Cerebral oximetry and tetracycline

[pgg]

I learned the most amazing thing recently.

The cerebral oximetry monitor rep from Medtronic told one of my partners that prior use of tetracycline makes the monitor read falsely low.

Kids don't get tetracycline because it'll color their developing adult teeth gray. Apparently it colors bone too, and absorbs near infrared light.

She took tetracycline as a teenager for acne. So she puts the monitor on her head and her brain sat reads 20%.

So she told me this and I thought, hey I took tetracycline as a teenager too, let's make this study N=2, and we went into an OR and put it on me

15%

While breathing 15 L/min O2 by mask+reservoir, SpO2 100%:

Still read 15%

Apparently both of our skulls are pigmented enough from tetracycline that near infrared light can't get through. It's been 35ish years since I've taken tetracycline.

And suddenly I have an explanation for why sometimes that monitor just reads 15-20% on some patients no matter what.

I had never heard this about tetracycline and cerebral oximetry before. Even searching the Google afterwards, didn't see anything.

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[pgg]

There is, obviously, a joke here about why I do dumb stuff sometimes. My wife was quick to point it out.

 

[T-burglar]

Great excuse for any mistakes you make in the future

 

[sevoflurane]

I learned the most amazing thing recently.

The cerebral oximetry monitor rep from Medtronic told one of my partners that prior use of tetracycline makes the monitor read falsely low.

Kids don't get tetracycline because it'll color their developing adult teeth gray. Apparently it colors bone too, and absorbs near infrared light.

She took tetracycline as a teenager for acne. So she puts the monitor on her head and her brain sat reads 20%.

So she told me this and I thought, hey I took tetracycline as a teenager too, let's make this study N=2, and we went into an OR and put it on me

15%

While breathing 15 L/min O2 by mask+reservoir, SpO2 100%:

Still read 15%

Apparently both of our skulls are pigmented enough from tetracycline that near infrared light can't get through. It's been 35ish years since I've taken tetracycline.

And suddenly I have an explanation for why sometimes that monitor just reads 15-20% on some patients no matter what.

I had never heard this about tetracycline and cerebral oximetry before. Even searching the Google afterwards, didn't see anything.

I knew it!!! Darn tetracycline.
Welp… back to ancef.

 

[Dr. Rude]

Great excuse for any mistakes you make in the future

I blame my adult onset Tourette syndrome.

 

[Gern Blansten]

I learned the most amazing thing recently.

The cerebral oximetry monitor rep from Medtronic told one of my partners that prior use of tetracycline makes the monitor read falsely low.

Kids don't get tetracycline because it'll color their developing adult teeth gray. Apparently it colors bone too, and absorbs near infrared light.

She took tetracycline as a teenager for acne. So she puts the monitor on her head and her brain sat reads 20%.

So she told me this and I thought, hey I took tetracycline as a teenager too, let's make this study N=2, and we went into an OR and put it on me

15%

While breathing 15 L/min O2 by mask+reservoir, SpO2 100%:

Still read 15%

Apparently both of our skulls are pigmented enough from tetracycline that near infrared light can't get through. It's been 35ish years since I've taken tetracycline.

And suddenly I have an explanation for why sometimes that monitor just reads 15-20% on some patients no matter what.

I had never heard this about tetracycline and cerebral oximetry before. Even searching the Google afterwards, didn't see anything.

Does the medtronic rep have any actual document on this issue or is it just anecdotal? I would love to read more about this if you find any additional information or if Medtronic has any information on it. This is the kind of esoteric information I love getting from SDN.

 

[pgg]

Does the medtronic rep have any actual document on this issue or is it just anecdotal? I would love to read more about this is you find any additional information or if Medtronic has any information on it. This is the kind of esoteric information I love getting from SDN.

I didn't talk to the rep. Could not find any data published anywhere about tetracycline. Lots of stuff about the usual things that affect oxygen saturation artifacts, but nothing on tetracycline. (I didn't do a thorough deep search, but nothing leaped out at me.)

