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 D5W \(1,000 \mathrm{~mL}\) was ordere to infuse over \(8 \mathrm{hr}\) at a rate of \(42 \mathrm{gtt} / \mathrm{min}(42\) macrogtt \(/ \mathrm{min})\) Drop factor: \(20 \mathrm{gtt} / \mathrm{mL}\) After \(4 \mathrm{hr}\), you notice that only \(400 \mathrm{~mL}\) has infused. Recalculate the rate in gtt/min for the remaining solution. Determine the percentage of change, and state your course of action.

Short answer

Adjust flow rate to 50 gtt/min. This is a 19.05% increase from the previous rate.

Step-by-step solution

Calculate Total Infusion Time Left

The initial infusion time was 8 hours. Since 4 hours have passed, the remaining infusion time is 8 hours - 4 hours = 4 hours.

Calculate the Remaining Volume to be Infused

Initially, 1,000 mL was to be infused. After 4 hours, 400 mL has been infused, so the remaining volume is 1,000 mL - 400 mL = 600 mL.

Convert Remaining Time from Hours to Minutes

The remaining time is 4 hours, which needs to be converted to minutes. Thus, 4 hours \( \times 60 \frac{\mathrm{minutes}}{\mathrm{hour}} = 240 \mathrm{minutes} \).

Calculate the New Flow Rate

Use the formula: \( \text{Flow rate} = \left(\frac{\text{Volume to infuse} \times \text{Drop factor}}{\text{Time in minutes}}\right)\). The remaining volume is 600 mL and the drop factor is 20 gtt/mL. Therefore, \( \text{Flow rate} = \left(\frac{600 \times 20}{240}\right) = 50 \mathrm{gtt/min}\).

Determine Percentage of Change

The original flow rate was 42 gtt/min. The new flow rate is 50 gtt/min. The percentage of change is \( \left(\frac{50 - 42}{42}\right) \times 100\% = 19.05\% \).

State Course of Action

Adjust the IV flow rate to 50 gtt/min for the remaining duration to ensure the patient receives the prescribed volume. Monitor the IV setup regularly to confirm the adjusted rate is maintained.

Key concepts

Drop Factor

The drop factor is an essential element in calculating IV flow rates. It is defined as the number of drops (gtt) that make up 1 mL of fluid. To put it simply, the drop factor tells us how many drops it takes to achieve one milliliter of the IV solution. Hospitals often use standard sets for this purpose, which are typically labeled with

• Micro set: usually 60 gtt/mL
• Macro set: often ranges from 10 to 20 gtt/mL

In this exercise, the drop factor is given as 20 gtt/mL. This means for every milliliter of solution, 20 drops are infused. This value allows us to convert the volume of solution into a number of drops, which helps in determining the rate at which a solution should be administered.

Percentage Change

Calculating the percentage change is crucial for assessing the difference between two values, in this case, the initial and new IV flow rates. It helps determine how much the flow rate has been adjusted from its original setting. To calculate the percentage change, we use the formula: \[\text{Percentage Change} = \left(\frac{\text{New Value} - \text{Old Value}}{\text{Old Value}}\right) \times 100\% \]In this context, the old value is 42 gtt/min and the new value is 50 gtt/min. Using the above formula, the percentage change results in 19.05%. Understanding this percentage helps to evaluate how significantly the flow rate was altered and assess if further adjustments might be needed.

Volume to be Infused

The volume to be infused is the total amount of IV fluid that needs to be administered to the patient. Knowing this helps ensure the correct dosage of the medication is delivered. Initially, the total volume to be infused here was 1,000 mL over the entire infusion period. After 4 hours, 400 mL had already been infused. Therefore, the remaining volume to be infused amounts to: \[\text{Remaining Volume} = 1,000 \text{ mL} - 400 \text{ mL} = 600 \text{ mL} \]This remaining volume becomes the critical value to determine how much more fluid the patient will receive to complete the prescribed treatment.

Time Conversion

Time conversion is often necessary when calculating IV flow rates because different units are used for setting the duration, such as hours, while the flow may need to be calculated per minute. This conversion is vital to ensure accuracy in administering treatments correctly.In this exercise, 4 hours had already elapsed out of an 8-hour session, so we need to account for only the 4 hours left. We convert these hours into minutes to match the units required for the flow rate calculation. Converting hours to minutes is done by multiplying the number of hours by 60, since there are 60 minutes in an hour. Therefore, \[4 \text{ hours} \times 60 \text{ minutes/hour} = 240 \text{ minutes} \]With this, you can use the correct time in minutes to calculate the IV flow rate accurately using the formula outlined in the solution.