THE AWAKE LOOK

An article in Journal Of Clinical Anesthesia describes direct laryngoscopy on awake subjects with remifentanil instead of topical anesthesia. Not for awake intubation, but as a way to predict difficult airways.

Background
The difficult airway is one of the big challenges in anesthesia. We come a long way by optimizing intubating conditions and by having a sensible plan in case of a difficult or impossible airway. But ideally we should be able to predict the difficult airways before they get us into trouble.

The problem is, that the methods we have for predicting difficult airways are not that great. The best we have got is the combination of the Mallampati score and the thyromental distance, which is only about 35% sensitive and 85% specific. Almost useless, considering what could be at stake. Clearly, we could use a better way of finding the difficult airways. The method presented in this study is not it, but is still pretty neat.

The study
In the study authors, Gupta & co, use remifentanil as a sole analgesic in order to allow for direct laryngoscopy and evaluation of the larynx in awake subjects. They then compared laryngoscopy views before and after induction in order to determine if direct laryngoscopy in the awake patient is a viable predictor of difficult laryngoscopy in the sleeping patient.

The method

  1. Patients were put in a sniffing position.
  2. O2 3L/min on nasal prongs.
  3. The remifentanil infusion was, based on weight, started at 0,1-0,6 microg/kg/min.
  4. The remifentanil infusion was titrated to the point where the subjects struggled to stay awake but still responded to commands.
  5. If the patient tolerated an oral airway and a forceful jaw-thrust the patient was deemed sedated enough.
  6. Now the infusion was terminated and the laryngoscopy could proceed.
  7. Two anesthetists assigned Cormack-Lehane (CL) grades to the airway.
  8. After laryngoscopy induction was given followed by a relaxant.
  9. Cormack-Lehane grades were again assigned to the unconscious and relaxed patient.

The results
81 patients were enrolled. Direct laryngoscopy failed in only one of the patients who was graded  CL 4. Of the remaining roughly half were graded easy intubations (CL 1 and 2a) while the other half was considered difficult  CL grades 2b,3 and 4) while still conscious. CL score for the conscious and unconscious patients are in the table below.

 

 

 

 

Sensitivity was 100% meaning all the difficult airways were found. Specificity was 57% meaning false positives remain a problem with this method. Partly this is explained by how most airways tend to improve with induction and muscle relaxant. Many of the airways graded difficult improved and were graded easy in the unconscious patients.

Direct laryngoscopy on the still awake paetients was achieved on average after 6,5 minutes. The unconscious patients were intubated on average after 13 minutes.

How does this fit in?
Not sure. Using remifentanil as an adjunct in awake laryngoscopy and awake intubation is hardly news.  This could however be an sneaky way of identifying the difficult airways in the suspicious cases.

Those cases where we are unsure if to proceed with a standard induction and muscle relaxant, or if we should take a step back and do an awake intubation. With this method we could, delay that decision until after direct laryngoscopy of a still awake patient.

By then, if we go for induction all we need to add is the anesthetic agent and relaxant. If we instead go for an awake intubation maybe spraying the vocal cords is all we need to intubate? For an awake intubation we could also swap for an awake video laryngoscopy and see if that gives us a view, and awake intubate from there.

An awake look and standard intubation could save us most of the 30-60 minutes that every old-school awake intubation seems to add to theatre time. It could also spare the patient from an awake intubation which, when not done properly, can be very distressing.

J Clin Anesth. 2012 Feb;24(1):19-24. Laryngoscopy in conscious patients with remifentanil: how useful is an “awake look”? Gupta S, Macneil R, Bryson G.

 

 

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4 Responses to THE AWAKE LOOK

  1. Minh Le Cong says:

    Weingart last month on EMRAP talks about doing this with ketamine. INteresting idea. My brother who is a retrieval anaesthetist in Adelaide tried to convince me to try remifentanil infusion for sedation of the acutely agitated patient requiring air transport. Still not convinced. Would you do it?

    • Thomas D says:

      Remifentanil is a great drug due to its ultra short onset and duration and very stable elimination, but it is also an extremely powerful opioid. So you’ll easily overdose the patient that’s just meant to be sedated. Not a big problem in-hospital. You stop the infusion for a bit, and the patient emerges. But that might be one extra thing you don’t want to worry about in an aircraft.

      Remi can certainly be used, but wouldn’t usually a sedative be a better choice than an analgesic? Especially as long as the agitation isn’t caused by pain? Also, I’m not sure if I see the need for an ultra short acting drug for this kind of patient. Might as well keep the patient sedated for the entire transport with a good kick in the head of a longer acting drug?

      Sounds like an interesting concept, though. I do love remi, as it’s so controllable and I’d love to hear your brother’s take on it for retrieval use. As always, in the right hands, if you’re comfortable and experienced with it, it’s all good.

  2. admin says:

    Minh,
    Where I work we commonly use remifentanil in carefully titrated infusions to help some COPD patients tolerate BiPap. I know there are some of references for that practice too. I am sure it can be used in retrieval too, because of it´s short duration. I guess it´s like all things anaesthesia – Everything is possible, as long as you do it right or don´t get caught doing it….

    • Minh Le Cong says:

      sounds right..I used to use fentanyl to make NIPPV via mask more comfortable for some patients..ameliorates the air hunger of hypercapnia..but nowadays mainly use ketamine. my brother has never done it on retrieval yet..just thought it was a novel idea for these disturbed patients needing air transport. His service is rolling out a ketamine protocol now based on my work.. I guess the good thing about the remi,is that not only is it short acting,its fully reversible….but as you point out that might lead you back to square one with agitated patient in the back of the aircraft!

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