IV Pressure Bag Use

The use of a pressure infusion bag is not restricted to the ACP scope of practice, and we encourage the PCP AIV scope to use this piece of equipment as necessary to increase the amount/speed to fluid that can be infused into a patient.

There are many factors that influence this relationship, the most important being IV catheter sizing.

As you may recall from Poiseuille’s law, flow is based on radius and length of the tubing. Increasing the radius of the tubing has the greatest effect on the flow rate. Doubling the radius of the IV catheter increases the flow rate by 16-fold. Further, Flow rates are inversely proportional to the length of the catheter. Thus, the wider and shorter the catheter, the more fluid can be infused.

This of course is a balancing act. As an example, it would be unnecessary to place a large catheter IV in an elderly patient who simply needs a single dose of dimenhydrinate. Conversely, a large bore catheter placed in a hypotensive cardiogenic shock patient is a different story.

For context, if you examine the packaging of an IV, it will list the flow rate. To illustrate this, depending on the model, a 20 gauge IV has a flow rate of approximately 60 mL/hour; a 16 gauge IV has a flow rate of approximately 220 mL/hr.

This rate however is based on gravity, in an “ideal” vein, and does not account for patient positioning, valves, vein rigidity, IV tubing resistance, etc. Since the IVs have a limited flow rate, we may need to add an adjunct (a pressure infuser bag) to assist in the speed of delivery.

Keep in mind, that as you add pressure to the fluid, this will increase the infusion, and thus will decrease the time between required patient reassessments (q250 mL for patients over 12 years of age & q100 mL for patients under 12 years of age). Don’t let these important assessments get missed due to the speed of infusion.