct answer: 8 mcg/kg/min Setup (dimensional analysis): 15 mL/hr × 3,200 mcg/mL ÷ 60 min/hr ÷ 100 kg Raw calculation: 15 × 3,200 = 48,000 mcg/hr; 48,000 ÷ 60 = 800 mcg/min; 800 ÷ 100 = 8 mcg/kg/min Rounding: Whole number — 8 mcg/kg/min. Final answer: 8 mcg/kg/min Rationale: Concentrated dopamine (800 mg/250 mL = 3,200 mcg/mL) delivers a higher mcg/kg/min for the same mL/hr than the standard 400 mg/250 mL bag. Clinical pearl: A "concentrated" or "double-strength" bag means the same mL/hr delivers twice the dose — this is a high-risk source of overdose.

40. Question 440. Scenario: A nurse receives the following handwritten orders in the ICU. Order: (as written) "Norepinephrine 4.0 mg in 250 mL D5W. Heparin 5,000 U bolus now." Available: (not needed) Question: Identify the two Joint Commission "Do Not Use" abbreviations/expressions in these orders.

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    Correct answer: Trailing zero ("4.0 mg") and the abbreviation "U" for units Setup (dimensional analysis): Not applicable (identification). Raw calculation: Not applicable. Rounding: Not applicable. Final answer: Two errors: (1) "4.0 mg" contains a trailing zero; (2) "U" is used for units (should be written "units") Rationale: The Joint Commission "Do Not Use" list prohibits the trailing zero (a decimal point and a zero after a whole number, which risks a 10-fold overdose if the decimal is missed) and the abbreviation "U" for units (which can be misread as "0," "4," or "cc"). The correct orders would be "Norepinephrine 4 mg in 250 mL D5W" and "Heparin 5,000 units bolus now." Clinical pearl: "U" and "IU" are on the official Do Not Use list; always write "units" and add a leading zero to decimal doses less than one (0.05, not .05).

41. Question 441. Scenario: A patient with unstable ventricular tachycardia has completed amiodarone loading and is now on a maintenance infusion. Order: Amiodarone 1 mg/min for 6 hours, then 0.5 mg/min. Available: Amiodarone 450 mg in 250 mL D5W (1.8 mg/mL). Question: (a) At what rate in mL/hr should the pump be set for the 1 mg/min phase? (b) At what rate in mL/hr should the pump be set for the 0.5 mg/min phase? Round both to the nearest tenth.

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    Correct answer: (a) 33.3 mL/hr; (b) 16.7 mL/hr Setup (dimensional analysis): (a) 1 mg/min × 60 min/hr ÷ 1.8 mg/mL (b) 0.5 mg/min × 60 min/hr ÷ 1.8 mg/mL Raw calculation: (a) 1 × 60 = 60 mg/hr; 60 ÷ 1.8 = 33.33 mL/hr (b) 0.5 × 60 = 30 mg/hr; 30 ÷ 1.8 = 16.67 mL/hr Rounding: (a) 33.3 mL/hr; (b) 16.7 mL/hr (nearest tenth). Final answer: (a) 33.3 mL/hr; (b) 16.7 mL/hr Rationale: Amiodarone 450 mg/250 mL = 1.8 mg/mL. Converting mg/min to mg/hr and dividing by concentration gives the pump rate for each phase. Clinical pearl: Amiodarone is dosed in mg/min (not mcg/kg/min) — convert to mg/hr by multiplying by 60 before dividing by mg/mL.

42. Question 442. Scenario: A patient in diabetic ketoacidosis is receiving an insulin infusion. Order: (infusion already running; verify the delivered dose) Available: Regular insulin 100 units in 100 mL NS (1 unit/mL) running at 7 mL/hr. Question: How many units/hr of insulin is the patient receiving? Round to a whole number.

