Basic IV Infusion Rates (Part 1) — practice set

Check yourself

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

1. Question 221. Scenario: A postoperative patient has a maintenance intravenous line running. Order: 0.9% sodium chloride (normal saline) 1,000 mL IV to infuse over 8 hours. Available: Electronic infusion pump. Question: At what rate (mL/hr) should the nurse program the infusion pump? Round to the nearest whole number.

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   Correct answer: 125 mL/hr Setup (dimensional analysis): 1,000 mL ÷ 8 hr Raw calculation: 1,000 ÷ 8 = 125.0 mL/hr Rounding: 125.0 is already a whole number; no further rounding needed. Final answer: 125 mL/hr Rationale: Pump rate (mL/hr) = total volume (mL) ÷ time (hr). Dividing 1,000 mL by 8 hours gives exactly 125 mL/hr, so the pump is programmed to deliver the entire liter evenly over the shift. Clinical pearl: On an infusion pump you always set mL/hr; never set a gravity drop factor on a pump.

2. Question 222. Scenario: A patient admitted with dehydration is receiving fluid replacement. Order: Lactated Ringer's 500 mL IV to infuse over 5 hours. Available: Electronic infusion pump. Question: Calculate the pump setting in mL/hr. Round to the nearest whole number.

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   Correct answer: 100 mL/hr Setup (dimensional analysis): 500 mL ÷ 5 hr Raw calculation: 500 ÷ 5 = 100 mL/hr Rounding: 100 is already a whole number; no rounding needed. Final answer: 100 mL/hr Rationale: mL/hr = volume ÷ time = 500 mL ÷ 5 hr = 100 mL/hr, a clinically appropriate maintenance rate. Clinical pearl: Keeping the mL/hr formula (volume over hours) straight avoids the common error of multiplying volume by hours.

3. Question 223. Scenario: A patient in the emergency department needs a small volume of IV fluid. Order: Lactated Ringer's 250 mL IV to infuse over 4 hours. Available: Electronic infusion pump. Question: What is the infusion rate in mL/hr? A. 60 mL/hr B. 62 mL/hr C. 63 mL/hr D. 65 mL/hr

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   Correct answer: C. 63 mL/hr Setup (dimensional analysis): 250 mL ÷ 4 hr Raw calculation: 250 ÷ 4 = 62.5 mL/hr Rounding: 62.5 mL/hr rounds UP to the nearest whole number, giving 63 mL/hr (round-half-up convention for infusion pumps). Final answer: 63 mL/hr Rationale: 250 mL over 4 hours = 62.5 mL/hr. Pumps are set to whole numbers, and 62.5 is conventionally rounded up to 63 mL/hr. Choosing 62 mL/hr would systematically under-deliver, and 60 mL/hr (option A) reflects rounding down to the nearest ten, which is incorrect. Clinical pearl: When a rate ends in exactly .5, nursing convention rounds up — never truncate a half unit.

4. Question 224. Scenario: A patient on a medical-surgical unit has a primary IV infusing by gravity (no pump available). Order: 0.9% sodium chloride 1,000 mL IV to infuse over 8 hours. Available: Gravity infusion set with a drop factor of 10 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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   Correct answer: 21 gtt/min Setup (dimensional analysis): (1,000 mL × 10 gtt/mL) ÷ (8 hr × 60 min/hr) Raw calculation: 10,000 gtt ÷ 480 min = 20.83 gtt/min Rounding: 20.83 rounds to the nearest whole drop → 21 gtt/min. Final answer: 21 gtt/min Rationale: gtt/min = (volume mL × drop factor gtt/mL) ÷ time in minutes. With a 10 gtt/mL set, a liter over 8 hours runs at about 21 gtt/min — a typical gravity rate. Clinical pearl: Always convert the hours to minutes in the denominator; forgetting the ×60 is the most frequent gtt/min error.

5. Question 225. Scenario: A patient with a mild fluid deficit is receiving IV fluids by gravity. Order: D5W (5% dextrose in water) 500 mL IV to infuse over 4 hours. Available: Gravity infusion set with a drop factor of 15 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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   Correct answer: 31 gtt/min Setup (dimensional analysis): (500 mL × 15 gtt/mL) ÷ (4 hr × 60 min/hr) Raw calculation: 7,500 gtt ÷ 240 min = 31.25 gtt/min Rounding: 31.25 rounds to the nearest whole drop → 31 gtt/min. Final answer: 31 gtt/min Rationale: The 15 gtt/mL set yields 7,500 drops over 240 minutes = 31.25, which rounds to 31 gtt/min. Drops cannot be fractional, so a whole number is required. Clinical pearl: A whole-drop answer is mandatory for gravity rates; you cannot deliver a fraction of a drop.

