2:1 Nitrous to Oxygen and wound healing.

[VentdependenT]

I don't know about you all but we seem to run a lot of 2:1 Nitrous to Oxygen verses 1:1. So what right?

Well I was having a discussion with one attending who argued to run it in the reverse proportion. He then refreshed my memory about a study with decreased wound infection in patients undergoing colon surgery with at least 50% oxygen.

Although we weren't doing a colon surgery it was hard for me to argue with him. Something about free radical generation and more o2 substrate avail for our peroxidation buddies to kill the bacteria. Also a decreased post op NOV perhaps.

Anyways I was wondering what your thoughts were on the subject.

Personally I run 1:1 because I believe the analgesic (not amnestic) effect of nitrous tops out at a half mac. I also run lower flows at 1/2 mac of sevo because of the whole 2 mac hour deal in the package insert.

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[ReefTiger]

It seems like I remember maximal analgesic effects of Nitrous being at like 33-40%. I'll have to double check though.

 

[VentdependenT]

It seems like I remember maximal analgesic effects of Nitrous being at like 33-40%. I'll have to double check though.

Me too I guess.

 

[Laryngospasm]

I don't know about you all but we seem to run a lot of 2:1 Nitrous to Oxygen verses 1:1. So what right?

Well I was having a discussion with one attending who argued to run it in the reverse proportion. He then refreshed my memory about a study with decreased wound infection in patients undergoing colon surgery with at least 50% oxygen.

Although we weren't doing a colon surgery it was hard for me to argue with him. Something about free radical generation and more o2 substrate avail for our peroxidation buddies to kill the bacteria. Also a decreased post op NOV perhaps.

Anyways I was wondering what your thoughts were on the subject.

Personally I run 1:1 because I believe the analgesic (not amnestic) effect of nitrous tops out at a half mac. I also run lower flows at 1/2 mac of sevo because of the whole 2 mac hour deal in the package insert.

The analgesic effect does not run out at half a mac of n20, also to answer your actual question there are confilicting studies on the o2 thing, its a pick your study kind of deal, there is also a new paper out, not sure where I saw it that talks about the anesthesiologists role in preventing wound infection, goes over the whole deal. IMHO, the best thing you can do is keep the patient warm.

 

[fakin' the funk]

http://www.ncbi.nlm.nih.gov/entrez/..._uids=16249417&query_hl=1&itool=pubmed_docsum

INTERVENTIONS: Patients were randomly assigned to either 30% or 80% fraction of inspired oxygen (FIO2) intraoperatively and for 6 hours after surgery. Anesthetic treatment and antibiotic administration were standardized. CONCLUSIONS: Patients receiving supplemental inspired oxygen had a significant reduction in the risk of wound infection. Supplemental oxygen appears to be an effective intervention to reduce SSI in patients undergoing colon or rectal surgery.

 

[Laryngospasm]

http://www.ncbi.nlm.nih.gov/entrez/..._uids=16249417&query_hl=1&itool=pubmed_docsum

INTERVENTIONS: Patients were randomly assigned to either 30% or 80% fraction of inspired oxygen (FIO2) intraoperatively and for 6 hours after surgery. Anesthetic treatment and antibiotic administration were standardized. CONCLUSIONS: Patients receiving supplemental inspired oxygen had a significant reduction in the risk of wound infection. Supplemental oxygen appears to be an effective intervention to reduce SSI in patients undergoing colon or rectal surgery.

I love it when people put a link to a study, theres more than one study, others contradict that one. You must make your own decision, but dont point to one study like its freakin gospel.

 

[dhb]

I love it when people put a link to a study, theres more than one study, others contradict that one. You must make your own decision, but dont point to one study like its freakin gospel.

I love it when someone thinks that because there's a link to a study it's freakin gospel! Come on do you think people on the forum are idiots? Plus you can't post a review of articles on the subject in each post!
Thanks for the clarification anyway

 

[VolatileAgent]

well, there's a lot of good data that suggests running a high o2 tension during colorectal surgery improves tissue oxygenation. also, we have an attending here who runs high co2 tensions as well (the whole oxygen dissociation curve and neutrophil oxidative burst thing), and there are studies to back that methodology up.

not gospel, but probably not a bad idea either.

 

[VentdependenT]

I love it when people put a link to a study, theres more than one study, others contradict that one. You must make your own decision, but dont point to one study like its freakin gospel.

Thaz the one.

 

[Laryngospasm]

http://www.ncbi.nlm.nih.gov/entrez/..._uids=16249417&query_hl=1&itool=pubmed_docsum

INTERVENTIONS: Patients were randomly assigned to either 30% or 80% fraction of inspired oxygen (FIO2) intraoperatively and for 6 hours after surgery. Anesthetic treatment and antibiotic administration were standardized. CONCLUSIONS: Patients receiving supplemental inspired oxygen had a significant reduction in the risk of wound infection. Supplemental oxygen appears to be an effective intervention to reduce SSI in patients undergoing colon or rectal surgery.

I apologize, I didnt realize you were just posting to the article he was refering too.

 

[VentdependenT]

Well as luck would have it August 2006 Anesthesiology journal's cover story is our role in preventing Surgical Site Infections.

We should strive for:

Euvolemia

Normoglycemia

Euthermia: I rarely warm the room for induction but perhaps I will in some non-peds populations. I friggen hate hot OR's man.

