A Practical Way To Reduce Venipuncture In Hospitalized Dogs

What if the IV catheter your hospitalized dog already has could spare them multiple needle sticks a day without sacrificing lab accuracy? We sit down with Dr. Bryan Welch to challenge a common assumption in small animal emergency and ICU care: that venipuncture is the only reliable way to get serial bloodwork. We talk through a validated push-pull blood sampling technique that uses a peripheral IV catheter to collect repeat samples while aiming to reduce stress, preserve veins, and lower the risk of oversampling and hospital-acquired anemia. 

Bryan breaks down the method step by step: flushing with sterile saline, drawing blood back, returning it to the patient, and repeating to clear dead space and reduce dilution. Then we dig into the results that matter to practicing veterinary teams, including how peripheral IV catheter samples compare with venipuncture right after placement and after at least 24 hours of continuous IV fluids and medications. We also clarify a point that trips up a lot of clinicians, statistically significant versus clinically relevant differences, using real examples of when a number changes but your treatment plan should not. 

We also cover the practical concerns that drive hesitation, hemolysis, clot formation, turbidity, and smear changes, plus what the study did and did not evaluate. Bryan shares where he would be cautious, including interpreting sodium potassium ratios for suspected hypoadrenocorticism, and offers simple implementation tips for teams trying the technique for the first time. If you want evidence-based ways to improve patient comfort and streamline hospitalized dog bloodwork, hit play, then subscribe, share with your ICU team, and leave a rating and review.

JAVMA article: https://doi.org/10.2460/javma.25.09.0635

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Transcript

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Lisa Fortier 0:31

Welcome to Epic Award-winning Veterinary Vertex, the AVMA Journal's podcast, where we delve into behind-the-scene look with manuscript authors. I'm editor-in-chief Lisa Fortier, joined by associate editor Sarah Wright. Today we're doing another little episode of Myth Busting, and we're discussing collection of blood samples using peripheral intravenous catheters with Brian Welch. Brian, thank you so much for sharing this uh information with us and taking time out to be on the podcast today.

Sarah Wright 1:00

Yeah, thanks for joining us, Brian.

Bryan Welch 1:01

Absolutely. Thank you, Lisa and Sarah, for having me. Pleasure to be here. And um, yeah, I'm honored to be interviewed about this project. I was, you know, really happy that people seem to be a fan of the manuscript and hopeful that people are getting some use out of it already.

Lisa Fortier 1:15

Yeah, very much so. Uh when you were thinking about this study, what clinical problem were you thinking of and aiming to solve when you were uh performing and writing this?

Bryan Welch 1:23

Yeah, it's a great question. So I've worked in a number of hospitals over the years where similar protocols that are not necessarily peer-reviewed have been kind of used in place of venipuncture, um, specifically for patients who are having blood work monitored, you know, two, three, multiple times per day who don't necessarily have things like central liner pick uh placement. And I really wanted to find a way that we could reduce venipuncture for samples in those patients while also having something that was specifically validated for our veterinary patients and not necessarily just extrapolated from human medicine. Um, you know, as an internist, I'm doing this a lot with blood sampling serially in my hospitalized patients. So this was something that I thought could be really useful for a lot of people going forward.

Sarah Wright 2:09

Yeah, this is a huge game changer. I'm so excited to get this out there to everyone. Anyone who works in a hospital, ICU with small animals, you need to listen to this upset. It's so important. So I'm excited to ask this next question too, Brian. Can you briefly explain the push-pull sampling technique for our listeners?

Results Versus Venipuncture

Bryan Welch 2:26

Yeah, absolutely. So it is essentially using peripheral IV catheters, just like a standard IV catheter for IV fluids, for collecting blood samples and monitoring blood samples on hospitalized patients. It was actually adapted from largely a protocol used for NICU patients on the human side of medicine and was validated in a previous study that was a smaller sample size for really specific indices. Um, what we're essentially using is the standard IV catheter. We specifically looked at the 20 gauge standard IV catheter length and the addition of just, you know, some 3mm syringes with some sterile saline. And essentially, what we're doing is flushing saline into the catheter and drawing blood back into a syringe, pushing it back into the patient, repeating that three times with the idea of clearing any dead space and any potential dilutional effect from IV fluids or medications that may be going through that catheter.

