The Vet Vault 3.2.1.

Why your NSAID toxicity patient doesn’t need twice maintenance fluid, a new approach to cultures for dermatology, why neutrophils are like Spiderman, and why can’t we achieve our goals?!

Hubert Hiemstra

Jul 05, 2024

A quick reminder about giving us some feedback on the podcast here please.

3 Clinical Pearls.

1. IV fluids for nephrotoxins

From episode 120 on the ECC feed. With Dr Corrin Boyd.

I’m planning my interview schedule for Science Week (have you booked your tickets yet? It’s a phenomenal line-up!), and a couple of the topics reminded me that I’ve never shared any pearls from one of our most popular episodes on here. In this episode, criticalist Dr Corrin Boyd dropped a bomb shell: You can’t ‘flush’ nephrotoxins out of the kidneys by putting your patient on twice maintenance fluid. We’re talking NSAIDs, grapes, lilies - all that sort of stuff. Or, like Corrin puts it: ‘The kidneys aren’t little toilets that you can flush!’ Here’s what you need to know:

The physiology that causes an increase in urine volume when we place an animal on more-than-maintenance iv fluids is actually very complicated, and not 100% understood. What we do know is that most of it happens in the DISTAL nephron, not in the proximal tubules, which is where most of the damage for most nephrotoxins occurs.
Not all nephrotoxins do their damage via direct damage to nephrons. Think NSAIDs, where the problem is decreased blood flow to the glomerulus. Or grapes, where we don’t even know what happens!
There is no data to show that supraphysiological fluids actually increase the rate of toxin excretion.
AND, a fluid overloaded kidney doesn’t work as well as a normal one: kidneys have a tight non-stretchy capsule, so if you pump it full of fluid you’ll start squishing the nephrons) And it’s much easier to fluid-overload an unhappy kidney. Ie - if the toxin that you’re worried about has actually done damage to the kidney you DEFINITELY don’t want to shove a bunch of extra fluid into your patient, as this can exacerbate the decreased kidney function.

So what does it all mean practically?

That grape dog or NSAID overdose patient, and even the cat that has eaten lilies, needs to maintain normal hydration levels. And as long as they are well they can achieve this by drinking water. Probably at home. They do not need to sit in your hospital for 2 or 3 days on a drip.

(It’s a very involved topic - I encourage you to listen to the full episode if you haven’t already.)

2. Don’t culture ears, but do culture skin (!?!)

From episode 165 on the medicine feed. With Dr Nellie Choi.

Back in episode 158 dermatologist Dr Nellie Choi talked to us about complicated otitis cases. Here’s a recap on why I’ll no longer be sending away many ear cultures, based on what I learnt from Nellie:

Culture and sensitivity results are based on the required serum levels of the antibiotic when delivered systemically, not what we would require to address the bacteria topically.
Even if the culture says the bacteria is resistant, you are more than likely going to clear the infection by drowning the bacteria with a topical antibiotic, because you are achieving such high concentrations of the drug.
In the majority of cases your client’s money is better spent on a decent ear clean to get rid of debris and the biofilm than on a culture.

So cultures are out for those derm cases… BUT, not so fast. In episode 165 Dr Nellie told us that culturing skin in your pyoderma patient s is actually a very good idea:

There are high levels of resistance in some countries to some of the first line skin abx, like cephalosporins.
Patients with ongoing or recurrent skin issues who have had multiple courses of antibiotics are definitely candidates for culture, as they are at high risk of having resistant bugs on them.
Note that in some countries you can’t legally dispense antibiotics without a culture guiding you!
NB: Don’t just culture the skin of every itchy dog (or send them home with antibiotics!) - ALWAYS confirm bacterial involvement first with in-house cytology.

3. Why neutrophils are like Spiderman.

From episode 162 on the ECC feed. With Dr Avalene Tan.

This is of no real practical relevance for most of us, but it’s too cool not to share! Dr Tan (who has a very useful website and newsletter that highlights the most exciting new literature in ECC) explained why IMHA patients are at risk of throwing clots:
- Did you know that in their efforts to catch and kill pathogens, neutrophils put out a ‘web’?!
- It’s called an extracellular trap, and it’s made from neutrophil DNA that is decorated with a bunch of enzymes and histones, and it’s possibly the coolest thing I’ve nerded out on this week!
- (It’s this very reactive trap that interacts with the coagulation system and can get it a bit over-excited. But wouldn’t you be excited if you met Spiderman!?)

Listen To The Podcasts

2 Other things

“Learning is necessary for understanding, but can be a joy in itself, enhancing the sense of being alive in a mysterious, unpredictable world.”
- Michael Foley
“Let me never fall into the vulgar mistake of dreaming that I am persecuted whenever I am contradicted.”
- Ralph Waldo-Emerson

1 Thing to think about.

I bought some new weights for my little home gym this week. It all started with a book on the five essential strength-building exercises that a friend gave me six months ago. I read it cover to cover, and I was pumped. (Mentally, not physically.) So, I bought a squat rack, an Olympic bar, and a bunch of weights. It felt really good—superior physical health, here I come!

But something’s wrong. Despite my enthusiasm and deep understanding on how to do the perfect rep, I'm still not really any stronger. So, I bought some more weights. Maybe I need a better book?

—

Did you know that only about a quarter of people who buy online courses actually start them? And what percentage of enthusiastic sign-ups do you think actually complete the average course? It’s around 5%.

Surprised? I was, for a bit, and then I looked at my shiny new under-used weights and squat rack, mostly unblemished, and my skinny legs…

—

How often have you bought that course, done the CE, read the book, subscribed to the app, (downloaded the podcast?!) and then failed to act—to do the heavy lifting that is the most essential ingredient to getting where you’d rather be?

What strategies do you have in place to counter this apparently all too common tendency? Share them in the comments.

Much love,

Hugh