November 2015, the Difficult Airway Society have published their updated guidelines for management of difficult intubation in adults. Again DAS provide an excellent overview on unanticipated difficult intubations in adults... worth reading for anyone involved in critical care!
When reading this article I couldn't help myself putting a special focus on the controversial issue of cricoid pressure (CP) for rapid sequence induction (RSI). This topic has become a major matter of debate as scientific evidence of its effect on preventing aspiration of gastric content is basically lacking. There is quite some evidence available showing that cricoid pressure might actually impair intubation or potentially harm the patient. More background information and links on this topic you can find here. While some guidelines have actually 'softened' or abandoned the recommendation for the use of CP, most of them have not... and continue to recommend CP. It was therefore of great interest to see what the panel of the DAS would come up with!
For anaesthetists working in Britain and Ireland the DAS guidelines are of special interest as they represent some sort of legal binding on how to proceed at their daily work. We took a closer look at the new guidelines... and got surprised:
"This (CP) is a standard component of rapid sequence induction in the UK". Ok... so no change there! This statement is pretty clear and leaves no space for interpretation - sounds imperative. A little less clear are the following text passages on why CP remains a standard component.
"It is often overlooked that cricoid pressure has been shown to prevent gastric distension during mask ventilation and was originally described for this purpose"... Well, actually cricoid pressure was originally described by Brian Arthur Sellick in the Lancet in 1961 as a preliminary report of an un-controlled case study and the purpose of cricoid pressure was to control regurgitation of gastric content during induction of anaesthesia.
CP and Gastric Insufflation
The reference cited in the context of gastric insufflation and cricoid pressure is an article by Salem and Sellik form Anaesthesia and Analgesia in 1974 (read the original article here). They write: one aim of CP is the prevention of aspiration. The other one is the prevention of gastric insufflation during mask ventilation. The presented evidence in that regard though is not really convincing:
a) A historical letter of Dr. William Cullen... dated back in 1774!
b) The other reference is an article by Salem himself on the 'efficacy of cricoid pressure in preventing gastric inflation during bag-mask ventilation in paediatric patients, but not adults!
Another article cited by the DAS (Obstetric Anaesthetists' Association/Difficult Airway Society difficult and failed tracheal intubation guidelines – the way forward for the obstetric airway Br. J. Anaesth. (2015) 115 (6): 815-818) actually recommends gentle ventilation with low insufflation pressure during RSI which should not overcome correctly applied cricoid pressure. This suggests that CP makes gentle bag-mask ventilation safe.
Indeed, Lawes et al. already showed in 1987 that when bag-mask ventilating, it was not possible to cause gas to enter the stomach in any patient with a patent airway when cricoid pressure was applied. BUT he also stated that: In the absence of cricoid pressure the lungs of all the patients could be ventilated “gently” satisfactorily by hand without gas entering the stomach.
The Bottom Line
Going through these overall brilliant guidelines by the DAS I still haven't been convinced about the usefulness of cricoid pressure and resume (once again):
- Cricoid pressure for rapid sequence induction remains a non-evidence-based manoeuvre and should be seriously questioned!
And by the way, I feel the DAS actually knows that. You have to acknowledge what Hagberg writes in the BJA editorial:
..."the application of CP during rapid sequence induction remains a matter of debate; some believe in its effectiveness in preventing pulmonary aspiration, whereas others believe it should be abandoned because of the paucity of scientific evidence of benefit and possible complications."
..."The literature does demonstrate that the use of CP is likely to make airway interventions, such as mask ventilation, SGA insertion, direct laryngoscopy, and intubation more difficult."
..."As a result of the lack of sufficient scientific evidence that CP reduces regurgitation, in addition to evidence that it may interfere with airway management..."
Difficult Airway Society DAS 2015 guidelines for management of unanticipated difficult intubation in adults, Br. J. Anaesth. 2015 OPEN ACCESS
BIJC post on Cricoid Pressure 04/2014
Hagberg et al. DAS 2015 Guidelines - Editorial, Br. J. Anaesth. 2015, 1-3 OPEN ACCESS
Lawes et al. Inflation Pressure, Gastric Insufflation and Rapid Sequence Induction, Br. J. Anaesth. 1987