Question

Determine the flow rate in \(\mathrm{gtt} / \mathrm{min}\) for each IV using a microdrip, then indicate \(\mathrm{mL} / \mathrm{hr}\) for a controller. (Consider the medication volume as part of the total dilution volume as shown in the chapter.) A child is to receive 10 units of a medication. The dosage of 10 units is contained in \(1 \mathrm{~mL}\). Dilute to \(30 \mathrm{~mL},\) and infuse in 20 minutes. A \(15-\mathrm{mL}\) flush is to follow. Medication is placed in a burette. Determine the rate in: a. \(\mathrm{gtt} / \mathrm{min}\) b. \(\mathrm{mL} / \mathrm{hr}\)

Short answer

a. 90 gtt/min b. 90 mL/hr

Step-by-step solution

Calculate Total Volume for Infusion

To determine the total volume for infusion, add the dilution volume and flush volume together. The dilution is 30 mL and the flush is 15 mL, giving a total volume of 45 mL. \[\text{Total Volume} = 30 \text{ mL} + 15 \text{ mL} = 45 \text{ mL}\]

Find Flow Rate in mL/min

Next, determine the rate at which the 30 mL needs to be infused in 20 minutes.\[\text{Volume} = 30 \text{ mL} \quad \text{Time} = 20 \text{ min}\]Calculate the flow rate:\[\text{Flow rate} = \frac{30 \text{ mL}}{20 \text{ min}} = 1.5 \text{ mL/min}\]

Calculate Total Infusion Time

The total infusion time includes both the medication infusion and the flush period. The medication infusion takes 20 minutes, and assuming the flush rate matches the medication infusion rate, it will take another 10 minutes (\(15 \text{ mL} \div 1.5 \text{ mL/min} = 10 \text{ min}\)). Total infusion time is:\[20 \text{ min} + 10 \text{ min} = 30 \text{ min}\]

Determine Flow Rate in gtt/min

Using a microdrip set (where 1 mL is approximately equal to 60 drops or gtt), convert the mL/min flow rate to gtt/min:\[\text{Flow rate} = 1.5 \text{ mL/min} \times 60 \text{ gtt/mL} = 90 \text{ gtt/min}\]

Convert Flow Rate to mL/hr for Controller

Convert the flow rate from mL/min to mL/hr for the controller. Since there are 60 minutes in an hour:\[\text{Flow rate} = 1.5 \text{ mL/min} \times 60 \text{ min/hr} = 90 \text{ mL/hr}\]

Key concepts

Understanding Microdrip

When administering IV fluids, the microdrip system is a precise way to deliver medication. Microdrips are especially handy for small doses. They measure fluid delivery in drops per minute (gtt/min). This system uses a drip factor where 1 mL equals 60 drops. Such precision is crucial for accurate dosing, especially when dealing with sensitive patients like children or the elderly. This makes calculating flow rates straightforward when you need to convert mL to gtt. By understanding the conversion, you can ensure the patient gets the exact medication they need.

Medication Dilution Basics

Medication dilution is a vital step in preparing IV solutions, providing the correct concentration of medicine. It involves mixing the medication with a diluent to achieve a desired volume. In this process, you increase the total fluid volume but keep the amount of medication constant. For instance, in the exercise, 10 units of medicine in 1 mL is diluted to 30 mL. This larger volume helps control the rate of delivery, ensuring the medication is neither too concentrated nor too dilute. Proper dilution is essential for safe and effective medication administration.

Exploring Flow Rate Conversion

Flow rate conversion helps determine how quickly an IV solution should be delivered. It's important to switch between different units like mL/min, gtt/min, or mL/hr, depending on the equipment you're using. To convert from mL/min to gtt/min with microdrip, multiply the mL/min rate by 60, since 1 mL equals 60 drops here. Thus, if you have a flow rate of 1.5 mL/min, the corresponding gtt/min is 90. Conversely, converting from mL/min to mL/hr involves multiplying by 60 to account for the minutes in an hour. These conversions ensure that you can use different IV sets and controllers seamlessly.

Calculating Infusion Time

Infusion time is the duration it takes for an IV fluid to be fully administered. It's the sum of both the medication infusion and any flush that follows. In the example exercise, the medication is infused over 20 minutes, and a 15 mL flush follows at the same rate, adding roughly 10 more minutes. Thus, the total time for this process is 30 minutes. Accurate calculation of infusion time ensures proper scheduling and administration, guarding against under or over-infusion of the medication.