Oxygen

[RedAirplane]

I've been doing a little digging after what I've read on this forum about not using 15 L/min of oxygen on every patient.

http://www.emsworld.com/article/10915304/the-dangers-of-giving-too-much-oxygen

This article says that in shock or hypoxia, high flow oxygen is needed, but in other situations, we were not taught a reason why we use so much oxygen.

I was taught a reason: a chest pain patient (or whatever major medical/trauma pt you have) is either in shock, or soon to be in shock, so treat for shock.

I'm a bit confused--is there something subtle that makes this reasoning not quite correct?

 

[DesertMedic66]

Why treat for shock in a patient who is not in shock?

Not every chest pain, SOB, ABD pain, and trauma patient is in shock and a high number of those patients will not go into shock.

One of the major issues with high flow oxygen is that is causes vasoconstriction. In our MI patients and stroke patients we do not want vasoconstriction.

There are also more issued with high flow oxygen such as free radicals and nitrogen washout.

 

[RedAirplane]

That's the key I was missing.

I know the bit about vasoconstriction, but I also had a hard time imagining a CP patient ever adequately perfusing. The heart is the pump and if it's not pumping right, hypoperfusion.

 

[STXmedic]

That's the key I was missing.

I know the bit about vasoconstriction, but I also had a hard time imagining a CP patient ever adequately perfusing. The heart is the pump and if it's not pumping right, hypoperfusion.

Yes, but chest pain does not necessarily equal impaired cardiac function. Even with legitimate ischemia, you can still have adequate cardiac output.

 

[Chewy20]

That's the key I was missing.

I know the bit about vasoconstriction, but I also had a hard time imagining a CP patient ever adequately perfusing. The heart is the pump and if it's not pumping right, hypoperfusion.

Chest pain is a lot different from a cardiac event. I have chest pain all of the time, non-cardiac related, as is the case most of the time in the field. Shock is systemic hypoperfusion and broken down into 4 major groups. Why would chest pain patients have to be in one of those groups? Whoever taught you that should not be teaching.

 

[DesertMedic66]

Yes, but chest pain does not necessarily equal impaired cardiac function. Even with legitimate ischemia, you can still have adequate cardiac output.

Chest pain is a lot different from a cardiac event. I have chest pain all of the time, non-cardiac related, as is the case most of the time in the field. Shock is systemic hypoperfusion and broken down into 4 major groups. Why would chest pain patients have to be in one of those groups? Whoever taught you that should not be teaching.

Both of these. There are a ton of different causes of chest pain. Everything from trauma, to MIs, to angina, to costochondritis.

Remember what the definition of shock (hypoperfusion) is and how it presents.

 

[RedAirplane]

May have poorly phrased, but the gist of what I was taught was treat per-emptively for shock with major illness/injury.

What you all are saying makes sense.

 

[Carlos Danger]

Why would chest pain patients have to be in one of those groups? Whoever taught you that should not be teaching.

I don't think that's fair. A lot of new people are unclear on the whole ACS continuum. Basics are pretty much taught that "chest pain = heart attack = shock = cardiac arrest".

Shock or not, the ONLY group that needs supplemental oxygen is those who are hypoxemic.

As long as Spo2 is above, say, 94-ish, additional inspired oxygen won't contribute significantly to arterial oxygen content. It may raise the Spo2 to 100 and that may make us feel better, but it makes no difference in the amount of oxygen delivered to the tissues. The bucket is already full; trying to add more just doesn't help anything.

 

[STXmedic]

I'm all for staying ahead of the curve, but that typically means being prepared and knowing what to potentially expect- not necessarily acting. If I see someone who looks like they are about to crash, I'm not going to give them epi just because I think they might need it in a few minutes.

 

[Brandon O]

Try also to distinguish between "shock," which is systemic tissue-level hypoxia (typically from global hypoperfusion, since that's the easiest way to achieve that), and "ischemia," which is local tissue-level hypoxia (typically from local hypoperfusion, such as... well, a clot).

In a typical MI, a portion of the heart is ischemic. The patient is not in shock unless that injury reduces the cardiac output (damages the pump) quite a lot. (Could this global hypoperfusion then increase the cardiac ischemia? Yeah, sure.)

 

[Clare]

Whoever taught you that is wrong.

Oxygen is a specific treatment for systemic hypoxia; it is not a "tonic-all" for patients who are unwell or injured.

As Brandon says, in the specific example of myocardial ischaemia, well, simply put, localised ischaemia is not generalised hypoxia so oxygen is not going to be helpful.

