# Oxygen Administration in CVA/Stroke Patients



## ethomas4 (Jun 14, 2011)

Hello,

I am an EMT with a question regarding O2 administration to stroke/CVA patients.


Recently I have read in many paramedic protocols (im not a medic, just wanted to do some extra reading) that extreme caution should be used in administering high amounts of O2 to CVA stroke patients but I can not find a good explanation of why...only some articles about a study done on  rats regarding the matter.

Can someone give me a better explanation and reasons why high amounts of O2 can be bad?

I have also seen... "titrate oxygen to a minimum necessary to achieve SP O2 greater than or equal to 94%" .... why? and how do you achieve that? what does that mean?

Thanks you!!!


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## Shishkabob (Jun 14, 2011)

ethomas4 said:


> Hello,
> 
> Recently I have read in many paramedic protocols (im not a medic, just wanted to do some extra reading) that extreme caution should be used in administering high amounts of O2 to CVA stroke patients but I can not find a good explanation of why...only some articles about a study done on  rats regarding the matter.
> 
> Can someone give me a better explanation and reasons why high amounts of O2 can be bad?


  Oxygen, especially in high concentrations, is a potent vasodilator (constricts blood vessels).  One reason is you're taking a clot / bleed that might be getting atleast a little blood by, and making the vessel smaller, thereby inhibiting any possible oxygenation you may have had.  Stroke also cause an increase in intracranial pressure / swelling.


Think of head injuries, and why we want to bag them, but not bag too fast.  You want to control intracranial pressure, but again, too much oxygen will just make things worse.  This is why we watch EtCO2 (carbon dioxide being expirated) when bagging a suspected head injury as well, hoping to maintain around 35mmHg of EtCo2.  





> I have also seen... "titrate oxygen to a minimum necessary to achieve SP O2 greater than or equal to 94%" .... why? and how do you achieve that? what does that mean?



Not everyone needs to have an SpO2 of 100%, therefor not everyone needs supplemental oxygen let alone 100% (misnomer) oxygen by a non-rebreather.

As for how you achieve it, there's a myriad of options.  Could be as simple as nothing giving any supplemental oxygen at all, or you could put them on a nasal cannula at 2 liters per minute... or 4...or 6, or put them on a partial rebreather mask, or a non-rebreather, or intubate, or do a surgical crich.


If you get a patient satting 92%, you could throw them on a nasal cannula.  If it raises their SpO2 to 94%, great, if not, you could consider upping the amount of oxygen you give them.


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## medichopeful (Jun 14, 2011)

ethomas4 said:


> Hello,
> I have also seen... "titrate oxygen to a minimum necessary to achieve SP O2 greater than or equal to 94%" .... why? and how do you achieve that? what does that mean?



I'll answer this really quick.  To "titrate" oxygen basically means to carefully adjust it until you get the desired SpO2.

The way you do this is pretty simple in theory, but can be difficult in practice.  I think the best way to explain it will be to use an example:

You're dispatched to a "difficulty breathing" call.  When you get there, you find the patient is at 89% SpO2 on room air.  You decide you want to get this up, so you put the patient on a NC @ 2lpm.  You then recheck the SpO2, and discover it's climbed to 92%.  Good, but not at the level your protocol wants.  So you turn the O2 up to 4lpm, and you then remeasure the SpO2.  This time, it's 95%.  You decide to leave the patient on that, as it's getting them the oxygen saturation that you want.

The adjusting of the flow rate is the titration you're looking for.

As far as the magic number of 94% goes, that's just one number you'll hear.  At 94% saturation (unless I'm mistaken), the hemoglobin is carrying enough oxygen to adequately "ventilate" the cells (in the eyes of some.  Some people will argue you need a higher SpO2, but that's a different discussion entirely )

I have an article on my computer about O2 and CVAs, give me a few and I'll try to locate it.

Hope this helps!
Eric


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## medichopeful (Jun 14, 2011)

I guess I lied, the article's not on my computer :sad:

I'd seriously suggest reading this though:
http://www.bryanbledsoe.com/handouts
(Go to "Can Oxygen Really be Bad?")

Eric


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## ethomas4 (Jun 14, 2011)

Thank you very much for the responses and the article!! I love this site.....


Linus, I just want to make sure that I am not missing something here. You said O2 is a potent vasoDILATOR (constricts blood vessels)---did you mean O2 is a potent vasoconstrictor? 

Thanks for your help!!


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## Shishkabob (Jun 14, 2011)

Gah, yes, meant constrictor.


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## Handsome Rob (Jun 14, 2011)

Lol...fail. Hey tex...don't go making everyone think us tx boys are confused....its the humidity, I swear. 

sent from my mobile command center. or phone. whatever.


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## JPINFV (Jun 15, 2011)

Linuss said:


> Not everyone needs to have an SpO2 of 100%, therefor not everyone needs supplemental oxygen let alone 100% (misnomer) oxygen by a non-rebreather.


I'd go so far as saying that no one needs an SpO2 of 100. 99 % tells me much more than 100%.


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## Shishkabob (Jun 15, 2011)

JPINFV said:


> I'd go so far as saying that no one needs an SpO2 of 100. 99 % tells me much more than 100%.



Ah, but you know what they say about absolutes


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## JPINFV (Jun 15, 2011)

Linuss said:


> Ah, but you know what they say about absolutes




Hehe... depends on who you ask...


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## lightsandsirens5 (Jun 15, 2011)

Linuss said:


> Ah, but you know what they say about absolutes



It is ALWAYS bad to have an absolute. ALWAYS! h34r:

lol!


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## usalsfyre (Jun 15, 2011)

I'm curious where 94% came from as well. 90-92% was the number I had been taught in multiple critical care classes. Then, last year 94% starts popping up in EMS literature...


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## MrBrown (Jun 15, 2011)

usalsfyre said:


> I'm curious where 94% came from as well. 90-92% was the number I had been taught in multiple critical care classes. Then, last year 94% starts popping up in EMS literature...



The same place that 15 LPM NRB did

 Sent from Browns smarypants phone


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## Too Old To Work (Jun 15, 2011)

The current AHA recommendation is, I believe no O2 for stroke patients who maintain a saturation of 94% or better. The British Thoracic Society in an article published in "Chest" back in 2009 (I think) said that no supplement O2 should be given to any patient with a saturation of 92% or greater. That included chest pain or respiratory distress. Of course I can't find the link to that one. It was interesting because it called for changes to both in hospital and pre hospital standards. 

This study doesn't discuss stroke, but it does discuss high concentration O2 administration to COPD patients. Note that they found lower mortality when the O2 was titrated to produce SpO2 of 88-92%. 

This study is interesting, and probably should have some implications for EMS. 

As with Albuterol, the "Oxygen won't hurt" meme is just part of the "Chicken Soup" school of medicine.


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## exodus (Jun 15, 2011)

Link no worky


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## Too Old To Work (Jun 15, 2011)

exodus said:


> Link no worky



I just checked them both and they seem fine other than being a bit slow.


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## platypus (Jun 16, 2011)

medichopeful said:


> I guess I lied, the article's not on my computer :sad:
> 
> I'd seriously suggest reading this though:
> http://www.bryanbledsoe.com/handouts
> ...




VERY INTERESTING ARTICLE! (well.. power point lol)


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