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    Correct answer: 7 units/hr Setup (dimensional analysis): 7 mL/hr × 1 unit/mL Raw calculation: 7 × 1 = 7 units/hr Rounding: Whole number — 7 units/hr. Final answer: 7 units/hr Rationale: At 1 unit/mL, 7 mL/hr delivers 7 units/hr. Clinical pearl: With a 1 unit/mL insulin drip, reading the pump in mL/hr is equivalent to units/hr — but always confirm the drip's actual concentration, since some facilities use 0.5 or 2 units/mL.

43. Question 443. Scenario: A 60 kg patient in septic shock is started on a "double-strength" norepinephrine infusion. Order: Norepinephrine 0.1 mcg/kg/min. Available: Norepinephrine 16 mg in 250 mL D5W (64 mcg/mL). Question: At what rate in mL/hr should the pump be set? Round to the nearest tenth.

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    Correct answer: 5.6 mL/hr Setup (dimensional analysis): 0.1 mcg/kg/min × 60 kg × 60 min/hr ÷ 64 mcg/mL Raw calculation: 0.1 × 60 × 60 = 360 mcg/hr; 360 ÷ 64 = 5.625 mL/hr Rounding: 5.625 rounds to 5.6 mL/hr (nearest tenth). Final answer: 5.6 mL/hr Rationale: Double-strength norepinephrine (16 mg/250 mL = 64 mcg/mL) delivers the ordered dose at a low 5.6 mL/hr, conserving volume. Clinical pearl: Higher-strength norepinephrine allows the same mcg/kg/min at a much lower mL/hr — verify concentration so you do not program the single-strength rate by habit.

44. Question 444. Scenario: A patient in vasodilatory shock is receiving vasopressin. Order: (infusion already running; verify the delivered dose) Available: Vasopressin 40 units in 100 mL NS (0.4 units/mL) running at 6 mL/hr. Question: What dose in units/min is being delivered? Round to the nearest hundredth.

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    Correct answer: 0.04 units/min Setup (dimensional analysis): 6 mL/hr × 0.4 units/mL ÷ 60 min/hr Raw calculation: 6 × 0.4 = 2.4 units/hr; 2.4 ÷ 60 = 0.04 units/min Rounding: Nearest hundredth — 0.04 units/min. Final answer: 0.04 units/min Rationale: Vasopressin 40 units/100 mL = 0.4 units/mL. Converting the hourly delivery to a per-minute dose yields 0.04 units/min. Clinical pearl: Vasopressin is documented in units/min; report the per-minute dose, not units/hr, when handing off.

45. Question 445. Scenario: A 68 kg patient with a pulmonary embolism is managed on a heparin drip using the following complete (hypothetical) protocol. Order: (Hypothetical protocol) - Bolus 80 units/kg IV. - Infusion 18 units/kg/hr (heparin 25,000 units in 250 mL = 100 units/mL). - Check aPTT every 6 hours: - aPTT < 50 sec: repeat bolus 80 units/kg and increase infusion by 4 units/kg/hr. - aPTT 50–100 sec: no change. - aPTT > 100 sec: decrease infusion by 3 units/kg/hr. Available: Heparin 25,000 units in 250 mL D5W (100 units/mL); heparin 5,000 units/mL vials. Question: Six hours later the aPTT is 38 sec. (a) How many units are in the initial bolus? (b) At what rate in mL/hr was the infusion started? (c) How many units are in the repeat bolus? (d) At what rate in mL/hr should the infusion now run? Round mL/hr to the nearest tenth.

