Cannulas and Cannulae


What are those little plastic devices patients receive when they are admitted to hospital?

They come in different colours – usually blue, pink or green, although some people are unfortunate enough to receive a grey or orange one; the colour you get is usually a reflection of how unwell you are (and their size).

These are vascular access devices, which allow doctors, nurses and paramedics to administer high doses of medicine rapidly into the blood stream.

Most people have them placed in the back of their hand (uncomfortable), in the forearm (difficult but most effective) or in what we call the antecubital fossa – that is, the inside of your elbow (relatively easy, quite uncomfortable, but sometimes ineffective). Very rarely, when doctors are struggling to ‘find a vein’ they might resort somewhere else in the body, such as the leg or foot.

In my experience, patients never enjoy having intravenous cannulae in place; I am not sure what most people understand about the purpose of these devices. Most suffer in silence, occasionally asking to have them removed if they are in an awkward position or if they become painful (which can be a sign of infection).

Let’s face-it, having tiny plastic tubes sticking into your vein is not natural, despite it being a fantastic invention of modern medicine – you might want to call them, a necessary evil.

The tubes can cause problems – sometimes the wrong drugs are administered, although this happens rarely and even less commonly, a drug is administered which a patient has an allergy to – this tends to result in a very rapid and very severe reaction, potentially precipitating anaphylactic shock.

That is when things go wrong.

Most of the time, cannulae are useful – enabling clinical staff to deliver intravenous fluids when a patient is dehydrated or unable to drink, a blood transfusion if they have bled, or powerful antibiotics, pain killers and other medicines that work quickly without having to be swallowed.

I can’t imagine what modern medicine would be like without these colourful pieces of plastic.

They don’t however come free – the cost is that they are sometimes painful, sometimes difficult to site (in people with small, hardened or clotted veins), can cause infections – by allowing bacteria a portal of entry into the body and, most commonly, they get caught on clothing which can be annoying.

Cannulae can also be harmful, beyond their potential for causing pain or complications, by proving a route for high dose medicines into the blood stream, people can receive overdoses of pain relief or too high doses of antibiotics which can lead to other problems; sometimes older people receive intravenous fluids when they appear to be drinking inadequately – this, very often, is because the tea is cold, out of sight or reach or there is not enough available. (Or is in the wrong receptacle – see this film)

We need to ensure that these very simple wonders of modern medicine are used appropriately and when not needed are removed, allowing people to feel that they are on the road to recovery – with the patient transforming back into a person.

If anyone reading this blog ever has a cannula in their vein, please be sure to check it is necessary, clean and not showing any signs of infection (red or sore), and, make sure it isn’t being used as a shortcut to caring.

If the doctor/nurse/paramedic wonders why you are asking, just mention this blog!


Published by rodkersh1948

Trying to understand the world, one emotion at a time.

One thought on “Cannulas and Cannulae

  1. Very interesting. As a GP I see and also hear from patients, that they are inadequately “nursed”during an acute hospital admission. Patients are intelligent beings and know when their basic care is inadequate yet will still often stick up for the nurses they see as being ” overworked” on a “short staffed” ward.
    Following a negative acute direct or indirect hospital experience, I have patients come to me refusing to be referred on to that hospital again under any circumstance and interestingly, in my experience, I have come across more patients with this as an advanced directive ( to refuse to go to that particular hospital) than actually making a decision about whether to refuse certain medical treatment. As GPs we nowadays go the extra mile to avoid hospital admissions and the possibility of inadequate care is usually factored in to the end decision.
    Patients should be able to take” basic care” for granted but sadly I seldom receive the positive reports of good care in hospital and when I do it is a pleasant surprise but also confirms that good “care” is not being taken for granted as it should be.
    On the up side, I’ve not come across many patients who have been sent home with a cannula still stuck in a limb, we used to see this quite a lot 15 + years ago.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: