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 shiftwater150 mLjuice100 mLice chips120 mLIV infusion100 mL/h × 8 hIV antibiotic2 × 100 mLurine200 mLurine375 mLurine300 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 patient weighs 85 kg. Find the average urine output U in mL/kg/h. Round to two decimal places.

85 kg8 hurine: 200 mLurine: 375 mLurine: 300 mLwound drain: 30 mL
U = mL/kg/h
2.IV fluids & fluid balanceHard
1000 mL400 mL infused125 mL/h13:30t = ? h

Practice exercise (made-up values, not clinical guidance). A 1000 mL bag runs by pump at 125 mL/h. At 13:30, 400 mL have already been infused. How many hours t until the bag is empty? Round to one decimal place.

1000 mL400 mL infused125 mL/h
t = h
3.IV infusion ratesMedium
V = ?20 gtt/mL35 gtt/min3 h

A drip runs at 35 gtt/min through a set of 20 gtt/mL. How many millilitres V does the patient receive in 3 hours?

35 gtt/min20 gtt/mL3 h
V = mL
4.IV infusion ratesHard
500 mg250 mL8 mL/h? mg/h

A bag contains 500 mg of a drug in 250 mL and runs at 8 mL/h. How many milligrams per hour D does the patient receive?

500 mg/250 mL8 mL/h
D = mg/h

3Solutions

1.IV fluids & fluid balance

Answer: U = 1.29 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

200 + 375 + 300 = 875 mL

Per kilogram per hour

U = 875/(85·8) = 1.287 ≈ 1.29 mL/kg/h

Answer

U = 1.29 mL/kg/h
2.IV fluids & fluid balance

Answer: t = 4.8 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.

Volume left

1000 − 400 = 600 mL

Time

t = 600/125 = 4.8 h

Answer

t = 4.8 h

That is about 4 h 48 min, so the bag runs out at about 18:18.

3.IV infusion rates

Answer: V = 315 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

35·60/20 = 105 mL/h

Volume

V = 105·3 = 315 mL

Answer

V = 315 mL
4.IV infusion rates

Answer: D = 16 mg/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.

Concentration

500/250 = 2 mg/mL

Dose rate

D = 2·8 = 16 mg/h

Answer

D = 16 mg/h

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