I wonder how many of the older patients we typically use cerebral oximeters for were on tetracycline as teenagers. Google tells me that it's been used for that indication since the 1950s but I wonder how widespread the practice was. I was in high school around 1990 and it was pretty common. I sort of remember that my older brothers (7 & 11 years older than me) suffered without it. Maybe that's because my parents liked me better, or maybe it was just less common in the 70s and early 80s.

We use cerebral oximetry on all our hearts. And every so often, I get someone who never tops 25-30%, for no apparent reason.

 

[T-burglar]

Lol holy moly that’s expensive . Every heart??

 

[pgg]

Lol holy moly that’s expensive . Every heart??

LOL yes

$100 per sensor I hear. Machine is "free" ...

x2

We use them for carotids too.

 

[Radar26]

Wonder if this is a similar problem across all manufacturers… we use Edward’s foresight for cerebral oximetry. I’ll email our rep today and inquire.

 

[abolt18]

Used them for every cardiac case in residency. Have used them zero times in my current practice. No one uses them here.

 

[PpfSuxTube]

I learned the most amazing thing recently.

The cerebral oximetry monitor rep from Medtronic told one of my partners that prior use of tetracycline makes the monitor read falsely low.

Kids don't get tetracycline because it'll color their developing adult teeth gray. Apparently it colors bone too, and absorbs near infrared light.

She took tetracycline as a teenager for acne. So she puts the monitor on her head and her brain sat reads 20%.

So she told me this and I thought, hey I took tetracycline as a teenager too, let's make this study N=2, and we went into an OR and put it on me

15%

While breathing 15 L/min O2 by mask+reservoir, SpO2 100%:

Still read 15%

Apparently both of our skulls are pigmented enough from tetracycline that near infrared light can't get through. It's been 35ish years since I've taken tetracycline.

And suddenly I have an explanation for why sometimes that monitor just reads 15-20% on some patients no matter what.

I had never heard this about tetracycline and cerebral oximetry before. Even searching the Google afterwards, didn't see anything.

Interesting can you ask the rep for details on this pls? Any evidence at all?

 

[GassYous]

Used them for every cardiac case in residency. Have used them zero times in my current practice. No one uses them here.

I'm not sure what the point of them are. If it's low, bring the bp up? Why not just keep the bp up? Is there even a measurable outcome?

 

[PpfSuxTube]

I'm not sure what the point of them are. If it's low, bring the bp up? Why not just keep the bp up? Is there even a measurable outcome?

I agree, my colleagues use them for every aortic case and anyone with prior stroke or tight carotids...
But never do anything differently with the results...

Is there any evidence for them?

 

[abolt18]

I'm not sure what the point of them are. If it's low, bring the bp up? Why not just keep the bp up? Is there even a measurable outcome?

In 5 years using them during cardiac cases, I have never seen anyone change anything in response to a drop in the cerebral oximetry, except MAYBE drive the MAP a little higher... Maybe.

 

[crash2500]

They can be useful in high volume and. Gives you an idea when you may want to consider stopping and likewise when you may want to transfuse.

 

[T-burglar]

They’re theoretically useful as an early warning of cannula misplacement. Poorly draining SVC cannulation in bicaval taped configuration or the aortic cannula into an arch vessel ostium for example. Or to monitor course of an SACP case.

In those cases obviously there is a meaningful intervention. I actually don’t disagree with using STO2 in most cases with cannulas, I just know that it’s expensive.

Many days I do miss the university because where I work now is broke as ****

 

[Gern Blansten]

I didn't talk to the rep. Could not find any data published anywhere about tetracycline. Lots of stuff about the usual things that affect oxygen saturation artifacts, but nothing on tetracycline. (I didn't do a thorough deep search, but nothing leaped out at me.)

I wonder how many of the older patients we typically use cerebral oximeters for were on tetracycline as teenagers. Google tells me that it's been used for that indication since the 1950s but I wonder how widespread the practice was. I was in high school around 1990 and it was pretty common. I sort of remember that my older brothers (7 & 11 years older than me) suffered without it. Maybe that's because my parents liked me better, or maybe it was just less common in the 70s and early 80s.

We use cerebral oximetry on all our hearts. And every so often, I get someone who never tops 25-30%, for no apparent reason.

I searched Google and pubmed and came up empty on the topic. Would be an interesting limitation if true.

