Q: How Does an IV Work? (This one has a VIDEO!)

Ah, yes. The dreaded IV needle. I call it an “IV needle” because that’s what everyone else calls it. The needle, however, is only a brief part of the transaction—yet it is the cause for all the fear.

These things are really called “IV catheters,” as that’s actually what they are. A catheter is, simply stated, a tube that goes inside the body for medical purposes. In this case, “IV” stands for “intravenous,” meaning “inside the vein.” So, when an IV is necessary, all we’ve gotta do is get a tube in one of your veins. No big deal. Now hold still…

“But I HATE needles!” you say.

This is a common declaration I get from patients as I approach with the IV. To this, I almost always tell them something along the lines of, “Well, that’s great! That means you’re sane. Had you told me you love needles and thrust your arm at me with excitement, I would’ve probably backed away slowly.”

So, yeah, it seems the needle part is the worst, and there’s definitely some misinformation floating around about IV’s, so it’s probably best to go through the process a little bit. Time to bring in a fake patient to help walk everyone through this whole experience. This time, a young woman named Ashley has come in, and her workup here at the ER requires an IV. With the installation of an IV, I can get Ashley’s bloodwork and have access to give her all of the IV medications she needs. But, Ashley, you look a little nervous. What’s up?

“I HATE needles!”

Oh, you missed that part. Sorry. Gotta stick you anyway. This should go without saying, but please hold as still as possible, as wiggling and dancing creates a moving target, so unless you’re a scared child, a confused adult, or someone who has a neuropathic reason why they can’t hold still, please hold still.

“But I don’t want a needle to stay inside my arm! What if it rips up my vein when I bend my arm?”

Ah, okay. Let’s dispel this myth right here and now. I know I said it’s just a catheter, but it takes some visual evidence to really hit the point home. Let’s step away from the clinical setting for a moment, as I just so happened to accidentally leave an IV in my scrubs pocket and then washed the scrubs, so the IV is useless and no longer returnable. And if medical equipment is no longer usable, it’s always a great idea to use it for education.

Without further ado, here’s my basic explanation of an IV catheter:

It’s my first crack at a video…forgive the extra “coffee shakes.”

There ya go. Nothing to be too scared of. As long as we get the IV into a vein, most of the time the rest of the installation goes well, and the needle is only a small part of the process. So, back to you, Ashley. I’m just going to put a tourniquet around your arm to make blood flow in your veins back up a bit to help dilate them to a little larger size (I’m guessing you’re okay with me making my targets a little bigger). I’m going to ask you to open and close your fist to pump a little more blood toward that tourniqueted dead end I’ve created, and now I’m ready to search for a vein.

“But I’m a hard stick!” Ashley announces.

Oh man, if I had a buck for every time I heard this, I’d double my wages, I swear. Usually, when people tell me they’re a hard stick, it’s because they’ve had bad experiences in places other than ER’s. If you want to find the medical personnel who install IV’s the most regularly, go to an ER. We are very well practiced at IV’s, and we get the most challenging patients on a regular basis. The only department I’d say is nearly as seasoned as ER’s at IV’s would be the crews in pre-op departments—the people you see before surgery. They get a constant line of people who need IV’s, and they also have surgeons breathing down their necks about where they prefer the IV’s installed on all their patients. ICU might be in third place, but they’re more seasoned at dealing with bigger tubes and machines. (NOTE: This ranking is all out the window when it comes to kids.)

Do you know what I do if someone tells me they’re a hard stick? I do the same thing I do for every IV start: try my best. The only thing I might change is perhaps I’ll ask where other people usually have good luck starting an IV. This goes for anyone, to be honest. As long as I don’t need to put an IV in a particular spot for a procedure, I’m okay with putting one wherever the patient suggests, as long as there’s actually a vein there. Other than that, if someone says they’re a hard stick, I don’t change a damn thing.

In Ashley’s case, I’m not changing a damn thing. She’s got a good vein right here, below the place where her elbow bends on her non-dominant arm so it shouldn’t kink off when she bends her arm. Perfect. Now, I’m just going to clean her arm here, take the cap off the IV, and…

“Can’t you use a smaller needle?”

Ugh. I get this all the time. There’s a myth going around that we can always use smaller IV’s “if we want.” While it’s true that there are different sizes of needle to choose from, for the most part, the bigger the better. In adults, the two best choices are either a 20-gauge (the pink one like I have in the video) or the larger 18-gauge. (I know the lower number being larger seems opposite, but it’s the same as any other hole-making needle size, much like getting your ears—or whatever—pierced.) Below is a picture of the various IV sizes.


