Most of us are always out for new techniques to make difficult cases easier. Videolaryngoscopy is one area of great change over the last decade. Here Andrew Weatherall looks at videolaryngoscopy as it relates to looking after the little kidlet airway. 

Seeing is believing. It can happen in a moment in sport. It’s the whole basis of magicians plying their trade.  Even people seeing mysterious circles appearing in crops want to believe.

Perhaps that impulse is why everyone wants to believe in videolaryngoscopy. And it makes sense. It’s persuasive. The view is better than your eyes alone. It must be better.

And yet … the evidence doesn’t help us back up our gut reaction. So the debate starts. It’s a pretty big debate too. Too big for here.

So let’s just talk about one bit. Let’s see where videolaryngoscopy fits in with kids.

Open Bias

I should declare an interest here. I like videolaryngoscopy. I work in operating theatres where it’s freely available. In our prehospital operation we use it as routine. This is not to say I don’t dig direct laryngoscopy. I just really like an intubating experience that’s a little more IMAX. That isn’t even because I’m particularly a gear junkie. I’m only interested in tech if it helps me do a better job looking after patients.

So what’s so great about videolaryngoscopy? It’s not the view that it gives. It’s the team that it gives. My subjective experience is that when taking on a  slightly challenging airway the greatest benefit of using videolaryngoscopy is that all members of the team managing the airway can appreciate what is going on.

Sharing the same vision is the quickest way to get everybody operating on the same page. It’s particularly beneficial in getting any airway assistant providing external laryngeal manipulation to line up the view in the best possible way.

These observations are the same ones that colleagues who are fans of videolaryngoscopy seem to make. They note some drawbacks too. (blood in the airway being the obvious one). More and more though, videolaryngoscopy is perceived as the go to option for the extra few % that makes intubation a sure thing.

So does the evidence match that perception? And if not, why not?

What’s the Problem?

Perhaps it’s worth remembering that difficult intubation in kids isn’t that common. Some of the morphological changes that might be associated with difficult intubation are relatively common on their own. Restrictions to neck extension, a small mouth and jaw, a big tongue and dysmorphic appearance may be associated with difficult intubation. Of course most with these features still have a straightforward intubation.

A team from Erlangen published a retrospective review not that long ago looking at this issue. Looking back over a period of 5 years (while excluding records that were incomplete or where intubation wasn’t relevant) they ended up looking at 8434 patients who had a total of 11219 procedures.  152 (1.35%) of direct laryngoscopies were classified as difficult laryngoscopies (grade III or IV views).

1.35% isn’t much. Note also that they are talking about laryngoscopy, not actual intubation or airway management. Certain surgery groups had a relatively higher rate (oromaxillofacial and cardiac surgery patients) as did kids under the age of 1. The wash-up is that if we were to choose videolaryngoscopy to help with difficult laryngoscopy, we’re choosing that for < 2% of the population. This choice is fine but we at least need to understand the size of the problem we’re trying to address.

The Numbers For VL

Well they’re in and they’re not particularly supportive of the idea that videolaryngoscopy in kids is vastly better. Here’s one study where Truview PCD and Glidescope didn’t help with the view and slowed things down. Here’s another small series where the Glidescope doesn’t necessarily help with the view.

Of course rather than keep picking out individual studies, we could try to take on board the evidence from a meta-analysis. Sun et al have done the hard work, looking at fourteen studies which had a randomised component to their study.

Their findings? Videolaryngoscopy generally improved the view of the airway in kids with normal airways or potentially difficult airways. However the time to intubation was longer in pretty much all groups. Interestingly, the rate of failure was much higher with videolaryngoscopy (there was lots of heterogeneity in the included studies so that particular finding probably needs more than a few grinds of the giant salt mill).

Cochrane has a review specifically in neonates which is useful … to demonstrate that there’s not enough useful evidence.

What Don’t the Studies Say?

Well it already looks like the answer is “much”. Perhaps this is what I take away from them.

1. The evidence doesn’t justify a move away from direct laryngoscopy

I think videolaryngoscopy is still best considered as a technique to use as an adjunct, building off really good direct laryngoscopy technique. If the spiel is that VL “improves your view by one Cormack and Lehane grade” then implicit in that is the assumption that your view was already optimised.

