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 shiftwater150 mLjuice120 mLice chips240 mLIV infusion80 mL/h × 12 hIV antibiotic2 × 50 mLurine400 mLurine450 mLurine325 mLvomit200 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 total intake I in mL. Count ice chips as half their volume.

water: 150 mLjuice: 120 mLice chips: 240 mLIV infusion: 80 mL/h × 12 hIV antibiotic: 2 × 50 mL
I = mL
2.IV fluids & fluid balanceHard
1000 mL→ 80 mL/hstart 08:00ttotal​ = ? h150 mL/h × 2 h

Practice exercise (made-up values, not clinical guidance). A 1000 mL infusion starts at 08:00 at 150 mL/h. After 2 hours the rate is changed to 80 mL/h and is not changed again. How many hours t after the start will the bag be empty? Round to one decimal place.

1000 mL150 mL/h · 2 h80 mL/h
t = h
3.IV infusion ratesMedium
250 mL15 gtt/mL4 h? gtt/min

Infuse 250 mL over 4 hours with a giving set of 15 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

250 mL4 h15 gtt/mL
R = gtt/min
4.IV infusion ratesHard
2 g500 mL? mL/h1.5 mg/min

A bag contains 2 g of a drug in 500 mL. The order is 1.5 mg per minute. At what rate R do you set the pump, in mL/h?

2 g/500 mL1.5 mg/min
R = mL/h

3Solutions

1.IV fluids & fluid balance

Answer: I = 1450 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.

Add the intake

oral: 150 + 120 = 270 mL
ice chips: 240/2 = 120 mL
IV infusion: 80·12 = 960 mL
IV antibiotic: 2·50 = 100 mL
I = 1450 mL

Answer

I = 1450 mL
2.IV fluids & fluid balance

Answer: t = 10.8 h

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.

First part

150·2 = 300 mL
1000 − 300 = 700 mL left

Second part

700/80 = 8.75 h

Total time

t = 2 + 8.75 = 10.75 ≈ 10.8 h

Answer

t = 10.8 h

That is about 10 h 45 min, so the bag runs out at about 18:45.

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

4·60 = 240 min

Drip rate

R = 250·15/240 = 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: R = 22.5 mL/h

Dose-based infusions: concentration = amount of drug in the bag/bag volume. Pump rate (mL/h) = dose per hour/concentration, and dose per hour = mL/h × concentration. Convert per-minute doses to per-hour (× 60) and keep the mass units the same (1 g = 1000 mg, 1 mg = 1000 mcg).

Concentration

2000 mg/500 mL = 4 mg/mL

Dose per hour

1.5·60 = 90 mg/h

Pump rate

R = 90/4 = 22.5 mL/h

Answer

R = 22.5 mL/h

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