The pink one, the 20-gauge, is what I showed you in the video, and there’s a reason why it was stowed away in my pocket—it’s my go-to size. I find it to be “old faithful,” as it can make it into veins from the hands to the upper arm, stay put and open, and you can use them for anything. I keep 18-gauges (the green one) as my second choice, and I usually install those for traumas or anything that might require faster infusions of fluids or drugs. For major traumas or anything involving larger-scale blood loss, I’ll go with a 16-gauge (the gray one) because you can get a lot of fluid/blood in REALLY fast. 16-gauge is also what they typically use for blood donations, though their needles are little different than IV’s.

By telling you that, I’m certainly not trying to dissuade you from donating blood. Donating blood is essential for survival of people on a daily basis. Ever had a surgery? They had blood on hold for you just in case anything went wrong. Yes, even a basic surgery. So if you think you’ll ever be in a simple position to possibly require blood, please donate—even though they use large needles.

And here’s the truth we all need to hear: THEY ALL HURT NO MATTER WHICH SIZE THEY ARE.

Yes, there’s a slight difference in the way they hurt, but the thing all the needles in the picture above have in common is that none of them are painless. They all suck for a few moments. And that’s the important part: it’s only for a few moments.

So, yes, technically, I could put a tiny little 24-gauge in Ashley (the yellow one—your favorite in the above picture), but what would that do for her? In case you didn’t notice, the smaller the needle, the shorter the hose. And that’s because the smaller the needle, the smaller the person. Honestly, unless I’m absolutely desperate for an IV and the only vein volunteering for the suffering is a tiny little thing in the middle of someone’s finger, I’ll NEVER use a 24-gauge on anyone other than an infant or a newborn. Why? Because that’s what the 24-gauge is made for. Not an adult who just doesn’t like needles.

Even in the case of the newborn, 24-gauges are frustrating. They are tiny little tubes, so they kink off, block off, and come loose so easily when compared with the other sizes. You saw in the video how relatively small the tube on the 20-gauge is. Yet, that’s a reliable size. Anything smaller on an adult is more likely to fail in a shorter amount of time, which means a second (or third or fourth) stick. There are appropriate sizes for each situation. Otherwise, why would anyone get anything other than the smallest needle?

So, Ashley, would you rather have one stick with a larger size, or would you like to have multiple sticks with something that makes you temporarily feel less afraid?

Ashley has agreed to have an adult-sized IV started, but she has decided to look away while I put it in. And that’s absolutely fine. Whatever it takes to keep still for the entire procedure. Thankfully, Ashley does well, as she used some spontaneous breathing techniques to keep herself calm and still during the procedure. I obtain the bloodwork we need and flush the IV with saline, which is what us nurses keep in those syringes seemingly wrapped in cellophane. It’s just saltwater, basically, and it’s meant to keep IV’s clear of blood as well as keep IV drugs separated in the tubing. What’s odd is that some people can taste and/or smell a saline flush through an IV. While there isn’t a cut and dried answer as to why this happens, the clear link is through the blood flow from a vein traveling through the respiratory system, creating a difference in the concentration of sodium in the blood as it moves through cardiorespiratory circulation. All I know is that it’s a benign reaction and I warn everyone about it so they don’t freak out—it’s a harmless side effect.

There we have it. Ashley has a beautiful IV started, it’s secured in a good place in her arm, she’s aware that there’s no needle in her vein, and we’re good to go.

“Wait. Why is the green one in? Isn’t that the 18-gauge? The BIGGER one?”

You shouldn’t have complained so much, my dear. Nurses get to choose the size, after all. You’re fine, though. Enjoy your IV that will be incredibly reliable for you and great for every single bit of testing and infusion. You’re welcome!

Have a question for the nurse? Ask here.

Who am I to give advice? Your answer is here.

And, of course, feel free to leave a comment. I’m okay with being corrected or engaging in conversation.

Related links:

“Why Can I Taste Saline and Medications When They’re Inserted Into My IV?” https://www.mcgill.ca/oss/article/you-asked/why-can-i-taste-saline-when-its-injected-my-iv

“Hit That Vein: Tips and Techniques for Inserting an IV Cannula” https://www.ausmed.com/cpd/articles/how-to-place-an-iv

“Helping Your Child Through an IV or Blood Test” https://www.massgeneral.org/children/assets/pdf/needle_insertion_pain_parent_handout.pdf

“How To Donate Blood for Newbies and Needle-Haters” https://redcrosschat.org/2014/01/30/how-to-donate-blood-for-newbies-and-needle-haters/

“Matching the Peripheral Intravenous Catheter to the Individual
Patient” https://www.sarb.be/site/assets/files/1142/05-rivera_et_al.pdf

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