IV Therapy: Tubing

IV fluids are infused through flexible tubing, often called an infusion set or primary set.  One end of plastic tubing is connected to the bag of fluid and the other is connected to the hub of the IV catheter.  There may be a smaller extension tube between the infusion set and the IV catheter hub.  This may be preferable to allow for patient mobility, temporarily independent of an IV pole.

Although there are many IV tubing manufacturers, there are two general sizes: micro drip and macrodrip sets.  Microdrip sets produce smaller drops and thus infuse fluid slower.  Every microdrip set will deliver 60 drops (gtt) per milliliter.  Macrodrip sets produce larger drops and thus infuse fluid at a greater rate.  Macrodrip sets deliver between 10 and 15 gtt per milliliter.  The infusion set may also have inline filters, stopcocks, access ports, and shutoff clamps.  It is recommended that you familiarize yourself with each accessory your facility uses and how it works prior to using it, as there are some variations between manufacturers.


Parts of a primary administration set. Note, only sets designed for use with glass bottles will include a vent.

The primary tubing will have several components attached, including a plastic spike, a drip chamber, a roller clamp, the syringe tip and locking collar, and medication ports.  Since most IV fluids are available in plastic bags that collapse as the fluid infuses, it is unnecessary to vent the tubing. Therefore most primary tubing will likely be designed without a vent.  If you are setting up fluids from a glass jar, you will need a primary set that contains a vent, located above the drip chamber.  The vent will allow for fluid flow out of the bottle as air flows into the bottle.

The following method of setting up your IV assembly should be followed to reduce the risk of introducing foreign bodies and air into the patient:

To introduce fluid into the primary line, first close the roller clamp on the primary line.  To do this, move the roller to the narrow end of the device, thus pinching the tubing closed.  Next, remove the plastic or rubber caps from the fluid bag and the plastic spike located at the top of the tubing.  Holding the fluid bag upside down, push the plastic spike into the exposed collar on the fluid bag until the top of the drip chamber cannot be advanced further into the fluid bag.  Return the bag to its proper position and squeeze the drip chamber to fill it at least half way.  Open the roller clamp to flush the fluid through the tubing by moving the roller to the wider end of the tubing, releasing pressure on the tubing and allowing fluid to flow freely past the clamp.  Close the clamp again as soon as fluid comes out of the distal end of the tubing.

The purpose of the the drip chamber is to visualize the rate at which fluid is infusing into the patient.  If the chamber becomes overfilled to the point that drip rates cannot be visualized, simply invert the bag and drip chamber, squeeze the chamber once with your fingers and return the bag to its functional position.  Reevaluate the flow of the IV infusion.  You may need to re-position the patient’s extremity or flush the IV line with saline to resume flow.

When the roller clamp is in the open position, it will slide easily up and down the tubing.  If you are using the roller clamp to set a drip rate, move it closer to the drip chamber to make it easier for yourself to reach the clamp while counting drops.  If the fluid flow is to be maximized, the roller clamp will be open, and may slide down the line.  To secure the clamp in place, you may need to move the roller slightly closer to the narrow end of the device, providing just enough pressure against the tube to hold the clamp in place, without any restrictions to flow.

At the distal end of the tubing is a male adapter that fits into the hub of the IV catheter.  A “locking collar” screws over the hub to maintain the connection, and can be found on most primary sets.

Many primary sets also contain access ports to be used for administering medications.  A bolus of medication may be delivered from a syringe, or a secondary line leading to a “piggyback” fluid bag may also be connected here.  Since most facilities uses needleless systems, the syringes and tubing will likely screw into the tubing port with luer lock technology.

A secondary infusion should be hung higher than the primary infusion.

Since the secondary infusion usually contains a medication, an infusion device such as a mechanical pump is recommended to ensure that it infuses over the prescribed length of time. If a pump is not available, hang the secondary infusion higher than the primary infusion.  There will often be a plastic hook or extension hanger available with the secondary tubing to accomplish this.  

When using the piggyback setup, both the primary and secondary lines should remain open.  To regulate the flow rate of the secondary infusion, use the roller clamp on the primary tubing to adjust the flow rate.  In this configuration, the secondary infusion will flow preferentially into the tubing, while the primary infusion will pause.  When the secondary infusion is complete, the primary infusion will resume. If the rate of delivery of the primary infusion is different than that of the secondary infusion, you must remember to adjust the rate as soon as possible after the secondary infusion is complete.

If your patient will receive subsequent doses of the secondary infusion, the bag and tubing may be left hanging.  The secondary tubing can be reused for 72 to 96 hours, depending on your facility’s policy.  If the assembly becomes contaminated, it must be discarded immediately.

The CDC guidelines recommend that tubing be changed according to the following schedule:

  • Replace tubing used to infuse blood or blood products or lipid-containing solutions at least every 24 hours.
  • Replace tubing used to infuse propofol every 6 to 12 hours, following the manufacturer’s guidelines.
  • Replace tubing used to infuse solutions containing dextrose and amino acids without lipids every 72 hours.
  • Replace other tubing every 96 hours.

The Intravenous Nurses Society (INS) recommendations should also be considered:

  • Replace tubing used to administer continuous infusions every 72 hours. In facilities with catheter-related infections and phlebitis rates of 5% or greater, the tubing should be replaced every 48 hours.
  • Replace tubing used for intermittent infusions through injection ports every 24 hours as frequent opening of the ports lead to a greater potential for contamination of both ends of this tubing.
  • Replace tubing used to infuse solutions that are more conducive to the growth of microorganisms, including parenteral nutrition, more frequently.

To be sure you are following the correct procedures, you should consult your facility’s policies.  

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