IV Flow Rates¶
Overview¶
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 Formula¶
This is the foundation of all IV flow rate calculations.
Simple Flow Rate Calculations¶
Example 1: Order: 1000 mL 0.9% NaCl over 8 hours What is the flow rate in mL/hr?
Example 2: Order: 500 mL D5W over 4 hours What is the flow rate in mL/hr?
Example 3: Order: 250 mL 0.45% NaCl over 3 hours What is the flow rate in 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 flow rates 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 What is the flow rate in mL/hr?
Convert 30 minutes to hours first: [30 \text{ min} \times \frac{1 \text{ hr}}{60 \text{ min}} = 0.5 \text{ hr}]
Then calculate rate: [\frac{100 \text{ mL}}{0.5 \text{ hr}} = 200 \text{ mL/hr}]
Example 5: Order: 250 mL over 90 minutes What is the flow rate in mL/hr?
Round to nearest whole number: 167 mL/hr
Calculating Volume from Rate and Time¶
Sometimes you need to find the total volume infused given a rate and a time period.
Example 6: An IV is running at 125 mL/hr. How much fluid will the patient receive in 6 hours?
Example 7: An IV is running at 75 mL/hr. How much fluid will the patient receive in 8 hours?
Remaining Volume and Time¶
Example 8: An IV of 1000 mL is running at 125 mL/hr. After 3 hours, how much fluid remains?
Step 1 — volume infused: [125 \text{ mL/hr} \times 3 \text{ hr} = 375 \text{ mL}]
Step 2 — volume remaining: [1000 \text{ mL} - 375 \text{ mL} = 625 \text{ mL}]
Step 3 — 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:
- Rate — mL/hr matches your calculation
- Volume to be infused (VTBI) — total volume of the bag
- Drug library — if pump has one, select correct drug
- Soft and hard limits — ensure alerts are active
- Second nurse check — for high alert medications
Practice Problems¶
Problem 1
Order: 1000 mL Lactated Ringer's over 10 hours What is the flow rate in mL/hr?
Answer
Problem 2
Order: 500 mL 0.9% NaCl over 6 hours What is the flow rate in mL/hr?
Answer
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
Convert time: [45 \text{ min} \times \frac{1 \text{ hr}}{60 \text{ min}} = 0.75 \text{ hr}]
Calculate rate: [\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
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}]
Approximately 2 hours and 40 minutes remaining.
Problem 6
Order: 250 mL over 20 minutes What is the flow rate in mL/hr?
Answer
Convert time: [20 \text{ min} \times \frac{1 \text{ hr}}{60 \text{ min}} = 0.33 \text{ hr}]
Calculate rate: [\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 for most clinical situations. Verify the order and confirm with the prescriber before programming the pump.
Clinical Tip
After programming an IV pump always trace the tubing from the bag to the patient before starting the infusion. This confirms the correct fluid is connected to the correct line and prevents wrong-route errors.