From the Research
The maximum safe fluid administration rate for an 18 gauge intravenous (IV) catheter is approximately 35.6 mL/min, as determined by a prospective study in healthy adult volunteers 1. This flow rate is significantly lower than the manufacturer's rating of 105 mL/min, highlighting the importance of actual measurement over theoretical estimates. The study compared the infusion rate of a single 18-g IV to two 20-g IVs and found that the two 20-g IVs were statistically significantly faster, with a mean difference in flow rate of 5.7 mL/min 1. When using an 18 gauge catheter for fluid administration, it's essential to monitor the patient for signs of fluid overload, such as increased blood pressure, respiratory distress, or edema. The actual flow rate may be lower depending on factors such as patient position, catheter length, fluid viscosity, and pressure gradient. Other studies have investigated the use of peripheral venous catheters, including midline venous catheters and peripherally inserted central catheters, but these do not provide direct evidence for the maximum safe fluid administration rate for an 18 gauge IV catheter 2, 3, 4, 5. Therefore, the recommendation is based on the most relevant and recent study available, which provides a clear estimate of the maximum safe fluid administration rate for an 18 gauge IV catheter. Key factors to consider when using an 18 gauge IV catheter include:
- Monitoring patient for signs of fluid overload
- Adjusting flow rate based on patient position, catheter length, fluid viscosity, and pressure gradient
- Being aware of the potential for lower actual flow rates compared to manufacturer's estimates.