6. Question 226. Scenario: A patient needs a small, rapid IV bolus over 30 minutes using a microdrip set. Order: 0.9% sodium chloride 100 mL IV to infuse over 30 minutes. Available: Microdrip infusion set with a drop factor of 60 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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   Correct answer: 200 gtt/min Setup (dimensional analysis): (100 mL × 60 gtt/mL) ÷ 30 min Raw calculation: 6,000 gtt ÷ 30 min = 200 gtt/min Rounding: 200 is already a whole number; no rounding needed. Final answer: 200 gtt/min Rationale: With a microdrip set (60 gtt/mL), 100 mL = 6,000 drops; over 30 minutes that is 200 gtt/min, delivering the bolus in the ordered 30 minutes. Clinical pearl: Microdrip sets (60 gtt/mL) are used for small or precise volumes; their gtt/min equals the mL/hr rate.

7. Question 227. Scenario: A patient is receiving a small-volume IV infusion by gravity. Order: 0.9% sodium chloride 250 mL IV to infuse over 2 hours. Available: Gravity infusion set with a drop factor of 20 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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   Correct answer: 42 gtt/min Setup (dimensional analysis): (250 mL × 20 gtt/mL) ÷ (2 hr × 60 min/hr) Raw calculation: 5,000 gtt ÷ 120 min = 41.67 gtt/min Rounding: 41.67 rounds to the nearest whole drop → 42 gtt/min. Final answer: 42 gtt/min Rationale: The 20 gtt/mL set produces 5,000 drops over 120 minutes = 41.67 gtt/min, rounded to 42 gtt/min. Clinical pearl: A 20 gtt/mL macrodrip set delivers fewer, larger drops per mL than a 15 or 60 gtt/mL set — always read the drop factor on the packaging.

8. Question 228. Scenario: A patient with symptomatic hypotension has an order for a rapid fluid bolus. Order: 0.9% sodium chloride 500 mL IV bolus to infuse over 30 minutes. Available: Electronic infusion pump. Question: At what rate (mL/hr) should the nurse set the pump? Round to the nearest whole number.

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   Correct answer: 1,000 mL/hr Setup (dimensional analysis): 500 mL ÷ 0.5 hr (30 min = 0.5 hr) Raw calculation: 500 ÷ 0.5 = 1,000 mL/hr Rounding: 1,000 is already a whole number; no rounding needed. Final answer: 1,000 mL/hr Rationale: 30 minutes is half an hour, so a 500 mL bolus over 30 minutes equals 500 ÷ 0.5 = 1,000 mL/hr. This is a rapid resuscitation rate appropriate only for an ordered fluid bolus. Clinical pearl: Convert minutes to hours (÷60) before dividing when calculating a pump rate from a time given in minutes.

9. Question 229. Scenario: A patient on a general floor is receiving a maintenance infusion by gravity. Order: D5W 1,000 mL IV to infuse over 6 hours. Available: Gravity infusion set with a drop factor of 20 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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   Correct answer: 56 gtt/min Setup (dimensional analysis): (1,000 mL × 20 gtt/mL) ÷ (6 hr × 60 min/hr) Raw calculation: 20,000 gtt ÷ 360 min = 55.56 gtt/min Rounding: 55.56 rounds to the nearest whole drop → 56 gtt/min. Final answer: 56 gtt/min Rationale: With a 20 gtt/mL set, 1,000 mL = 20,000 drops over 360 minutes = 55.56 gtt/min, rounded to 56 gtt/min. Clinical pearl: Gravity rates should be counted over a full minute and verified periodically, since tubing position and vein patency can alter the actual drip.

10. Question 230. Scenario: A pediatric patient requires a small IV infusion delivered through a microdrip set. Order: 0.9% sodium chloride 75 mL IV to infuse over 15 minutes. Available: Microdrip infusion set with a drop factor of 60 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 300 gtt/min Setup (dimensional analysis): (75 mL × 60 gtt/mL) ÷ 15 min Raw calculation: 4,500 gtt ÷ 15 min = 300 gtt/min Rounding: 300 is already a whole number; no rounding needed. Final answer: 300 gtt/min Rationale: A microdrip set delivers 60 gtt/mL, so 75 mL = 4,500 drops over 15 minutes = 300 gtt/min. Note that at this rate counting by watch is difficult; a pump is preferred for accuracy when available. Clinical pearl: Very high drip rates are impractical to count reliably by gravity — this is a signal to use a pump or an alternative delivery method.

11. Question 231. Scenario: A nurse is verifying the duration of an ordered infusion before hanging a new bag. Order: 0.9% sodium chloride 1,000 mL IV to infuse at 125 mL/hr. Available: Electronic infusion pump. Question: How many hours will it take for the entire 1,000 mL to infuse?

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    Correct answer: 8 hours Setup (dimensional analysis): 1,000 mL ÷ 125 mL/hr Raw calculation: 1,000 ÷ 125 = 8 hr Rounding: 8 is exact; no rounding needed. Final answer: 8 hours Rationale: Duration = volume ÷ rate = 1,000 mL ÷ 125 mL/hr = 8 hours, confirming the bag will run for a full shift. Clinical pearl: Duration and rate are inverse problems — the same three numbers (volume, rate, time) can be rearranged depending on what is being asked.

