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 shiftjelly120 mLsoup150 mLIV infusion75 mL/h × 12 hIV antibiotic2 × 100 mLurine375 mLurine425 mLwound drain70 mL

Practice exercise (made-up values, not clinical guidance). The record shows a patient's intake and output for one 12-hour shift. The IV infusion ran at the rate shown for the whole shift. Find the fluid balance B = intake − output in mL (a negative answer means a net loss).

jelly: 120 mLsoup: 150 mLIV infusion: 75 mL/h × 12 hIV antibiotic: 2 × 100 mLurine: 375 mLurine: 425 mLwound drain: 70 mL
B = mL
2.IV fluids & fluid balanceHard
1000 mL80 mL/hstart 13:3018:00: ? mL

Practice exercise (made-up values, not clinical guidance). A 1000 mL bag was started at 13:30 and runs by pump at 80 mL/h. How many mL V are left in the bag at 18:00?

1000 mL80 mL/h13:30 → 18:00
V = mL
3.IV infusion ratesMedium
V = ?15 gtt/mL20 gtt/min12 h

A drip runs at 20 gtt/min through a set of 15 gtt/mL. How many millilitres V does the patient receive in 12 hours?

20 gtt/min15 gtt/mL12 h
V = mL
4.IV infusion ratesHard
900 mL60 gtt/mL42 gtt/mint = ? h

A drip runs at 42 gtt/min through a set of 60 gtt/mL. There are 900 mL left in the bag. How many hours t until it is empty? Round to one decimal place.

42 gtt/min60 gtt/mL900 mL
t = h

3Solutions

1.IV fluids & fluid balance

Answer: B = 500 mL

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 intake

oral: 120 + 150 = 270 mL
IV infusion: 75·12 = 900 mL
IV antibiotic: 2·100 = 200 mL
total intake = 1370 mL

Total output

375 + 425 + 70 = 870 mL

Balance

B = 1370 − 870 = 500 mL

Answer

B = 500 mL

Positive: more fluid went in than came out.

2.IV fluids & fluid balance

Answer: V = 640 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

13:30 → 18:00 = 4.5 h

Volume infused

80·4.5 = 360 mL

Volume left

V = 1000 − 360 = 640 mL

Answer

V = 640 mL
3.IV infusion rates

Answer: V = 960 mL

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.

Rate in mL/h

20·60/15 = 80 mL/h

Volume

V = 80·12 = 960 mL

Answer

V = 960 mL
4.IV infusion rates

Answer: t = 21.4 h

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.

Rate in mL/h

42·60/60 = 42 mL/h

Time left

t = 900/42 = 21.43 ≈ 21.4 h

Answer

t = 21.4 h

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