Calculations of IV fluids

Calculating Intravenous Fluids

Introduction to IV Fluid Calculations

• The discussion begins with an overview of intravenous fluid calculations, emphasizing the importance of understanding these methods for students.

• Two primary methods of administering intravenous fluids are introduced: continuous infusion and intermittent infusion.

Types of IV Infusion Methods

• Continuous infusion involves a steady delivery of fluids or drugs, while intermittent infusion is characterized by periodic administration.

• The speaker highlights the significance of knowing how to calculate IV flow rates, especially in emergency situations where precise dosing is critical.

Understanding Drip Factors

• Different drip factors are explained: macro drip sets deliver 10 to 20 drops per ml (larger drops), while micro drip sets provide 60 drops per ml (smaller drops).

• The distinction between macro and micro drips is reiterated, emphasizing their respective applications in clinical settings.

Calculation Methodology

Method One: Three-Step Process

• The first method for calculating IV flow rates involves a three-step process starting with determining the solution volume as ordered by the doctor.

• Step two converts ml per hour into ml per minute, followed by converting this figure into drops per minute based on the drip factor.

Example Calculation

• An example using sodium module orders 1000 ml of D5 water with potassium chloride over eight hours is presented.

• The calculation proceeds through cross-multiplication to determine dosages accurately, demonstrating practical application in real scenarios.

Detailed Flow Rate Calculation Steps

First Example Breakdown

• For the first example, 1000 ml divided by 8 hours results in a flow rate of 125 ml/hour. This value is then converted into minutes.

• Final calculations yield a drop rate of approximately 21 drops per minute using a macro drip set calibrated at 10 drops/ml.

Second Example Overview

• A second example discusses infusing 1.2 liters of normal saline over six hours with a drop factor of 15 drops/ml.

IV Flow Rate Calculation Methods

Method 1: Three-Step Process

• The drop factor is established as 15 drops per ml, leading to a calculation of 3.33 times 15, resulting in approximately 50 drops per minute.

• This method involves a three-step process for calculating IV flow rates, contrasting with the two-step process outlined in Method 2.

• A specific doctor's order is referenced: administering 1000 ml of D5W (5% dextrose in water) with potassium chloride (KCl) at a rate of 20 mEq over eight hours.

• The first step calculates the infusion rate by dividing the total volume (1000 ml) by the time (8 hours), yielding an infusion rate of 125 ml/hour.

• The second step multiplies this rate by the drop factor (10 drops/ml), resulting in approximately 21 drops per minute after rounding.

Method 2: Two-Step Process

• For another example, calculating the IV flow rate for infusing 1.2 liters of normal saline over six hours begins with converting liters to milliliters (1200 ml).

• The first step determines that this equates to an infusion rate of 200 ml/hour when divided by six hours.

• In the second step, multiplying this hourly rate by the drop factor (15 drops/ml), results in a total of about 50 drops per minute after further calculations.

Method 3: One-Step Formula

• Transitioning to Method Three, which simplifies calculations into one formula involving total fluid amount and drop factor.

• An example using D5W and KCl again illustrates how to calculate total volume administered over time; here it’s set at eight hours for clarity.

• The formula used is Total Volume x Drop Factor / Total Time in minutes; thus, for this case, it results in approximately 21 drops/minute after necessary conversions and calculations.

Practice Problems and Application

• A practice problem involves calculating bolus dosage for heparin based on patient weight; initial bolus is set at a specific unit/kg ratio.