 

[makemoney2024]

I'm not sure what the point of them are. If it's low, bring the bp up? Why not just keep the bp up? Is there even a measurable outcome?

No. There are no better outcomes at least for CEAs. In fact, when the numbers go down and the surgeon then decides to shunt, those patients end up with a higher prevalence of stroke from all the little calcium bits breaking off and going into their brain. We use it to make ourselves feel better. And we can give more pressors if needed I guess.

 

[Radar26]

A drop in the cerebral ox has been the first sign of the gundry slipping out during ACP on circ arrrst. I let the surgeon know and they look and pop it back in and the cerebral ox shoots right back up. Not ground breaking but hopefully it helps reduce some of that pump head people get from circ arrest cases…

 

[Iso4ane]

With how they work, you could’ve been just really thick skulled.

 

[dabears505]

Had a case yesterday where the cerebral sats were in the 20s and the surgeon was yelling at me. I of course didn't pay attention to the baseline sats. I told the surgeon he's a fool for not knowing his patient took tetracycline as a child. Still waiting for patient to wake up this morning.

 

[MirrorTodd]

Had a case yesterday where the cerebral sats were in the 20s and the surgeon was yelling at me. I of course didn't pay attention to the baseline sats. I told the surgeon he's a fool for not knowing his patient took tetracycline as a child. Still waiting for patient to wake up this morning.

lol I'm sure it's just the pecedex taking a while to wear off.

 

[drmwvr]

A drop in the cerebral ox has been the first sign of the gundry slipping out during ACP on circ arrrst. I let the surgeon know and they look and pop it back in and the cerebral ox shoots right back up. Not ground breaking but hopefully it helps reduce some of that pump head people get from circ arrest cases…

Wouldn't there be blood squirting everywhere?

 

[kb1900]

Wouldn't there be blood squirting everywhere?

Not if it falls into a place that’s not exactly in the field and the surgeons eyes are elsewhere. With some anastamoses they may not look at anything outside their loupes FOV for 5+ minutes at a time. Perfusuon may not have a pressure line to check corroborate pressure response to flow either

 

[BLADEMDA]

Go to:

Abstract​

Tetracyclines are a broad-spectrum class of antibiotics that have unclear actions with potentially lasting effects on bone metabolism. Initially isolated from Streptomyces, tetracycline proved to be an effective treatment for Gram +/− infections. The emergence of resistant bacterial strains commanded the development of later generation agents, including minocycline, doxycycline, tigecycline, sarecycline, omadacycline, and eravacycline. In 1957, it was realized that tetracyclines act as bone fluorochrome labels due to their high affinity for the bone mineral matrix. Over the course of the next decade, researchers discerned that these compounds are retained in the bone matrix at high levels after the termination of antibiotic therapy. Studies during this period provided evidence that tetracyclines could disrupt prenatal and early postnatal skeletal development. Currently, tetracyclines are most commonly prescribed as a long-term systemic therapy for the treatment of acne in healthy adolescents and young adults. Surprisingly, the impact of tetracyclines on physiologic bone modeling/remodeling is largely unknown. This article provides an overview of the pharmacology of tetracycline drugs, summarizes current knowledge about the impact of these agents on skeletal development and homeostasis, and reviews prior work targeting tetracyclines’ effects on bone cell physiology. The need for future research to elucidate unclear effects of tetracyclines on the skeleton is addressed, including drug retention/release mechanisms from the bone matrix, signaling mechanisms at bone cells, the impact of newer third generation tetracycline antibiotics, and the role of the gut-bone axis.