12. Question 232. Scenario: A nurse is calculating how long a fluid bolus will take to complete. Order: 0.9% sodium chloride 1,000 mL IV to infuse at 150 mL/hr. Available: Electronic infusion pump. Question: How long will this infusion take to complete? A. 6 hr 7 min B. 7 hr C. 6 hr 40 min D. 6 hr 24 min

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    Correct answer: C. 6 hr 40 min Setup (dimensional analysis): 1,000 mL ÷ 150 mL/hr Raw calculation: 1,000 ÷ 150 = 6.6667 hr Rounding: Convert the fractional hour: 0.6667 hr × 60 = 40 min → 6 hours 40 minutes. Final answer: 6 hr 40 min Rationale: 1,000 ÷ 150 = 6.67 hours. The 0.67 hour is 40 minutes (not 7 minutes), so the correct duration is 6 hours 40 minutes. Option A mistakes 0.67 hr for 7 minutes, option D misreads it as 0.4 hr (24 min), and option B wrongly rounds to a whole hour. Clinical pearl: Convert a decimal hour to minutes by multiplying the decimal by 60; do not read "0.67 hr" as "67 minutes."

13. Question 233. Scenario: The nurse hangs an IV at the start of the day shift and needs to know when to hang the next bag. Order: 0.9% sodium chloride 1,000 mL IV to infuse at 125 mL/hr, starting at 0900. Available: Electronic infusion pump. Question: At what time (24-hour clock) will this infusion be complete?

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    Correct answer: 1700 Setup (dimensional analysis): Duration = 1,000 mL ÷ 125 mL/hr = 8 hr; completion = 0900 + 8 hr. Raw calculation: 0900 + 0800 = 1700 Rounding: Not applicable (time, not a measured quantity). Final answer: 1700 Rationale: A liter at 125 mL/hr runs for exactly 8 hours, so an infusion started at 0900 completes at 1700 (5:00 PM). Clinical pearl: Always state completion times on a 24-hour clock to avoid AM/PM ambiguity in the record.

14. Question 234. Scenario: An afternoon infusion is started and the nurse must document the expected completion time. Order: 0.9% sodium chloride 500 mL IV to infuse at 150 mL/hr, starting at 1430. Available: Electronic infusion pump. Question: At what time (24-hour clock) will this infusion be complete?

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    Correct answer: 1750 Setup (dimensional analysis): Duration = 500 mL ÷ 150 mL/hr = 3.3333 hr = 3 hr 20 min; completion = 1430 + 3 hr 20 min. Raw calculation: 1430 + 3 hr 20 min = 1750 Rounding: Not applicable. Final answer: 1750 Rationale: 500 ÷ 150 = 3.33 hours, i.e., 3 hours 20 minutes. Adding that to 1430 gives 1750 (5:50 PM). Clinical pearl: When adding minutes across an hour boundary, add the hours first, then the minutes, then carry (1430 + 3:20 → 17:30 + 0:20 → 17:50).

15. Question 235. Scenario: During hourly rounding, the nurse assesses an IV that has been running since the start of the shift. Order: 0.9% sodium chloride 1,000 mL IV to infuse at 100 mL/hr, started at 0600. Available: Electronic infusion pump. Question: At 1000 (4 hours into the infusion), how many mL have been infused and how many mL remain in the bag?

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    Correct answer: 400 mL infused; 600 mL remaining Setup (dimensional analysis): Infused = 100 mL/hr × 4 hr; Remaining = 1,000 mL − infused. Raw calculation: Infused = 400 mL; Remaining = 1,000 − 400 = 600 mL Rounding: Not applicable. Final answer: 400 mL infused; 600 mL remaining Rationale: At 100 mL/hr for 4 hours, 400 mL have infused; subtracting from the original 1,000 mL leaves 600 mL still in the bag. Clinical pearl: "Volume remaining" checks support safe handoff and help predict when a new bag must be available.

16. Question 236. Scenario: A patient on the night shift has an IV infusing by gravity. Order: 0.9% sodium chloride 1,000 mL IV to infuse over 6 hours. Available: Gravity infusion set with a drop factor of 15 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 42 gtt/min Setup (dimensional analysis): (1,000 mL × 15 gtt/mL) ÷ (6 hr × 60 min/hr) Raw calculation: 15,000 gtt ÷ 360 min = 41.67 gtt/min Rounding: 41.67 rounds to the nearest whole drop → 42 gtt/min. Final answer: 42 gtt/min Rationale: A 15 gtt/mL set yields 15,000 drops over 360 minutes = 41.67 gtt/min, rounded to 42 gtt/min. Clinical pearl: The same drop factor and volume but a different duration (6 hr vs. 8 hr) changes the rate — always re-derive rather than reuse a memorized number.

