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Three Part Question

In [patients undergoing emergency RSI] does [cricoid pressure] reduce the [incidence of aspiration of gastric contents/ morbidity/mortality]?

Clinical Scenario

You are about to perform a rapid sequence intubation on a 26 year old man with a severe head injury. You have been told that the gentleman has consumed a significant amount of alcohol in the last 3 hours. The nurse asks you whether the application of Cricoid pressure will stop him aspirating.

Search Strategy

MEDLINE 1950–Nov week 1 2012 via OvidInterface: (Sellick\'s manoeuvre.mp OR cricoid pressure.mp)

Embase1988–Nov 2012 via Ovid Interface: (Sellick\'s manoeuvre.mp OR cricoid pressure.pm LIMIT to human and English language)

Cochrane Library via the Wiley Interface: ‘cricoid’

Search Outcome

340 Papers were found, one review article, three articles and one article detailing a proposed trial were found to be relevant to the question.

328 Papers were found, two additional abstracts were included.

No relevant Cochrane reviews were found.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Ellis et al, 2007, UK/Austalia	Clinical and cadaveric studies	Review article	Risk of regurgitation and aspiration during anaesthetic	Overall value for elective surgery in adults 0.014–0.1%	Search limited to English language. No grey literature search. No author contact
			Evidence of benefit of cricoid pressure	Cadaver studies suggest cricoid pressure will prevent regurgitation
			Evidence of aspiration despite cricoid pressure	Case reports and medicolegal cases provide evidence of aspiration occurrence despite cricoid pressure
			Anatomical basis for effect	CT and MRI scans suggest the oesophagus lies lateral to the vertebral body in ∼50% of patients. On MRI scans with cricoid pressure on, 90.5% of patients have a laterally displaced oesophagus with only 28.6% having complete oesophageal opposition
			Effects of cricoid pressure on tracheal intubation	Mixed results from various studies with cricoid pressure reported to worsen views in a variable proportion of patients. The only blinded randomised study did not show any difference in success rates for intubation between cricoid or sham cricoid pressure
			Complications of cricoid pressure	Include oesophageal perforation, cricoid cartilage fracture and haemorrhage in the presence of thyroid goitre
Fenton et al, 2009, Malawi/UK	Outcomes of female patients undergoing general anaesthetic for caesarean section in 27 hospitals in Malawi between January 1998 and June 2000	Prospective observational study	Of 4934 women having general anaesthetic documentation about the use of cricoid pressure available for 4891. 2985 had cricoid pressure applied	139 Women reported to have regurgitated or vomited. In 30 women this was at induction of anaesthesia. 24 (0.8%) had cricoid pressure, six (0.3%) did not have cricoid pressure applied	Anaesthetists often clinical officers (not medically qualified) and may have had limited or no training regarding cricoid pressure use. Self documented retrospectively whether cricoid pressure had been applied. Patients often had presented late, in extremis
Rice et al, 2009, USAS	24 Adult non-sedated volunteers underwent MRI scan with and without cricoid pressure applied	Observational study	Measured antero-posterior diameter of the hypopharynx at the level of the cricoid cartilage	In all patients the post-cricoid hypopharynx anteroposterior diameter was reduced to less than 6.1 mm, which is considered to be the thickness of both walls of the hypopharynx and therefore represent lumen obliteration	Small number. Not sedated. Unlikely to represent population requiring RSI. Scans not assessed independently. Interpretation of radiological image rather than clinical outcome
Ajmal, 2012, Pakistan	224 Patients undergoing general anaesthesia due to an acute abdomen over an 8-year period. No cricoid pressure applied, patients placed in Trendelenberg position and had nasogastric suction	Prospective cohort study	Primary endpoint was incidence of regurgitation, secondary endpoint was arterial oxygen desaturation	No episodes of clinical regurgitation recorded. One patient (0.4%) had documented arterial oxygen desaturation	Currently only available as abstract
Salem et al, 2012, USA/Saudi Arabia	59 Morbidly obese (BMI>40) anaesthetised patients	Observational study	Ability to pass 20 Fr and 36 Fr gastric tubes in the presence and then absence of cricoid pressure in intubated patients	Unable to pass gastric tube in any patient while cricoid pressure applied. Could pass tubes once cricoid pressure relieved	Currently only available as abstract. Not blinded. Small number. Not clear if this is representative of clinical risk

Comment(s)

Cricoid pressure has been described as the ‘linchpin of rapid sequence induction’ and has gradually become widely accepted as the standard of practice during anaesthesia in the UK and USA since it was first proposed by Sellick (1961). However, it is not widely used in other countries and it is difficult to demonstrate differences in rates of aspiration. Although it is an apparently simple manoeuvre with a sensible underlying theory of benefit there have also been concerns about its safety and efficacy, in particular that cricoid pressure may interfere with airway management, obscure the laryngeal view and create difficulties in passing the endotracheal tube. This could lead to a failure of airway techniques and subsequent morbidity and mortality. The limited evidence presented in this review cannot confirm the perceived clinical benefit of cricoid pressure in reducing the incidence of aspiration during an emergency RSI but there is also little in the way of demonstrated harm. It is difficult to envisage a randomised controlled trial being performed: the overall incidence of aspiration is very small so the trial would have to be very large; blinding would be difficult/impossible; it may also be difficult to engage clinicians who may already have an opinion as to whether it is of perceived efficacy or not. Trethewy et al (2012) have proposed a trial that could overcome some of these issues by blinding the anaesthetist and the applicator to the effectiveness of the cricoid pressure, while measuring the force applied using covered scales. Instead of attempting to randomly assign patients and blind the clinicians, the authors are relying on the reported unreliability of operator effectiveness, in which 47% of staff apply too little and 28% too much force (Clark et al, 2005), to demonstrate any correlation between effective cricoid pressure levels and the incidence of aspiration. The results of this trial are eagerly awaited.

Editor Comment

RSI, rapid sequence induction.

Clinical Bottom Line

There is little evidence to support the widely held belief that the application of cricoid pressure reduces the incidence of aspiration during a rapid sequence intubation.

References

1. Ellis D, Harris T, Zideman D. Cricoid pressure in emergency department rapid sequence tracheal intubations: a risk–benefit analysis. Ann Emerg Med 2007;50:653–65.
2. Fenton P, Reynolds F. Life-saving or ineffective? An observational study of the use of cricoid pressure and maternal outcome in an African setting. Int J Obstet Anesth 2009;18:106–10.
3. Rice M, Mancuso A, Gibbs C, et al. Cricoid pressure results in compression of the postcricoid hypopharynx: the esophageal position is irrelevant. Anesth Analg 2009;109:1546–52.
4. Ajmal M. Deviation from classic rapid sequence induction technique of general anaesthesia: outcomes in a series of 224 high-risk cases. Conference publication (various pagings). Anaesthesia 2012;67:76.
5. Salem M, Zeidan A, Al-Temyat S, et al. Conference publication (various pagings). Br J Anaesth 2012;108:ii333–4.
6. Sellick B. Cricoid pressure to control regurgitation of stomach contents during induction of anaesthesia. Lancet 1961;2:404–6.
7. Trethewy C, Burrows J, Clausen D, et al. Effectiveness of cricoid pressure in preventing gastric aspiration during rapid sequence intubation in the emergency department: study protocol for a randomised controlled trial. Trials 2012;13:17.
8. Clark R, Trethewy C Assessment of cricoid pressure application by emergency department staff. Emerg Med Australas 2005;17:376–81.