For the vast majority of patients who have a grade I/POGO 100 laryngoscopy, videolaryngoscopy can’t improve your view (obviously). However you may reach the same view with slightly more ease. This applies particularly to videolaryngoscopy options that build off a standard laryngoscope design (rather than the Glidescope for example which has its own special learning curve).

Wouldn’t logic say if you need to work less to achieve grade I, II or even III views, your technique runs the risk of becoming reliant on the extra % that videolaryngoscopy gives you? For video laryngoscopes that operate pretty much like standard laryngoscopes with a little bit extra, you need your technique with direct laryngoscopy to get you most of the way there. The “video” bit is for the last few percent.

So good training in direct laryngoscopy techniques remains vital.  Practitioners will still need to understand the difference in technique required for different laryngoscopes and what the implications are for patient positioning to optimise success rates.

2. More nuance in the research would be helpful

Meta-analysis relies on the contributing papers. There’s presently a bit of heterogeneity there, including in the level of experience in those using the devices. Follow-up studies (or just fresh studies) when people have become highly used to videolaryngoscopy would be an interesting addition to the literature – how long does proficiency take to develop?

What about managing the unanticipated difficult airway case? That seems to be a whole area that isn’t well addressed by the current literature. Or measurement of decision-making and overall management of the airway when videolaryngoscopy is available?

There’s also a tendency to focus on clumps of trees rather than the whole forest. This is pretty common to airway papers. Often the focus seems to be on ‘time to tracheal intubation’ (which isn’t the worst surrogate to choose) or, less productively, on the view of the glottis or first pass success. This touches on the same territory discussed by Alan Garner here on measuring surrogates rather than clinically meaningful parameters.

Seeing the glottis more doesn’t equate to the airway being managed.  First pass success isn’t the most vital of measures. Time to tracheal intubation from laryngoscope in hand might be a little more helpful, but is it more useful than time from induction to airway secure in the patient with a difficult airway? Should we be reporting on desaturation rates with one technique over another given that the aim of airway management isn’t just the bit of plastic?

3. Measuring teams

The other feature the literature doesn’t inform is that subjective sense of utilising the team better in difficult airway management. It would be really interesting to see some research that examined the impact of videolaryngoscopy on the ways teams worked together or communicated in the management of the airway. Or what about performance of teams managing the airway in out of theatre locations? As things stand the thing I subjectively feel is the best feature of videolaryngoscopy doesn’t seem to have been evaluated.

 

So where does that leave me? Not really anywhere different. Probably where it leaves me is in need of checking my own position on the seeing vs believing spectrum.

In the absence of evidence from other people I should probably rigorously examine my personal practice. Practice the use of different techniques until I feel proficient. Then measure my actual performance and see what my own benchmark performances are. Perhaps really rigorous personal auditing (not the Scientology version) is the next step in understanding how VL should fit into my practice and how it measures up to DL.

It’s only after that that I’ll really know if I’m seeing what I think I’m seeing.

 

The References:

Heinrich S, Birkholz T, Ihmsen H, Irouschek A, Ackermann A, Schmidt J. Incidence and predictors of difficult laryngoscopy in 11,219 pediatric anesthesia procedures. Pediatr Anesth. 2012;22:729-36.

Riveros R, Sung W, Sessler DI, Sanchez IP,  Mendoza ML, Mascha EJ, Niezgoda J. Comparison of the Truview PCD and the GlideScope video laryngoscopes with direct laryngoscopy in pediatric patients: a randomised trial. Can J Anesth 2013;60:450-7.

Lee JH, Park YH, Byon HJ, Han WK, Kim HS, Kim CS, Kim JT. A Comparative Trial of the GlideScope Video Laryngoscope to Direct Laryngoscope in Children with Difficult Direct Laryngoscopy and an Evaluation of the Effect of Blade Size. Anesth Analg 2013;117:176-81.

Sun Y, Lu Y, Huang Y, Jiang H. Pediatric video laryngoscope versus direct laryngoscope: a meta-analysis of randomized controlled trials. Pediatr Anesth. 2014;24:1056-65.

Lingappan K, Arnold JL, Shaw TL, Fernandes CJ, Pammi M. Videolaryngoscopy versus direct laryngoscopy for tracheal intubatio in neonates (Review) Cochrane Database of Systematic Reviews 2015. dii: 10.1002/14651858.

Over on Minh Le Cong’s site, he’s also previously shared something a little more positive on videolaryngoscopy.

The image here came from Flickr Creative Commons and is unaltered. It was posted by Alibi 0591.