Tetracyclines and bone: unclear actions with potentially lasting effects

Tetracyclines are a broad-spectrum class of antibiotics that have unclear actions with potentially lasting effects on bone metabolism. Initially isolated from Streptomyces, tetracycline proved to be an effective treatment for Gram +/− infections. ...

www.ncbi.nlm.nih.gov

Tetracyclines have a high affinity for the bone matrix and are retained within the skeleton for extended periods after discontinuing treatment10,11. This raises the question whether tetracyclines retained in the bone matrix can have prolonged effects on bone modeling and remodeling processes.72,73 Recognizing that long durations of therapy results in cumulative retention in the skeleton,10,11 tetracyclines administered for acne are likely retained in the bone matrix at high concentrations. Roughly 10% of the adult human skeleton is remodeled each year, which includes about 30% of trabecular bone and 3% of cortical bone.147–149 Given that tetracyclines are prominently deposited on trabecular surfaces8,9 due to the higher remodeling rate of cancellous bone,147,149 this highlights the potential for tetracycline drugs released from the bone matrix to have lasting effects. Investigations are needed to understand mechanisms by which tetracycline drugs bind the bone matrix, the concentration of drug retained in the skeleton, and how drug / metabolite release from the bone impacts bone modeling / remodeling processes.

 

[drmwvr]

Not if it falls into a place that’s not exactly in the field and the surgeons eyes are elsewhere. With some anastamoses they may not look at anything outside their loupes FOV for 5+ minutes at a time. Perfusuon may not have a pressure line to check corroborate pressure response to flow either

Dang....missing a few liters a minute into the field? I'd hope the assistant or even the scrub would notice that...and it sure wouldn't be coming back to the circuit...not doubting your statement, but if the fail safe ends up being the NIRS I'd hope that's a one off deal....

 

[GassYous]

Dang....missing a few liters a minute into the field? I'd hope the assistant or even the scrub would notice that...and it sure wouldn't be coming back to the circuit...not doubting your statement, but if the fail safe ends up being the NIRS I'd hope that's a one off deal....

I have heard of a patient being bled out into a garbage can

 

[drmwvr]

I have heard of a patient being bled out into a garbage can

yeah but were they watching the NIRS?

 

[GassYous]

yeah but were they watching the NIRS?

Probably would have prevented the whole thing

 

[Blockit]

I had always seen them advocated as a way to assess and prevent cerebral hypoperfusion in the beach chair when the surgeon wants the BP lower lower lower. However, I’ve never been at a place that was willing to spend the money for it.

 

[drmwvr]

Probably would have prevented the whole thing

I'd think just looking at the blood pressure would be at least as good...

 

[Beeftenderloin]

Not sure if it’s been posted on here before, probably has, but this was one of my all time favorite papers I read in fellowship.

Near-infrared spectroscopy in vegetables and humans: An observational study - PubMed

Commonly eaten vegetables have NIRS measurements similar to those seen in healthy humans.

pubmed.ncbi.nlm.nih.gov

Kahn RA, Anyanwu A. Near-infrared spectroscopy in vegetables and humans: An observational study. Eur J Anaesthesiol. 2018 Dec;35(12):907-910. doi: 10.1097/EJA.0000000000000855. PMID: 30020143.

 

[pgg]

N=3

From my partner's case yesterday. Patient took tetracycline for several years as a teenager.

 

[DG51]

I agree, my colleagues use them for every aortic case and anyone with prior stroke or tight carotids...
But never do anything differently with the results...

Is there any evidence for them?

You should be doing something differently with the results. My strategy...push down on the stickers and tape them to the patient's forehead if I don't like the numbers.

 

[nimbus]

Not sure if it’s been posted on here before, probably has, but this was one of my all time favorite papers I read in fellowship.

Near-infrared spectroscopy in vegetables and humans: An observational study - PubMed

Commonly eaten vegetables have NIRS measurements similar to those seen in healthy humans.

pubmed.ncbi.nlm.nih.gov

Kahn RA, Anyanwu A. Near-infrared spectroscopy in vegetables and humans: An observational study. Eur J Anaesthesiol. 2018 Dec;35(12):907-910. doi: 10.1097/EJA.0000000000000855. PMID: 30020143.

They should have had an ortho group too.

 

[nimbus]

Probably a related phenomenon.


Edit: @pgg referred to this in the original post.

Tetracycline and other tetracycline-derivative staining of the teeth and oral cavity - PubMed

Tetracyclines (TCN) were introduced in 1948 as broad-spectrum antibiotics that may be used in the treatment of many common infections in children and adults. One of the side-effects of tetracyclines is incorporation into tissues that are calcifying at the time of their administration. They have...

pubmed.ncbi.nlm.nih.gov