Cricoid pressure - the debate

Overview

Since it’s first description by British anesthesiologist Brian Sellick in 1961, cricoid pressure has become a standard of practice for preventing the aspiration of gastric contents during rapid sequence induction (RSI) or modified RSI.  In the original publication, the maneuver included using one’s thumb and second finger to occlude of the upper end of the of the esophagus by applying backward pressure to the cricoid cartilage against the body of the C5 vertebra. Sellick's study involved filling cadaver stomachs with water and placing the bodies in Trendelenberg position while using the maneuver, with success noted by lack of water in the oropharynx.

  • Considering its widespread use, the evidence supporting the use of cricoid pressure is of surprisingly poor quality. Many studies, including Sellick’s, are small, observational, unblinded, non-controlled and only involved human or animal cadavers. In addition, it is often not easy to compare results of different studies due to the variability in methodolgy. For example, some researchers investigated cricoid pressure with naso- or orogastric tubes in situ while others used the native esophagus.
  • The value of the cricoid pressure maneuver has also been questioned because it is often applied in an inconsistent fashion in actual clinical practice. For example, Sellick described full extension of the head and neck in order to bring the cervical vertebrae more anteriorly. This is not always possible in a clinical setting, especially in patients presenting with a potentially unstable cervical spine. Also, full neck extension is likely to make laryngoscopy more difficult and is therefore usually avoided. Sellick claimed that mask ventilation is safe during application of cricoid pressure. However, this is often omitted in practice despite several studies demonstrating a lack of gastric insufflation while mask ventilating with cricoid pressure applied properly (Moynihan 1993). Although gastric insufflation occurs at lower insufflation pressures in paralyzed patients, cricoid pressure may off-set this effect.
  • Many of the critics also note the lack of knowledge and skill in many providers regarding the surface anatomy, hand/ finger position, and amount of force involved in “proper” cricoid pressure. In a study of nurse anesthetists in 2009 (Beaver et al), only 55% of providers correctly identified the cricoid cartilage, while only 17.8% of providers applied pressure within the recommended adult range (30-40 N or 3-4kg of force).  Importantly, there was no correlation between knowledge of the correct amount force and actual application of that force. In an Australian emergency department study in 2005 (Clark et al) assessing the use of cricoid pressure amongst emergency room physicians and nurses, only 25% of providers applied the 30-40N range fof pressure.  Amongst those who were incorrect, 75% had pressures below 30N, and 35% had pressures in excess of 40N.  Interestingly, there was no difference in sex, age, years of experience, or occupation (physician or nurse); and only half of the staff who correctly applied cricoid pressure could identify the correct pressure. Ideally, pressure should be sufficient to cause esophageal occlusion, while pressures greater than 40N have been associated with complications (i.e. reduction in tidal volumes during mask ventilation).  There has been general agreement that less pressure should be used in smaller adults and children, but there is no consensus on those exact values.  Despite the lack of familiarity many providers have with this range of force, practitioners are able to accurately reproduce cricoid pressure in the target range with training, to within 2 N (Herman et al 1996).
  • In addition, significant anatomic variability exists between patients which might impact the efficacy of the maneuver. For example, in pediatric patients the cricoid cartilage is usually located higher in the neck compared to adults. It is also smaller and has a greater backward inclination of the posterior portion (lamina). The significance of these differences for cricoid pressure application is unclear. We also know that the esophagus lies lateral to the cricoid ring in as much as 50% of patients (Smith 1993). However, some recent studies, including one based on MRI imaging (Rice et al, 2009) and one using the Glidescope for laryngoscopy (Zeidan et al, 2012) have suggested that the compression of the hypopharyngeal unit and occlusion of the esophagus during cricoid pressure does not depend on esophageal position.

Complications and adverse effects of cricoid pressure

The most important complications are reduced visibility on larygoscopy and difficulty with ventilation. Namely a reduction in attainable tidal volume and increases in peak inspiratory pressure have been reported. Much more severe but probably very rare complications of cricoid pressure have been published as case reports. These include esophageal rupture when patients vomited, cricoid fractures and subconjunctival hemorrhages. Palmer et al. (2000) examined the side effects of cricoid pressure using fiberoptic bronchoscopy through an LMA with different pressures applied (20, 30, and 44 N). They found that at 44 N, cricoid deformation was present in 90% of patients, while 50% had cricoid occlusion and 60% were difficult to ventilate.


Medicolegal issues

Analysis of ata from the ASA Closed Claims Database (Domino) found that, between 1990 and 2007, 17% of suits were attributable to respiratory complications, and 3% of the total claims were specifically due to aspiration.  Comparison of the data from 1970- 1989 and 1990- 2007 shows a trend toward an increasing proportion of claims related to aspiration and difficult intubation. These researchers also found that only 60% of aspiration events occurred during induction, while 19% occurred intraoperatively after induction, and 12% occurred in the immediate postoperative period. Interestinglyly the larger damage awards were given in cases where providers decided to omit cricoid pressure ($513,125 without cricoid pressure vs $211,500 when using cricoid pressure).


Summary

In general cricoid pressure appears to be a safe maneuver when applied properly within the target pressure range. Contraindications include active vomiting because of the risk of esophageal tearing and tracheal or cricoid cartilage fratures. Unwanted effects of cricoid pressure application, particularly with use of excessive pressure, include airway obstruction, more difficult laryngoscopy and intubation as well as difficult ventilation. The main risk of inadequate pressure on the other hand is aspiration.  More investigation needs to be done into how useful the maneuver is, but generally we as providers require more education about cricoid pressure, and  standardization of instruction and application of force.


References

Beavers et al. Analysis of the application of cricoid pressure: implications for the clinician. Journal of Perianesthesia Nursing. 2009:24: 92-102.

Clark et al. Assessment of cricoid pressure application by emergency department staff. Emergence Medicine Australasia. 2005; 17: 376-381

Domino K, et al. Closed Claims’ Analysis. Best Practice & Research Clinical Anaesthesiology.2011;25: 263-276.

Domino K, et al. An update on pediatric anesthesia liability: a closed claims analysis.  Anesth Analg. 2007; 104: 147-153

Herman NL et al. Cricoid pressure: teaching the recommended level. Anesth Analg. 1996; 83:859-63

Moynihan RJ et al. The effect of cricoid pressure on preventing gastric insufflation in infants and children. Anesthesiology. 1993; 78: 652-656.

Palmer et al. The effect of cricoid pressure on the cricoid cartilage and vocal cords: an endoscopic study in anesthetised patients. Anaesthesia 2000; 55(3); 263-8.

Rice MJ et al. Cricoid pressure results in the compression of the postcricoid hypopharynx: the esophogeal position is irrelevant. Anesth Analg. 2009; 109:1546-1552.

Sellick BA. Cricoid pressure to control regurgitation of stomach contents during induction of anesthesia. Lancet. 1961;2:404-406.

Smith KJ et al. Cricoid pressure displaces the esophagus: an observational study using magnetic resonance imaging. Anesthesiology 2003; 99:60-4.

Ziedan et al. The effectiveness of cricoid pressure for occluding the esophageal entrance in anesthetized and paralyzed patients: an experimental and observational glidescope study. Anesth Analg 2014. 118; 580-586.