Vascular Catheterization Frequently Asked Questions

How long will my catheter stay patent?

Catheter patency duration is affected by multiple factors. If all factors are followed, patency for all vessels in both mice and rats, can last many months. Read the Five Keys to Patency

What are the factors influencing patency?

There are five factors influencing patency. The first and most important factor is the catheter tip position. The other four factors are: the use of a closed system such as the Vascular Access Button™ (VAB™), catheter material and tip profile, the use of sterile components including your flush and lock solutions and the use of the positive pressure technique when locking the catheter. Learn more

What is the ideal catheter tip placement for the jugular vein?

The ideal tip placement for a jugular vein catheterization is the entrance of the right atrium. See this blog for more information

What is the ideal catheter tip placement for the carotid artery? 

The ideal tip placement for a carotid artery catheterization is the entrance of the aortic arch. See this blog for more information

What is the ideal catheter tip placement for the femoral vein?

The ideal tip placement for a femoral vein catheterization is in the inferior vena cava caudal to the renal veins.

What is the ideal catheter tip placement for the femoral artery?

The ideal tip placement for a femoral artery catheterization is the abdominal artery caudal to the renal arteries.

How can I predict the tip location during surgery?

The catheter tip location can be predicted by measurements carried out on cadavers prior to performing the survival surgery. Such measurements should be taken from anatomical landmarks or measurements from anatomical landmarks to the ideal catheter tip location. These measurements will become the catheter insertion length and the collar (or bead) on the catheter should correspond to the insertion length.

What is the collar or bead for on the catheter?

The main purpose of the collar (also called bead) on the catheter is to define the catheter insertion length. It also serves as an anchor by placing sutures rostrally and caudally to it during surgery. Our catheters come with either a fixed or movable bead. Make sure you order the ones that will best fit your needs. See all Catheters

Why should I use a Vascular Access Button™ (VAB™)?

There are many reasons why you should use a VAB™. Low-stress sampling and infusion, extended catheter patency duration and the possibility of group housing your animals with the addition of the metal cap on the VAB™’s port. Learn more

Why should I use a polyurethane catheter?

PU is the material of choice because of its biocompatibility. PU is a happy medium between silicone and polyethylene. It is less porous than silicone and less rigid than polyethylene. It is also the best material for subcutaneous connections as when the catheter is attached to the VAB™’s connector. Learn more

Why should I use a round tip catheter?

A round tip catheter, compared to square or bevel tips, is less traumatic to the lining of the blood vessels and therefore, increases patency duration. Learn more

Why should I use sterile supplies and solutions?

Aseptic technique and using sterile supplies and solutions is non negotiable when it comes to survival surgery and catheter maintenance. Using non sterile supplies and lock and flush solutions may lead to infections and decrease patency duration. Learn more

Why should I use Positive Pressure Technique?

If positive pressure is not used when disconnecting the syringe from the VAB™’s port, blood will enter in the catheter and may clot, leading to catheter blockage and loss of patency. See this blog and video for more information 

How frequently should I maintain my catheter?

When using a closed system such as with the VAB™, the recommended maintenance schedule is seven days. 

What lock solution should I use to fill the catheter’s dead volume?

The 500 IU/ml Heparin/Dextrose or Heparin/Glycerol lock solutions are popular because of the CRL/Dr. Luo paper. However, this study was done with externalized catheters sealed with plugs, i.e., an open system, and not with VABs™, which provide a closed system. The study was evaluating the lock solutions for catheters implanted in the venous system, more specifically, in the femoral vein. The high viscosity of the Heparin/Glycerol lock solution prevents evaporation while the Heparin/Dextrose minimizes bacteria growth which are both desirable with an open system, but not necessary with the closed system provided by the Vascular Access Button™. The risk of using these high heparin concentration solutions is due to their introduction into the bloodstream. However, the high viscosity of the Heparin/Glycerol solution may be necessary for the arterial system due to the higher blood pressure which can allow blood to infiltrate into the catheter.  Therefore, the best approach might be to use the lower and safer concentration heparin solutions such as the 10 or 20 IU/ml heparinized saline (called flush solutions) with the VAB™ in the venous system to lock the catheter. The heparinized saline is much safer to use as it eliminates the risk of introducing high concentration of heparin into the bloodstream. This formulation is available in the form of sterile easy to use prefilled sterile syringes. The higher viscosity Heparin/Glycerol solution can then be used for the arterial system preventing blood entry into the catheter. This formulation is available in the form of vials with or without Instech’s needle free PinPort™ technology built into the cap