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    Correct answer: (a) 5,440 units; (b) 12.2 mL/hr; (c) 5,440 units; (d) 15 mL/hr Setup (dimensional analysis): (a) 80 units/kg × 68 kg (b) 18 units/kg/hr × 68 kg ÷ 100 units/mL (c) repeat bolus = 80 units/kg × 68 kg (d) (18 + 4) units/kg/hr × 68 kg ÷ 100 units/mL Raw calculation: (a) 80 × 68 = 5,440 units (b) 18 × 68 = 1,224 units/hr; 1,224 ÷ 100 = 12.24 mL/hr (c) 80 × 68 = 5,440 units (d) 22 × 68 = 1,496 units/hr; 1,496 ÷ 100 = 14.96 mL/hr Rounding: (b) 12.24 → 12.2 mL/hr; (d) 14.96 → 15.0 mL/hr (nearest tenth). Final answer: (a) 5,440 units; (b) 12.2 mL/hr; (c) 5,440 units; (d) 15 mL/hr Rationale: An aPTT of 38 sec is subtherapeutic (< 50 sec), so the protocol requires a repeat 80 units/kg bolus and a 4 units/kg/hr rate increase (to 22 units/kg/hr). Clinical pearl: Tracking the cumulative heparin boluses and the drip rate changes on the MAR helps the provider interpret the next aPTT correctly.

46. Question 446. Scenario: A 70 kg patient in cardiogenic shock is started on dopamine and titrated upward. Order: Dopamine 5 mcg/kg/min; if MAP remains < 65 after 2 hours, increase to 7.5 mcg/kg/min. Available: Dopamine 400 mg in 250 mL D5W (1,600 mcg/mL = 1.6 mg/mL). Question: (a) At what rate in mL/hr should the pump be started? (b) At what rate in mL/hr should the pump be set after the upward titration? (c) How many mg of dopamine did the patient receive during the first 2 hours (at the starting rate)? Round mL/hr to the nearest tenth and mg to a whole number.

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    Correct answer: (a) 13.1 mL/hr; (b) 19.7 mL/hr; (c) 42 mg Setup (dimensional analysis): (a) 5 mcg/kg/min × 70 kg × 60 min/hr ÷ 1,600 mcg/mL (b) 7.5 mcg/kg/min × 70 kg × 60 min/hr ÷ 1,600 mcg/mL (c) 13.125 mL/hr × 2 hr × 1.6 mg/mL Raw calculation: (a) 5 × 70 × 60 = 21,000 mcg/hr; 21,000 ÷ 1,600 = 13.125 mL/hr (b) 7.5 × 70 × 60 = 31,500 mcg/hr; 31,500 ÷ 1,600 = 19.6875 mL/hr (c) 13.125 × 2 = 26.25 mL; 26.25 × 1.6 = 42 mg Rounding: (a) 13.1 mL/hr; (b) 19.7 mL/hr (nearest tenth); (c) 42 mg (whole). Use the unrounded rate for the 2-hour total to avoid rounding error. Final answer: (a) 13.1 mL/hr; (b) 19.7 mL/hr; (c) 42 mg Rationale: This integrates the forward pump-rate calculation, a titration to a new rate, and a total-dose reconstruction using the actual volume infused. Clinical pearl: When totaling the amount of a drug delivered, use the unrounded rate and time, then round only the final total.

47. Question 447. Scenario: An 80 kg ventilated patient requires deep sedation. Order: Propofol 25 mcg/kg/min. Available: Propofol 1,000 mg in 100 mL (10 mg/mL). Question: At what rate in mL/hr should the pump be set? Round to a whole number.

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    Correct answer: 12 mL/hr Setup (dimensional analysis): 25 mcg/kg/min × 80 kg × 60 min/hr ÷ 10,000 mcg/mL Raw calculation: 25 × 80 × 60 = 120,000 mcg/hr; 120,000 ÷ 10,000 = 12 mL/hr Rounding: Whole number — 12 mL/hr. Final answer: 12 mL/hr Rationale: Propofol 1,000 mg/100 mL = 10 mg/mL = 10,000 mcg/mL. The high concentration means a modest 12 mL/hr delivers 25 mcg/kg/min. Clinical pearl: Propofol is a lipid emulsion with a high drug concentration; the mL/hr is low relative to the mcg/kg/min dose — verify the concentration and the "1% vs 2%" product.

