Question

Calculate the IV flow rate in \(\mathrm{gtt} / \mathrm{min}\) for the following IV administrations, unless another unit of measure is stated. An IV of \(1,000 \mathrm{~mL}\) D5 \(1 / 2 \mathrm{NS}\) has been ordered to infuse at \(125 \mathrm{~mL} / \mathrm{hr}\). Drop factor: \(15 \mathrm{gtt} / \mathrm{mL}\) The IV was hung at 7 AM. At 11 AM, you check the IV, and there is \(400 \mathrm{~mL}\) left. Recalculate the rate in \(\mathrm{gtt} / \mathrm{min}\) for the remaining solution. Determine the percentage of change, and state your course of action.

Short answer

Rate is 37.5 gtt/min with a 20% increase in speed; adjust to 31.25 gtt/min.

Step-by-step solution

Calculate Total Volume Infused

The IV initially had a total volume of 1,000 mL. By 11 AM, 400 mL remains. Therefore, the volume that has already been infused is: \[ 1,000 \, \text{mL} - 400 \, \text{mL} = 600 \, \text{mL} \]

Calculate Infusion Time Elapsed

The infusion started at 7 AM and was checked at 11 AM. The time that has elapsed is:\[ 11 \, \text{AM} - 7 \, \text{AM} = 4 \, \text{hours} \]

Calculate Actual Infusion Rate

The rate can be calculated using the total volume infused over time:\[ \text{Rate} = \frac{600 \, \text{mL}}{4 \, \text{hours}} = 150 \, \text{mL/hr} \]

Convert Actual Infusion Rate to Drops Per Minute

To find the infusion rate in \(gtt/min\), use the drop factor (15 gtt/mL):\[ \text{Infusion rate in } gtt/min = 150 \, \text{mL/hr} \times \frac{15 \, \text{gtt/mL}}{60 \, \text{minutes/hour}} \]\[ = 37.5 \, \text{gtt/min} \]

Calculate Percentage Change in Infusion Rate

The original prescription was for 125 mL/hr.The percentage change in rate is:\[ \text{Percentage Change} = \left(\frac{150 \, \text{mL/hr} - 125 \, \text{mL/hr}}{125 \, \text{mL/hr}}\right) \times 100\%\]\[ = 20\% \] increase.

Decision and Course of Action

The IV was running 20% faster than ordered. Adjust the infusion rate to slow it to the originally prescribed rate of 125 mL/hr, which corresponds to 31.25 gtt/min.

Key concepts

Infusion Rate

The infusion rate is a critical concept in IV therapy, determining the speed at which intravenous fluids are delivered to a patient. It is usually expressed in milliliters per hour (mL/hr) or drops per minute (gtt/min). Calculating the correct infusion rate ensures that the patient receives the right amount of medication or fluid within a given time.
For example, if an IV is set to infuse at 150 mL/hr, it means that in one hour, 150 milliliters of fluid will enter the patient's bloodstream. To convert this to drops per minute, a drop factor (more on this later) is used. This conversion is essential when using a gravity drip, allowing health professionals to visually regulate the fluid flow by counting the drops in a set time.

Percentage Change

Percentage change is a valuable calculation in evaluating how a current process differs from a set standard or previous status. It expresses the difference as a percentage to understand the scale of deviation.
To calculate percentage change in an infusion rate, you subtract the original rate from the new rate, divide by the original rate, and then multiply by 100. For example, if an initial rate was 125 mL/hr but was later found to be 150 mL/hr, the percentage increase is calculated as follows:

• Difference = 150 mL/hr - 125 mL/hr = 25 mL/hr.
• Percentage Change = (25 / 125) × 100 = 20%.

An increase like this means that the infused volume is higher than intended, and adjustments might be necessary to comply with the original prescription.

IV Administration

Intravenous (IV) administration is a crucial method of delivering medications or fluids directly into a patient's vein, ensuring rapid absorption and immediate effect. It is especially useful in emergency situations or when oral administration is not viable.
There are several ways to administer IV therapy: using an infusion pump for precise control, or a gravity drip where the rate is manually set using a roller clamp and measured using the drop factor. Correct IV administration depends on accurate calculations of the infusion rate and adjustments as needed to meet the treatment plan.
Healthcare providers must continually monitor IV therapy to ensure it meets the prescribed rate and volume, adjusting as necessary for patient safety and optimal outcomes.

Drop Factor

The drop factor is an important concept in calculating the infusion rate without an electronic infusion pump. It refers to the number of drops (gtt) in one milliliter (mL) of a solution. Common drop factors are 10, 15, 20, or 60 gtt/mL, chosen based on the desired infusion rate and equipment available.
For example, if the drop factor is 15 gtt/mL and you need to convert an infusion rate from mL/hr to gtt/min, you use the formula:

• Infusion rate in gtt/min = (Rate in mL/hr × Drop factor) / 60.

This helps in setting manual IV drips accurately. Without understanding the drop factor, it would be difficult to ensure that the patient receives the right volume within the prescribed time frame. Adjustments are often necessary, especially if the initial rate was incorrect, as can be determined from a percentage change calculation.