What is the dead volume of a 1Fr catheter per centimeter?

The dead volume is 0.3µl per centimeter.

What is the dead volume of a 2Fr catheter per centimeter?

The dead volume is 1.5µl per centimeter.

What is the dead volume of a 3Fr catheter per centimeter?

The dead volume is 3µl per centimeter.

What does Fr (French) mean?

The term ‘French’ (Fr, Fg, FR, F, CH or Ch) is a unit of measure invented by Joseph-Frédéric-Benoît Charrière, a Swiss-born French manufacturer of surgical instruments. His name Charrière was difficult to pronounce for people who did not speak French, leading to naming the unit of measure French instead of Charrière. 

How does the French scale work?

1Fr equals 1/3 or 0.33 mm of the catheter’s outside diameter, 2Fr equals 2/3 or .67 mm of the catheter’s outside diameter, 3Fr equals 1 mm of the catheter’s outside diameter and so forth.

What is the dead volume of the VAB™?

Rat VAB™ Dead Volumes (VABR)

Part Number
White Port
2.2µl 2.5µl 4.0µl 4.2µl 4.0µl 4.0µl
Red Port
      4.2µl 4.6µl 4.4µl
Blue Port
        4.0µl 4.0µl
Green Port


Mouse VAB™ Dead Volumes (VABM)

Part Number
White Port
2.5µl 3.7µl 2.5µl 2.4µl 2.3µl
Red Port
      2.4µl 2.3µl


Does laminar flow affect the catheter’s dead volume?

Yes, the flow of fluids in rodent catheters is almost always governed by laminar flow. In laminar flow, fluid at the center of the tube moves faster than fluid at the edge which is held up by contact with the tube wall. This means that you may have to increase the volume of the lock solution to ensure the catheter’s dead volume is completely filled. The more viscous the solution is, the more laminar flow effect you will have. See this blog for more information. 

How much blood can I withdraw as a single sample?

As a general rule, the maximum of blood that should be withdrawn for one sample should not exceed 10% of the circulating blood volume. If more samples are needed, a recovery period of 3-4 weeks should be allowed in between samples.

How do I calculate this for a rat?

The total circulating blood volume of a rat is, on average, 64 ml/kg. The blood volume for a 250 g rat is ~16ml, therefore the volume for one sample should not exceed 1.6ml.

How do I calculate this for a mouse?

The total circulating blood volume of a mouse is, on average, 58 ml/kg. The total blood volume for a 25 g mouse is ~1.45 ml, therefore the volume for one sample should not exceed 0.15 ml or 15 µl. 

How much blood can I withdraw for multiple samples?

As a general rule, for multiple samples on mice and rats, no more than 1% of the circulating volume per day can be withdrawn

How do I secure the catheter in place once in the vessel?

The catheter is secured in place by tying both the rostral and caudal sutures around it. The caudal suture is tied over the catheter and vessel. The rostral suture, which was used to ligate the vessel, is then tied over the catheter itself.

What type of suture material should I use to ligate the vessel and to secure the catheter once in the vessel?

Non absorbable suture must be used for these purposes. Silk is used as it provides the best knot security for a non absorbable suture. 6.0 silk works very well for these applications in both mice and rats. 

Should I use the right or left jugular vein for catheterization?