17. Question 237. Scenario: A patient is receiving a moderate-volume infusion by gravity. Order: D5W 750 mL IV to infuse over 5 hours. Available: Gravity infusion set with a drop factor of 10 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 25 gtt/min Setup (dimensional analysis): (750 mL × 10 gtt/mL) ÷ (5 hr × 60 min/hr) Raw calculation: 7,500 gtt ÷ 300 min = 25 gtt/min Rounding: 25 is already a whole number; no rounding needed. Final answer: 25 gtt/min Rationale: With a 10 gtt/mL set, 750 mL = 7,500 drops over 300 minutes = 25 gtt/min exactly. Clinical pearl: A 10 gtt/mL macrodrip set is the least precise for small volumes; use it only for large-volume infusions.

18. Question 238. Scenario: A patient requires a 90-minute IV infusion delivered by gravity. Order: 0.9% sodium chloride 250 mL IV to infuse over 90 minutes. Available: Gravity infusion set with a drop factor of 15 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 42 gtt/min Setup (dimensional analysis): (250 mL × 15 gtt/mL) ÷ 90 min Raw calculation: 3,750 gtt ÷ 90 min = 41.67 gtt/min Rounding: 41.67 rounds to the nearest whole drop → 42 gtt/min. Final answer: 42 gtt/min Rationale: Time is already in minutes (90), so the denominator does not need a ×60 conversion. 250 mL × 15 = 3,750 drops over 90 minutes = 41.67 → 42 gtt/min. Clinical pearl: When the ordered time is given in minutes, plug it directly into the gtt/min formula and skip the hour conversion.

19. Question 239. Scenario: A gravity infusion is running and the nurse must document the equivalent pump rate for the handoff report. Order: IV fluid to infuse by gravity at 25 gtt/min. Available: Gravity infusion set with a drop factor of 10 gtt/mL. Question: What is the equivalent infusion rate in mL/hr?

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    Correct answer: 150 mL/hr Setup (dimensional analysis): mL/hr = (gtt/min ÷ gtt/mL) × 60 min/hr = (25 gtt/min ÷ 10 gtt/mL) × 60 min/hr Raw calculation: (25 ÷ 10) × 60 = 2.5 × 60 = 150 mL/hr Rounding: 150 is already a whole number; no rounding needed. Final answer: 150 mL/hr Rationale: Reversing the drip-rate formula: first find mL/min (25 gtt/min ÷ 10 gtt/mL = 2.5 mL/min), then multiply by 60 to get 150 mL/hr. Clinical pearl: To convert gtt/min to mL/hr, divide by the drop factor, then multiply by 60 — the inverse of the gravity calculation.

20. Question 240. Scenario: A patient needs a small volume infused over 45 minutes on an infusion pump. Order: 0.9% sodium chloride 100 mL IV to infuse over 45 minutes. Available: Electronic infusion pump. Question: At what rate (mL/hr) should the nurse set the pump? A. 133 mL/hr B. 125 mL/hr C. 150 mL/hr D. 100 mL/hr

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    Correct answer: A. 133 mL/hr Setup (dimensional analysis): 100 mL ÷ 0.75 hr (45 min = 0.75 hr) Raw calculation: 100 ÷ 0.75 = 133.33 mL/hr Rounding: 133.33 rounds to the nearest whole number → 133 mL/hr. Final answer: 133 mL/hr Rationale: 45 minutes = 0.75 hour, so 100 mL ÷ 0.75 = 133.33 mL/hr, rounded to 133 mL/hr. Option B (125) omits the partial-hour conversion, and option D (100) ignores the time constraint. Clinical pearl: 45 min = 0.75 hr, 30 min = 0.5 hr, 15 min = 0.25 hr — memorizing these quarter-hour decimals speeds up pump-rate math.

21. Question 241. Scenario: A patient has a slow maintenance infusion running by gravity overnight. Order: 0.9% sodium chloride 1,000 mL IV to infuse over 12 hours. Available: Gravity infusion set with a drop factor of 15 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 21 gtt/min Setup (dimensional analysis): (1,000 mL × 15 gtt/mL) ÷ (12 hr × 60 min/hr) Raw calculation: 15,000 gtt ÷ 720 min = 20.83 gtt/min Rounding: 20.83 rounds to the nearest whole drop → 21 gtt/min. Final answer: 21 gtt/min Rationale: Over 12 hours the same 15,000 drops are spread across 720 minutes, giving 20.83 → 21 gtt/min, a slow maintenance drip appropriate overnight. Clinical pearl: Doubling the infusion time halves the drip rate — a useful reasonableness check.

22. Question 242. Scenario: A night nurse starts an IV and must calculate when the infusion will finish. Order: 0.9% sodium chloride 1,000 mL IV to infuse at 80 mL/hr, starting at 2130. Available: Electronic infusion pump. Question: At what time (24-hour clock) will this infusion be complete? State whether it is the same day or the following day.

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    Correct answer: 1000 the following day Setup (dimensional analysis): Duration = 1,000 mL ÷ 80 mL/hr = 12.5 hr = 12 hr 30 min; completion = 2130 + 12 hr 30 min. Raw calculation: 2130 + 12 hr = 0930; 0930 + 30 min = 1000 (next day). Rounding: Not applicable. Final answer: 1000 the following day Rationale: A liter at 80 mL/hr takes 12.5 hours. Starting at 2130, 12 hours later is 0930, plus 30 minutes = 1000 the next morning. Crossing midnight is the key pitfall here. Clinical pearl: Any duration that pushes past 2400 crosses into the next calendar day — document the date change explicitly.

