Arterial catheterization

Theo van den Herik VTS (ECC) and Kris Gommeren DVM, MSc, PhD, Dipl. ECVIM-CA (Internal Medicine), Dipl. ECVECC     

Arterial catheters are indicated for blood gas analysis and to measure arterial blood pressure during anesthesia and in critical care patients. Arterial blood gas analysis is indicated to assess oxygenation in dyspneic patients, allowing assessment of partial oxygen pressures. Invasive arterial blood pressure measurement is considered the gold standard, as it is more reliable than non-invasive methods such as Doppler and oscillometric measurements. Moreover, invasive monitoring allows for continuous monitoring and morphologic evaluation of the pressure wave during a cardiac cycle. Invasive blood pressure monitoring does require an arterial line and expensive measuring equipment. Non-invasive blood pressure measurement requires fewer skills and equipment but is less reliable. Doppler provides systolic pressure readings. Oscillometric devices calculate mean blood pressure and extrapolate systolic and diastolic pressures based on the device’s algorithm. However, oscillometric devices may be less reliable in cats, small dogs, as well as in lower pressure ranges and in arrhythmic patients, making them less well-suited for emergency and critical care patients. A high-definition oscillometric device has been marketed that may overcome some of these issues, although some studies have questioned such claims. Arterial catheters are typically placed under sedation or general anesthesia, as the procedure may be painful, and patient movement decreases the likelihood of successful placement. There are factors influencing selection of arterial catheter site:

  • Patient mobility
  • Potential for catheter contamination
  • Fixation of the catheter
  • Planned procedure

As cats have poorly developed collateral blood vessels, arterial catheters should be left in place for only 24 hours and should ideally not be placed too distally in the selected limb. Moreover, they should be clearly labelled to alert medical team members and help avert inadvertent intraarterial administration of certain fluids and medications.


(fig. 90.1)


Easy to palpate

Easy to secure

Easily dislodged with movement

Easily contaminated with fecal material 

Smaller catheters necessary

Dorsalis pedis

Easy to palpate 

Easiest to cannulate 

Less danger of hemorrhage with coagulopathies

May be affected by obesity

Smaller catheters necessary

Risk for hypoperfusion of the distal part of the limb

Easy to palpate

Difficult to place by metacarpal pad

Thromboses can easily occur

Easy to palpate

Risk of hemorrhage, particularly with coagulopathies 

Affected by obesity 

Easily dislodged with movement

Placing arterial catheters


Film dressing
2% chlorhexidine solution
Three-way stopcock
70-96% isopropyl alcohol
0.9% NaCl
Intravenous catheter
16G needle or #11 scalpel blade
Fixation spray


Extension set


Fill the three-way stopcock and extension line (often included in the transducer set)

with 0.9% NaCl, ensuring no visible air bubbles remain

Select artery

Clip the area around the artery wide enough to ensure the needle does not get contaminated

Aseptically prepare area with 2% chlorhexidine solution

Disinfect with alcohol 70-96%

Catheter placement

Cover the tail or paw with a sterile cover

Assess position and trajectory of the artery using your index finger

Make a small stab opening with a 16G needle or #11 scalpel blade

Place the catheter under the skin

Using your index finger as a guide, advance the catheter in small steps, whilst checking for the

appearance of a flash of blood in the hub of the catheter (fig. 90.2)

If no blood appeared, the catheter should be withdrawn slowly, looking at the hub for the

appearance of blood (in case the artery has been pierced through and through)

In order to redirect the catheter, it should first be withdrawn into the subcutaneous tissue

If blood appears in the catheter hub, the catheter should be

advanced into the artery while the needle is kept in place

Remove the needle, and connect the hub with a three-way stopcock and extension line

Catheter fixation

Adhesive spray can be sprayed on the clipped part of the paw

Place a first piece of tape under the catheter

Place a piece of tape over each wing of the catheter

Place a final piece of tape over the connection of the catheter with the extension line

Cover the insertion opening with an occlusive sterile dressing

Wrap the tail or paw in a bandage

Cover the cotton bandage with a top layer

Attach the extension line to the outer layer

Clearly label the arterial line (fig. 90.3)


The catheter and bandage must be checked at least twice daily, as well as whenever the arterial pressure tracing or readings are abnormal. The insertion site must be assessed for redness, swelling, moistness, and pain. Moreover, the extremity distal to the insertion site must be assessed for signs of poor perfusion such as pain and decreased temperature. Whenever in doubt, the arterial catheter should be removed immediately.

Complications Bleeding can occur whenever the line is inadvertently disconnected, three-way stopcocks are not closed and protected correctly, and/or connecting lines are damaged, etc. The catheter can also slip out of the artery or kink at the insertion site, resulting in a loss of pressure readings. Every cat in which an arterial line is placed should be placed in an ICU to ensure permanent monitoring.


  • Coagulopathy.
  • Primary coagulopathy (e.g., thrombocytopenia (<40,000 platelets/µL).
  • Secondary coagulopathy (e.g., vitamin K antagonists, liver dysfunction).
  • Hypercoagulable states (e.g., hyperadrenocorticism, immune-mediated hemolytic anemia).
  • Skin lesions or infections at the insertion site.

Point-Of-Care ultrasonography guided arterial line placement

POCUS helps with visualization of the artery and catheter needle, allowing for catheter placement by a trained person. The needle can be followed during its trajectory through subcutaneous tissues and into the artery both out of plane (perpendicular) and in plane (parallel). In cats, the femoral artery is usually selected. The artery and vein are running next to each other, but both can be distinguished based on the pulsatile movements of the artery, its poorly collapsibility when applying gentle pressure compared to the vein, and/or using color Doppler.


Arterial catheterization

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