IV Fluids and Fluid Balance: cram pack

Formula sheets, the key method steps for every topic and 4 practice problems, with full solutions at the back.

New problemsBack to the course

In the print window, choose “Save as PDF” to keep a copy on your device.

1Formulas and methods

IV fluids & fluid balance

Holliday–Segar per hour
4 mL/kg (first 10 kg) + 2 mL/kg (next 10 kg) + 1 mL/kg (each kg above 20)
Holliday–Segar per day
100 / 50 / 20 mL/kg for the same bands
Fluid balance
intake − output
Ice chips
count as half their volume
Urine output
mL/kg/h = mL / (kg × h)
Infusion time
time (h) = volume left (mL) / rate (mL/h)
Volume infused
mL = rate × time

IV infusion rates

Pump rate
mL/h = volume (mL)/time (h)
Drip rate
drops/min = volume (mL) × drop factor / time (min)
Infusion time
time (h) = volume (mL)/rate (mL/h)

Method

  1. Pump rate in mL/h: volume divided by time in hours.
  2. Drip rate in drops/min: volume × drop factor divided by time in minutes.
  3. For time remaining: volume left divided by the rate.
  4. Round as the question or the equipment requires.

2Practice problems

1.IV fluids & fluid balanceMedium
IntakeOutput12-hour shiftmilk200 mLjuice100 mLwater200 mLIV infusion50 mL/h × 12 hIV antibiotic2 × 100 mLurine175 mLurine425 mLurine175 mLurine300 mLwound drain50 mLvomit250 mL

Practice exercise (made-up values, not clinical guidance). The record shows a patient's intake and output for one 12-hour shift. The patient weighs 62 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.

62 kg12 hurine: 175 mLurine: 425 mLurine: 175 mLurine: 300 mLwound drain: 50 mLvomit: 250 mL
U = mL/kg/h
2.IV fluids & fluid balanceHard
1000 mL125 mL/hstart 10:3014:30: ? mL

Practice exercise (made-up values, not clinical guidance). A 1000 mL bag was started at 10:30 and runs by pump at 125 mL/h. How many mL V are left in the bag at 14:30?

1000 mL125 mL/h10:30 → 14:30
V = mL
3.IV infusion ratesMedium
500 mL15 gtt/mL8 h? gtt/min

Infuse 500 mL over 8 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

500 mL8 h15 gtt/mL
R = gtt/min
4.IV infusion ratesHard
290 mLleft? mL/h4 h left

500 mL was ordered over 8 hours. After 4 hours you find that 290 mL is still in the bag, and the order must still finish on time. By what percentage Δ must the original pump rate be increased?

500 mL / 8 hafter 4 h: 290 mL
Δ = %

3Solutions

1.IV fluids & fluid balance

Answer: U = 1.44 mL/kg/h

Intake and output: intake counts everything that goes in (oral fluids, IV infusions, IV medications and flushes, tube feeds); ice chips count as half their volume. Output counts urine, drains, vomit and other losses. Balance = total intake − total output; a negative balance is a net loss. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.

Total urine

175 + 425 + 175 + 300 = 1075 mL

Per kilogram per hour

U = 1075/(62·12) = 1.445 ≈ 1.44 mL/kg/h

Answer

U = 1.44 mL/kg/h
2.IV fluids & fluid balance

Answer: V = 500 mL

Infusion time: time (h) = volume to infuse (mL)/rate (mL/h); use the volume still left in the bag, not the bag size. Volume infused = rate × time. Convert decimal hours to hours and minutes with the fraction × 60 (0.5 h = 30 min, not 50 min). The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.

Elapsed time

10:30 → 14:30 = 4 h

Volume infused

125·4 = 500 mL

Volume left

V = 1000 − 500 = 500 mL

Answer

V = 500 mL
3.IV infusion rates

Answer: R = 16 gtt/min

Infusion rates: a pump is set in mL/h = volume/time in hours. A gravity drip is counted in drops per minute: gtt/min = volume (mL) × drop factor (gtt/mL)/time (min). The drop factor is printed on the tubing package: macrodrip sets deliver 10, 15 or 20 gtt/mL (blood sets often 10 gtt/mL in the US, 15 in the UK) and microdrip sets 60 gtt/mL. Always use the drop factor the question or package gives.

Time in minutes

8·60 = 480 min

Drip rate

R = 500·15/480 = 15.63 ≈ 16 gtt/min

Answer

R = 16 gtt/min

At the bedside you round to the nearest whole drop: 16 gtt/min.

4.IV infusion rates

Answer: Δ = 16 %

Infusion rates: a pump is set in mL/h = volume/time in hours. A gravity drip is counted in drops per minute: gtt/min = volume (mL) × drop factor (gtt/mL)/time (min). The drop factor is printed on the tubing package: macrodrip sets deliver 10, 15 or 20 gtt/mL (blood sets often 10 gtt/mL in the US, 15 in the UK) and microdrip sets 60 gtt/mL. Always use the drop factor the question or package gives.

Original rate

500/8 = 62.5 mL/h

New rate

R = 290/4 = 72.5 mL/h

Percentage change

Δ = (72.5 − 62.5)/62.5·100% = 16%

Answer

Δ = 16%

Many hospitals allow such an adjustment up to 25% without a new order; check local policy.

ExamProblems · examproblems.com/courses/iv-fluids-and-fluid-balance