23. Question 243. Scenario: A patient on a continuous IV is reassessed during the evening shift. Order: 0.9% sodium chloride 1,000 mL IV to infuse at 40 mL/hr, started at 1200. Available: Electronic infusion pump. Question: At 1800 (6 hours into the infusion), how many mL have been infused and how many mL remain in the bag?

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    Correct answer: 240 mL infused; 760 mL remaining Setup (dimensional analysis): Infused = 40 mL/hr × 6 hr; Remaining = 1,000 mL − infused. Raw calculation: Infused = 240 mL; Remaining = 1,000 − 240 = 760 mL Rounding: Not applicable. Final answer: 240 mL infused; 760 mL remaining Rationale: At 40 mL/hr for 6 hours, 240 mL have infused, leaving 760 mL in the bag. This slow rate is typical of a keep-vein-open or low-maintenance infusion. Clinical pearl: The remaining-volume check is essential before hanging a second bag or discontinuing an infusion.

24. Question 244. Scenario: A nurse must estimate the total time for a patient's ordered fluid volume across a 24-hour period. Order: 0.9% sodium chloride 1,500 mL IV total to infuse at 125 mL/hr. Available: Electronic infusion pump. Question: How many hours will it take to infuse the full 1,500 mL?

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    Correct answer: 12 hours Setup (dimensional analysis): 1,500 mL ÷ 125 mL/hr Raw calculation: 1,500 ÷ 125 = 12 hr Rounding: 12 is exact; no rounding needed. Final answer: 12 hours Rationale: A total of 1,500 mL at 125 mL/hr runs for exactly 12 hours, informing how many bags must be available for the shift. Clinical pearl: For multi-bag orders, calculate total time first, then map it onto the shift to plan bag changes.

25. Question 245. Scenario: A patient receives a 1-hour IV infusion through a microdrip set. Order: 0.9% sodium chloride 100 mL IV to infuse over 1 hour. Available: Microdrip infusion set with a drop factor of 60 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 100 gtt/min Setup (dimensional analysis): (100 mL × 60 gtt/mL) ÷ (1 hr × 60 min/hr) Raw calculation: 6,000 gtt ÷ 60 min = 100 gtt/min Rounding: 100 is already a whole number; no rounding needed. Final answer: 100 gtt/min Rationale: With a microdrip set, 100 mL = 6,000 drops over 60 minutes = 100 gtt/min. Note this equals the mL/hr rate (100 mL/hr) — the defining feature of a 60 gtt/mL set. Clinical pearl: With a microdrip (60 gtt/mL) set, gtt/min numerically equals mL/hr, giving an instant cross-check.

26. Question 246. Scenario: A gravity infusion is running and the nurse converts the drip rate to a pump rate for documentation. Order: IV fluid to infuse by gravity at 30 gtt/min. Available: Gravity infusion set with a drop factor of 15 gtt/mL. Question: What is the equivalent infusion rate in mL/hr? A. 120 mL/hr B. 150 mL/hr C. 90 mL/hr D. 60 mL/hr

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    Correct answer: A. 120 mL/hr Setup (dimensional analysis): mL/hr = (30 gtt/min ÷ 15 gtt/mL) × 60 min/hr Raw calculation: (30 ÷ 15) × 60 = 2 × 60 = 120 mL/hr Rounding: 120 is already a whole number; no rounding needed. Final answer: 120 mL/hr Rationale: 30 gtt/min on a 15 gtt/mL set means 2 mL are delivered each minute (30 ÷ 15 = 2), so over 60 minutes the rate is 120 mL/hr. Clinical pearl: Dividing gtt/min by the drop factor first gives mL/min — a clean intermediate step before multiplying by 60.

27. Question 247. Scenario: A patient receives a fluid infusion over 3½ hours by gravity. Order: 0.9% sodium chloride 500 mL IV to infuse over 3.5 hours. Available: Gravity infusion set with a drop factor of 20 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 48 gtt/min Setup (dimensional analysis): (500 mL × 20 gtt/mL) ÷ (3.5 hr × 60 min/hr) Raw calculation: 10,000 gtt ÷ 210 min = 47.62 gtt/min Rounding: 47.62 rounds to the nearest whole drop → 48 gtt/min. Final answer: 48 gtt/min Rationale: 3.5 hours = 210 minutes. A 20 gtt/mL set yields 10,000 drops over 210 minutes = 47.62 gtt/min, rounded to 48 gtt/min. Clinical pearl: Convert mixed times (e.g., 3.5 hr) to total minutes before using the gtt/min formula to avoid off-by-30-minute errors.

