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Nitrous Oxide

Discussion in 'Anesthesiology' started by Dryacku, Dec 15, 2008.

  1. Dryacku

    Dryacku Member
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    Only a CA-1

    I love using nitrous on some of my patients and I feel that I have a good grasps of the contraindications

    I use it mainly at the end of the cases for quicker wake ups and for patients that running hypotensive

    Some of my attendings love it some refuse to let me use it. Anyone ever have a bad experience with nitrous oxide and dont use it now because of that experience? or any other thoughts on it?
     
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  3. Planktonmd

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    It's a good tool to have, not perfect but useful.
    Most people who claim they had bad experiences with N2O they did because they used in the wrong patient or for the wrong indication.
     
  4. drccw

    drccw ASA Member
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    I like nitrous.. I used to use it a lot
    back in the older days my cases typically all got nitrous...
    50% nitrous + ISO... was a great anesthetic.. cheap as well... and they woke up wicked quick....

    these days we don't even have an iso vaporizer... I use a lot of des these days...

    ask your attendings why that won't let you use it...
    that enzyme... bah... mental masturbation.. clinically insignificant...
    PONV? Juries out... but we do know that the inhalational agents and narcotics are associated with nausea.... in my mind nitrous keeps the amount of both of those lower... thus... even if it does cause PONV... it's a wash...

    use it, become familiar with it.. i feel that it's becoming a dinosaur, like droperidol....
     
  5. dhb

    dhb Member
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    Nitrous is fine, i don't even see more ponv as some have claimed
     
  6. jwk

    jwk CAA, ASA-PAC Contributor
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    I hope not - as long as there are no clear cut definitive studies that it's a bad thing overall, I'll still use it.

    Kinda like one of my old docs from years ago - he quit using cyclopropane when they removed the tanks from the machines.
     
  7. drccw

    drccw ASA Member
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    We've got a couple places where they don't even have nitrous in our hospital.... when it comes down to it you don't really need it anymore...

    it's a shame.. i love it... I also like the nitrous/propofol infusion anesthetic... it's super smooth and I use it in my patients who claim they always get PONV... it's my anesthetic of choice for them...

    of course I also give them drop too....
     
  8. geauxg8rs

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    The true artistry of residency is in doing the technique the way your attending wants and letting him think that you are totally on board with his lame logic.
    There is more than one way to skinna cat.
    You need people to make fun of when you are talking to your buds

    When Dr. Feelgood MD PhD CMYCV wants to do his CABG with a toradol induction and paralyze with Mayan Curare and run the patient on 21% Fi02. Just say "wow that is really cool, I never would have thought of doing it that way, Thanks Doctor MegaEgo. "

    What you are saying under your breath is "How long do I have to agree with him before he leaves and I can sit on my arse and get this anesthetic goin."
     
  9. SleepIsGood

    SleepIsGood Support the ASA !
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    Personally I try to avoid it. There are soo many damn 'contraindications', why memorize them if you arent using it period.

    I do like to use it toward the end though. I wonder what sort of effect that it will have (ie, is it like with the inhalational agents when you switch from sevo to des, it really doesnt decrease waking up time)?

    The whole PONV property it has, and this applies to neostigmine for reversal at all. I wonder what impact these two agents have on PONV since for the most part we all give some sort of anti-emetic, ondansetron/metoclompradie,etc
     
    #8 SleepIsGood, Dec 15, 2008
    Last edited: Dec 15, 2008
  10. cchoukal

    cchoukal Senior Member
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    I'm using it right now! there was just a study in anesthesiology that demonstrated decreased arterial dilatation and increased homocystiene, and I try to avoid it in people with ischemic disease in the heart and brain, in addn to the usual contraindications. but even then, 10 minutes at the end of a case probably has a negligible impact.
     
  11. Dryacku

    Dryacku Member
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    So from the sound of things nobody here has had a horrible experience?
    Ive only done this for six months and everythings been good so far (knock on wood). But that is true if it was that bad it would have been pulled long ago.
     
  12. Hawaiian Bruin

    Hawaiian Bruin Breaking Good
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    :laugh: That's the funniest and truest damn thing I've heard all day.
     