Hyperoxia? Perhaps. It seems that the reduced infections were seen if 80% O2 was continued for around a 4 hour period post op (including transfer of pt out of OR) that some benefit was seen.

 

[dhb]

We should strive for:

Euvolemia

Normoglycemia

Euthermia

That's basically keeping things as normal as possible

 

[militarymd]

That's basically keeping things as normal as possible

Let me ask everyone here this?

What's normal about:

-breathing substituted hydrocarbons that interrupt central and peripheral nervous system function in undefined ways.

-ventilation via a plastic tube with a machine.

-having various parts of your body opened, poked, and manipulated by another human being.

-receive sodium and water through a puncture in your vein.

-having your neuromuscular junctions blocked so that, should the substituted hydrocarbons don't shut your brain off enough, you are unable to move.

There is nothing normal about having anesthesia and surgery.....so why should we keep things normal????

-Why should the oxygen tension be "normal"?
-Why should the carbon dioxide tension be "normal"?
-Why should your temperature be "normal"?
-Why should your fluid/volume/sodium status be "normal"?

I would submit to you that there is no "normal"....do we keep core temperatures "normal' during circulatory arrest? I hope not.

The physiologic parameters which we manipulate should be manipulated to values which improve outcome.....whether they are "normal" numbers or not remain to be seen....and probably depends on a variety of factors:

-underlying medical condition
-disease process involved
-surgical procedure planned
-desired outcome
- and HEAVENS FORBID....patient satisfaction (PONV kind of crap)

 

[IN2B8R]

The physiologic parameters which we manipulate should be manipulated to values which improve outcome.....whether they are "normal" numbers or not remain to be seen....and probably depends on a variety of factors:

-underlying medical condition
-disease process involved
-surgical procedure planned
-desired outcome
- and HEAVENS FORBID....patient satisfaction (PONV kind of crap)[/QUOTE]



very well said.

 

[fakin' the funk]

There is nothing normal about having anesthesia and surgery.....so why should we keep things normal????

The physiologic parameters which we manipulate should be manipulated to values which improve outcome.....whether they are "normal" numbers or not remain to be seen....and probably depends on a variety of factors:

Why the diatribe against "normal"? The only reason to keep things "normal" (e.g. euthermia) is b/c the literature supports it, not because of ideology. You're right, those substituted hydrocarbons ain't normal, and they've been working pretty well.

 

[dhb]

The physiologic parameters which we manipulate should be manipulated to values which improve outcome.....whether they are "normal" numbers or not remain to be seen....and probably depends on a variety of factors:

How do we really know what really improves outcome? are they studies that have compared 79% vs 80% O2? or x mg of a vs y mrg of b? is the machine really giving you exactly what have it programmed for?
Unless you're going for ground breaking discoveries i still think (although i might change my mind) that in normal practice it's best to keep things you can control as normal as you can

 

[dhb]

What's normal about:

-breathing substituted hydrocarbons that interrupt central and peripheral nervous system function in undefined ways.

-ventilation via a plastic tube with a machine.

-having various parts of your body opened, poked, and manipulated by another human being.

-receive sodium and water through a puncture in your vein.

-having your neuromuscular junctions blocked so that, should the substituted hydrocarbons don't shut your brain off enough, you are unable to move.

There is nothing normal about having anesthesia and surgery.....so why should we keep things normal?

Could this be a sophism?

 

[militarymd]

Why the diatribe against "normal"? The only reason to keep things "normal" (e.g. euthermia) is b/c the literature supports it, not because of ideology. You're right, those substituted hydrocarbons ain't normal, and they've been working pretty well.

So when you go on CPB, you want to keep the blood temperature at 37 C...to prevent mediastinitis post op?

So when you have some one with inflammatory lung disease (ARDS)....you're going to ventilate them with 10 cc/kg tidal volumes with plateau pressures around 45 cm of water to maintain a Partial pressure of carbon dioxide of 40 mm Hg?

So when you have some one with a non-anion gap metabolic acidosis secondary to 3 liters of normal saline, you're going to give some Sodium bicarbonate now?

I have just listed 3 specific examples without spending any time thinking about it where "normal" numbers are associated with worse outcomes....

 

[hndrx1a]

Well, not nitrous- but will twin turbos do?...for militarymd...

http://dagostinoracing.com/media/lthlpsi.wmv

 

[SilverStreak]

How about STABLE instead of normal mil? I think the point is that anesthesia providers should strive to keep the patient stable using all their tricks-drugs, temp, volume, gas, ventilation. No, breathing through a plastic tube is not "normal", it keeps the patient "stable" during the operation, which is a time when the patient's normal physiologic mechanisms are altered and supplemented by anesthesia so an invasive surgery can be performed.

What is normal will vary from patient to patient and surgery to surgery, and as Mil points out, striving for normal values can be dangerous in various patient scenarios. However, I think everyone can recognize/agree on what a stable patient looks like, and hopefully a stable patient who is "fixed" or has better quality of life will be the end result of the combined efforts of surgery and anesthesia together. The hardest thing is how to keep a patient stable and have a good outcome? There are plenty of different ways, is one approach better than the other? I think it is a situation by situation call.

To me, vent's orginal query is asking about the better way to do gas and the effect on patient outcomes. Is one way better than another way. I think these kinds of questions are hard to answer b/c there are so many factors involved, this is part of the reason why different studies have different answers.