28. Question 248. Scenario: The nurse notices a primary IV bag is running low and calculates how much longer it will last. Available: Electronic infusion pump. The bag currently contains 400 mL and is infusing at 50 mL/hr. Order: Continue the current IV infusion at 50 mL/hr until the bag is empty. Question: How many hours will it take for the remaining 400 mL to infuse?

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    Correct answer: 8 hours Setup (dimensional analysis): 400 mL ÷ 50 mL/hr Raw calculation: 400 ÷ 50 = 8 hr Rounding: 8 is exact; no rounding needed. Final answer: 8 hours Rationale: The remaining 400 mL at 50 mL/hr will infuse in exactly 8 hours, so a replacement bag is not needed until then. Clinical pearl: "Time remaining" = remaining volume ÷ rate; use it to plan when to spike the next bag.

29. Question 249. Scenario: A patient has an order that the nurse must prepare for both a pump and a gravity backup. Order: 0.9% sodium chloride 1,000 mL IV to infuse over 8 hours. Available: Electronic infusion pump OR gravity set with a drop factor of 15 gtt/mL. Question: Calculate (a) the pump rate in mL/hr, and (b) the gravity flow rate in gtt/min. Round each to the nearest whole number/drop.

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    Correct answer: (a) 125 mL/hr; (b) 31 gtt/min Setup (dimensional analysis): (a) 1,000 mL ÷ 8 hr (b) (1,000 mL × 15 gtt/mL) ÷ (8 hr × 60 min/hr) Raw calculation: (a) 1,000 ÷ 8 = 125 mL/hr (b) 15,000 gtt ÷ 480 min = 31.25 gtt/min Rounding: (a) 125 is whole. (b) 31.25 rounds to the nearest whole drop → 31 gtt/min. Final answer: (a) 125 mL/hr; (b) 31 gtt/min Rationale: The same order is expressed two ways: a pump delivers 125 mL/hr, while a 15 gtt/mL gravity set delivers 31.25 → 31 gtt/min. Both deliver the liter over 8 hours. Clinical pearl: When preparing a pump and a gravity backup, compute both rates so a pump failure never interrupts therapy.

30. Question 250. Scenario: A patient has a large ordered volume that must be converted to a pump rate and a gravity rate. Order: D5W 1.5 L IV to infuse over 12 hours. Available: Electronic infusion pump OR gravity set with a drop factor of 20 gtt/mL. Question: Calculate (a) the pump rate in mL/hr, and (b) the gravity flow rate in gtt/min. Round each to the nearest whole number/drop.

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    Correct answer: (a) 125 mL/hr; (b) 42 gtt/min Setup (dimensional analysis): (a) 1.5 L = 1,500 mL; 1,500 mL ÷ 12 hr (b) (1,500 mL × 20 gtt/mL) ÷ (12 hr × 60 min/hr) Raw calculation: (a) 1,500 ÷ 12 = 125 mL/hr (b) 30,000 gtt ÷ 720 min = 41.67 gtt/min Rounding: (a) 125 is whole. (b) 41.67 rounds to the nearest whole drop → 42 gtt/min. Final answer: (a) 125 mL/hr; (b) 42 gtt/min Rationale: Converting 1.5 L to 1,500 mL first is essential. The pump rate is 125 mL/hr, and the 20 gtt/mL gravity rate is 41.67 → 42 gtt/min. Clinical pearl: Liter-to-milliliter conversion (1 L = 1,000 mL) must always precede the rate calculation when volumes are written in liters.

31. Question 251. Scenario: A nurse starts an afternoon fluid bolus and must document both the duration and the completion time. Order: 0.9% sodium chloride 500 mL IV to infuse at 150 mL/hr, starting at 1600. Available: Electronic infusion pump. Question: How long will the infusion take, and at what time (24-hour clock) will it be complete?

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    Correct answer: 3 hr 20 min; completes at 1920 Setup (dimensional analysis): Duration = 500 mL ÷ 150 mL/hr = 3.3333 hr = 3 hr 20 min; completion = 1600 + 3 hr 20 min. Raw calculation: 1600 + 3 hr 20 min = 1920 Rounding: Not applicable. Final answer: 3 hr 20 min; completes at 1920 Rationale: 500 ÷ 150 = 3.33 hours (3 hours 20 minutes). Starting at 1600, the infusion completes at 1920 (7:20 PM). Clinical pearl: Report duration and completion time together — a duration alone is not actionable for the next nurse.

32. Question 252. Scenario: A home-care nurse is verifying how long a patient's gravity infusion will last before the next visit. Order: 0.9% sodium chloride 100 mL IV to infuse by gravity at 20 gtt/min. Available: Microdrip infusion set with a drop factor of 60 gtt/mL. Question: How long will this 100 mL infusion take to complete? A. 5 hr B. 3 hr C. 6 hr D. 8 hr

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    Correct answer: A. 5 hr Setup (dimensional analysis): Time (min) = (100 mL × 60 gtt/mL) ÷ 20 gtt/min Raw calculation: 6,000 gtt ÷ 20 gtt/min = 300 min = 5 hr Rounding: Not applicable. Final answer: 5 hours Rationale: A microdrip set means 100 mL = 6,000 drops; at 20 gtt/min that is 300 minutes = 5 hours. Option B (3 hr) mistakes 300 minutes for 3 hours, and option C (6 hr) reflects a division error. Clinical pearl: To find duration from a drip rate, divide total drops by gtt/min to get minutes, then convert to hours.