  13. huktonfonix

    huktonfonix board certified!
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    At the same time keep in mind that you can always learn something new. Some things that seem f'd up at the time, make a lot more sense when you try it out yourself or adapt it for your own usage. I used to think the semi deep extubation was messed up early in residency. Now its another valuable tool. Having said that, some people really do some messed up stuff
     
  14. leviathan

    leviathan Drinking from the hydrant
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    How would you guys rate nitrous in terms of its potency for analgesia?
     
  15. SleepIsGood

    SleepIsGood Support the ASA !
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    Typically speaking, it's not analgesic. Attendings of mine have stated that individuals considered it slightly analgesic due to the fact that patients did not "feel" things. It's not clear as to whether they actually didnt 'feel' things or if it was due to the fact they were not 'with it'.

    As far as I know, it would not be considered an analgesic, although the 'discoverer' of N2O came about it after he observed a few individuals who had partaken in 'N20 frolicks' painlessly ambulating after they bruised themselves.
     
  16. huktonfonix

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    Mr. Barash disagrees. Does anyone have any studies to the contrary?
     
  17. Bertelman

    Bertelman Maverick!
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    Couldn't the same be said for fentanyl or morphine?
     
  18. Planktonmd

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    It is definitely an analgesic.
    To really define analgesia you have to start with the definition of pain, and I think we all agree that pain is a subjective "feeling" caused by a stimulus.
    Anything that prevents or modifies this "feeling" is analgesic.
     
  19. huktonfonix

    huktonfonix board certified!
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    this reminds me of the pain discussion between tenesma/womansurg
     
  20. jetproppilot

    jetproppilot Turboprop Driver
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    :laugh::laugh:
     
  21. ncdoc1974

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    I find N2O to be a completely useless drug in the presence of everything else we have at our fingertips...If I never use it again it would be too soon. I think that people that do use it are hacks that are trying to sugarcoat a poor anesthetic.
     
  22. Bertelman

    Bertelman Maverick!
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    So you're confident you'll never use it again??


    HACK!


    I find that people who use sweeping, judgmental generalizations denouncing the skills or qualifications of people they have never met, particularly on anonymous internet forums, are either hopelessly insecure, or stubbornly close-minded.

    I'll be signing up for your refresher course lecture denouncing the use of N2O and everyone who uses it next year in New Orleans.
     
  23. Arch Guillotti

    Arch Guillotti Senior Member
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    That is a pretty narrow viewpoint dude. Is there soem particular reason you have such a strong negative view of nitrous?
     
  24. ncdoc1974

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    Sweet.
     
  25. ncdoc1974

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    I used to use N2O a lot, then pushed back some...try to go a month without using it...if you can & can do it smoothly, then great...And if you do this, I bet you will like it...So much that you will open up your mind like I have and realize it is a useless and unnecessary drug and you will probably never use it again...I am going on 4 years N2O free and proud of it.
     
  26. Arch Guillotti

    Arch Guillotti Senior Member
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    Does this involve some sort of support group?

    ;)
     
  27. ncdoc1974

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    I just don't understand why it is necessary & if you eliminate it you will eliminate the potential side effects caused by it...Keep it simple. Additionally, running patients on as close to 100% O2 as possible appears to be gaining some steam in the current literature in terms of PONV, rate of infection & cardioprotection in the elderly...
     
  28. ncdoc1974

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    We might need to make one for all the N2O addicts on this board!
     
  29. Bertelman

    Bertelman Maverick!
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    Hopefully that steam is a little stronger than the stuff propelling the initiation of periop b-block therapy a few years ago.

    I have an attending who swore it off a few years ago, and I really respect him (for other reasons). I'm sure one day I'll challenge myself and go cold turkey, and will probably be just fine. In the mean time, N2O protects me on those cases when I am coming in for landing, vaporizer off with low flows, when the surgeon decides to hand off the suture to the intern, or worse yet, the med student.
     
  30. ncdoc1974

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    Point taken...in private practice you will not be worring about an unpredictable closure...One thing I've noted through the years, in patients around 50 years old and older, if you have enough narcotic on board so the patient is only breathing 6-8 times per minute on closure, they hardly ever move with 0.3-0.5%Sevo running, then you can dump the sevo when they are putting the dressing on and the patient will have their eyes open by the time the stretcher is in the room...be careful trying this on an 18 year old...
     
  31. Planktonmd

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    Really!
    I wish I could feel this strongly about anything in anesthesia or in medicine in general.
    You either have more knowledge and experience than all of us which allows you to make such a statement with such confidence or you simply don't know what you are talking about.
    I have a strong feeling it is the second possibility (no offense intended).
     