 

[BOS 101]

Why treat for shock in a patient who is not in shock?

Not every chest pain, SOB, ABD pain, and trauma patient is in shock and a high number of those patients will not go into shock.

One of the major issues with high flow oxygen is that is causes vasoconstriction. In our MI patients and stroke patients we do not want vasoconstriction.

There are also more issued with high flow oxygen such as free radicals and nitrogen washout.

Could you explain a little of what free radicals are and nitrogen washout? and how 02 effects it etc Id be grateful

 

[ThadeusJ]

Free radicals in very simplistic terms, if you think of it in these terms, it makes complete sense: take your O2 and split it into two O- atoms...then add water (H2O). Add them together you get H2O2 which is peroxide. There are other things that are formed as well but this one can be visualized easily. Put some peroxide on a cut and watch it foam up. Think about what it does to the tissues on a molecular level. You have enzymes which break these down quickly but they are produced at a slower rate that necessary if the body is overwhelmed by far too high oxygen delivery (or if there is liver damage). Peroxide running around in the body starts to ruin more than a few things. Therefore, trying to help by over supplying the body with oxygen has been scientifically proven to actually do damage at the tissue level.

Nitrogen washout is formed by replacing the normal 80% of room air with oxygen. The theory is that the amount of nitrogen remains the same during inhalation and exhalation, stenting the airways open. If you replace the nitrogen with 100% oxygen, the oxygen will be absorbed and you won't have the nitrogen on exhalation to work as the stent. therefore the nitrogen is "washed out", causing alveolar collapse.

 

[DesertMedic66]

Could you explain a little of what free radicals are and nitrogen washout? and how 02 effects it etc Id be grateful

Free radicals in very simplistic terms, if you think of it in these terms, it makes complete sense: take your O2 and split it into two O- atoms...then add water (H2O). Add them together you get H2O2 which is peroxide. There are other things that are formed as well but this one can be visualized easily. Put some peroxide on a cut and watch it foam up. Think about what it does to the tissues on a molecular level. You have enzymes which break these down quickly but they are produced at a slower rate that necessary if the body is overwhelmed by far too high oxygen delivery (or if there is liver damage). Peroxide running around in the body starts to ruin more than a few things. Therefore, trying to help by over supplying the body with oxygen has been scientifically proven to actually do damage at the tissue level.

Nitrogen washout is formed by replacing the normal 80% of room air with oxygen. The theory is that the amount of nitrogen remains the same during inhalation and exhalation, stenting the airways open. If you replace the nitrogen with 100% oxygen, the oxygen will be absorbed and you won't have the nitrogen on exhalation to work as the stent. therefore the nitrogen is "washed out", causing alveolar collapse.

This. Thank you @ThadeusJ

 

[Brandon O]

Terrific explanations, Thadeus.

 

[ThadeusJ]

Its far more complicated than this of course but I have worked with people who could draw the molecular equation inside and out yet not answer the question, "But what does it mean?". At the end of the day, you administer enough oxygen to achieve the results you want and once attained, no more. Please keep in mind that as a result of shunts and diffusion issues, you may need 100% oxygen and a whole lot of PEEP on a mechanical ventilator just to achieve SpO2 levels in the 80's.

You can never assume that a non-rebreather mask is too much nor nasal cannula not enough until you assess the patient and look at their situation (now there's a concept). Protocols that state, "For illness "X", administer "Y" oxygen" are false logic and only serve those who truly don't know what they are doing. You administer the oxygen you need in order to achieve and maintain the endpoint you are aiming for.

 

[BOS 101]

Free radicals in very simplistic terms, if you think of it in these terms, it makes complete sense: take your O2 and split it into two O- atoms...then add water (H2O). Add them together you get H2O2 which is peroxide. There are other things that are formed as well but this one can be visualized easily. Put some peroxide on a cut and watch it foam up. Think about what it does to the tissues on a molecular level. You have enzymes which break these down quickly but they are produced at a slower rate that necessary if the body is overwhelmed by far too high oxygen delivery (or if there is liver damage). Peroxide running around in the body starts to ruin more than a few things. Therefore, trying to help by over supplying the body with oxygen has been scientifically proven to actually do damage at the tissue level.

Nitrogen washout is formed by replacing the normal 80% of room air with oxygen. The theory is that the amount of nitrogen remains the same during inhalation and exhalation, stenting the airways open. If you replace the nitrogen with 100% oxygen, the oxygen will be absorbed and you won't have the nitrogen on exhalation to work as the stent. therefore the nitrogen is "washed out", causing alveolar collapse.

thank you my man