33. Question 253. Scenario: A patient is to receive two sequential IV bags and the nurse must calculate the total infusion time and completion time. Order: Bag 1: 0.9% sodium chloride 1,000 mL at 125 mL/hr; then Bag 2: 0.9% sodium chloride 500 mL at 100 mL/hr. Start Bag 1 at 0800. Available: Electronic infusion pump. Question: What is the total infusion time for both bags, and at what time (24-hour clock) will the second bag be complete?

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    Correct answer: 13 hours total; completes at 2100 Setup (dimensional analysis): Bag 1: 1,000 mL ÷ 125 mL/hr = 8 hr Bag 2: 500 mL ÷ 100 mL/hr = 5 hr Total = 8 + 5 = 13 hr; completion = 0800 + 13 hr. Raw calculation: 0800 + 13 hr = 2100 Rounding: Not applicable. Final answer: 13 hours total; completes at 2100 Rationale: The two bags run 8 hours and 5 hours respectively, totaling 13 hours. Starting at 0800, the second bag finishes at 2100 (9:00 PM). Clinical pearl: For sequential bags, sum each bag's duration before adding to the start time so the end time is computed once.

34. Question 254. Scenario: A patient's small-volume infusion is ordered over 8 hours using a microdrip set. Order: 0.9% sodium chloride 250 mL IV to infuse over 8 hours. Available: Microdrip infusion set with a drop factor of 60 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop. (Note the relationship between gtt/min and mL/hr when using a microdrip set.)

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    Correct answer: 31 gtt/min Setup (dimensional analysis): (250 mL × 60 gtt/mL) ÷ (8 hr × 60 min/hr) Raw calculation: 15,000 gtt ÷ 480 min = 31.25 gtt/min Rounding: 31.25 rounds to the nearest whole drop → 31 gtt/min. Final answer: 31 gtt/min Rationale: The microdrip rate is 31.25 → 31 gtt/min. Because the set is 60 gtt/mL, this equals the mL/hr rate: 250 mL ÷ 8 hr = 31.25 mL/hr, confirming the equivalence. Clinical pearl: For any 60 gtt/mL microdrip set, gtt/min and mL/hr are the same number — a built-in safety check.

35. Question 255. Scenario: A patient's infusion rate is changed mid-infusion and the nurse recalculates the time until the bag is empty. Order: 0.9% sodium chloride 1,000 mL IV at 125 mL/hr, started at 0800. At 1200, the provider changes the rate to 75 mL/hr. Available: Electronic infusion pump. Question: At 1200, how many mL remain in the bag, and at what time (24-hour clock) will the bag be empty?

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    Correct answer: 500 mL remain; bag empty at 1840 Setup (dimensional analysis): Infused by 1200 = 125 mL/hr × 4 hr = 500 mL Remaining = 1,000 − 500 = 500 mL Time at new rate = 500 mL ÷ 75 mL/hr = 6.6667 hr = 6 hr 40 min Completion = 1200 + 6 hr 40 min Raw calculation: 1200 + 6 hr 40 min = 1840 Rounding: Not applicable. Final answer: 500 mL remain; bag empty at 1840 Rationale: Four hours at 125 mL/hr delivers 500 mL, leaving 500 mL. At the new rate of 75 mL/hr, 500 mL takes 6.67 hours (6 hr 40 min), so the bag empties at 1840 (6:40 PM). Clinical pearl: When a rate changes mid-infusion, always recompute from the volume remaining at the moment of the change, not from the original volume.

36. Question 256. Scenario: A late-night infusion is started and the nurse must document the expected completion time. Order: 0.9% sodium chloride 250 mL IV to infuse at 100 mL/hr, starting at 2230. Available: Electronic infusion pump. Question: At what time (24-hour clock) will this infusion be complete? State whether it is the same day or the following day.

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    Correct answer: 0100 the following day Setup (dimensional analysis): Duration = 250 mL ÷ 100 mL/hr = 2.5 hr = 2 hr 30 min; completion = 2230 + 2 hr 30 min. Raw calculation: 2230 + 2 hr = 0030; 0030 + 30 min = 0100 (next day). Rounding: Not applicable. Final answer: 0100 the following day Rationale: 250 mL at 100 mL/hr takes 2.5 hours. Starting at 2230, the infusion crosses midnight and completes at 0100 the following day. Clinical pearl: Starting near midnight means the completion date differs from the start date — document both date and time.