    #30 Planktonmd, Dec 17, 2008
    Last edited: Dec 17, 2008
  32. coprolalia

    coprolalia Bored Certified
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    :laugh:

    I, like Bertelman, would love to hear you say this out loud to everyone you meet at the next ASA. It's easy to be bombastic and cocksure when no one knows who you are.

    -copro
     
  33. ncdoc1974

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    I said it. And I meant it...It is my opinion, and you are entitled to yours...I see absolutely no use for this drug in my practice...plain and simple...I would be glad to share my opinion with anyone at the ASA meeting...the only decent argument for using N2O on here came from a resident unsure about closure times when a med student gets the suture in hand...I am a bit surprised I am the only N2O free anesthesiologist on here...oh yea, and did I mention I don't use sux either? (unless absolutely necessary i.e. life or death scenario)
     
  34. Planktonmd

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    I also think N2O is a very good tool to use in OB anesthesia especially when you are doing a c section under GA and you want an agent that supplements your vapors without relaxing the uterus and can be titrated rapidly and easily.
    But that is my opinion and I obviously don't have your depth of knowledge and experience.
     
  35. ncdoc1974

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    Oh yea, some other things that bug me:
    1) Anesthesiologists who don't know how to place peripheral nerve catheters under stimulation
    2) Anesthesiologists who don't know how to place peripheral nerve catheters at all
    3) Anesthesiologists who don't know how to do U/S guided blocks
    4) Anesthesiologists who don't know how to do peripheral blocks for awake intubations and always rely on nebulizing instead
    5) Anesthesiologists who do all of their awake intubations nasally rather than orally
    6) Anesthesiologists who do their popliteal blocks posterior rather than lateral
    7) Anesthesiologists who prefer a bronchial blocker to a double lumen tube
    8) Anesthesiologists who try to do anything but a pure TIVA during SSEP and MEP monitoring cases
    9) Anesthesiologists who use fentanyl in their thoracic epidural infusions rather than morphine or dilaudid
    I could go on...but I will stop...Any residents reading this-If you "resemble" any of these statements, challenge your attendings...make them teach you these invaluable skills if they can...it will help in the future when you are in private practice...Otherwise, someone like me may think you are a hack.
     
  36. ncdoc1974

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    Point taken...Knock on wood, I have not had to put a mom to sleep in the past 4 years (I do "not so busy" OB only a few times a month & have been lucky) I'll admit I might reach for it then, but only if I was in dire need...C/S for fetal distress with our OBs tend to be less than 20 min skin to skin...Do I really need it? mmm...
     
  37. Planktonmd

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    +pity+
     
  38. Arch Guillotti

    Arch Guillotti Senior Member
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    Eh that is pretty much how it is around here:cool:.
     
  39. Dryacku

    Dryacku Member
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    How about hypotension

    I know theres many other ways to treat hypotension and to look for the cause, but if my cause is the volatile anesthetic, how bout nitrous in those cases?

    I also understand it is easy to live without once your good enough, but I still have not heard one true bad experience from anyone?

    Every drug has a million contraindication and possible side effects, however we still use them regurarly even though there maybe other alternatives

    Anyways any bad experiences?
     
  40. aphistis

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    10) Excessively negative people.
     
  41. fakin' the funk

    fakin' the funk ASA Member
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    That's the RAISON d'ETREof this forum, cop.
     
  42. coprolalia

    coprolalia Bored Certified
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    Well, qualitatively, you are making a different argument here. In your first opining, you categorically dismissed N2O as a useless and needless agent, and anyone who uses it as a "hack" anesthesiologist. I'm just saying that you would likely not be so bold as to blurt out such an extremist position publicly in an open forum where you could be identified, at the risk of being humiliated by people far more intelligent and experienced than yourself. I just don't believe the world is quite so black-and-white as you, and that categorically saying that nitrous has no value and that your colleagues that use it are hacks is quite judgmental and offers insight into a person who is rigid, close-minded, and believes that there is only two ways to do things: his own way and the wrong way.

    In the second part of your rant (above), you then go on to state preferences... and not-quite-so absolutely. Fine. I have certain preferences too. The interesting thing about our profession is that there exist far more than one way to climb a tree. If you're suggesting that more training and better understanding of anatomy and how to do blocks is valuable, I won't disagree. But, just because you know how to do a certain procedure doesn't mean it is necessarily the best option in a particular circumstance.

