A CRI delivers a drug continuously at a dose per kg per hour. The amount of drug added to the fluid bag is back-calculated from the dose, weight, and how long the bag should last.
The example
2 µg/kg/min context shown as mg/hr.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | Dose × wt × hrs | total drug |
| 3 | ÷ concentration | → mL to add |
The formula
The formula:
How it works
How it works:
- Total drug needed = dose/kg/hr × weight × hours the bag runs.
- Divide by the drug concentration (mg/mL) for the volume of drug to add.
- Keep units consistent — convert µg to mg and minutes to hours first.
- Set the fluid pump rate so the bag empties over the intended hours.
Educational use only — not veterinary or medical advice. Dosing, fluid rates, and protocols must be set and verified by a licensed veterinarian for the individual patient. Always double-check against the drug label and a current formulary.
Try it: interactive demo
Dose (mg/kg/hr), weight, hours, drug mg/mL.
Variations
Total drug (mg)
Before volume:
µg/kg/min to mg/kg/hr
Unit convert:
Pump rate
Bag ÷ hours:
Pitfalls & errors
Unit conversions. µg→mg (÷1000) and min→hr (×60) before the formula.
Bag run time. Match the pump rate so the bag lasts the intended hours.
Not advice. CRIs must be calculated and checked by a veterinarian.
Practice workbook
Frequently asked questions
How do I calculate a CRI in Excel?
How do I convert µg/kg/min to mg/kg/hr?
How do I set the pump rate?
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