Most of us being trained as anaesthetists in the last couple of years have learnt to perform a rapid sequence induction (RSI) including the application of cricoid pressure (aka the Sellick manoeuvre) in order to prevent aspiration of gastric content.
Over the last couple of years though this manoeuvre has been seriously questioned as scientific evidence is lacking and there are concerns that cricoid pressure might actually be potentially harmful.
A lot has been written on this topic so far and some great reviews can be found easily on the internet thanks to the concept of Open Free Access Meducation (FOAMed, see below). Still I would like to add some thoughts on to this discussion and maybe mention one or two more interesting facts.
Cricoid pressure was actually first described by Sellick in the Lancet in 1961 as a preliminary report and basically represented an un-controlled case study in which no or only insufficient information on the studies patient population was provided. There was no standardisation of the force for cricoid pressure as of the medications used for induction. There was also no information on the quality of laryngoscopy and intubation. Steinmann and Priebe (abstract in english) have exactly analysed this publication and found some relevant methodological shortcomings. It is therefore remarkable that this publication led to an anaesthetic dogma practised all over the world.
As mentioned in the European Resuscitation Council Guidelines of 2005, studies in anaesthetised patients show that cricoid pressure impairs ventilation in many patients, increases peak inspiratory pressures and causes complete obstruction in up to 50% of patients depending on the amount of pressure applied (Petito, Lawes, Hartsilver, Allman, Hocking, Mac, Ho, Shorten).
The incidence of a difficult intubation is significantly higher in preclinical emergency situations than in an elective theatre environment (Timmermann A et al. Resuscitation 2007;70(2):179-185). It is therefore possible, that cricoid pressure itself actually is one of the reasons why unexperienced emergency physicians experience additional difficulties when intubating ‘in the field’.
One concern often mentioned is the fear that non-adherence to current guidelines by not applying cricoid pressure might have adverse legal implications. But what do current guidelines actually say? Priebe et al. partially looked at this in 2012. Several guidelines indeed still recommend cricoid pressure, sometimes even with less force in the awake patient. But some guidelines have started to implement current evidence.
The 2010 Clnical Practice Guidelines on General Anaesthesia for Emergency Situations by the Scandinavian Society of Anaesthesiology and Intensive Care Medicine state following:
(i) The use of CP cannot be recommended on the basis of scientific evidence (recommendation E, supported by non-randomized, historic controls, case series, uncontrolled studies and expert opinion)
(ii) The use of CP is therefore not considered mandatory but can be used on individual judgement (recommendation E).
(iii) If facemask ventilation becomes necessary, CP can be recommended because it may reduce the risk of causing inflation of the stomach (recommendation D, supported by non-randomized, contemporaneous controls)
The 2005 European Resuscitation Council Guidelines (page 1322, pdf here) puts it this way:
– The routine use of cricoid pressure in cardiac arrest is not recommended.
– Studies in anaesthetised patients show that cricoid pressure impairs ventilation in many patients, increases peak inspiratory pressures and causes complete obstruction in up to 50% of patients depending on the amount of cricoid pressure (in the range of recommended effective pressure) that is applied.
Still though it has to be mentioned that the Difficult Airwas Society (DAS) continues to recommend cricoid pressure for RSI on it’s website. The current recommendation though seems to date back to 2004 and the question is mentioned on their website whether any pressure should be applied before loss of consciousness.
Also the Association of Anaesthetists in Great Britain and Ireland recommends cricoid pressure in their AAGBI Safety Guidelines of 2009 on pre-hospital anaesthesia. It is also mentioned that ‘badly applied cricoid pressure is a cause of a poor view at laryngoscopy. It may need to be adjusted or released to facilitate intubation or ventilation’.
While the discussion on this issue in adults will continue the dogma of cricoid pressure might soon fall in paediatric patients as Neuhaus D et al. published a Swiss trial in 2013 where they could show that a controlled rapid sequence induction without cricoid pressure is actually safe.
Further research is on its way: Trethrewy E et al. Trials. 2012 Feb 16;13:17. Until then it seems as if we are faced with guidelines mostly still in favour for cricoid pressure and evidence based medicine, which is rather discouraging us of further performing this procedure. It is good practice to constantly question current guidelines and further improve them for the patient’s sake. Indeed you have to ask yourself on how far you want to stick to current guidelines for legal reasons or if you change your practice according to emerging evidence.
Some of the hospitals I worked at in Switzerland have stopped performing cricoid pressure for RSI some years ago and haven’t encountered any worsening in their patient outcomes. Taking into account that most RSI in the ICU resemble emergency intubations out of hospital rather than the controlled environment of a theatre I feel there are good reasons to start re-evaluating and possibly change current guidelines.
Other very interesting resources of information can be found here (FOAMed):
– Update 02/05/14: Minh Le Cong published a statement of the NAP 4 investigators on his blog website: statement from NAP 4 (on prehospitalmed.com)
… The discussion goes on!