What Are The Differences Between Primary And Secondary IV Administration Sets?

Primary Administration Set

The primary administration set refers to a thin, flexible, plastic tubing called the infusion set. This administration set is connected to the bag or bottle of intravenous (IV) fluid.

The primary administration set could have a macro-drip or micro-drip set in terms of the rate of infusion.

• The macro-drip set delivers 10, 15, or 20 drops/ml, while a micro-drip set gives 45 or 60 drops/ml.

• The macro-drip set is used for routine primary infusions in adults. In contrast, the micro-drip set is used for pediatric or neonatal care. Small amounts of fluids will be infused over a long time.

Specifically, the primary administration set is used for continuous infusion of fluids or medications. It is the one directly inserted into the IV fluid bag or bottle.

Secondary Administration Set 

The secondary administration set also refers to flexible tubing. Still, this time it is not directly connected to the IV fluid. It is connected to another bottle or bag, usually a mini bag/bottle.

The secondary administration set contains fluid or medication that will be infused over time at prescribed intervals and then stopped until the next dose is required. This is also called intermittent IV infusions, intermittent IV medication, piggyback medication, secondary medication, or mini-bag medication.

This medication is given in small volumes of sterile IV solutions, like 25 ml to 250 ml, and infused over a desired length of time, such as 30 minutes every 4 hours or as a single dose. Some medications cannot be infused so rapidly, like aminophylline, lest the patient will suffer from cardiac arrest and will possibly die. Through the secondary administration set, we can control infusing a particular drug at the prescribed rate.

For the secondary administration set to be more effective, it must be connected to a primary administration set. For this reason, the secondary administration set is highly dependent on the primary administration set. The secondary administration set needs to be connected with, and drain its content into, the primary administration set.

Definition Of Terms Concerning The Administration Sets 

Priming volume 

The priming volume refers to the quantity of fluid needed to fill the entire length of the IV administration set.

Before starting any infusion, the primary administration set and the secondary administration set will be primed with fluid. All the air in their tubes will be driven away.

The priming volume needs to be noted and recorded because this is the amount of fluid that has not entered the patient’s venous system after the infusion.  

Drug volume  

The amount of fluid that is left in the IV bottle/bag after deducting the priming volume is the so-called drug volume.

Residual volume

After the infusion, when the drug volume has been totally infused, the amount of fluid or medication left in the administration set is called the residual volume.

Summary of Differences Between Primary Administration Set and Secondary Administration Set

In the following table, the differences between the primary administration set and the secondary administration set will be enumerated:

Differences	Primary Administration Set	Secondary Administration Set
Connection with the main IV fluid bottle/bag	It should be directly connected to it	It should not be connected to it
Connection with a mini bag or bottle	Not connected to it	It should be connected to it
Main use	For continuous infusion	For intermittent or single infusion(s)
Size of the IV bottle/bag	Most of the time, 1 liter	250 ml up to 500 ml
Distal connection	The distal end is connected to the venous system of the patient.	The distal end is connected to the port of the primary administration set.

Reason For Separation Of Functions

All the fluid that is in the main IV bottle/bag needs to be infused. This must be done because the entire amount has been included in in the computation of fluid requirements for a particular patient. If some amount is not infused, such as the residual volume, this leads to a reduction in the total fluid that is administered.

When a drug or medication needs to be infused intermittently, this is usually admixed in a saline solution and placed in a mini bottle/bag. If this infusion is passed through a primary administration set, a certain amount of drug is not passed on to the patient because the residual volume is most of the time left in the tubing. Suppose this is done several times in a day, which will lead to a significant reduction in the amount of drug that should be infused into the patient. 

Through the method of setting up a secondary administration set, all the drug volume that is in the mini bottle/bag can be seen to be infused. At the same time, the fluid that is in the tubing of the secondary administration set—the residual volume—can be seen to be totally infused, too, and then flushed in with the fluid coming and flowing from the primary administration set. With this method, the total content of the mini bag/bottle wherein the secondary administration set is directly connected is used up and infused into the venous system of the patient.

Medical staff will hook the mini bag/bottle containing much-needed drug(s) or medications to a primary administration set in many healthcare facilities. After the infusion, it seemed that all of the fluid in the mini bag/bottle had been infused. After closer examination, however, a significant amount of fluid was not infused because around 25 ml was retained in the primary administration set. The fluid retained in the primary administration set was substantial because it contained the drug(s) that the patient direly needed. Suppose this practice of using primary administration set for mini bag/bottle is done several times in a day. In that case, there will be a significant reduction in the amount of drug(s) infused into the patient. To avoid this, medical staff should hook a mini bag/bottle containing important drug(s) to a secondary administration set whose advantages were enumerated in the preceding.