The jugular on the animal’s right side should be used for catheterization. When accessing the right atrium, the right jugular vein is a more direct, shorter route compared to the left jugular vein.

Should I use the right or left carotid artery for catheterization?

The carotid on the animal’s left side should be used for catheterization. If the right carotid is used, it will occlude/partially occlude blood circulation to the subclavian artery as they both originate from the brachiocephalic trunk (also called the Innominate artery). The brachiocephalic trunk originates from the aortic arch. The left carotid artery originates directly from the aortic arch making it the best selection.

Should I use the right or left femoral vein or the left or right artery for catheterization?

It does not matter as much with the femoral vein or artery as there are no anatomical differences between the right and left sides. 

Should I soak the felt disk of my VAB™prior to implanting it subcutaneously?

Yes, we recommend soaking the felt disk aseptically in sterile saline prior to its subcutaneous implantation. Placing it in sterile saline when starting the procedure will ensure an appropriate saturated disk. A dry felt disk may cause some irritation to the adjacent tissues.
Download the Rat VAB™ Instructions for Use
Download the Mouse VAB™ Instructions for Use

What is the best position for the VAB™?

The VAB™’s felt disk should be placed subcutaneously in the animal’s interscapular area.

In which direction should the VAB™’s connector should be oriented?

Most surgeons orient the VAB™ connector caudally (toward the tail) of the animal. But we have also seen some surgeons orienting it rostrally (toward the nose) or laterally. There is no right or wrong, but ensure the connector does not get in the way of animal movement (if placed too rostrally for example) and that there is some slack from the catheter to allow for growth and movement of the animal.

What causes seromas?

Seromas are caused by forming an overlarge subcutaneous pocket for the VAB™’s disk. This generates dead space which will later be filled with an abnormal accumulation of serous fluids. Seromas are seen most commonly in rats and not in mice. 

How can I prevent seromas?

Making the subcutaneous pocket the right size for the VAB™’s disk is the best way to prevent seroma formation. Also make sure the pocket is not too small as this can put some pressure on the skin causing irritation or worst, pressure necrosis of the skin.

How long should it take me to perform a vascular catheterization?

An experienced surgeon takes about 20 minutes to complete the entire procedure. As a general guideline, anyone planning on performing survival surgery should practice without recovering animals until reaching approximately 30 minutes per procedure. 

Does Instech offer surgical training?

Yes, Instech has launched an education program and now provides virtual surgical training. Learn more 

Can I reuse the metal caps I utilized to group house my animals?

Yes, the metal caps can be cleaned, autoclaved and reused multiple times.

Can I reuse the VAB™?

No, for numerous reasons, it is not practical to reuse the VAB™ on multiple animals. In most cases, tissues will grow into the felt disk and there will also be blood on it which will make the VAB™ impossible to be cleaned and reused. Second, there is absolutely no way to guarantee the internal port and its septum are completely clean in order to avoid cross-contamination. If you are practicing and not recovering animals, it is fine to reuse your VAB™ throughout the day.

Is there a maximum of times the VAB™’s port can be punctured?

Our Vascular Access Buttons™’s ports have been tested and can be punctured over 200x over its lifetime. 

Can I connect the VAB™ to any types of vessels?

Yes, the VAB™ can be connected to a vein or an artery. It can also be connected to an organ such as the intestines and a duct such as the bile duct.

Should I use a microscope to do catheterizations?

A microscope is the best tool to perform an atraumatic surgery. It allows you to see fine details that could not otherwise be detected with the naked eye. It also enables you to be ergonomically correct when performing the procedure. A microscope with a tilting binocular head is ideal as it further helps with ergonomics. You should also have an illumination source such as a microscope ring light or a dual gooseneck fiber optic light.

What instruments should I use to perform catheterizations?

Micro instruments such as those sold by Fine Science Tools (FST) are ideal to perform catheterizations on rodents. For ease and convenience, Instech and FST collaborated and put together these Vascular Catheterization Surgical Packs