predicting difficult intubation

Dr Sheeba Hakak.

What is difficult intubation?A requirement for more than one

attempt/intubator or special blades/aids.A restricted view on laryngoscopy using a

cormack lehane classification, or its modifications or the proportion of glottis that is visible.

An arbitrary number in an intubation difficulty scale.

Is predicting difficult intubation- worthwhile exercise or pointless ritual?Many attempts to develop means of

predicting difficult intubation ,basis for which are quite easy but are they likely to be useful.

Is it difficulty to intubate or Failure to intubate we need to measure?

Ultimate definition of difficulty is failure since we should be able to manage difficult intubation (by definition!), so it is the prediction of failure that we need to know, not of difficulty.

Is difficult intubation common?

No, it is very rare.

Is there a 100% specific and 100% sensitive test to predict difficult intubation?

No!!!!!!

So as long as test is not 100% specific 100% sensitive there will always be unpredictability.

Comparative analysis of various physical factors and scoring systems Sen ( % ) Sp ( % )

PPV( % )NPV( % )Obesity 81.8 72.76 6.34 99.43 Inter incisor gap 18.8 94.14 6.6 98.1Thyromental distance  72.7 96.5 32.0 99.4Head and Neck movement 86.36 86.0 34.6 99.7Prognathism 4.5 96.3 2.7

97.9Wide and Short neck 45.5 87.9 7.8 98.6High arched palate 40.1 99.38 60.0 98.67Protruding incisor 4.6 95.9 2.5

97.79Mallampati scoring system 77.3 98.2 48.5 99.5Cormack and Lehane’s 100 99.7 88 100

scoring system

Does the predictibility of a test help us acurately to predict difficulty of intubation?No. As the positive predictive value of all

these tests is very low even if the sensitivity and specificity is high.

So what to do?

Have a clear idea about what we are going to do if a test suggests a patient may be difficult knowing probably that they wont be.

So rather than wasting our time on thinking about difficult or not difficult intubation isn’t it better to invest on management of difficult intubation.

Why Check Ventilation before Neuromuscular Blockade?

Failure to ventilate and intubate a Sedated and paralyzed patient can lead to hypoxic brain damage.

Earliest theoretical Reference: Chapter on Tracheal Intubation in Textbook of Anesthesia by Prof. Gal and White (third edition). Recommendation not based on any published work according to authors.

Our practices and beliefs…How many of you check whether you can

ventilate a sedated patient before administering Neuromuscular blocking agent?

Is it a good or bad practice?

Airway Guidelines

No advise on the administration of neuromuscular blockers when faced with difficult bag and mask ventilation and teachings at hospital level seems inconsistent.

Question???How many times have you really woken up a

sedated patient up, when it was difficult to ventilate by bag and mask before using neuro-muscular blocking agent?

Even if you tried to how much time will it take for a sedated patient to breathe if you failed to ventillate a patient?

How much time does it take for the brain to get damaged by hypoxia?

FactsNot practically possible to wake up a patient

if we fail to bag and mask rather we try something else to Ventilate before catastrophic desaturation occurs.

Sufficient sedative agents need to be given to check whether we can bag and mask the patient but will it allow rapid return of consciousness.

Facts continue….Experience tells us that Bag and mask

ventilation becomes easier with neuromuscular blockers.

Should difficulty occur then absence of Neuromuscular blockers may hinder rescue of situation as laryngoscopy can’t be performed and intubation is even more difficult without neuromuscular blockade.

Facts Continue…..Some causes of difficult bag and mask

ventilation like Opioid induced rigidity and Laryngospasm can only be treated by administering Neuromuscular blocking agents.

Definitely not acceptable…

Administer neuromuscular blockade to a patient in whom it is obvious that FMV and intubation are going to be difficult.

But then don’t even administer propofol before you are prepared for difficult airway.

But if you think it is going to be easy…you have administered propofol Isn’t it is logical to make it easy for yourself.

Fearlessly go ahead and administer Neuromuscular blockers as soon as possible after sedation.

Otherwise your fear will sink all the people onboard on your ship.

Believe me if you are still fearful

Use ROCURONIUM

As Sugammadex works and its available in our hospital, for your satisfaction!!!! May be you will never use it for this purpose as none has until now.

Study done by R.H.Bromhead and his colleagues

Online survey of 136 anesthetists (trainee and non trainee).

Aim: To determine whether anesthetists routinely confirm their ability to ventilate by a facemask before administration of NMB and rationale for its practice.

ResultsVentilate by face mask before administering

NMB agents.57%(78) checked routinely.32% never checked.19% choice depends on given scenario.

Results continue……Depending on Experience those with <5 yrs (24) were almost all

checkers.

those with >16 yrs (26) only 38% were checkers.

Is gender of the doctor important ?Yes of course, females are significantly more

likely to be checkers.

Consultants and males are more likely to be non checkers.

Reasons given to justify choices

Both checkers and non checkers thought that they were confirming to Best Practice.

Majority of checkers (57%) identified ability to escape wake up.

Have always done it this way (62%).

Asked if respondents changed their practice?

Of the non checkers 69% had changed to this technique.

No respondent had changed from non checker to checker.

Technique respondents would teach to a less experienced trainee

65% would teach checker technique.

11% would teach non checker technique.

Rest depending on scenario.

Non checkers who will not volunteer their technique in FRCA exam

32 (63%)

If difficult to bag and mask Place a laryngeal mask airway (85%)

Administer a neuromuscular blocking agent (89%)

No difference between checkers and non checkers.

Then administer neuromuscular blockers as soon as possible is logical, as you are not going to wake up the patient.

Khaterpal and his colleagues study in 2009Review of 50000 anesthetists found that of 77

patients whom were impossible to BVM ventilate, 73 were given a NMB agent and intubated.

So if paralysis assists ventilation and permits airway instrumentation when a patient becomes problematic then why should an anesthetist wait until the situation becomes difficult before administering the drug?

So I leave it for you to decideLearn tests for difficult not difficult

intubation or management of difficult intubation.

Give or not give neuromuscular blockers before bag and mask ventilation or concentrate on airway management.