    There are certain skills and procedures that I have learned in residency that, quite frankly, I have become better at doing than some of my attendings. It does not mean that I feel superior to them. Likewise, I'm certain that there are experiences and knowledge areas that they possess which I do not. All of us have knowledge gaps.

    I would make a serious effort to check your arrogance. Karma has an interesting way of burning people who exhibit such flagrant attitudes about things. And, you may think it's okay to exagerrate on an internet forum for effect, but when this becomes a continuing habit it tends to change who you are... and suddenly you find yourself becoming more and more in the real world the caricature you protray here. Trust me. Been there. Done that.

    -copro
     
  43. TheSandMan

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    Could you elaborate on #9 above? I would think that with a continuous infusion, a short acting narcotic would be better
     
  44. Jacky29

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    Yeah, but that is the q for me: to sugarcoat the anesthetic to make it as poor as possible or not? What is better and why?
    :bang::)!
     
  45. Planktonmd

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    :confused:
     
  46. Jacky29

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    Hey, people! Dont be mean, say sth!;)
     
  47. Josh L.Ac.

    Josh L.Ac. MSA/LAc & BSN/RN --> AA-S
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    Internets, how do gibberish?
     
  48. xjohns1

    xjohns1 SDN Angel
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    we still offer pt-administered nitrous to our laboring patients on the L & D ward. at least one of our ob anesthesia attendings (and i haven't personally reviewed the literature) says it's no better than placebo. but, women have sought out specifically the option of nitrous. some of these pts had connections to europe, where it's still used extensively in the setting of labor.
     
  49. Fastrach

    Fastrach New Member
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    Wow, that's kickin' it old skool....
     
  50. Planktonmd

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    Wow!
    I am assuming you are in the U.S.
    May I ask where??
     
  51. BLADEMDA

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    [​IMG]Home > August 2007 > Is It Time to Retire High-concentration Nitrous Oxide?

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    Anesthesiology:
    August 2007 - Volume 107 - Issue 2 - pp 200-201
    doi: 10.1097/01.anes.0000271868.07684.5c
    Editorial Views

    Is It Time to Retire High-concentration Nitrous Oxide?

    Hopf, Harriet W.

    Free Access
    Continued Medical Education




    Article Outline
    [​IMG] Author Information



    Department of Anesthesiology, University of Utah, Salt Lake City, Utah. [email protected]
    CME This editorial accompanies the article selected for this month's Anesthesiology CME Program. After reading the article and editorial, go to http://www.asahq.org/journal-cme to take the test and apply for Category 1 credit. Complete instructions may be found in the CME section at the back of this issue.
    This Editorial View accompanies the following article: Myles PS, Leslie K, Chan MTV, Forbes A, Paech MJ, Peyton P, Silbert BS, Pascoe E, ENIGMA Trial Group: Avoidance of nitrous oxide for patients undergoing major surgery: A randomized controlled trial. Anesthesiology 2007; 107:221-31.
    Accepted for publication May 15, 2007. The author is not supported by, nor maintains any financial interest in, any commercial activity that may be associated with the topic of this article.


