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IV Flow Rates

An IV flow rate tells you how many milliliters of fluid to deliver per hour (mL/hr). This is the standard unit for programming electronic infusion pumps in clinical practice.

The Basic Relationship

\[\text{Flow rate (mL/hr)} = \frac{\text{Volume (mL)}}{\text{Time (hr)}}\]

Simple Flow Rate Calculations

Example 1: Order: 1000 mL 0.9% NaCl over 8 hours

\[\frac{1000 \text{ mL}}{8 \text{ hr}} = 125 \text{ mL/hr}\]

Example 2: Order: 500 mL D5W over 4 hours

\[\frac{500 \text{ mL}}{4 \text{ hr}} = 125 \text{ mL/hr}\]

Example 3: Order: 250 mL 0.45% NaCl over 3 hours

\[\frac{250 \text{ mL}}{3 \text{ hr}} = 83.3 \text{ mL/hr}\]

Round to nearest whole number: 83 mL/hr

Rounding IV rates

IV pump rates are set in whole numbers (mL/hr). Always round to the nearest whole number unless your facility pump supports decimal rates.

Time Conversion

Orders are sometimes written in minutes rather than hours.

Example 4: Order: 100 mL 0.9% NaCl over 30 minutes

\[30 \cancel{\text{ min}} \times \frac{1 \text{ hr}}{60 \cancel{\text{ min}}} = 0.5 \text{ hr}\]
\[\frac{100 \text{ mL}}{0.5 \text{ hr}} = 200 \text{ mL/hr}\]

Example 5: Order: 250 mL over 90 minutes

\[90 \cancel{\text{ min}} \times \frac{1 \text{ hr}}{60 \cancel{\text{ min}}} = 1.5 \text{ hr}\]
\[\frac{250 \text{ mL}}{1.5 \text{ hr}} = 166.7 \text{ mL/hr}\]

Round to: 167 mL/hr

Calculating Volume from Rate and Time

\[\text{Volume (mL)} = \text{Rate (mL/hr)} \times \text{Time (hr)}\]

Example 6: An IV is running at 125 mL/hr. How much fluid will the patient receive in 6 hours?

\[125 \text{ mL/hr} \times 6 \text{ hr} = 750 \text{ mL}\]

Remaining Volume and Time

Example 7: A 1000 mL IV is running at 125 mL/hr. After 3 hours, how much fluid remains and how much longer will it run?

Volume infused: [125 \text{ mL/hr} \times 3 \text{ hr} = 375 \text{ mL}]

Volume remaining: [1000 \text{ mL} - 375 \text{ mL} = 625 \text{ mL}]

Time remaining: [\frac{625 \text{ mL}}{125 \text{ mL/hr}} = 5 \text{ hr}]

Pump Programming

Verify pump settings

When programming an IV pump always verify:

  1. Rate — mL/hr matches your calculation
  2. Volume to be infused (VTBI) — total volume of the bag
  3. Drug library — if pump has one, select the correct drug
  4. Soft and hard limits — ensure alerts are active
  5. Second nurse check — for high alert medications

Trace the line

After programming, trace the tubing from the bag to the patient before starting the infusion. This confirms the correct fluid is connected to the correct line.

Practice Problems

Problem 1

Order: 1000 mL Lactated Ringer's over 10 hours What is the flow rate in mL/hr?

Answer
\[\frac{1000 \text{ mL}}{10 \text{ hr}} = 100 \text{ mL/hr}\]

Problem 2

Order: 500 mL 0.9% NaCl over 6 hours What is the flow rate in mL/hr?

Answer
\[\frac{500 \text{ mL}}{6 \text{ hr}} = 83.3 \text{ mL/hr}\]

Round to: 83 mL/hr

Problem 3

Order: 150 mL 0.9% NaCl over 45 minutes What is the flow rate in mL/hr?

Answer
\[45 \cancel{\text{ min}} \times \frac{1 \text{ hr}}{60 \cancel{\text{ min}}} = 0.75 \text{ hr}\]
\[\frac{150 \text{ mL}}{0.75 \text{ hr}} = 200 \text{ mL/hr}\]

Problem 4

An IV is running at 100 mL/hr. How much fluid does the patient receive in 12 hours?

Answer
\[100 \text{ mL/hr} \times 12 \text{ hr} = 1200 \text{ mL}\]

Problem 5

A 1000 mL bag is running at 150 mL/hr. After 4 hours, how much fluid remains and how much longer will it run?

Answer

Volume infused: [150 \text{ mL/hr} \times 4 \text{ hr} = 600 \text{ mL}]

Volume remaining: [1000 - 600 = 400 \text{ mL}]

Time remaining: [\frac{400 \text{ mL}}{150 \text{ mL/hr}} = 2.67 \text{ hr}]

Convert decimal hours to minutes: [0.67 \text{ hr} \times 60 \text{ min/hr} = 40 \text{ min}]

2 hours and 40 minutes remaining.

Problem 6

Order: 250 mL over 20 minutes What is the flow rate in mL/hr?

Answer
\[20 \cancel{\text{ min}} \times \frac{1 \text{ hr}}{60 \cancel{\text{ min}}} = 0.33 \text{ hr}\]
\[\frac{250 \text{ mL}}{0.33 \text{ hr}} = 757.6 \text{ mL/hr}\]

Round to: 758 mL/hr

Verify this rate

Rates above 500 mL/hr are unusual. Verify the order and confirm with the prescriber before programming.

Self-Check