Airway management in the critically ill is complicated. The intensive care unit is where we congregate difficult airway patients, if someone’s had a difficult airway in theatre unexpectedly– or expectedly. We often put them on the high-dependency unit, or the intensive care unit afterwards. Any swollen, inflammatory, infected airways go to intensive care. Major airway cases go to intensive care, post-op. That’s where we congregate and concentrate our difficult airway patients. Also, of course, intensive care patients are intubated for days or weeks. So the opportunity for problems to arise is quite high. I think it’s important to point out that in intensive care, difficult airway management is related to anatomical difficulties and anatomical abnormalities, but also physiological abnormalities.
A physiologically-difficult airway is one which is made more difficult for the operator by the poor physiological state of the patient. Patient already being hypoxic, they tolerate apnoea and airway interventions very poorly, they have significant V/Q mismatch, they’re PEEP dependent. And these patients will desaturate, turn blue very, very quickly, and this makes the entire procedure far more difficult. In terms of cardiovascular problems, they may be shocked, they’ll tolerate induction or positive pressure ventilation very poorly, or– the opposite, of course, is that there may be fluid overloaded, and any large positive fluid balances will result in a swollen airway, particularly if the patient’s been prone, for instance. All these things add to the difficulty in securing the airway.
There’s the question of kits that’s used, and equipment that’s used, to manage the airway in the critically ill. Sometimes that’s not the same as the equipment that operators are used to using in other areas of the hospital, like operating rooms or ED. They may not be used to the equipment that they’re handed in critical care– that’s a problem. We noticed in NAP4 that the number of times capnography was used during airway interventions was very low compared to the almost universal use in operating room practise. This was related to over 70% or 80% of airway deaths, or incidence of serious breakdown. They’re attended often by junior doctors out of hours, working long, stressful shifts, they have responsibilities elsewhere.
The actual bedside attendants are nurses, and although they’re very experienced, they’re not primary airway operators. Suction, like turning the patients, all of these can lead displaced airways. Particularly dangerous is the partially displaced airway, which if an airway is fully displaced, the diagnosis is obvious. Partial displacement is dangerous, because it leads to delay in diagnosis. Almost all ICU patients are at risk of aspiration and again, NAP4 showed that in anaesthetic practise certainly, aspiration is the single most common cause of patient mortality. What we’ve learned over the last few years is the importance of planning airway interventions.
Traditionally, this has almost never been done thoroughly in the critical care environment, and we’ve learned that the real trick to successful airway management in the critically ill is to plan it well. And that means using a well-constructed checklist, which looks at preparing the patient, preparing the equipment you’re going to use, preparing the team, and also preparing for airway difficulty. In my unit, we get the nursing staff to prepare the patients according to a very rigorous checklist, and to prepare the equipment. In terms of preparing the team, and preparing for difficulty, the actual airway operator runs that part of the checklist. That way, the whole team knows what the plan is, shares the mental model, and is ready for problems.
One crucial difference in critical care airway management is that there is usually no bailout. If it all goes wrong in an operating room, usually the airway intervention and surgery can be deferred at least for, say, half an hour or an hour, to get help, to get extra kit. In the critically ill, when they’re being intubated for respiratory failure or for some other pathology, the bailout option isn’t available. Also, awake techniques probably aren’t indicated in most patients. Human factors is crucial in airway management outside of the operating room. You’re doing procedures which are regularly associated with significant morbidity, occasioning mortality, using staff that you often don’t know.
On my unit, we have 20 critical care beds, that means we have over 100 different nursing staff. We have eight consultants. At any one time, you may have one of 10 junior doctors. If you do the maths on that particular set of patients, if you need four or five members of staff around the bed in order to actually perform the intubation, that means the chances of those– any team of four or five people having ever done that procedure before are about 100,000 to 1. That makes teamwork and preparing the patient, preparing the team, and preparing for what you’re going to do, incredibly important.