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
IntakeOutput8-hour shiftjuice200 mLjelly100 mLice chips200 mLIV infusion80 mL/h × 8 hIV antibiotic1 × 100 mLurine300 mLurine325 mLurine400 mLurine350 mLwound drain30 mL

Practice exercise (made-up values, not clinical guidance). The record shows a patient's intake and output for one 8-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). Count ice chips as half their volume.

juice: 200 mLjelly: 100 mLice chips: 200 mLIV infusion: 80 mL/h × 8 hIV antibiotic: 1 × 100 mLurine: 300 mLurine: 325 mLurine: 400 mLurine: 350 mLwound drain: 30 mL
B = mL
2.IV fluids & fluid balanceHard
500 mL150 mL infused120 mL/h15:00t = ? h

Practice exercise (made-up values, not clinical guidance). A 500 mL bag runs by pump at 120 mL/h. At 15:00, 150 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.

500 mL150 mL infused120 mL/h
t = h
3.IV infusion ratesMedium
20 gtt/mL60 mL/h? gtt/min

An infusion is ordered at 60 mL/h, but no pump is available. It runs by gravity through a giving set of 20 gtt/mL. Find the drip rate R in drops per minute.

60 mL/h20 gtt/mL
R = gtt/min
4.IV infusion ratesHard
400 mL20 gtt/mL20 gtt/mint = ? h

A drip runs at 20 gtt/min through a set of 20 gtt/mL. There are 400 mL left in the bag. How many hours t until it is empty? Round to one decimal place.

20 gtt/min20 gtt/mL400 mL
t = h

3Solutions

1.IV fluids & fluid balance

Answer: B = −265 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: 200 + 100 = 300 mL
ice chips: 200/2 = 100 mL
IV infusion: 80·8 = 640 mL
IV antibiotic: 1·100 = 100 mL
total intake = 1140 mL

Total output

300 + 325 + 400 + 350 + 30 = 1405 mL

Balance

B = 1140 − 1405 = −265 mL

Answer

B = −265 mL

Negative: the patient lost more fluid than went in.

2.IV fluids & fluid balance

Answer: t = 2.9 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.

Volume left

500 − 150 = 350 mL

Time

t = 350/120 = 2.917 ≈ 2.9 h

Answer

t = 2.9 h

That is about 2 h 55 min, so the bag runs out at about 17:55.

3.IV infusion rates

Answer: R = 20 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.

Millilitres per minute

60/60 = 1 mL/min

Drip rate

R = 1·20 = 20 gtt/min

Answer

R = 20 gtt/min
4.IV infusion rates

Answer: t = 6.7 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

20·60/20 = 60 mL/h

Time left

t = 400/60 = 6.667 ≈ 6.7 h

Answer

t = 6.7 h

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