Vascular access 101: how to hit those tricky veins!

NursingProceduresEmergency & Critical Care
Written By Laura Jones

There’s nothing quite like the satisfaction of hitting those tricky veins on the first try - am I right?

Vascular access is a fundamental skill for the veterinary nurse. A big part of our role consists of placing and maintaining indwelling vascular devices - since so many of our patients require IV medications, fluids, and blood samples.

But what options are there for patients with really difficult peripheral veins?

What options do we have in patients requiring multiple blood samples?

What options do we have for patients who need specialised fluids?

And what about arterial catheterisation - when do we do that, and how does it differ to venous access?

In this post, I’m going to talk to you all about the different options for securing venous and arterial access - and provide you with a few tips on hitting those tricky veins!

Let’s talk IV access

We have a few options for intravenous access. Most of the time, we’ll be placing ‘standard’ IV catheters - short, over-the-needle peripheral IVs that remain in place for typically 1-5 days.

We also have a few longer-term or more advanced options. These include peripherally-inserted central catheters (aka PICC lines), and central venous catheters (aka jugular catheters, central lines or CVCs). These are typically referred to as ‘advanced’ vascular access devices and are usually used in a referral/emergency clinic setting, or in patients with complex medical conditions requiring multiple fluids, medications and samples.

Peripheral IV catheters

Standard IVs are placed via an over-the-needle technique into a peripheral vein. They are a great option for short-term venous access, and are typically placed in:

  • The cephalic veins

  • The lateral saphenous veins

  • The medial saphenous veins

There are also a few other vessels I like to go for in patients where the ‘usual veins’ have been used lots and lots, and are phlebitic or fibrosed. These include:

  • The marginal ear vein (this is a great one for those floppy-eared dogs, like Basset Hounds or Dachshunds!)

  • The metatarsal vein (this is a great one for our ‘lankier’ dogs like sighthounds)

  • The accessory cephalic veins, dorsal common digital veins and collateral veins around the cephalic

When placing the catheter, aseptic technique is key. A large site should be clipped, allowing not just the catheter itself, but the hub, and attached connector, to sit within the clipped field.

The site is then disinfected as for a minor surgical procedure - initially with antimicrobial skin solution (e.g. chlorhexidine gluconate) and then with isopropyl alcohol, or a chlorhexidine-in-alcohol spray or applicator.

The vein is raised by an assistant and visualised. It should not be palpated after it has been disinfected - if you need to feel the vein, make sure you re-prepare the skin afterwards! After visualisation, the catheter is introduced at a shallow angle and fed off of the stylet and into the vessel, once blood appears in the stylet. It is then secured in place, any required blood samples collected from it, and a T-connector or bung attached.

What if the vein is tricky?

Struggling to hit the vein? Try these:

  • Pre-flushing the stylet with sterile saline, which can make visualisation a little easier

  • Moving to a smaller catheter size (if appropriate)

  • Check the length of your catheter against your site - if the catheter will be too long to sit in the site comfortably, without kinking or likely pressure errors, move to a shorter catheter

  • If you hit the vein but can’t advance, keep the catheter tip in place where you are, take a new catheter (either the same size or a size down) and place this above it. This will mean you can go back into the same site without it blowing. The tape you place under the new IV to secure it can then act as a bandage over the one you remove.

  • Don’t go for a recently used vein, or a vein that looks phlebitic - they’ll be harder to hit and are often uncomfortable. I like to look at the amount of hair re-growth over the sites in my regular patients, and go for the least clipped option. Whilst it means an additional clipped patch for your patient, it can also mean an easier, more comfortable catheter.

How do we care for and maintain these catheters?

Once your IV is in, we need to care for it. This includes regular flushing of the catheter (we perform this every 4 hours for patients not on fluids, but we’re still lacking good quality evidence on this topic in this industry!) with normal saline. Heparin is not required, since it makes no significant difference to catheter patency.

We also need to observe the catheter and site regularly for signs of phlebitis (inflammation of the vessel). We see either mechanical, chemical or bacterial phlebitis in our patients:

  • Bacterial phlebitis is associated with the accidental introduction of pathogens such as bacteria and their by-products (e.g. toxins). They come from intraluminal or extraluminal sources, such as contaminated fluids or medications, or contamination on the patient’s skin or nurse’s hand.

  • Chemical phlebitis is associated with the specific vein not being suitable for the type of fluid/medication being given. An example of this is parenteral nutrition, which contains high levels of glucose. This solution can’t be given through a peripheral vein, as it will cause too much chemical phlebitis - instead, a central line is required.

  • Mechanical phlebitis is associated with the catheter directly.

If you want to know exactly what to check when you perform your catheter care, I’ve created a checklist just for you! This includes all of the things that I check when I’m looking at IVs - I like to do this every 12 hours. Download it below!

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Peripherally-inserted central catheters

PICC lines are long catheters placed in a peripheral vein (usually the medial or lateral saphenous veins). However, as the catheter is much longer than a standard IV, it ends in a larger vessel, allowing us to obtain repeated blood samples from it.

They are placed either via the Seldinger technique (over a guidewire), via a peel-away introducer, or through a ‘drum’ introducer device.

A PICC placed via the peel-away method. Note that this video is on a cadaver for educational purposes, so no drape has been placed and the catheter has been measured directly against the animal’s fur.