Lisa Fortier 3:28

Brian, at a really high level, how did the samples from the catheter compare to venicture?

Statistical Versus Clinical Differences

Bryan Welch 3:33

Yeah, at a high level, overall they were very comparable. And you know, what we looked at specifically was comparing samples from the first time of IV catheter placement, but instead of just drawing blood through a freshly placed catheter, like has been demonstrated previously, we actually flushed the catheter beforehand so that we could simulate um the protocol. And then we would recheck this on patients that have been on IV fluids and IV medications with no necessary um specifications of what those fluids or medications had to be after at least 24 hours of continuous IV fluids. And on both the intake samples and after 24 hours of intravenous fluids, the samples overall were quite comparable.

Sarah Wright 4:16

So now I have an important distinction question for you. So you mentioned statistically significant but not clinically relevant differences in your manuscript. What does this mean in practice?

Hemolysis Clots And Sample Quality

Bryan Welch 4:26

Yes, that is a really good question. Um, I think we all, you know, when when it comes to manuscripts and data and studies that are done, there's a really big uh focus on the p-value. And, you know, is it statistically significant or is it not? And statistically significant, all that really means that there's a demonstrable difference between two different samples. It doesn't necessarily mean it's anything that's going to be significant in changing a treatment plan for that patient. And I think the best way of kind of considering this is, you know, with a blended to see, for example, like a platelet count. You know, if I have a platelet count on a patient of 146,000, and you know, my PIVC sample reads 146. And let's say, for example, the venipuncture sample for that patient read 163. That's not going to change how I manage that patient. It's not going to change their prognosis, it's not going to change their diagnosis. You know, the difference of, you know, 30,000 to 100,000 would be a significant clinical decision-making difference. That is not an issue that we ran into with this protocol. Um, I think the the other piece to really consider, and we did specifically look at uh this with our study, was the um the ASVCP guidelines essentially for repeat blood work measurements and essentially what they consider total allowable error on repeat sampling for patients. So rerunning the same lab work on the same patient on the same machine and how much variability they are willing to accept. And we fell well within those limits for every single indice that they had recommendations for.

Lisa Fortier 6:06

Really great information. Uh, and even as an orthopedic surgeon, I know the difference between 30 and 100. What about uh interference from things like hemolysis or clot formation? Did you see any of those uh things happen in your sample collection?

Bryan Welch 6:21

Yeah, we did look at that specifically as well, as well as um some additional things like toxic change to neutrophils and turbidity of the sample, because you know, those were all things that theoretically we could see a difference of when we're collecting blood in a different way. And we actually found essentially no difference on any of the variables. Um, the only difference is that for one of the time points, the venipuncture samples were actually more likely to have clot formation rather than the PIBC samples. So no difference in hemolysis, aside from one time point favoring PIBC samples, there was no difference in clot formation, no difference in toxic change, and no difference in turbidity.

After 24 Hours On Fluids

Sarah Wright 7:02

So, Brian, did sampling after 24 hours of fluids and medications impact reliability?

When To Avoid This Method

Bryan Welch 7:09

No, and that was really, I think, the big takeaway from this study is after a minimum of 24 hours of continuous IV fluids and medications, the samples were still very comparable. And again, while there may have been some slight statistically different variables for certain indices, many of which we did not see, um, the clinical significance was very much lacking. Um, and one thing that was really specific to our study, and I I do get this question sometimes as well, if they lost their initial IV catheter that was placed and had the initial samples collected from it, they had to be removed from the study. So we really wanted to make sure it was the same catheter, the same leg, the same IV fluids and medications going through it for that full 24 hours.

Lisa Fortier 7:57

Wow, that's great. Um, are there any cases, any disease indications, anything where you'd where you would avoid using the catheter and still go with venipuncture?

