Question

Calculate the IV flow rate in \(\mathrm{gtt} / \mathrm{min}\) for the following IV administrations, unless another unit of measure is stated. Infuse \(300 \mathrm{~mL}\) of \(\mathrm{D} 5 \mathrm{~W}\) at \(75 \mathrm{~mL} / \mathrm{hr}\). Drop factor: \(60 \mathrm{gtt} / \mathrm{mL}\)

Short answer

75 gtt/min.

Step-by-step solution

Understand the Given Information

You are given the total volume to be infused which is 300 mL, the infusion rate is 75 mL/hr, and the drop factor is 60 gtt/mL. We need to find the IV flow rate in drops per minute (gtt/min).

Use the Flow Rate Formula

The formula to calculate the IV flow rate in gtt/min is:\[\text{Flow Rate (gtt/min)} = \left( \frac{\text{Volume to Infuse (mL)}}{\text{Time (min)}} \right) \times \text{Drop Factor (gtt/mL)}\]Since we are only concerned with the infusion rate, we use the formula:\[\left( \frac{75 \text{ mL}}{60 \text{ min}} \right) \times 60 \text{ gtt/mL}\]

Calculate the Conversion of Time to Minutes

Since the infusion rate is given per hour (75 mL/hr), convert this to mL per minute:\[\text{Flow Rate (mL/min)} = \frac{75 \text{ mL}}{60 \text{ min}} \]This equals 1.25 mL/min.

Calculate Drops per Minute

Insert the converted flow rate into the formula to calculate the drops per minute:\[\left( 1.25 \text{ mL/min} \right) \times 60 \text{ gtt/mL} = 75 \text{ gtt/min}\]

Verify the Calculation

The calculation shows that with a flow rate of 1.25 mL/min and a drop factor of 60 gtt/mL, the flow rate is correctly calculated as 75 gtt/min.

Key concepts

Infusion Rate

The infusion rate refers to how quickly or slowly an IV fluid is administered to the patient. It's important to ensure the correct rate to provide the appropriate amount of fluids effectively and safely. In our example, the infusion rate is specified as 75 mL/hour. This number tells us that every hour, 75 mL of the solution will be delivered to the patient. Understanding the infusion rate is crucial for healthcare providers to manage the administration of fluids or medications through intravenous therapy.

Drop Factor

The drop factor is a key component of calculating how IV fluids are administered. It is defined as the number of drops (gtt) in a milliliter (mL) produced by a specific type of IV tubing. In our example, the drop factor is 60 gtt/mL. Different IV setups have different drop factors depending on their design. Typical drop factors can range from 10 to 20 for macrodrops or 60 for microdrops like in this case. Knowing the drop factor allows us to calculate the IV flow rate in terms of drops per minute, an essential piece of information in medical contexts.

mL/min Conversion

Converting milliliters per hour to milliliters per minute is a necessary step in intravenous calculations, especially when calculating the actual flow rate in gtt/min. Since the infusion rate is initially given in mL/hour, it's important to convert it to mL/min to align with the typical time measurement for drip rates. To achieve this, divide the hourly infusion rate by 60, as there are 60 minutes in an hour. For our calculation, the conversion of 75 mL/hour results in an infusion of 1.25 mL per minute, a crucial intermediary step in the complete IV flow rate calculation.

gtt/min

Calculating the flow rate in drops per minute (gtt/min) is the final step that combines our understanding of both the drop factor and the conversion of mL per minute. This calculation tells us how many drops of IV fluid are delivered per minute. To find gtt/min, multiply the flow rate in mL/min by the drop factor (gtt/mL). In our scenario, multiplying 1.25 mL/min by the drop factor of 60 yields a flow rate of 75 gtt/min. This is a crucial figure that ensures the actual fluid delivery matches the prescribed infusion rate, avoiding both under and over-infusion.