Calculate the flow rate in gtt/min using the formula method or dimensional analysis.
An IV medication in 60 mL of 0.9% NS is to be administered in 45 min. The drop factor is a microdrop.
The correct answer and explanation is :
To calculate the flow rate in gtt/min (drops per minute), we will use the formula method, since this is a straightforward IV calculation.
Given:
- Volume to be infused: 60 mL
- Time: 45 minutes
- Drop factor: microdrop = 60 gtt/mL
Formula:
$$
\text{Flow rate (gtt/min)} = \left( \frac{\text{Volume (mL)} \times \text{Drop factor (gtt/mL)}}{\text{Time (min)}} \right)
$$
Step-by-step calculation:
$$
\text{Flow rate} = \frac{60 \, \text{mL} \times 60 \, \text{gtt/mL}}{45 \, \text{min}} = \frac{3600}{45} = 80 \, \text{gtt/min}
$$
✅ Correct Answer: 80 gtt/min
Detailed Explanation (300+ words):
This problem is an example of a common intravenous (IV) infusion calculation in clinical nursing practice. It requires the nurse to determine how fast an IV medication should be administered in terms of drops per minute (gtt/min). This ensures the patient receives the medication at a safe and therapeutic rate.
The formula used includes three critical pieces of information:
- Volume to be infused (in mL) – This is the total fluid the nurse is ordered to administer, which in this case is 60 mL of 0.9% Normal Saline (NS).
- Time for the infusion (in minutes) – This tells how long the volume should be infused over. In this scenario, the time is 45 minutes.
- Drop factor (gtt/mL) – This is determined by the IV tubing set being used. A microdrop set always delivers 60 gtt/mL regardless of the manufacturer. This is commonly used for pediatric or small-volume infusions due to the smaller drop size.
The formula plugs these values in, multiplying volume by drop factor and dividing by time to get gtt/min. It is important to carry out this calculation correctly to avoid under- or over-infusion. If too slow, the medication may be ineffective; if too fast, it could cause adverse effects.
Microdrop tubing is especially helpful for precise medication delivery, and accurate calculations like this are essential for patient safety.