Care-wise, careful aseptic technique and monitoring is again required to minimise the risk of phlebitis. I perform PICC care every 12 hours, and again following the points on the IV care checklist above.

In addition to this, I carefully label the bandage as a PICC line, so people can see it is not a standard IV catheter. I also place alcohol disinfecting caps on any injection ports not in use, to safeguard against contamination.

Central venous catheters

CVCs are catheters placed into the jugular vein. They can be placed in either jugular - but are usually placed on the right side in patients who are likely to need O tubes, since these go on the left.

They are made up of multiple individual catheter lumens (usually 3 - a white one, blue one and brown one), wrapped into one outer catheter. This means that each catheter has separate lines within it, that we can use to give incompatible fluids or medications. We can also use one of them (normally the distal one, which in most cases is the brown port) to collect jugular blood samples.

How are they placed?

They are usually placed via the Seldinger technique (over a guidewire) or using a peel-away introducer:

A CVC placed via the Seldinger method. Note that this video is on a cadaver for educational purposes, so no drape has been placed and the catheter has been measured directly against the animal’s fur.

When are they used?

There are many indications for CVC placement, including:

  • Patients with difficult peripheral veins where a standard IV cannot be placed

  • Very small patients where a standard IV cannot be placed

  • Patients receiving multiple incompatible fluids and medications

  • Patients requiring multiple, frequent blood samples

  • Patients requiring parenteral nutrition

  • Patients requiring central venous pressure measurement

When are they not used?

Like any other indwelling device, CVCs come with contraindications. These include patients with coagulopathies or thrombocytopenia, patients with increased intracranial or intraocular pressure (since obstructing the jugular veins increases this further) and patients with local wounds or infection over the catheter site.

How do we care for them?

Aseptic technique is a major consideration when it comes to CVC care. The introduction of contamination into the central circulation carries potential disastrous complications to our patients. The catheter site should be checked regularly for signs of phlebitis or perivascular administration (as detailed in the IV catheter care checklist). Gloves should always be worn when handling the catheter, ports or dressing, and sterile gloves used to handle and clean the catheter insertion site directly.

I like to inspect and clean the site, then place a new dressing every 12 hours. I place a sterile dressing over the site, then cover this with a layer of padded bandage, then conforming bandage. I then use a length of stockinette to contain the ports, to avoid them dangling from the patient.

I also cover the ports with alcohol disinfectant caps, just like a PICC line - then flush any ports not in continual use every 4 hours, again with normal saline.

I’ve also put a central line care checklist together for you! You can download and print this, and use it to ensure your site has been checked, and use the space for notes to mention any concerns. Download it below!

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How do you sample via a PICC or central line?

I’ve mentioned we can use CVCs and PICC lines to collect blood samples. We do this using a method called the push-pull technique. This is how to do it:

  1. Flush the catheter with the same volume of saline as the catheter dead space (usually 0.3-0.5ml)

  2. Withdraw 3 x this volume of blood and saline back into the same syringe

  3. Reinfuse this back into the patient, then repeat this process another 3 times into the same syringe

  4. Switch to a new syringe and collect your sample, then flush the catheter with 0.9% saline once you're done!

What about arterial catheters?

At times, we’ll catheterise an artery rather than a vein. There are really only two indications for this:

  1. To monitor invasive blood pressure

  2. To obtain arterial blood samples

We do not use these catheters for medication administration - it causes severe thrombophlebitis if done, so the only thing that should go in these lines is saline.

They need regular (near-constant) flushing as they can clot rapidly. We usually do this via a 100ml saline bag, connected to a giving set and placed in a pressure infusion bag.

How to place arterial catheters

Arterial catheters are usually placed in the dorsal pedal artery (on the medial aspect of the metatarsals), but can also be placed in the coccygeal artery or femoral artery. This is how we do it:

  1. The area over the dorsal pedal artery is clipped and aseptically prepared.

  2. Hand hygiene is performed and the catheter is pre-flushed with saline.

  3. A small nick is made in the skin to facilitate catheter placement.

  4. The dorsal pedal pulse is palpated with the non-dominant hand and the catheter advanced through the incision at a 45 degree angle, towards where the pulse is felt.

  5. When a flashback of blood is seen in the catheter, it is slowly and carefully advanced, then secured in place with tape and a T-connector attached.

  6. The catheter and line must be clearly labelled 'arterial' and ideally dressed in a different colour to venous catheters, to avoid accidental use.

Arterial catheter considerations

There are a few key things to consider when managing arterial catheters.

Firstly - we don't leave indwelling arterial lines in cats for long periods (>2 hours) as they don't have collateral circulation, so the arterial line will compromise blood flow to the tissues below it. This means they can get distal limb necrosis due to the poor circulation. If you’re placing one in a cat, Top tip: agree a removal time with the clinician, and set a timer or schedule it on the patient's hospital record!

Secondly, we can’t really maintain these in very awake or mobile patients, since they will move around a lot (which affects invasive blood pressure results) and may traumatise or remove their catheter, resulting in haemorrhage.


So that’s an overview of our most common vascular access options, and how they are placed and maintained! When planning vascular access for your patient, consider their specific condition, their intended treatment, and the need for ongoing blood samples. Plan your catheter care and maintenance according to the individual patient and their catheter type, and don’t forget to download those checklists to monitor your catheter sites!


References and Further Reading

Laura Jones
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