IV calculations

Calculation of Basic IV Drip Rates

Background: Intravenous Fluids

  • IV Therapy: Involves the administration of fluids, blood, medications, and nutrients directly into the bloodstream.

Safety Alert

  • Nurse Responsibilities:

    • Administer IV therapy to the correct patient at the appropriate rate.

    • Monitor the patient’s response to prevent adverse reactions.

    • Infusions that are too rapid or inappropriate can lead to severe complications.

IV Infusion Sets

  • Types of Drip Sets:

    • Microdrip: 60 gtt/mL

      • Suitable for slow infusion of small volumes.

    • Macrodrip: Check package for specifics (commonly 10 gtt/mL or 15 gtt/mL).

      • Used for larger volumes over shorter time frames.

Choosing the Infusion Set

  • Microdrip:

    • For long-duration infusions.

    • Ideal for small fluid amounts.

  • Macrodrip:

    • Specified for large fluid volumes in a short time frame.

    • Counting microdrips can be cumbersome; macrodrips simplify the process.

Electronic Infusion Devices

  • Functions of Electronic Pumps:

    • Specific tubing for machine compatibility.

    • Volumetric Pumps: Deliver precise fluid amounts at constant rates.

    • “Smart” Pumps: Include safety features, programmed medication references, and infusion rate safety ranges.

IV Orders

  • Criteria for Prescriber Orders:

    • Name of the IV solution.

    • Medication to be added (if applicable).

    • Total volume to be administered.

    • Infusion time frame.

    • Rate calculated as: Amount of Fluid / Time (e.g., 1000 mL over 8 hours or 125 mL/hour).

Calculating IV Flow Rates

  • Drop Factor Calculation:

    • Essential to know the drop factor for the specific tubing used (how many drops per mL).

    • Standard calculations involve converting mL/hour to drops/minute (gtt/min).

    • Always round gtt/min to the nearest whole number.

Drip Rate Example

  • Calculation Scenario:

    • Order: 1000 mL D5W at 120 mL/hour with macrodrip 15 gtt/mL.

    • Drip Rate: 120 mL/hr × 15 gtt/mL ÷ 60 min/hr = 30 gtt/min.

Duration of IV Infusion

  • Calculate Time:

    • Formula: Total Volume / Rate (mL/hr).

    • E.g., 500 mL at 125 mL/hour → 500 mL / 125 mL/hr = 4 hours.

IV Calculation Practice

  • Example 1:

    • Continuous infusion of Normal Saline at 125 mL/hr with a drop factor of 15 gtt/mL results in:

      • gtt/min = 125 mL/hr × 15 gtt/mL ÷ 60 = 31.25 gtt/min -> 31 gtt/min when rounded.

    • Pump Setting: 125 mL/hr.

  • Example 2:

    • Physician Order: Iron dextran 100 mg in 200 mL of 0.9% NSS over 6 hours.

      • Rate: 33.33 mL/hr

      • Volume to Infuse (VTBI): 200 mL.

Case Study Practice

  • Patient Case:

    • Patient Mr. Flint, ordered 1L Normal Saline at 100 mL/hr, infusion begins at 0800.

    • Completion Time: IV bag will finish at 1800 (or 6 PM).