Comfort Workflow And Key Takeaways

Bryan Welch 8:07

I think the only scenario that I would really have pause is animals who have aggression issues handling their pause. Um, we didn't specifically look at very small breed dogs or cats, and that is something that I think is worth looking into. We also did not look at this in severely thrombocytopenic patients or severely anemic patients, mostly because of the increased risk for repeated blood sampling in those patients and trying to avoid oversampling them. But those are actually patients that I think could really benefit from something like this. You know, not having to repeat venipuncture on our ITP patients and not having to oversample blood on our IMHA patients, for example. Those are things that could be really beneficial. Um, the one thing that I would say um in terms of specific things I would avoid looking at with this protocol is things like the sodium potassium ratio. You know, if you're looking at the difference between a sodium potassium ratio of, let's say, 23 or 26, and you're worried about potential hypoadreno corticism. As an internist, I'd say you should run a baseline cortisol. It shouldn't really change things all that much, but it is something that can be skewed by this protocol based on our data.

Sarah Wright 9:20

So, how might this change patient comfort or hospital workflow?

Bryan Welch 9:25

That was the big goal, is improving patient comfort. And there's been a lot of studies from the research side of veterinary medicine of morbidity and mortality associated with venipuncture and oversampling of these patients. And hospital-acquired anemia is a huge problem both in human and veterinary medicine. So, by using a protocol that is, we'll say, less traumatic, quote unquote, for the patient, and also is something that could potentially be handled by a single individual on a compliant patient or a critically ill patient, I think overall there's a lot of benefits. So avoiding oversampling of patients, avoiding the morbidity associated with repeat venipuncture, saving, you know, vessels for patients where that can be a really critical and limiting resource. And also, I think, you know, from the nursing side of things, a lot of the nurses that I've worked with who have used this protocol much prefer it when they're able to, opposed to, you know, traditional venipuncture sampling.

Lisa Fortier 10:28

For that whole veterinary team that you're talking about, what is the takeaway that you would like them to remember from your manuscript in this podcast?

Practical Tips And Closing

Bryan Welch 10:37

I think, you know, for me, the big takeaways I would want people to have is don't be afraid to try something new that has solid data to support it. I think there are definitely people out there who have, you know, I've come across and have asked me about my manuscript and still have hesitation. Um, you know, we've done something the same way for so long, it's hard to kind of break that mold. And I think, you know, this is without question, at least to my knowledge, the the largest sample set that we've had that's demonstrated that this is a realistic option for hospitalized patients and doesn't need special training, doesn't need special, you know, um instrumentation for the patient and can be really beneficial. Um I think you know, being open to it, trying it in your hospital is what I would I would want people to take from this.

Lisa Fortier 11:26

What uh given all your experience, what practical tip or word of caution would you give to that those veterinary teams just starting to use it?

Bryan Welch 11:35

I think when you're first doing it, using it on a a large breed dog who's a compliant patient is great because the first couple times you do it, I do think it can feel, you know, maybe a little bit clunky, even you know, for the video that we provided in association with the manuscript. That video specifically was collected of a pa uh individual who had never performed it before. So she had no prior training in performing the PIBC pre-sampling method. And it really only took her, I can't remember the exact timing, but maybe two minutes, if I were to recall. Um, so it's not something that should take a whole lot of time. But if you haven't done it before, make sure you just have all the equipment lined up, ready to go, and ideally a compliant patient, just so that you're not struggling both with the patient and a new uh a new training tool.

Sarah Wright 12:27

Yeah, again, this is such a great Mythbuster episode. I think this is practical, this is useful, and we'll hopefully help so many teams that are listening to this episode. So thank you so much, Brian.

Bryan Welch 12:36

Yeah, absolutely. Thanks for having me.

Sarah Wright 12:39

For our listeners and viewers, you can read Brian's article in Javma. I'm Sarah Wright here with Lisa Fortier. Be sure to tune in next week for another episode of Veterinary Vertex, and don't forget to leave us a rating and review on Apple Podcasts or wherever you listen.