Order Entry and Processing is 22.5% of the scored PTCE (the PTCB exam). Answer 10 exam style questions on IV flow rates and pediatric dosing and see exactly which concepts would cost you points on test day.
Start the 10 questions →An order calls for 1,000 mL of lactated Ringer's to infuse over 12 hours. What is the flow rate in mL/hr, rounded to the nearest whole number?
These questions cover IV flow rate (mL/hr), IV drip rate: microdrip set, IV drip rate: macrodrip set, infusion time and infusion end time (24-hour clock). Each one shows the correct answer and why every other option is wrong, so a miss tells you exactly what to review before the PTCE.
Prefer to read first? Every question from the practice set above, with the correct answer and why each wrong option is wrong.
Answer: A. Flow rate = volume / time = 1,000 mL / 12 hr = 83.3 mL/hr, rounded to 83 mL/hr.
Why not B: 42 mL/hr spreads the bag over 24 hours instead of 12.
Why not C: 167 mL/hr would run the bag in 6 hours, half the ordered time.
Why not D: 8.3 mL/hr is a decimal-place error. 1,000 / 12 = 83.3.
Exam tactic: mL/hr = total mL / total hours.
Answer: D. gtt/min = mL/hr x drop factor / 60 min = 50 x 60 / 60 = 50 gtt/min. With a 60 gtt/mL set, gtt/min always equals mL/hr.
Why not A: 3,000 is drops per hour (50 x 60). It must be divided by 60 minutes.
Why not B: 13 gtt/min uses a 15 gtt/mL set (50 x 15 / 60) instead of the 60 gtt/mL microdrip.
Why not C: 17 gtt/min uses a 20 gtt/mL set (50 x 20 / 60) instead of the 60 gtt/mL microdrip.
Exam tactic: Microdrip (60 gtt/mL): gtt/min = mL/hr.
Answer: C. Time = 6 hr x 60 = 360 min. gtt/min = 900 mL x 10 gtt/mL / 360 min = 9,000 / 360 = 25 gtt/min.
Why not A: 150 is the flow rate in mL/hr (900 / 6), not drops per minute.
Why not B: 38 gtt/min uses a 15 gtt/mL drop factor instead of the stated 10 gtt/mL.
Why not D: 50 gtt/min uses a 20 gtt/mL drop factor instead of the stated 10 gtt/mL.
Exam tactic: gtt/min = mL x drop factor / minutes. Use the drop factor printed on the set.
Answer: B. Time = volume / rate = 1,000 / 120 = 8.33 hours. 0.33 hour x 60 min = 20 minutes. Total = 8 hours 20 minutes.
Why not A: 8 hours 33 minutes reads the decimal 8.33 hours as 33 minutes. 0.33 hour x 60 = 20 minutes.
Why not C: 8 hours drops the remaining 0.33 hour. At 120 mL/hr, 8 hours delivers only 960 mL.
Why not D: 12 hours corresponds to a rate of about 83 mL/hr, not 120 mL/hr.
Exam tactic: Convert the decimal part of hours to minutes by multiplying by 60.
Answer: A. Duration = 1,200 mL / 150 mL/hr = 8 hours. 0900 + 8 hours = 1700 (5:00 PM).
Why not B: 1800 adds 9 hours. 1,200 / 150 = 8 hours, not 9.
Why not C: 0500 is 5:00 AM. 0900 + 8 hours is 5:00 PM, written 1700 on the 24-hour clock.
Why not D: 1500 adds 6 hours, which would require a rate of 200 mL/hr.
Exam tactic: On the 24-hour clock, times after noon are 1300 and above.
Answer: D. Concentration = 25,000 units / 500 mL = 50 units/mL. Rate = 1,000 units/hr / 50 units/mL = 20 mL/hr.
Why not A: 50 is the concentration (units per mL), not the infusion rate.
Why not B: 10 mL/hr uses 100 units/mL, the concentration of 25,000 units in 250 mL, not in 500 mL.
Why not C: 200 mL/hr is a decimal-place error that would deliver 10,000 units/hr.
Exam tactic: mL/hr = ordered amount per hour / concentration per mL.
Answer: A. Volume = rate x time = 75 mL/hr x 24 hr = 1,800 mL.
Why not B: 3.1 divides the rate by 24 instead of multiplying by it.
Why not C: 180 mL is a decimal-place error. 75 x 24 = 1,800.
Why not D: 2,400 mL corresponds to 100 mL/hr, not 75 mL/hr.
Exam tactic: Volume = mL/hr x hours.
Answer: D. mL/min = 25 gtt/min / 15 gtt/mL = 1.67 mL/min. mL/hr = 1.67 x 60 = 100 mL/hr (or 25 x 60 / 15 = 100).
Why not A: 375 multiplies gtt/min by the drop factor. Drops must be divided by gtt/mL to get mL.
Why not B: 1.7 is the rate in mL per minute (25 / 15). It must be multiplied by 60.
Why not C: 6.25 multiplies by the drop factor and divides by 60, the formula run backwards.
Exam tactic: mL/hr = gtt/min x 60 / drop factor.
Answer: C. 30 minutes = 0.5 hour. Rate = 100 mL / 0.5 hr = 200 mL/hr.
Why not A: 50 mL/hr multiplies 100 mL by 0.5 hour instead of dividing. At 50 mL/hr the bag takes 2 hours.
Why not B: 3.3 is the rate in mL per minute (100 / 30), not per hour.
Why not D: 100 mL/hr would infuse the bag over 60 minutes, not 30.
Exam tactic: For infusions under an hour, convert minutes to hours first.
Answer: B. Dose = 5 mg/kg x 10 kg = 50 mg. Doses per day = 24 / 8 = 3. Daily total = 50 x 3 = 150 mg.
Why not A: 50 mg is a single dose. Every 8 hours means 3 doses per day.
Why not C: 200 mg uses 4 doses per day (every 6 hours).
Why not D: 330 mg multiplies the weight by 2.2. The weight is already in kg.
Exam tactic: Per-dose order: mg/kg x kg, then x doses per day for the daily total.
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