IV Drip Rate Calculator (Dose Driven)
Calculate infusion rates based on desired dosage, patient weight, and drug concentration.
Formula used: [(Dose x Weight x 60) / Concentration] = mL/hr.
Please double-check all calculations with clinical protocols before administration.
Understanding Dose-Driven IV Rate Calculations
In critical care settings, calculating intravenous (IV) drip rates accurately is a fundamental skill for nurses and paramedics. Unlike simple gravity infusions based purely on volume over time, dose-driven calculations are required when a specific amount of a medication (like dopamine, dobutamine, or nitroprusside) must be delivered based on the patient's body weight.
The Core Formula
To determine the flow rate for a weight-based medication, you must account for the patient's weight, the desired dose (usually in micrograms per kilogram per minute), and the concentration of the drug in the solution. The standard calculation process involves these steps:
- Step 1: Determine the Total Dose per Minute.
(Weight in kg) × (Dose in mcg/kg/min) = Total mcg/min needed. - Step 2: Determine the Concentration.
(Total Drug mg × 1000) / (Total Volume mL) = Concentration in mcg/mL. - Step 3: Calculate Flow Rate in mL/min.
(Total mcg/min) / (Concentration in mcg/mL) = mL/min. - Step 4: Convert to Hourly Rate (for Pumps).
(mL/min) × 60 = mL/hr. - Step 5: Calculate Drip Rate (for Gravity).
(mL/min) × (Drop Factor of Tubing) = drops per minute (gtt/min).
Common Drop Factors
The "Drop Factor" refers to how many drops it takes to equal 1 milliliter (mL) of fluid. This is determined by the administration set (tubing) you are using:
- Microdrip (60 gtt/mL): Used for pediatrics or potent medications requiring precise flow control. With microdrip tubing, 60 drops equal 1 mL.
- Macrodrip (10, 15, or 20 gtt/mL): Used for rapid fluid replacement or routine adult infusions. The packaging on the tubing will specify the factor.
Clinical Example
Consider a patient weighing 80 kg who requires Dopamine at 5 mcg/kg/min. The pharmacy sends a bag containing 400 mg of Dopamine in 250 mL of D5W.
1. Total Dose: 80 kg × 5 mcg = 400 mcg/min.
2. Concentration: 400 mg = 400,000 mcg. 400,000 / 250 = 1,600 mcg/mL.
3. Flow Rate: 400 mcg/min / 1,600 mcg/mL = 0.25 mL/min.
4. Pump Setting: 0.25 × 60 = 15 mL/hr.
5. Gravity (60 gtt set): 0.25 × 60 = 15 gtt/min.