    DURING the past decade, anesthesiologists have increasingly recognized that the effects of anesthesia reach beyond the postanesthesia care unit. Researchers have extended their vision beyond studies of pain and postoperative nausea and vomiting in the postanesthesia care unit (still important outcomes) to studies of the impact of anesthesia on a broad range of postoperative outcomes, including cardiac complications and surgical wound infection. Myles et al.,1 in this issue of Anesthesiology, report an outstanding, large (2,050 patients), multicenter, pragmatic randomized controlled trial of the effect of intraoperative gas selection on a wide range of postoperative complications. Patients undergoing major surgery were randomly assigned to receive 80% oxygen with 20% nitrogen versus 30% oxygen with 70% nitrous oxide intraoperatively. Patients assigned to the high inspired oxygen-nitrous oxide avoidance group had fewer major postoperative complications and less frequent severe postoperative nausea and vomiting, and were more rapidly discharged from the intensive care unit, although hospital stay did not differ between groups. The authors conclude, The routine use of nitrous oxide in patients undergoing major surgery should be questioned. An alternative conclusion would be that the routine use of high inspired oxygen (which precludes high inspired nitrous oxide) in patients undergoing major surgery should become routine.
    A number of well-designed randomized controlled trials have demonstrated outcome benefits of maintaining intraoperative normothermia, including reduced blood loss in hip arthroplasty,2 reduced surgical site infection in colon surgery,3,4 and reduced cardiac morbidity and mortality in patients undergoing vascular surgery.5 Perioperative administration of &#946; blockers6 or clonidine7 reduces cardiac morbidity and mortality in patients at risk for coronary artery disease undergoing noncardiac surgery. Although most of these studies have not been repeated, and controversy remains about their generalizability, the results have rapidly been adopted in clinical guidelines and by regulatory (Joint Council on Accreditation of Healthcare Organizations) and insurance (Centers for Medicare and Medicaid Services) agencies.
    Two large, well-designed randomized controlled trials in colon surgery3,4 showed a 40-50% reduction in surgical site infection in patients given 80% inspired oxygen intraoperatively and for a period of time postoperatively. Conflicting data from another small, real-world randomized trial8 have limited rapid clinical adoption. The current study by Myles et al.1 may help to accelerate that process.
    Another reason for slower clinical adoption of high inspired oxygen is the concern of many anesthesiologists that it could cause oxygen toxicity or increased atelectasis. Oxygen toxicity is not a risk in the short term (less than days), and therefore is not pertinent in the operating room. Some degree of atelectasis is inevitable in all patients undergoing major surgery. Akca et al.9 demonstrated similar degrees of atelectasis in colon surgery patients randomly assigned to 80% versus 30% oxygen (balance nitrogen) intraoperatively. Myles et al. found that high inspired nitrous oxide caused more atelectasis than high inspired oxygen. Therefore, these issues should not limit the use of high inspired oxygen.
    The authors of the current study intended to examine the value of avoidance of nitrous oxide in reducing postoperative complications. The difficulty in designing such a study is that you cannot change the concentration of nitrous oxide without replacing the gas with another, such as nitrogen, oxygen, or helium. The nitrous oxide avoidance group also received 80% oxygen, previously suggested to be of benefit in preventing surgical site infection and postoperative nausea and vomiting, whereas the 70% nitrous oxide group received only 30% oxygen. Therefore, it is impossible to determine whether the beneficial effects reported resulted from high inspired oxygen, avoiding nitrous oxide, or a combination of the two. Fleischmann et al.10 found no difference in surgical site infection rate when comparing 70% nitrogen-30% oxygen versus 70% nitrous oxide-30% oxygen as the intraoperative gas mixture, but did not include an 80% oxygen group. These results suggest that avoidance of nitrous oxide may be less important than high inspired oxygen.
    In the end, it may not matter to clinicians whether the benefits found in the study by Myles et al. resulted from avoidance of nitrous oxide or administration of high inspired oxygen, because administration of high inspired oxygen by necessity requires avoidance of 70% nitrous oxide. There is certainly plentiful evidence that nitrous oxide use is associated with an increased incidence of postoperative nausea and vomiting.11 Conversely, a randomized controlled trial in colon surgery patients demonstrated that high inspired oxygen reduced postoperative nausea and vomiting,12 suggesting that the reduced incidence in the study by Myles et al. could also result from high inspired oxygen. A number of other potential adverse effects of nitrous oxide have been reported in the literature, although their clinical relevance is not clear.11 There is some evidence for lack of harm from nitrous oxide (the study by Fleischmann et al.10), but there is little evidence for benefit. Myles et al. add a compelling argument for eliminating nitrous oxide use in patients undergoing major surgery by showing potential harm from nitrous oxide (whether directly or through reducing the capacity to provide a high inspired oxygen concentration).
    As a practical matter, especially with the introduction of new anesthetic agents in recent years, it is relatively easy to exclude nitrous oxide-or to include high inspired oxygen-in one's practice. Nitrous oxide is certainly useful for inhalation inductions in children, as well as for analgesia in laboring parturients or in patients having dental procedures. It is preferred by many anesthesiologists because of its reputation for providing a smoother landing-although this is not substantiated by scientific evidence. On the other hand, nitrous oxide avoidance is standard practice in patients in whom nitrous oxide is contraindicated, as is the case with pneumothorax or bowel distention, for example.
    Would eliminating nitrous oxide use or adopting routine use of high inspired oxygen in major surgery in response to this article represent making a change based on too little evidence? Possibly. There are certainly shortcomings in the study, including lack of standardization of potential confounding factors such as timing and choice of prophylactic antibiotic administration and maintenance of normothermia. On the other hand, in such a large study, the confounders should have similar impact in each group. Anesthesiologists had the option to cross over based on personal preference or patient circumstances. This happened a small percentage of the time. Because it is such a large study, these crossovers seem not to have had much impact. In any case, the study is a pragmatic one, and such crossovers are likely to happen in real clinical practice as well. Therefore, this article gives a result that likely has meaning not just in a carefully controlled group of patients, but in the large variety of patients presenting for major surgery.
    This study is not the last word on nitrous oxide, but it is an important one that is likely to have a major impact on clinical practice in anesthesia. I personally stopped using nitrous oxide nearly a decade ago because of previous trials demonstrating the importance of high tissue oxygen in preventing wound complications. I am pleased to have added justification for residents who challenge me to provide evidence to support my clinical practice.
    Harriet W. Hopf, M.D.
    Department of Anesthesiology, University of Utah, Salt Lake City, Utah. [email protected]

