Overview
This lecture covers pharmacy calculations for IV flow rates, including key concepts, unit conversions, calculation methods, and examples relevant for clinical practice.
What are IV Flow Rates?
- IV flow rate is the volume of medication delivered per unit of time via the intravenous (IV) route.
- Common units include milliliters per hour (mL/hr) and drops per minute (gtts/min).
IV Administration Sets & Drop Factors
- IV sets connect the IV bag to the patient and can use a gravity drip chamber or electronic pump.
- Drop factor (gtts/mL) defines how many drops make up one milliliter; varies by set type.
- Macro sets deliver larger drops (e.g., 10 gtts/mL); micro sets deliver smaller drops (e.g., 60 gtts/mL).
Common Conversions for Calculations
- 1 L = 1000 mL
- 1 hr = 60 min
- 1 g = 1000 mg
- 1 mg = 1000 mcg
Methods for Flow Rate Calculations
- Method 1: Set up fractions so units cancel, leaving only desired units, then multiply and divide as needed.
- Method 2: Set up equivalent fractions, cross-multiply, and divide to solve for the unknown (x).
Examples of Flow Rate Calculations
- To find mL/hr: Divide total mL by hours of infusion.
- To find mL per X minutes: Convert hours to minutes, set up fractions, and solve for mL infused per time interval.
- To find drops/min: Multiply mL by drop factor, divide by total minutes of infusion.
- For medications with dosing limits (e.g., vancomycin), convert to required units and use provided rate to find total infusion time.
Key Terms & Definitions
- Flow Rate — Volume of IV fluid delivered per unit time (e.g., mL/hr or gtts/min).
- Drop Factor (gtts/mL) — Number of drops needed to make 1 mL of solution.
- Macro Set — IV set delivering large drops (e.g., 10 gtts/mL).
- Micro Set — IV set delivering small drops (e.g., 60 gtts/mL).
- Cross Multiplication — Mathematical process to solve proportions.
Action Items / Next Steps
- Practice converting between units (L, mL, hr, min, g, mg, mcg).
- Complete flow rate calculation practice problems using both methods.
- Review drop factors for IV sets used in your clinical setting.