37. Question 257. Scenario: A pump becomes unavailable and the nurse must convert a pump rate to an equivalent gravity drip rate. Order: 0.9% sodium chloride to infuse at 60 mL/hr. Available: Gravity infusion set with a drop factor of 20 gtt/mL. Question: What gravity flow rate (gtt/min) delivers 60 mL/hr with this set? A. 20 gtt/min B. 30 gtt/min C. 15 gtt/min D. 40 gtt/min

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    Correct answer: A. 20 gtt/min Setup (dimensional analysis): gtt/min = (60 mL/hr × 20 gtt/mL) ÷ 60 min/hr Raw calculation: (60 × 20) ÷ 60 = 1,200 ÷ 60 = 20 gtt/min Rounding: 20 is already a whole number; no rounding needed. Final answer: 20 gtt/min Rationale: Converting a pump rate to gravity: 60 mL/hr with a 20 gtt/mL set = 60 × 20 ÷ 60 = 20 gtt/min. Option B (30) incorrectly uses a 15 gtt/mL set, and option D (40) doubles the correct answer. Clinical pearl: The conversion formula gtt/min = (mL/hr × drop factor) ÷ 60 lets you switch any pump order to gravity in one step.

38. Question 258. Scenario: A patient has a two-stage fluid order with different rates for each stage. Order: Stage 1: 0.9% sodium chloride 1,000 mL IV to infuse over 6 hours; then Stage 2: 0.9% sodium chloride 500 mL IV to infuse over 5 hours. Available: Electronic infusion pump. Question: Calculate the pump rate (mL/hr) for Stage 1 and for Stage 2. Round each to the nearest whole number.

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    Correct answer: Stage 1: 167 mL/hr; Stage 2: 100 mL/hr Setup (dimensional analysis): Stage 1: 1,000 mL ÷ 6 hr Stage 2: 500 mL ÷ 5 hr Raw calculation: Stage 1: 1,000 ÷ 6 = 166.67 mL/hr Stage 2: 500 ÷ 5 = 100 mL/hr Rounding: Stage 1: 166.67 rounds to the nearest whole number → 167 mL/hr. Stage 2: 100 is already whole. Final answer: Stage 1: 167 mL/hr; Stage 2: 100 mL/hr Rationale: The two stages have different rates: the liter over 6 hours runs at 166.67 → 167 mL/hr, and the 500 mL over 5 hours runs at 100 mL/hr. Clinical pearl: Staged (or "titrated-rate") orders require a separate rate calculation for each stage — never apply one rate to both.

39. Question 259. Scenario: A patient's IV rate is increased partway through the infusion, and the nurse must recalculate the remaining volume and completion time. Order: 0.9% sodium chloride 1,000 mL IV at 125 mL/hr, started at 0700. At 1100, the provider increases the rate to 200 mL/hr. Available: Electronic infusion pump. Question: At 1100, how many mL remain in the bag, and at what time (24-hour clock) will the bag be empty?

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    Correct answer: 500 mL remain; bag empty at 1330 Setup (dimensional analysis): Infused by 1100 = 125 mL/hr × 4 hr = 500 mL Remaining = 1,000 − 500 = 500 mL Time at new rate = 500 mL ÷ 200 mL/hr = 2.5 hr = 2 hr 30 min Completion = 1100 + 2 hr 30 min Raw calculation: 1100 + 2 hr 30 min = 1330 Rounding: Not applicable. Final answer: 500 mL remain; bag empty at 1330 Rationale: From 0700 to 1100 the bag delivered 500 mL (4 hr × 125). The remaining 500 mL at the increased 200 mL/hr takes 2.5 hours, so the bag empties at 1330 (1:30 PM). Clinical pearl: Rate increases shorten the time to empty non-linearly; always recompute remaining volume first, then divide by the new rate.

40. Question 260. Scenario: A newly oriented nurse has calculated a gravity drip rate and asks a colleague to double-check it. Order: 0.9% sodium chloride 1,000 mL IV to infuse over 8 hours. Available: Gravity infusion set with a drop factor of 15 gtt/mL. Question: The new nurse calculated 50 gtt/min. Is this rate correct? If not, identify the error and state the correct flow rate in gtt/min (rounded to the nearest whole drop).

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    Correct answer: No — the rate is too fast. Correct rate: 31 gtt/min. Setup (dimensional analysis): gtt/min = (1,000 mL × 15 gtt/mL) ÷ (8 hr × 60 min/hr) Raw calculation: 15,000 gtt ÷ 480 min = 31.25 gtt/min Rounding: 31.25 rounds to the nearest whole drop → 31 gtt/min. Final answer: 31 gtt/min (the 50 gtt/min calculation is an error) Rationale: The correct gravity rate is 31.25 → 31 gtt/min. A rate of 50 gtt/min would infuse the liter far faster than ordered: 50 gtt/min on a 15 gtt/mL set = 50 ÷ 15 = 3.33 mL/min × 60 = 200 mL/hr, delivering the liter in about 5 hours instead of 8 — a fluid-overload risk. The error likely came from omitting the hour-to-minute conversion (using 1,000 × 15 ÷ 8 ≈ 1,875, or transposing the formula). Clinical pearl: A gravity rate that looks suspiciously fast should trigger a recheck of the drop factor and the time conversion — an error here can cause serious fluid overload.