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    References


    1. Myles PS, Leslie K, Chan MTV, Forbes A, Paech MJ, Peyton P, Silbert BS, Pascoe E, ENIGMA Trial Group: Avoidance of nitrous oxide for patients undergoing major surgery: A randomized controlled trial. Anesthesiology 2007; 107:221-31
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    2. Schmied H, Kurz A, Sessler D, Kozek S, Reiter A: Mild intraoperative hypothermia increases blood loss and allogeneic transfusion requirements during total hip arthroplasty. Lancet 1996; 347:289-92
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    3. Greif R, Akca O, Horn EP, Kurz A, Sessler DI: Supplemental perioperative oxygen to reduce the incidence of surgical-wound infection. Outcomes Research Group. N Engl J Med 2000; 342:161-7
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    4. Belda FJ, Aguilera L, Garcia de la Asuncion J, Alberti J, Vicente R, Ferrandiz L, Rodriguez R, Company R, Sessler DI, Aguilar G, Botello SG, Orti R: Supplemental perioperative oxygen and the risk of surgical wound infection: A randomized controlled trial. JAMA 2005; 294:2035-42
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    5. Frank SM, Fleisher LA, Breslow MJ, Higgins MS, Olson KF, Kelly S, Beattie C: Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events: A randomized clinical trial. JAMA 1997; 277:1127-34
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    6. Mangano DT, Layug EL, Wallace A, Tateo I: Effect of atenolol on mortality and cardiovascular morbidity after noncardiac surgery. Multicenter Study of Perioperative Ischemia Research Group. N Engl J Med 1996; 335:1713-20
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    7. Wallace AW, Galindez D, Salahieh A, Layug EL, Lazo EA, Haratonik KA, Boisvert DM, Kardatzke D: Effect of clonidine on cardiovascular morbidity and mortality after noncardiac surgery. Anesthesiology 2004; 101:284-93
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    8. Pryor KO, Fahey TJ III, Lien CA, Goldstein PA: Surgical site infection and the routine use of perioperative hyperoxia in a general surgical population: A randomized controlled trial. JAMA 2004; 291:79-87
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    9. Akca O, Podolsky A, Eisenhuber E, Panzer O, Hetz H, Lampl K, Lackner FX, Wittmann K, Grabenwoeger F, Kurz A, Schultz AM, Negishi C, Sessler DI: Comparable postoperative pulmonary atelectasis in patients given 30% or 80% oxygen during and 2 hours after colon resection. Anesthesiology 1999; 91:991-8
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    10. Fleischmann E, Lenhardt R, Kurz A, Herbst F, Fulesdi B, Greif R, Sessler DI, Akca O: Nitrous oxide and risk of surgical wound infection: A randomised trial. Lancet 2005; 366:1101-7
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    11. Myles PS, Leslie K, Silbert B, Paech MJ, Peyton P: A review of the risks and benefits of nitrous oxide in current anaesthetic practice. Anaesth Intensive Care 2004; 32:165-72
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    12. Greif R, Laciny S, Rapf B, Hickle RS, Sessler DI: Supplemental oxygen reduces the incidence of postoperative nausea and vomiting. Anesthesiology 1999; 91:1246-52
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    © 2007 American Society of Anesthesiologists, Inc.


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