48. Question 448. Scenario: A 75 kg patient is receiving a propofol infusion. Order: (infusion already running; verify the delivered dose) Available: Propofol 1,000 mg in 100 mL (10 mg/mL) running at 15 mL/hr. Question: (a) How many mg/hr of propofol is the patient receiving? (b) What dose in mcg/kg/min is being delivered? Round mg/hr to a whole number and mcg/kg/min to the nearest tenth.

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    Correct answer: (a) 150 mg/hr; (b) 33.3 mcg/kg/min Setup (dimensional analysis): (a) 15 mL/hr × 10 mg/mL (b) 15 mL/hr × 10 mg/mL × (1,000 mcg / 1 mg) ÷ 60 min/hr ÷ 75 kg Raw calculation: (a) 15 × 10 = 150 mg/hr (b) 150,000 mcg/hr ÷ 60 = 2,500 mcg/min; 2,500 ÷ 75 = 33.33 mcg/kg/min Rounding: (a) 150 mg/hr (whole); (b) 33.3 mcg/kg/min (nearest tenth). Final answer: (a) 150 mg/hr; (b) 33.3 mcg/kg/min Rationale: Propofol at 10 mg/mL delivers 150 mg/hr, which converts to 33.3 mcg/kg/min for this 75 kg patient — a high-end sedation dose. Clinical pearl: Propofol doses are often reported both ways (mg/hr for the provider, mcg/kg/min for the protocol) — be fluent in converting between them.

49. Question 449. Scenario: A patient with acute chest pain is started on a nitroglycerin infusion. Order: Nitroglycerin 10 mcg/min (note: nitroglycerin is ordered per minute, not per kg). Available: Nitroglycerin 50 mg in 250 mL D5W (200 mcg/mL). Question: At what rate in mL/hr should the pump be set? Round to a whole number.

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    Correct answer: 3 mL/hr Setup (dimensional analysis): 10 mcg/min × 60 min/hr ÷ 200 mcg/mL Raw calculation: 10 × 60 = 600 mcg/hr; 600 ÷ 200 = 3 mL/hr Rounding: Whole number — 3 mL/hr. Final answer: 3 mL/hr Rationale: Nitroglycerin 50 mg/250 mL = 200 mcg/mL. The fixed (non-weight-based) mcg/min dose converts to 3 mL/hr. Clinical pearl: Nitroglycerin is ordered in mcg/min and is not weight-based — do not multiply by patient weight.

50. Question 450. Scenario: A patient is receiving a nitroglycerin infusion that is being titrated upward for chest pain. Order: Titrate nitroglycerin from the current dose to 40 mcg/min. Available: Nitroglycerin 50 mg in 250 mL D5W (200 mcg/mL) currently running at 6 mL/hr. Question: (a) What dose in mcg/min is the patient currently receiving? (b) At what rate in mL/hr should the pump be set to deliver 40 mcg/min? Round both to a whole number.

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    Correct answer: (a) 20 mcg/min; (b) 12 mL/hr Setup (dimensional analysis): (a) 6 mL/hr × 200 mcg/mL ÷ 60 min/hr (b) 40 mcg/min × 60 min/hr ÷ 200 mcg/mL Raw calculation: (a) 6 × 200 = 1,200 mcg/hr; 1,200 ÷ 60 = 20 mcg/min (b) 40 × 60 = 2,400 mcg/hr; 2,400 ÷ 200 = 12 mL/hr Rounding: Whole numbers — 20 mcg/min and 12 mL/hr. Final answer: (a) 20 mcg/min; (b) 12 mL/hr Rationale: The current 6 mL/hr delivers 20 mcg/min. Doubling the dose to 40 mcg/min doubles the rate to 12 mL/hr. Clinical pearl: For fixed-dose mcg/min infusions, doubling the dose doubles the pump rate — a quick proportionality check that can catch programming errors.